Part 4: Paleness

By Dr. Inge Heinzl, Editor and Marisabel Caballero, Global Technical Manager Poultry

We already showed bad feathering, mouth and beak lesions, bone issues, and foot pad lesions as signs of mycotoxin contamination in the feed, but there is another indicator: paleness. Paleness can signify a low count of red blood cells resulting from blood loss or inadequate production of these cells. Other possibilities are higher bilirubin levels in the blood due to an impaired liver, leading to jaundice or missing pigmentation.

The mycotoxins mainly causing anemia are Aflatoxins, Ochratoxin, DON, and T-2 toxin

Anemia can be diagnosed using parameters such as red blood cell count, hemoglobin levels, and hematocrit/packed cell volume (PCV). Numerous studies have examined the impact of mycotoxins on hematological parameters. They reveal their propensity to affect red blood cell production by impairing the function of the spleen and inducing hematological alterations. On the other hand, anemia can be caused by blood loss. Due to affecting coagulation factors, mycotoxins can lead to internal hemorrhages. The gut wall damage, probably due to secondary infections such as coccidiosis and necrotic enteritis, can entail bloody diarrhea in various animal species.

Impact on the production of blood cells

Low values of blood parameters such as red blood cells, hemoglobin, and hematocrit can result from inadequate production due to impacted production organs. The World Health Organization (WHO, 1990) and European Commission (European Commission, 2001) have identified hematopoietic tissues as targets for necrosis caused by T-2 toxin. Chu (2003) even stated that “the major lesion of T-2 toxin is its devastating effect on the hematopoietic system in many mammals, including humans”. Pande et al. (2006) suggested that reduced hemoglobin values result from decreased protein synthesis due to mycotoxin contamination, a notion supported by Pronk et al. (2002), who described trichothecenes as potent inhibitors of protein, DNA, and RNA synthesis, particularly affecting tissues with high cell division rates. Additionally, the European Commission (2001) highlighted the sensitivity of red blood cell progenitor cells (in this trial, the cells of mice, rats, and humans) to the toxic effects of T-2 and HT-toxins. DAS also seems to attack the hematopoietic system, as shown in humans (WHO, 1990). A further cause for anemia might be low feed intake or nutrient absorption, which inhibits adequate iron absorption and leads to iron deficiency. In their case report, Bozzo et al. (2023) assumed that renal failure and a resulting impaired excretion capacity caused by OTA might even increase the half-life of the toxins. This would enhance their effects on their target organs, such as the liver and bone marrow, and lead to anemia.

Several studies utilizing different animal species and mycotoxin dosages have been conducted to assess the effects of Aflatoxins, Ochratoxin, and T-2 Toxin on hematological parameters. The following table provides a summary of some of these studies.

Animal species	Dosage	Impact	Reference
T-2 Toxin and other Trichothecenes
Broilers	T-2 – 0, 1, 2, and 4 mg T-2 toxin/kg n=30 per group	Significant reduction in hemoglobin at 1, 2, and 4 ppm; PCV significantly reduced at 4 ppm	Pande et al., 2006
Broilers	T-2 – 0 and 4 mg/kg diet n=60 per group	Decrease in hemoglobin, mean corpuscular volume, and mean corpuscular hemoglobin concentration	Kubena et al., 1989a
Broilers	4, 16, 50, 100, 300 ppm for seven days n=5-20 chickens per group	Anemia; significant reduction of hematocrit (50 and 100 ppm); survivors had atrophied lymphoid organs and were anemic	Hoerr et al., 1982
Yangzhou goslings	0, 0.2, 0.4, 0.6, 0.8, 1.0, 2.0 mg/kg; n=6 per group	Red blood cell count decreased in the 2.0 mg/kg group along with an increase in mean corpuscular hemoglobin (p<0.05) and reduced mean platelet volume (P<0.05)	Gu et al., 2023
Broilers	2 ppm; 32 birds per group	Anemia, as indicated by significantly (P<0.05) lower total erythrocyte count (TEC) values, lower hemoglobin levels, and packed cell volume; additional thrombocytopenia could be the cause of bleeding	Yohannes et al., 2013
DON
Broilers	5 and 15 mg/kg of feed for 42 days	Decrease in erythrocytes, mean corpuscular volume (MCV), and mean corpuscular hemoglobin concentration (MCHC) at 15 mg/kg; decrease in hematocrit and hemoglobin at both levels of DON.	Riahi, 2021
Piglets	0.6 mg/kg and 2.0 mg/kg	Significant decrease in mean corpuscular volume	Modrá et al., 2013
Broilers	16 mg/kg diet n=60 per group	Significant decrease in mean corpuscular volume	Kubena et al., 1989c
Ochratoxin
Broilers	2 mg/kg diet singly or combined with DAS 6 mg/kg	Reduced mean corpuscular hemoglobin values	Kubena et al., 1994
Broilers	2 mg/kg diet	Significant decrease in hemoglobin, hematocrit, mean corpuscular volume and mean corpuscular hemoglobin concentration	Kubena et al., 1989b
Aflatoxins
Broilers	2.5 µg/g	Decrease in red blood cell count	Huff et al., 1988
Broilers	≥1.25 µg/g	Significant decrease in hemoglobin and erythrocyte count	Tung et al., 1975
AFB1 + OTA
Laying hens	Natural feed contamination OTA – 31 ± 3.08 µg/kg and AFB1 – 5.6 ± 0.33 µg/kg dry weight	Anemia signs (pale appearance of combs and wattles), evidenced by the discoloration of the content of the femoral medullary cavity.	Bozzo et al., 2023

Table 1: The effects of different mycotoxins on hematological parameters – hematopoiesis

In their meta-analysis, Andretta et al. (2012) reported that the presence of mycotoxins in broiler diets decreased the hematocrit and the hemoglobin concentration by 5% and 15%, and aflatoxin alone decreased the parameters by 6% and 20%.

It should be evident that a simultaneous occurrence of several mycotoxins even aggravates the situation. In an experiment involving Sprague Dawley rats, administering T-2, DON, NIV, ZEA, NEO, and OTB decreased hematocrit and red blood cell counts across all mycotoxins. However, for DON, NIV, ZEN, and OTB, red blood cell values showed partial recovery after 24 hours (Chattopadhyay, 2013). Perhaps the organism learns to cope with the mycotoxins.

The examples show that Trichothecenes, such as T-2 toxin, DON, and others, as well as Ochratoxins and Aflatoxins, impact blood parameters such as hematocrit, hemoglobin, red blood cell count, and mean corpuscular volume. All these changes might lead to paleness of the skin and birds’ feet and combs.

Blood loss caused by bleeding or destruction of erythrocytes

The second possibility for anemia is blood loss due to injuries or lesions. In addition to directly causing hemorrhages, mycotoxins can promote secondary infections such as coccidiosis, which damages the gut and may produce bloody feces.

Parent-Massin (2004) e.g. reports on rapidly progressing coagulation problems after the ingestion of trichothecenes leading to septicemia and massive hemorrhages. Table 2 shows more examples of mycotoxins causing paleness due to blood loss.

Animal species	Dosage	Impact	Reference
T-2 Toxin and other Trichothecenes
Cats	T-2 toxin – 0.06-0.1 mg/kg body weight/day	Bloody feces, hemorrhages	Lutsky et al., 1978
Cats	T-2 toxin – 0.08 mg/kg BW every 48 h until death	Bloody feces	Lutzky and Mor, 1981
Pigeon	DAS in oat, sifting	Emesis and bloody stools	Szathmary (1983)
Calves	0.08, 0.16, 0.32, or 0.6 mg/kg BW per day for 30 days; 1 calf per treatment	Bloody feces at doses ≥0.32 mg/kg BW per day	Pier et al., 1976
Ochratoxin
Rats	Single dosages of 0, 17, or 22 mg/kg BW in 0.1 Mol/L NaHCO3, gavage	Multifocal hemorrhages in many organs	Albassam et al., 1987
DON
Broilers	0, 35, 70, 140, 280, 560, and 1120 mg/kg body weight	Ecchymotic hemorrhages throughout the intestinal tract, liver, and musculature; relationship to hemorrhagic anemia syndrome seems warranted	Huff et al., 1981
Sterigmatocystin (ST)
10-12-day old chicks (93-101 g)	10 and 14 mg/kg BW intraperitoneal	Hemorrhages and foci of necrosis in the liver	Sreemannarayana et al., 1987
Aflatoxins
Broiler chickens	100 µg/kg feed	Hemorrhages in the liver	Abdel-Sattar, 2019
Turkeys	500 and 1000 ppb in the diet	Bloody diarrhea, spleens with hemorrhages, petechial hemorrhages in the small intestine	Giambrone et al., 1984
Broilers	0, 0.625, 1.25, 2.5, 5.0, and 10.0 mg/kg of diet combined with Infectious Bursal Disease	Slight hemorrhages in the skeletal muscles; decreased hematocrit and hemoglobin due to hemolytic anemia.	Chang and Hamilton, 1981
Broilers	0, 1, and 2 mg AFB1/kg of diet	Downregulation of the genes involved in blood coagulation (coagulation factor IX and X) and upregulation of anticoagulant protein C precursor, an inactivator of coagulation factors Va and VIIIa, and antithrombin-III precursor with 2 mg/kg	Yarru, 2009
Pigs	1-4 mg/kg, 4 weeks 0.4-0.8 mg/kg, 10 weeks	Hemorrhages	Henry et al., 2001

Table 2: The effects of different mycotoxins on hematological parameters – blood loss

Poor pigmentation

The fourth reason for paleness can be inadequate pigmentation. According to Hy Line (2021), the so-called pale bird syndrome is characterized by poor skin and egg yolk pigmentation and is caused by reduced absorption of fat and carotenoid pigments in compromised birds. This is also the case when the diets contain pigment supplements. Tyczkowski and Hamilton (1986) observed in their experiment with chickens exposed to doses of 1-8 µg of Aflatoxins/g of diet for three weeks that aflatoxins can cause poor pigmentation in chickens, probably by impairing carotenoids absorption but also transport and deposition. Osborne et al. (1982) asserted that carotenoids were significantly (P<0.05) depressed by 2 ppm ochratoxin as well as by 2.5 ppm aflatoxin in the diet.

Another possibility is oxidative stress due to the mycotoxin challenge. As pigments also serve as antioxidants, they may be expended for this purpose and are no longer available for pigmentation.

Paleness in poultry – a reason to think about mycotoxins

Paleness can have different causes, some of which are influenced by mycotoxins. If your chickens or hens are pale, checking the feed concerning mycotoxins is always recommended. A feed analysis can give information about possible contamination (see our tool MasterRisk).

In the case of contamination, effective products binding the mycotoxins and mitigating the adverse effects of these harmful substances can help protect your birds. As paleness is usually not the only effect of mycotoxins but also a decrease in growth, toxin binders can help maintain the performance of your animals.

References:

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Albassam, M. A., S. I. Yong, R. Bhatnagar, A. K. Sharma, and M. G. Prior. “Histopathologic and Electron Microscopic Studies on the Acute Toxicity of Ochratoxin a in Rats.” Veterinary Pathology 24, no. 5 (September 1987): 427–35. https://doi.org/10.1177/030098588702400510.

Andretta, I., M. Kipper, C.R. Lehnen, and P.A. Lovatto. “Meta-Analysis of the Relationship of Mycotoxins with Biochemical and Hematological Parameters in Broilers.” Poultry Science 91, no. 2 (February 2012): 376–82. https://doi.org/10.3382/ps.2011-01813.

Bhat, RameshV, Y Ramakrishna, SashidharR Beedu, and K.L Munshi. “Outbreak of Trichothecene Mycotoxicosis Associated with Consumption of Mould-Damaged Wheat Products in Kashmir Valley, India.” The Lancet 333, no. 8628 (January 1989): 35–37. https://doi.org/10.1016/s0140-6736(89)91684-x.

Bozzo, Giancarlo, Nicola Pugliese, Rossella Samarelli, Antonella Schiavone, Michela Maria Dimuccio, Elena Circella, Elisabetta Bonerba, Edmondo Ceci, and Antonio Camarda. “Ochratoxin A and Aflatoxin B1 Detection in Laying Hens for Omega 3-Enriched Eggs Production.” Agriculture 13, no. 1 (January 5, 2023): 138. https://doi.org/10.3390/agriculture13010138.

Chang, Chao-Fu, and Pat B. Hamilton. “Increased Severity and New Symptoms of Infectious Bursal Disease during Aflatoxicosis in Broiler Chickens.” Poultry Science 61, no. 6 (June 1982): 1061–68. https://doi.org/10.3382/ps.0611061.

Chattopadhyay, Pronobesh, Amit Agnihotri, Danswerang Ghoyary, Aadesh Upadhyay, Sanjeev Karmakar, and Vijay Veer. “Comparative Hematoxicity of Fusarium Mycotoxin in Experimental Sprague-Dawley Rats.” Toxicology International 20, no. 1 (2013): 25. https://doi.org/10.4103/0971-6580.111552.

European Commission. “Opinion of the Scientific Committee on Food on Fusarium Toxins Part 5: T-2 Toxin and HT-2 Toxin.” Food.ec.europa. Accessed May 30, 2001. https://food.ec.europa.eu/document/download/a859c348-a38e-404c-a2af-c3e29a3a8777_en?filename=sci-com_scf_out88_en.pdf.

Giambrone, J.J., U.L. Diener, N.D. Davis, V.S. Panangala, and F.J. Hoerr. “Effect of Purified Aflatoxin on Turkeys.” Poultry Science 64, no. 5 (May 1985): 859–65. https://doi.org/10.3382/ps.0640859.

Gu, Wang, Qiang Bao, Kaiqi Weng, Jinlu Liu, Shuwen Luo, Jianzhou Chen, Zheng Li, et al. “Effects of T-2 Toxin on Growth Performance, Feather Quality, Tibia Development and Blood Parameters in Yangzhou Goslings.” Poultry Science 102, no. 2 (February 2023): 102382. https://doi.org/10.1016/j.psj.2022.102382.

Henry, H., T. Whitaker, I. Rabban, J. Bowers, D. Park, W. Price, F.X. Bosch, et al. “Aflatoxin M1.” Aflatoxin M1 (JECFA 47, 2001). Accessed July 29, 2024. https://inchem.org/documents/jecfa/jecmono/v47je02.htm.

Hoerr, F., W. Carlton, B. Yagen, and A. Joffe. “Mycotoxicosis Caused by Either T-2 Toxin or Diacetoxyscirpenol in the Diet of Broiler Chickens.” Fundamental and Applied Toxicology 2, no. 3 (May 1982): 121–24. https://doi.org/10.1016/s0272-0590(82)80092-4.

Huff, W.E., J.A. Doerr, P.B. Hamilton, and R.F. Vesonder. “Acute Toxicity of Vomitoxin (Deoxynivalenol) in Broiler Chickens,” Poultry Science 60, no. 7 (July 1981): 1412–14. https://doi.org/10.3382/ps.0601412.

Huff, W.E., R.B. Harvey, L.F. Kubena, and G.E. Rottinghaus. “Toxic Synergism between Aflatoxin and T-2 Toxin in Broiler Chickens.” Poultry Science 67, no. 10 (October 1988): 1418–23. https://doi.org/10.3382/ps.0671418.

Hy-Line. “Mycotoxins: How to deal with the threat of mycotoxicosis.” Hy-Line International. Accessed July 29, 2024. https://www.hyline.com/.

Klein, P. J., T. R. Vleet, J. O. Hall, and R. A. Coulombe. “Dietary Butylated Hydroxytoluene Protects against Aflatoxicosis in Turkey.” Poisonous plants and related toxins, November 24, 2003, 478–83. https://doi.org/10.1079/9780851996141.0478.

Kubena, L.F., R.B. Harvey, T.S. Edrington, and G.E. Rottinghaus. “Influence of Ochratoxin A and Diacetoxyscirpenol Singly and in Combination on Broiler Chickens.” Poultry Science 73, no. 3 (March 1994): 408–15. https://doi.org/10.3382/ps.0730408.

Kubena, L.F., R.B. Harvey, W.E. Huff, D.E. Corrier, T.D. Philipps, and G.E. Rottinghaus. “Influence of Ochratoxin A and T-2 Toxin Singly and in Combination on Broiler Chickens.” Poultry Science 68, no. 7 (July 1989): 867–72. https://doi.org/10.3382/ps.0680867.

Kubena, L.F., R.B. Harvey, W.E. Huff, D.E. Corrier, T.D. Phillips, and G.E. Rottinghaus. “Influence of Ochratoxin A and T-2 Toxin Singly and in Combination on Broiler Chickens.” Poultry Science 68, no. 7 (July 1989): 867–72. https://doi.org/10.3382/ps.0680867.

Kubena, L.F., W.E. Huff, R.B. Harvey, T.D. Phillips, and G.E. Rottinghaus. “Individual and Combined Toxicity of Deoxynivalenol and T-2 Toxin in Broiler Chicks.” Poultry Science 68, no. 5 (May 1989): 622–26. https://doi.org/10.3382/ps.0680622.

Lutsky, I.I., and N. Mor. “Alimentary Toxic Aleukia (Septic Angina, Endemic Panmyelotoxicosis, Alimentary Hemorrhagic Aleukia): T-2 Toxin-Induced Intoxication of Cats.” The American journal of pathology, 1980. https://pubmed.ncbi.nlm.nih.gov/6973281/.

Lutsky, Irving, Natan Mor, Boris Yagen, and Avraham Z. Joffe. “The Role of T-2 Toxin in Experimental Alimentary Toxic Aleukia: A Toxicity Study in Cats.” Toxicology and Applied Pharmacology 43, no. 1 (January 1978): 111–24. https://doi.org/10.1016/s0041-008x(78)80036-2.

MEJ, Pronk, Schothorst RC, and H.P. van Egmond. “Toxicology and Occurrence of Nivalenol, Fusarenon X, Diacetoxyscirpenol, Neosolaniol and 3- and 15- Acetyldeoxynivalenol; a Review of Six Trichothecenes.” Home – Web-based Archive of RIVM Publications, November 7, 2002. https://rivm.openrepository.com/handle/10029/9184.

Modra, Helena, Jana Blahova, Petr Marsalek, Tomas Banoch, Petr Fictum, and Martin Svoboda. “The Effects of Mycotoxin Deoxynivalenol (DON) on Haematological and Biochemical Parameters and Selected Parameters of Oxidative Stress in Piglets.” Neuro Endocrinol Lett. 34, no. Suppl 2 (2013): 84–89.

Osborne, D.J., W.E. Huff, P.B. Hamilton, and H.R. Burmeister. “Comparison of Ochratoxin, Aflatoxin, and T-2 Toxin for Their Effects on Selected Parameters Related to Digestion and Evidence for Specific Metabolism of Carotenoids in Chickens,” Poultry Science 61, no. 8 (August 1982): 1646–52. https://doi.org/10.3382/ps.0611646.

Pande, Vivek, Nitin Kurkure, and A.G. Bhandarkar. “Effect of T-2 Toxin on Growth, Performance and Haematobiochemical Alterations in Broilers .” Indian Journal of Experimental Biology 44, no. 1 (February 2006): 86–88.

Pier , A.C., S.J. Cysewski, J.L. Richard , A.L. Baetz, and L. Mitchell. “Experimental Mycotoxicoses in Calves with Aflatoxin, Ochratoxin, Rubratoxin, and T-2 Toxin.” Proceedings, annual meeting of the United States Animal Health Association, 1976. https://pubmed.ncbi.nlm.nih.gov/1078072/.

Resanovic, Radmila, Ksenija Nesic, Vladimir Nesic, Todor Palic, and Vesna Jacevic. “Mycotoxins in Poultry Production.” Zbornik Matice srpske za prirodne nauke, no. 116 (2009): 7–14. https://doi.org/10.2298/zmspn0916007r.

Riahi, Insaf, Virginie Marquis, Anna Maria Pérez-Vendrell, Joaquim Brufau, Enric Esteve-Garcia, and Antonio J. Ramos. “Effects of Deoxynivalenol-Contaminated Diets on Metabolic and Immunological Parameters in Broiler Chickens.” Animals 11, no. 1 (January 11, 2021): 147. https://doi.org/10.3390/ani11010147.

Sreemannarayana, O., A. A. Frohlich, and R. R. Marquardt. “Acute Toxicity of Sterigmatocystin to Chicks.” Mycopathologia 97, no. 1 (January 1987): 51–59. https://doi.org/10.1007/bf00437331.

Stack, Jim, and Mike Carlson. “Fumonisins in Corn.” DigitalCommons@University of Nebraska – Lincoln, 2003. https://core.ac.uk/download/pdf/188054556.pdf.

Szathmary, C.I. “Trichothecene Toxicoses and Natural Occurrence in Hungary.” Essay. In Ueno, Y: Developments in Food Science IV. Trichothecenes, 229–50. New York: Elsevier, 1983.

Tung, Hsi-Tang, F.W. Cook, R.D. Wyatt, and P.B. Hamilton. “The Anemia Caused by Aflatoxin.” Poultry Science 54, no. 6 (November 1975): 1962–69. https://doi.org/10.3382/ps.0541962.

Tyczkowski, Juliusz K., and Pat B. Hamilton. “Altered Metabolism of Carotenoids during Aflatoxicosis in Young Chickens,” Poultry Science 66, no. 7 (July 1987): 1184–88. https://doi.org/10.3382/ps.0661184.

WHO. “Selected Mycotoxins : Ochratoxins, Trichothecenes, Ergot / Published under the Joint Sponsorship of the United Nations Environment Programme, the International Labour Organisation and the World Health Organization.” World Health Organization, January 1, 1990. https://apps.who.int/iris/handle/10665/39552.

Yohannes, T., A. K. Sharma, S. D. Singh, and V. Sumi. “Experimental Haematobiochemical Alterations in Broiler Chickens Fed with T-2 Toxin and Co-Infected with IBV.” Open Journal of Veterinary Medicine 03, no. 05 (2013): 252–58. https://doi.org/10.4236/ojvm.2013.35040.

Part 3: Bone disorders and foot pad lesions

By Dr. Inge Heinzl, Editor, and Marisabel Caballero, Global Technical Manager Poultry

 

Bone health is essential for animals and humans. Besides giving structural support, allowing movement, and protecting vital organs, the bones release hormones that are crucial for mineral homeostasis and acid balance and serve as reservoirs of energy and minerals (Guntur & Rosen, 2012; Rath, N.C. & Durairaj, 2022; Suchacki et al., 2017).

Bone disorders and foot pad lesions are considerable challenges in poultry production, especially for fast-growing birds with high final weights. Due to pain, the animals do not move, and dominant, healthy birds may restrict lame birds’ access to feed and water. In consequence, these birds are often culled. Moreover, processing these birds is problematic, and often, they must be discarded or downgraded.

Foot pad lesions, another common issue in poultry production, can also have significant economic implications. On the one hand, pain restricts birds from eating and drinking and reduces weight gain. On the other hand, for many producers, chicken feet constitute a substantial part of the economic value of the bird; therefore, discarding them represents a significant financial loss. Additionally, to push poultry production in the right direction concerning animal health and welfare, a foot pad scoring system at the processing plant is in place in European countries.

Mycotoxins affect bones in different ways

Mycotoxins, depending on their target organs, can have diverse effects on the skeleton of birds. For example, mycotoxins that target the liver can disrupt calcium metabolism, which in turn affects the mineralization of the bones (rickets) and the impairment of chondrocytes can slow down bone growth (e.g., tibial dyschondroplasia). When the kidneys are impacted, urate clearance decreases, plasma uric acid consequently increases, and urate crystals form in the synovial fluid and tendon sheaths of various joints, particularly the hock joints. These examples highlight the complex and varied ways mycotoxins can impact poultry bone health.

Inadequate bone mineralization and strength – Rickets and layer cage fatigue

Sufficient bone mineralization is essential for the stability of the skeleton. Calcium (Ca), Vitamin D, and Phosphorous (P) deficiency leads to inadequate mineralization, weakens the bone, and can cause soft and bent bones or, in the case of layers, cage fatigue – a collapse of the spinal bone- and paralysis. Inadequate bone mineralization can be caused in different ways, among them:

1. Decrease in the availability of the nutrients necessary for mineralization. This can occur if the digestibility of these nutrients deteriorates
2. Impact on the Ca/P ratio—A ratio of 1 – 2:1 is vital for adequate bone development (Loughrill et al., 2016). Mycotoxins can alter absorption and transporters for one or both elements, altering their ratio.
3. Impact on the Vitamin D receptor, affecting its expression or the transporters for Ca and P.

Aflatoxins can impair bone mineralization by different modes of action. An important one is the impairment of the digestibility of Ca and P: Kermanshahi et al. (2007) fed broilers diets with high levels of aflatoxins (0.8 to 1.2 mg AFB1/kg feed) for three weeks, which resulted in a significant reduction of Ca and P digestibility. Other researchers, however, did not find an effect on Ca and P digestibility with lower aflatoxin levels:  Bai et al. (2014) feeding diets contaminated with 96 (starter) and 157 µg Aflatoxins (grower) per kg of feed to broilers and Han et al. (2008) saw no impact on cherry valley ducks with levels of 20 and 40 µg AFB1/kg diet.

Indirectly, a decrease in the availability of Ca and P due to aflatoxin-contaminated feed can be shown by blood or tibia levels of these minerals, as demonstrated by  Zhao et al. (2010): They conducted a trial with broilers, resulting in blood serum levels of Ca and P levels significantly (P<0.05) dropped with feed contaminated with 2 mg/kg of AFB1. Another trial conducted by Bai et al. (2014) showed decreased Ca in the tibia and reduced tibial break strength.

To get more information about the effect of mycotoxins on bone mineralization and the utilization of Ca, P, and Vit. D in animal organisms, Costanzo et al. (2015) challenged osteosarcoma cells with 5 and 50 ppb of aflatoxin B1. They asserted a significant down-modulation of the expression of the Vitamin D receptor. Furthermore, they assumed an interference of AFB1 with the actions of vitamin D on calcium-binding gene expression in the kidney and intestine.  Paneru et al. (2024) could confirm this downregulation of the Vit D receptor and additionally of the Ca and P transporters in broilers with levels of ≥75 ppb AFB1. They also saw a significant reduction in tibial bone ash content at AFB1 levels >230 ppb, a decreased trabecular bone mineral content and density at AFB1 520 ppb, and a reduced bone volume and tissue volume of the cortical bone of the femur at the level of 230 ppb (see Figure 1). They concluded that AFB1 levels of already 230 ppb contribute to bone health issues in broilers.

Figure 1: Increasing doses of AFB1 (<2 ppb – 560 ppb) deteriorate bone quality (Paneru, 2024): Cross-sectional images of femoral metaphysis with increasing AFB1 levels (left to right). The outer cortical bone is shown in light grey, and the inner trabecular bone in blue. Higher levels of AFB1 (T4 and T5) show a disruption of the trabecular bone pattern (less dense blue pattern with thinner and more fragmented bone strands and with wide spaces between the trabecular bone) (shown in white).

All experiments strongly suggest that aflatoxins harm bone homeostasis. Additional liver damage, oxidative stress, and impaired cellular processes can exacerbate bone health issues.

Trichothecenes also negatively impact bone mineralization. Depending on the mycotoxin, they may affect the gut, decreasing the absorption of Ca and P and probably provoking an imbalance in the Ca/P ratio.

For instance, when T-2 toxin was fed to Yangzhou goslings at 0.4, 0.6, and 0.8 mg/kg of diet, it decreased the Ca levels (halved at 0.8 mg/kg) and increased the P levels in the blood serum, so the Ca/P ratio decreased from the adequate ratio of 1 – 2 to 0.85, 0.66, and 0.59 (P<0.05) (Gu et al., 2023). The alterations of the Ca and P levels, the resulting decreasing Ca/P ratio, and an additional increase in alkaline phosphatase (ALP) suggest that T-2 toxin negatively impacts Ca absorption, increases ALP, and, therefore, disturbs calcification and bone development.

Other studies show that serum P levels decreased in broilers fed DON-contaminated feed with levels of only 2.5 mg/kg (Keçi et al., 2019). One reason for the lower P level is probably the lower dry matter intake, affecting Ca and P intake. Ca serum level is not typically reduced, which can be explained by the fact that Ca plays many critical physiological roles (e.g., nerve communication, blood coagulation, hormonal regulation), so the body keeps the blood levels by reducing bone mineralization. Another explanation is delivered by Li et al. (2020): After their trial with broilers, they stated that dietary P deficiency is more critical for bone development than Ca deficiency or Ca & P deficiency. The results of the trial conducted by Keçi et al. with DON (see above) were reduced bone mineralization, affected bone density, ash content, and ash density in the femur and tibiotarsus with a stronger impact on the tibiotarsus than on the femur.

In line with trichothecenes effects in Ca and P absorption, Ledoux et al. (1992) suppose that diarrhea caused by intake of fumonisins leads to malabsorption or maldigestion of vitamin D, calcium and phosphorus, having birds with rickets as a secondary effect.

Ochratoxin A (OTA) impairs kidney function, negatively affects vitamin D metabolism, reduces Ca absorption, and contributes to deteriorated bone strength (Devegowda and Ravikiran, 2009). Indications from Huff et al. (1980) show decreased tibia strength after feeding chickens OTA levels of 2, 4, and 8 µ/g, and Duff et al. (1987) report similar results also in turkey poults.

A further mycotoxin possibly contributing to leg weakness is cyclopiazonic acid produced by Aspergillus and Penicillium. This mycotoxin is known for leading to eggs with thin or visibly racked shells, indicating an impairment of calcium metabolism (Devegowda and Ravikiran, 2009). Tran et al. (2023) also showed this fact with multiple mycotoxins.

The co-occurrence of different mycotoxins in the feed – the standard in praxis – increases the risk of leg issues. A trial with broiler chickens conducted by Raju and Devegowda (2000) showed a bone ash-decreasing effect of AFB1 (300 µg/kg), OTA (2 mg/kg), and T-2 toxin (3 mg/kg), fed individually but an incomparable higher effect when fed in combination.

Impairment of bone growth – tibial dyschondroplasia (TD)

In TD, the development of long bones is impaired, and abnormal cartilage development occurs. It is frequent in broilers, with a higher incidence in males than females. It happens when the bone grows, as the soft cartilage tissue is not adequately replaced by hard bone tissue. Some mycotoxins have been related to this condition: According to Sokolović et al. (2008), actively dividing cells such as bone marrow are susceptible to T-2 toxin, including the tibial growth plates, which regulate chondrocyte formation, maturation, and turnover.

T-2 toxin: In a study with primary cultures of chicken tibial growth plate chondrocytes (GPCs) and three different concentrations of T-2 toxin (5, 50, and 500 nM), He et al. (2011) found that T-2 toxin decreased cell viability, alkaline phosphatase activity, and glutathione content (P < 0.05). Additionally, it increased the level of reactive oxygen species and malondialdehyde in a dose-dependent way, which could be partly recompensated by adding an antioxidant (N-acetyl-cysteine). They concluded that T-2 toxin inhibits the proliferation and differentiation of GPCs and contributes, therefore, to the development of TD, altering cellular homeostasis. Antioxidants may help to reduce these effects.

Gu et al. (2023) investigated the closely bodyweight-related shank length and the tibia development in Yangzhou goslings fed feed with six different levels (0 to 2.0 mg/kg) of T-2 toxin for 21 days. They determined a clear dose-dependent slowed tibial length and weight growth (p<0.05), as well as abnormal morphological structures in the tibial growth plate. As tibial growth and shank length are closely related to weight gain (Gu et al., 2023; Gao et al., 2010; Ukwu et al., 2014; Yu et al., 2022), their slowdown indicates lower growth performance.

Fumonisin B1 is also a potential cause of this kind of leg issue. Feeding 100 and 200 mg/kg to day-old turkey poults for 21 days led to the development of TD (Weibking et al., 1993). Possible explanations are the reduced viability of chondrocytes, as found by Chu et al. (1995) after 48 h of exposure, or the toxicity of FB1 to splenocytes and chondrocytes, which was shown in different primary cell cultures from chicken (Wu et al., 1995).

Bacterial chondronecrosis with osteomyelitis lameness (BCO) can be triggered by DON and FUM

BCO presents a highly critical health and welfare issue in broiler production worldwide, and it is estimated that 1-2 % of condemnations in birds at the marketing age result from this disease. What is the reason? Today’s fast-growing broilers are susceptible to stress. This enables pathogenic bacteria to compromise epithelial barriers, translocate from the gastrointestinal tract or the pulmonary system into the bloodstream, and colonize osteochondrotic microfractures in the growth plate of the long bone. This can lead to bone necrosis and subsequent lameness.

In their experiment with DON and FUM in broilers, Alharbi et al. (2024) showed that these mycotoxins reduce the gut’s barrier strength and trigger immunosuppressive effects. They used contaminations of 0.76, 1.04, 0.94, and 0.93 mg DON/kg of feed and 2.40, 3.40, 3.20, and 3.50 mg FUM/kg diet in the starter, grower, finisher, and withdrawal phases, respectively. The team observed lameness on day 35; the mycotoxin groups always showed a significantly (P<0.05) higher incidence of cumulative lameness.

The increase in uric acid leads to gout

In general, mycotoxins, which damage the kidneys and, therefore, impact the renal excretion of uric acid, are potentially a factor for gout appearance.

One of these mycotoxins is T-2 toxin. With the trial mentioned before (Yangzhou goslings, 21 days of exposure), Gu et al. (2023) showed that the highest dosage of the toxin (2.0 mg/kg) significantly increased uric acid in the blood (P<0.05), possibly leading to the deposit of uric acid crystals in the joints and to gout.

Huff et al. (1975) applied Ochratoxin to chicks at 0, 0.5, 1.0, 2.0, 4.0, and 8.0 µg/g of feed during the first three weeks of life. They found ochratoxin A as a severe nephrotoxin in young broilers as it caused damage to the kidneys with doses of 1.0 µg/g and higher. At 4.0 and 8.0 µg/g doses, uric acid increased by 38 and 48%, respectively (see Figure 2). Page et al. (1980) also reported increased uric acid after feeding 0.5 or 1.0 mg/kg of Ochratoxin A to adult white Leghorn chickens.

Figure 2: Effect of Ochratoxin A on plasma uric acid (mg/100 ml) (according to Huff et al., 1975)

Foot pad lesions – a further hint of mycotoxicosis

Foot pad lesions often result from wet litter, originating from diarrhea due to harmed gut integrity. Frequently, mycotoxins impact the intestinal tract and create ideal conditions for the proliferation of diarrhea-causing microorganisms and, therefore, secondary infections. Some also negatively impact the immune defense system, allowing pathogens to settle down or aggravate existing bacterial or viral parasitic diseases. In general, mycotoxins affect the physical (intestinal cell proliferation, cell viability, cell apoptosis), chemical (mucins, AMPs), immunological, and microbial barriers of the gut, as reported by Gao et al. (2020). Here are some examples of the adverse effects of mycotoxins leading to intestinal disorders and diarrhea:

• Mycotoxins can modulate intestinal epithelial integrity and the renewal and repair of epithelial cells, negatively impacting the intestinal barrier’s intrinsic components; for instance, DON can significantly reduce the transepithelial electrical resistance (TEER)(Grenier and Applegate, 2013). A higher permeability of the epithelium and a decreased absorption of dietary proteins can lead to higher protein in the digesta in the small intestine, which serves as a nutrient for pathogens including perfringens (Antonissen et al., 2014; Antonissen et al., 2015).
• The application of Ochratoxin A (3 mg/kg) increased the number of S. typhimurium in the duodenum and ceca of White Leghorn chickens (Fukata et al., 1996). Another trial with broiler chicks at a concentration of 2 mg/kg aggravated the symptoms due to an infection by S. gallinarum (Gupta et al., 2005).
• In a trial by Grenier et al., 2016, feed contaminated with DON (1.5 mg/kg), Fumonisin B (20 mg/kg), or both mycotoxins aggravated lesions caused by coccidia.
• DON impacts the mucus layer composition by downregulating the expression of the gene coding for MUC2, as shown in a trial with human goblet cells (Pinton et al., 2015). The mucus layer prevents pathogenic bacteria in the intestinal lumen from contacting the intestinal epithelium (McGuckin et al., 2011).
• Furthermore, DON and other mycotoxins decrease the populations of lactic acid-producing bacteria, indicating a shift in the microbial balance (Antonissen et al., 2016).
• FB1 causes intestinal disturbances such as diarrhea, although it is poorly absorbed in the intestine. According to Bouhet and Oswald (2007), the main toxicological effect ascertained in vivo and in vitro is the accumulation of sphingoid bases associated with the depletion of complex sphingolipids. This negative impact on the sphingolipid biosynthesis pathway could explain other adverse effects, such as reduced intestinal epithelial cell viability and proliferation, modification of cytokine production, and impairment of intestinal physical barrier function.
• T-2 toxin can disrupt the immune response, enhance the proliferation of coli in the gut, and increase its efflux (Zhang et al., 2022).

All these mycotoxins can cause foot pad lesions by impacting gut integrity or damaging the gut mucosa. They promote pathogenic organisms and, thus, provoke diarrhea and wet litter.

Mitigating the negative impact of mycotoxins on bones and feet is crucial for performance

Healthy bones and feet are essential for animal welfare and performance. Mycotoxins can be obstructive. Consequently, the first step to protecting your animals is to monitor their feed. If the analyses show the occurrence of mycotoxins at risky levels, proactive measures must be taken to mitigate the issues and ensure the health and productivity of your poultry.

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By Dr. Ajay Bhoyar, Global Technical Manager, EW Nutrition

In modern, intensive poultry production, the imminent threat of resistant Eimeria looms large, posing a significant challenge to the sustainability of broiler operations. Eimeria spp., capable of developing resistance to our traditional interventions, has emerged as a pressing global issue for poultry operators. The resistance of Eimeria to conventional drugs, coupled with concerns over drug residue, has necessitated a shift towards natural, safe, and effective alternatives.

Several phytogenic compounds, including saponins, tannins, essential oils, flavonoids, alkaloids, and lectins, have been the subject of rigorous study for their anticoccidial properties. Among these, saponins and tannins in specific plants have emerged as powerful tools in the fight against these resilient protozoa. In the following, we delve into innovative strategies that leverage the potential of these compounds, particularly saponins and tannins, to prevent losses by mitigating the risk of resistant Eimeria in poultry production.

Understanding resistant Eimeria in broiler production

The World Health Organization Scientific Group (World Health Organization, 1965) developed the definition of resistance in broad terms as ‘the ability of a parasite strain to survive and/or to multiply despite the administration and absorption of a drug given in doses equal to or higher than those usually recommended but within the limits of tolerance of the subject’.

The high reproduction rate of Eimeria spp. allows them to evolve quickly and develop resistance to drugs used for their control. Moreover, the resistant strains of Eimeria can persist in the environment due to their ability to form resistant oocysts, leading to the re-infection of animals and further spread of resistant strains.

Resistant Eimeria strains present many challenges in modern poultry farming, significantly impacting overall productivity and economic sustainability. However, one of the primary challenges is the reduced efficacy of traditional anti-coccidial drugs.

Eimeria resistance occurs in different types

There are different possibilities as to why Eimeria are resistant to specific drugs.

Acquired resistance results from heritable decreases in the sensitivity of specific strains and species of Eimeria to drugs over time. There are two types of acquired resistance: partial and complete. These types depend upon the extent of sensitivity lost. There is a direct relationship between the concentration of the drug and the degree of resistance. A strain controlled by one drug dose may show resistance when a lower concentration of the same drug is administered.

Cross-resistance is the sharing of resistance among different compounds with similar modes of action (Abbas et al., 2011). This, however, may not always occur (Chapman, 1997).

Multiple resistance is resistance to more than one drug, even though they have different modes of action (Chapman, 1993).

Natural substances can bring back the efficacy of anticoccidial measures

It was found that if a drug to which the parasite has developed resistance is withdrawn from use for some time or combined with another effective drug, the sensitivity to that drug may return (Chapman, 1997).

Botanicals and natural identical compounds are well renowned for their antimicrobial and antiparasitic activity, so they can represent a valuable tool against Eimeria (Cobaxin-Cardenas, 2018). The mechanisms of action of these molecules include degradation of the cell wall, cytoplasm damage, ion loss with reduction of proton motive force, and induction of oxidative stress, which leads to inhibition of invasion and impairment of Eimeria spp. development (Abbas et al., 2012; Nazzaro et al., 2013). Natural anticoccidial products may provide a novel approach to controlling coccidiosis while meeting the urgent need for control due to the increasing emergence of drug-resistant parasite strains in commercial poultry production (Allen and Fetterer, 2002).

Saponins and Tannins: Nature’s Defense against Eimeria Challenge

Phytogenic solutions, specifically those based on saponins and tannins, have recently surfaced as promising alternatives to mitigate the Eimeria challenge in poultry production. By harnessing the power of these natural compounds, poultry producers can boost the resilience of their flocks against the Eimeria challenge, promoting both the birds’ welfare and the industry’s sustainability.

Saponins are glycosides found in many plants with distinctive soapy characteristics due to their ability to foam in water. In the context of Eimeria, saponins can disrupt the integrity of the parasites’ cell membranes. When consumed, saponins can interfere with the protective outer layer of Eimeria, weakening the parasite and rendering it vulnerable to the host’s immune responses. This disruption impedes the ability of Eimeria to attach to the intestinal lining and reproduce, effectively curtailing the infection.

Tannins are polyphenolic compounds with astringent properties, occurring in various plant parts, such as leaves, bark, and fruits. Choosing the proper tannin at the right level and time is crucial to realize the benefits of tannin-based feed additives.

In the context of Eimeria, tannins exhibit several mechanisms of action. Firstly, they bind to proteins within the parasites, disrupting their enzymatic activities and metabolic processes. This interference weakens Eimeria, hindering its ability to cause extensive damage to the intestinal lining. Secondly, tannins are anti-inflammatory, reducing the inflammation caused by Eimeria infections. Additionally, tannins act as antioxidants, protecting the intestinal cells from oxidative stress induced by the parasite.

When incorporated into broilers’ diets, saponins and tannins create an unfavorable environment for Eimeria, inhibiting their growth and propagation within the host. Moreover, these compounds fortify the broiler’s natural defenses, enhancing its ability to resist Eimeria infections. By leveraging the innate properties of saponins and tannins, the impact of resistant Eimeria strains can effectively be managed and mitigated, fostering healthier flocks and sustainable poultry production.

What is Pretect D?

Pretect D is a unique proprietary blend of phytomolecules, including saponins and tannins, that supports the control of coccidiosis challenges in poultry production. It can be used alone or in combination with coccidiosis vaccines, ionophores, and chemicals as part of a shuttle or rotation program.

Fig.1. Key active ingredients of Pretect D

Modes of action of Pretect D

Pretect D exhibits multiple modes of action to optimize gut health during challenging times. Due to its anti-protozoal, anti-inflammatory, immunomodulatory, and antioxidant properties, it

1. effectively decreases oocyst excretion and disease spread
2. promotes restoring the mucosal barrier function and improves intestinal morphology
3. protects the intestinal epithelium from inflammatory and oxidative damage.

The beneficial effects of Pretect D

The beneficial effects of Pretect D’s inclusion in the coccidiosis control program include improving overall gut health and broiler production performance.

In a challenge study with Cobb 500 broiler chicks under a mixed Eimeria inoculum challenge, it was evident that the group receiving Pretect D (@500g/ton) in the feed throughout the 35-day rearing period had less coccidia-caused lesions (D27) than the broilers challenged and fed control diets.

Fig. 2: Pretect D reduced coccidia-caused lesions in broilers

In another field study, a traditional anticoccidial program (Starter and Grower I feeds: Narasin + Nicarbazin, Grower II feed: Salinomycin, Finisher/ withdrawal feeds: No anticoccidial) was compared with a program combining anticoccidials with Pretect D (Starter and Grower I feeds: Narasin + Nicarbazin, Grower II and Finisher feeds: Pretect D). The addition of Pretect D significantly reduced OPG count and lowered the coccidiosis lesion score compared to the control (Fig. 3).

Fig.3. Pretect D reduced broilers’ coccidiosis lesion score and OPG count

Consequently, broilers receiving Pretect D showed better overall production performance.

Fig. 4. Overall improved production performance by Pretect D

Pretect D: Application Strategies

The introduction of an effective phytogenic combination in the coccidiosis control program can help mitigate the drug resistance issue. Such a natural anticoccidial solution can be used as a standalone, preferably in less challenging months, as well as in combination with chemicals (shuttle/ rotation) or a coccidiosis vaccine (bio-shuttle), reducing the need for frequent drug use.

Shuttle programs are commonly employed for managing coccidiosis, and they yield a satisfactory level of success. Within these programs, multiple drugs from distinct classes of anticoccidials are administered throughout a single flock. For instance, one class of drug is utilized in the starter feed, another in the grower stage, reverting to the initial class for the finisher diet and concluding with a withdrawal period.

In rotation programs, anticoccidial drugs are alternated between batches rather than within a single batch.

Conclusions

Coccidiosis is considered one of the most economically significant diseases of poultry and the development of anticoccidial resistance has threatened the profitability of the broiler industry. Therefore, regularly monitoring Eimeria species to develop resistance against different anticoccidial groups is crucial to managing resistance and choosing an anticoccidial. It would be rewarding to use an effective phytogenic solution in the coccidiosis control program as a strategic and tactical measure and to focus on such integrated programs for drug resistance management in the future.

References:

Abbas, R.Z., D.D. Colwell, and J. Gilleard. “Botanicals: An Alternative Approach for the Control of Avian Coccidiosis.” World’s Poultry Science Journal 68, no. 2 (June 1, 2012): 203–15. https://doi.org/10.1017/s0043933912000268.

Abbas, R.Z., Z. Iqbal, D. Blake, M.N. Khan, and M.K. Saleemi. “Anticoccidial Drug Resistance in Fowl Coccidia: The State of Play Revisited.” World’s Poultry Science Journal 67, no. 2 (June 1, 2011): 337–50. https://doi.org/10.1017/s004393391100033x.

Allen, P. C., and R. H. Fetterer. “Recent Advances in Biology and Immunobiology ofEimeriaSpecies and in Diagnosis and Control of Infection with These Coccidian Parasites of Poultry.” Clinical Microbiology Reviews 15, no. 1 (January 2002): 58–65. https://doi.org/10.1128/cmr.15.1.58-65.2002.

Chapman, H. D. “Biochemical, Genetic and Applied Aspects of Drug Resistance inEimeriaParasites of the Fowl.” Avian Pathology 26, no. 2 (June 1997): 221–44. https://doi.org/10.1080/03079459708419208.

Chapman, H.D. “Resistance to Anticoccidial Drugs in Fowl.” Parasitology Today 9, no. 5 (May 1993): 159–62. https://doi.org/10.1016/0169-4758(93)90137-5.

Cobaxin-Cárdenas, Mayra E. “Natural Compounds as an Alternative to Control Farm Diseases: Avian Coccidiosis.” Farm Animals Diseases, Recent Omic Trends and New Strategies of Treatment, March 21, 2018. https://doi.org/10.5772/intechopen.72638.

Nazzaro, Filomena, Florinda Fratianni, Laura De Martino, Raffaele Coppola, and Vincenzo De Feo. “Effect of Essential Oils on Pathogenic Bacteria.” Pharmaceuticals 6, no. 12 (November 25, 2013): 1451–74. https://doi.org/10.3390/ph6121451.

Pop, Loredana Maria, Erzsébet Varga, Mircea Coroian, Maria E. Nedișan, Viorica Mircean, Mirabela Oana Dumitrache, Lénárd Farczádi, et al. “Efficacy of a Commercial Herbal Formula in Chicken Experimental Coccidiosis.” Parasites &amp; Vectors 12, no. 1 (July 12, 2019). https://doi.org/10.1186/s13071-019-3595-4.

World Health Organization Technical Report Series No. 296, (1965) pp:. 29.

by Marisabel Caballero, Global Technical Manager, and Madalina Diaconu, Global Manager Gut Health, EW Nutrition

In practical poultry production, multiple stress factors occur simultaneously: nutrition, management, environment, etc.. The effects of these factors are additive, leading to chronic stress, a condition in which animals cannot regain homeostasis and continuously deviate the use of resources to inflammation and restoring the gut barrier-function (Das et al., 2011). As a result, the gut microbiome is altered and oxidative stress ensues (Mishra et al., 2019). In this situation, health and productivity are compromised.

The feed supplied to production animals is designed to help them express their genetic potential. However, some feed components are also continuous inflammatory triggers. Anti-nutritional factors, oxidized lipids, and mycotoxins induce a low-grade inflammatory response (Cardoso Del Pont et al., 2020). Other factors that trigger gut health issues include the environment, management, and pathogens.

Feed interventions have shown to increase productivity and improve gut-related biomarkers, demonstrating a mitigation effect over the challenge factors (Deminicis et al., 2020; Latek et al., 2022).

Meta-analysis of broiler studies shows consistent results

As broilers are continuously challenged during the production period, the effects of an in-feed phytogenic (Ventar D – EW Nutrition GmbH) were extensively researched in broiler meat production. 21 trials in different locations (7 in Europe, 6 in the USA, 4 in Japan, 3 in Middle East, and 2 in India), with different production levels (grouped by EPEF) and challenges were analyzed to establish Ventar D’s benefits for the broiler production industry in terms of performance and sustainability. In all trials, the treatment group consisted of a supplementation of the basal feed with Ventar D at a dose 100 g/ton. The control groups were not supplemented with any gut health improvement feed additive.

Of these 21 trials, 14 had corn/soybean meal-based diets and 7 had high fiber diets (based on wheat and rye, which constituted a challenge as no NSP-enzymes were included). Reused litter (by 12 to 14 flocks, previous to the trial) also was used as a challenge. 18 trials were performed in research facilities and 3 in commercial farms.

Consistency in the results from Ventar D could be demonstrated as 19 out of 21 trials showed an improvement in FCR, lowering 3.4 points on average; 18 /21 trials showed higher body weight, with an average of 64 grams more; and 17 trials showed lower mortality than the control group, averaging 1.19 percentual points of reduction. The phenolic compounds included in Ventar D, such as thymol, possess antioxidant, anti-inflammatory, and antibacterial activities, which account for improving gut health and thus increasing performance in production animals.

The European Poultry Efficiency Factor (EPEF) was used to establish the performance level of each flock. This index is based on the average daily weight gain, mortality, and feed conversion, and takes in consideration the age of the flock at collection, allowing to make comparisons on performance within and between farms.

Of the 21 trials, 10 control groups had an EPEF lower than 375, and were considered of low performance level, in 8 the EPEF was between 375 and 425 and considered of medium performance, and for 3 the performance was considered high having an EPEF of 425 or more.

Ventar D increased performance at all levels (Figure 1). However, the effects were challenge-dependent:
Low performing flocks averaged an 8% increase in EPEF, and high performing flocks increased 4%, indicating that Ventar D can help broilers to overcome challenges commonly found in poultry production, and boost performance even with excellent farm and management conditions. These results concur with a meta-analysis by Valle Polycarpo and collaborators (2022), finding that a microbial challenge can influence the performance of phytogenic feed additives.

 

Overall, this analysis demonstrates that effective nutritional interventions can give consistent results and constitute effective tools to help production animals overcome stress and enhance productivity.

Conference report

At the recent EW Nutrition Poultry Academy, Judy Robberts, Technical Service Manager, Aviagen discussed the management of broilers for growth & production efficiency. She noted that the first 7 days is the most critical period in the life of a broiler chicken. “In this period chicks are the most efficient at converting feed to weight, however, its digestive and immune systems are still immature, so you want to get your chicks off to the best possible start,” she said.

“Seven-day weights are a key KPI of the success of brooder management – chicks should weigh at least 4 times their initial body weight. Also, each 1 gram of bodyweight at 7-days of age is equivalent to 10 grams at 35-days.The goal of management during the first week is to ensure that chicks consume enough feed and water because chick weight at 7 days of age is strongly correlated to final body weight at slaughter,” noted Ms. Roberts.

To ensure chicks got off to the best start, her presentation included 6 essential factors for house preparation and brooder set-up for the successful placement of chicks:

Planning

Planning should start well before chicks arrive on farm. The expected delivery date, time and number of chicks should be established with the supplier well in advance of chick placement. It is impossible to do the best possible chick placement if you do not know what you are going to receive, at least several days in advance. For example, the age and vaccination status of the donor flock. This will ensure that the appropriate brooding set-up is in place and that the chicks can be unloaded and placed as quickly as possible.

Chick placements should be planned so that chicks from different aged donor flocks can be brooded separately. Chicks from young donor flocks will achieve target body weights more easily if kept separate until the time of grading at 28 days of age.

Also, is the capacity of the equipment, such as feeders, drinkers, water pressure etc., capable of meeting the needs of the number of chicks to be placed? Do you have necessary supplies, such as chick paper, on hand?

Equipment test

• After cleaning and disinfection is completed, check that all water, feed, heat, ventilation, and lighting equipment is fully functioning and properly, adjusted for the needs of day-old chicks before the chicks arrive. Heaters should be checked and serviced before starting pre-heating.

Litter and pre-heating

Chicks do not have the ability to regulate body temperature for the first 5 days and are not able to fully control their body temperature until about 14 days of age. They quickly become chilled if placed on cold litter, which hinders their search for feed and water. In case of floor rearing, bring in the litter after preheating the floor for at least 24 hours (commencing from when the floor is dry and depending on heater type and capacity, season and building insulation) before chicks arrive to allow the litter to reach 28-30°C. Floor temperature is more important than air temperature because chicks are in contact with litter via bare feet. If the floor is cold, chicks lose body heat to the floor through their feet and through their body when they sit down. Measure temperatures throughout the brooding area with a digital on the litter surface and approximately 2 cm above the litter, as this is where the chicks will be placed.

Litter should be evenly spread, and at least 5cm deep to provide adequate insulation from cold house floors. Air temperature will rise rapidly after the heat is turned on, but it takes much longer to thoroughly warm the mass of litter on the floor. Litter should have good moisture absorption and water holding capacity. Uneven litter can restrict access to feed and water and may lead to a loss in uniformity.

Preheating can ensure that the litter is properly dried prior to placement to reduce bacterial growth and ammonia production.

Brooding area set-up

Allow an initial chick stocking density of 40-50 chicks/m², do not give excess of floor space. The size of the brooding area will also be determined by the output of the heat source.

Light intensity should be30-40 lux, uniform and continuous for the first 48 hours to ensure chicks find food and water.

The use of a brooder guard is recommended for the first 5-7 days to confine chicks to near the heat source. The guard should be about 50 cm high. If made of solid material, such as cardboard, it can also protect the chicks from drafts. Brooders should be 2 m away from brooder edge.

Minimum ventilation set-up

Ventilation distributes heat evenly throughout the house and maintains optimum air quality in the brooding area. Minimum ventilation should begin with house preheating 24-48 hours prior to placement to remove waste gases and excess moisture.

Target that 24 hours before chicks arrive to achieve 28-30^oC air and floor temperature, and relative humidity should be 60-70% when chicks enter the house to prevent dehydration. Humidity exceeding 70% limits the amount of evaporation, causing wet litter and excessive litter caking.

Young birds are very susceptible to drafts, so air speed in the brooding area (at chick level) should be less than 0.15m/second.

• Allow enough air exchange with a minimum ventilation rate at placement of 0.09m³/hour. Use a 5 minute fan cycle (with a thermostat override) – 30-45 seconds on.
• Make sure temperature and humidity sensors are placed correctly. For spot brooding, 2 meters away from the edge of each brooder, and for whole-house brooding at the center and two additional sensors at the end wall of the house. Sensors should not in contact with birds and out of direct lines with heating system.

Feed and water supply

Starter feed should be ordered to ensure delivery 1-2 days before chick placement.

Once the chicks arrive, they need to begin drinking and eating as soon as possible. Poor quality crumble or pellets will result in reduced feed intake and poor performance. Feed distribution should minimize the physical deterioration in crumble and pellets. The amount of fine particles (<1 mm) in sieved crumbles or mini-pellet should be below 10%.

Turn on the mechanical feeding system and ensure all pans or chain feeders are filled. Automatic pan feeders should be buried into the litter, so chicks can easily access them.

Spread a thin layer of starter feed onto chick paper to cover at least 80% of the paper area and fill any feeder trays 1-2 hours prior to chick arrival to prevent feed and water from becoming too hot. At least 20-30% of the total feed offered should be placed on paper. Paper should be positioned alongside the automated feed and drinking systems to aid in the transition from temporary to automated systems. Replenish feed on paper in small amounts given frequently. At placement, chicks should be placed directly onto paper, so that feed is immediately found.

If using paper, the feed area should cover at least 80% of the brooding area (avoid drinkers and feeders)

Never place supplemental feed or water directly under or near brooders. Ensure that supplementary feed never runs empty and always remains fresh.

Water is the most immediate need when chicks arrive at the house because they can easily dehydrate during hatching, processing, and transport to the farm. Chicks must have unlimited access to clean and fresh water (18-21°C). Cold water will chill the chicks.

• Flush drinkers 2-3 times to remove any remaining disinfectant. Remove dust and litter from cups. Adjust drinker line height to bird’s eye level. Ensure the placement of supplementary drinkers and feeders allows easy access for chicks and workers.

At placement, lower nipple drinkers to the chick’s eye level with sufficient water pressure to produce a droplet of water suspended from the nipple without dripping

Ms. Robberts concluded that “if house preparation is done properly then chicks are ready for a good start.” If there is any delay, it is always better that the chicks waits inside the truck (if its environmentally controlled) rather than getting cold waiting in the house. Chicks cannot become cold or heat stressed!”

By Dr. Ajay Bhoyar, Global Technical Manager, EW Nutrition

Pathogenic Enterococcus cecorum (EC) is emerging as a significant challenge in poultry production worldwide, causing substantial losses to commercial flocks. EC has become a considerable concern for the poultry industry, not only because of its rapid spread and negative impact on broiler health but also because of its increasing antibiotic resistance. As a result, there is a growing need to explore alternative ways of controlling this bacterium. There is no silver bullet yet as a replacement for antibiotics to limit the load of E. cecorum. Maintaining optimum gut health to avoid E. cecorum leakage during the first week of the broiler’s life can control losses due to E. cecorum.

Phytogenic compounds, which are derived from plants, have gained attention in the last decades as a potential solution for controlling common gut pathogens. These natural compounds have been found to possess antimicrobial properties and can help improve gut health in broilers. In this article, we will discuss the current state of E. cecorum and explore potential strategies, including using phytogenic compounds as support in controlling economic losses due to this emerging pathogen in broiler production.

Enterococcus cecorum and its negative impact on broiler production

E. cecorum is a component of normal enterococcal microbiota in the gastrointestinal tract of poultry. These are facultatively anaerobic, gram-positive cocci. Over the past 15 years, pathogenic strains of E. cecorum have emerged as an important cause of skeletal disease in broiler and broiler breeder chickens (Broast et al., 2017; Jackson et al., 2004 and Jung et al., 2017). Along with the commensal strains of EC, the pathogenic strains also occur and can result in Enterococcal spondylitis (ES), also known as “kinky back”, a serious disease of commercial poultry production in which the bacteria translocate from the intestine to the free thoracic vertebrae and adjacent notarium or synsacrum, causing lameness, hind-limb paresis and, in 5 to 15% of cases, mortality (de Herdt et al., 2008; Martin et al., 2011; Jung and Rautenschlein, 2014). The compression of the spinal cord due to infection of the free thoracic vertebra results in the so-called “kinky back” in the skeletal phase of E. cecorum infection. Kinky back is also a common name for spondylolisthesis, a developmental spinal anomaly. EC is normally found in the gastrointestinal tract and may need the help of other factors, such as a leaky gut, to escape the gastrointestinal tract. The emergent pathogenic strains of E. cecorum have developed an array of virulence factors that allow these strains to 1) colonize the gut of birds in the early life period; 2) escape the gut niche; 3) spread systemically while evading the immune system; and 4) colonize the damaged cartilage of the free thoracic vertebra (Borst, 2023). The E. cecorum can invade internal organs and produce lesions in the pericardium, lung, liver, and spleen.

The negative impact of E. cecorum on broiler economics, health, and welfare

Enterococcus cecorum can harm broiler health, welfare, and economics. This can result in decreased profitability for broiler producers.

The broiler flocks infected with E. cecorum may have reduced feed intake/ nutrient absorption and reduced growth rates, leading to a higher feed conversion ratio, longer production cycles, and lower weight gain. The morbidity and mortality from E. cecorum infection can be as high as 35 % and 15%, respectively. The higher condemnations of up to 9.75% at the processing plant can further add to the losses (Jung et al., 2018).  This can result in significant economic losses for producers.

Further, E. cecorum infections can impair the immune function of broilers, making them more susceptible to other pathogens and reducing their overall health and welfare. Pathogenic E. cecorum is an opportunistic pathogen that can gain momentum during coinfection with E. coli and other gut pathogens, causing a leaky gut. Therefore, a holistic approach to gut health management may help reduce the losses.

Antibiotic resistance in E. cecorum

E. cecorum has been found to be resistant to multiple antibiotics. Multidrug resistant pathogenic E. cecorum could be recovered from lesions in whole birds for sale at local grocery stores (Suyemoto et al., 2017). Antibiotic resistance can make it difficult to treat and control infections in broilers. This can lead to increased use of multiple antibiotics, which can contribute to the development of antibiotic-resistant bacteria and pose a risk to human health.

Transmission of E. cecorum in broiler flocks

Despite the rapid global emergence of this pathogen, and several works on the subject, the mechanism by which pathogenic E. cecorum spreads within and among vertically integrated broiler production systems remains unclear (Jung et. al.2018). The role of vertical transmission of pathogenic E. cecorum remains elusive. Experimentally infected broiler breeders apparently do not pass the bacterium into their eggs or embryos (Thoefner and Peter, 2016). However, it has been noted that a very low frequency of infected chicks can cause a flock-wide outbreak.

Horizontal transmission: E. cecorum can be transmitted between birds within a flock through direct contact or exposure to contaminated feces, feed, or water.

While the mode of transmission between flocks has not been definitively identified, pathogenic E. cecorum demonstrates rapid horizontal transmission within flocks. It can spread rapidly within flocks via fecal-oral transmission.

Personnel and equipment: E. cecorum can be introduced into a flock through personnel or equipment that has been in contact with infected birds or contaminated materials. For example, personnel working with infected flocks or equipment used in infected flocks can spread the pathogen to uninfected flocks.

Symptoms and diagnosis of E. cecorum in broilers

Enterococcus cecorum infections in broilers can present a range of symptoms, from mild to severe. The most common symptom noticed with E. cecorum is paralysis, which is due to an inflammatory mass that develops in the spinal column at the level of the free thoracic vertebra (FTV). Recognition of this spinal lesion has given rise to several disease names for pathogenic E. cecorum infection, which include vertebral osteomyelitis, vertebral enterococcal osteomyelitis and arthritis, enterococcal spondylitis (ES), spondylolisthesis and, colloquially, “kinky-back” (Jung et al. 2018).

E. cecorum infections can exhibit increased mortality due to septicemia in the early growing period. In this sepsis phase, the clinical signs of E. cecorum may include fibrinous pericarditis, perihepatitis, and air-sacculitis. These lesions might be confused with other systemic bacterial infections like colibacillosis. Therefore, a pure culture is needed for the correct diagnosis of E. cecorum.

The second phase of mortality due to dehydration and starvation of the paralyzed birds can be observed during the finisher phase peaking during 5-6 weeks of age. Paralysis from infection of the free thoracic vertebra is the most striking feature of this disease, with affected birds exhibiting a classic sitting position with both legs extended cranially (Brost et al., 2017).

Diagnosis of E. cecorum in broilers can be challenging, as the symptoms of infection can be similar to those of other bacterial or viral infections. However, a combination of clinical signs, post-mortem examination, and laboratory testing can help to confirm the presence of E. cecorum. Laboratory tests such as bacterial culture and polymerase chain reaction (PCR) can be used to identify the pathogen and also to determine its antibiotic susceptibility. Veterinarians and poultry health professionals can work with producers to develop a diagnostic plan and implement appropriate control measures to manage E. cecorum infections in broiler flocks.

Prevention and Control of Enterococcus cecorum

The broiler producers/ managers should work with their veterinarians and poultry health professionals to develop an integrated approach to control the spread of E. cecorum and prevent its negative impact on broiler health and productivity.

Currently, there is no commercial vaccine available for preventing pathogenic E. cecorum infection. Therefore, controlling Enterococcus cecorum infection in broiler flocks requires a multifaceted approach that addresses the various modes of transmission and bacterial resistance to antibiotics.

Implementing strict biosecurity protocols, such as controlling access to the farm, disinfecting equipment and facilities, and implementing proper hygiene protocols throughout the integrated broiler operation, can help to minimize the risk of transmission.

Thorough washing of trays and chick boxes in the hatchery with hot water (60-62°C) mixed with an effective disinfectant can reduce the possible vertical transmission of E. cecorum. The vertical transmission may also be prevented by adopting the practice of separating the dirty floor eggs from clean hatching eggs and setting them in the lower racks of the incubator.

Generally, pathogenic isolates from poultry were found to be significantly more drug-resistant than commensal strains (Borst et al., 2012). The selection of an effective antibiotic for the treatment of E. cecorum should be made based on the results of the antibiotic sensitivity test. Antibiotic therapy may not help with paralyzed birds, which ultimately need to be culled. Reducing the use of antibiotics and implementing prudent use practices can help to reduce the development of antibiotic resistance in E. cecorum and other bacteria.

Probiotics can help to maintain the balance of the gut microbiota and may have a protective effect against E. cecorum infections. Fernandez et al. (2019) reported the inhibitory activities of proprietary poultry Bacillus strains against pathogenic isolates of E. cecorum in vitro, but effects are highly strain-dependent and vary significantly among different pathogenic isolates.

Phytogenic compounds and organic acids have been shown to have antimicrobial properties. Phytomolecule-based preparations may help to control E. cecorum infections in broiler flocks in the first week of life, reducing the chances of its translocation from the intestine.

Phytomolecules-based liquid formulations for on-farm drinking water application can also be a handy tool to manage gut health challenges, especially during risk periods in the life of broilers. Such liquid phytomolecule preparations can help to quickly achieve the desired concentration of the active ingredients for a faster antimicrobial effect.

However, these alternatives to antibiotics may be effective only when the E. cecorum is still localized within the gut during the first two weeks of the broiler chicken’s life.

Phytomolecules, also known as phytochemicals, are naturally occurring plant compounds that have been found to have antimicrobial properties. Especially for commercial poultry, nutraceuticals such as phytochemicals showed promising effects, improving the intestinal microbial balance, metabolism, and integrity of the gut due to their antioxidant, anti-inflammatory, immune modulating, and bactericidal properties (Estevez, 2015). Phytogenic compounds have been studied for their potential use in controlling gut pathogens in poultry. Here are some of the roles that phytomolecules can play in controlling gut pathogens:

Antimicrobial activity: Several phytomolecules, such as essential oils, flavonoids, and tannins, have been found to have antimicrobial activity.  Hovorková et al (2018) studied the inhibitory effects of hydrolyzed plant oils (palm, red palm, palm kernel, coconut, babassu, murumuru, tucuma, and Cuphea oil) containing medium-chain fatty acids (MCFAs) against Gram-positive pathogenic and beneficial bacteria. They concluded that all the hydrolyzed oils were active against all tested bacteria (Clostridium perfringens, Enterococcus cecorum, Listeria monocytogenes, and Staphylococcus aureus), at 0.14–4.5 mg/ml, the same oils did not show any effect on commensal bacteria (Bifidobacterium spp. and Lactobacillus spp.). However, further research is needed to test the in-vivo efficacy of phytogenic compounds against pathogenic E. cecorum infections in poultry.

Anti-inflammatory activity: The other coinfecting gut pathogens of E. cecorum can cause inflammation in the intestinal tract of poultry. This can lead to reduced feed intake and growth. Some phytomolecules have been found to have anti-inflammatory activity and can reduce the severity of inflammation. Capsaicin, a naturally occurring bioactive compound in chili peppers, was found to have antioxidant and anti-inflammatory activity. The tendency of capsaicin to substantially diminish the release of COX-2 mRNA is thought to be the reason for its anti-inflammatory effects (Liu et al., 2021).  Thyme oil reduced the synthesis and gene expression of TNF-α, IL-1B, and IL-6 in activated macrophages in a dose-dependent manner, with upregulation of IL-10 secretion (Osana and Reglero, 2012). Cinnamaldehyde has been shown to decrease the expression of several cytokines, such as IL-1 β, IL-6, and TNF-α, as well as iNOS and COX-2, in in-vitro studies (Pannee et al., 2014).

Antioxidant activity: Oxidative stress may contribute to the development of E. cecorum infections in poultry. Phytomolecules, such as polyphenols and carotenoids, have been found to have antioxidant activity and can reduce oxidative stress in the gut of poultry, which can help to prevent E. cecorum infections. Polyphenols widely exist in a variety of plants and have been used for various purposes because of their strong antioxidant ability (Crozier et al., 2009). Quercetin, a flavonoid compound widely present in vegetables and fruits, is well-known for its potent antioxidant effects (Saeed et al., 2017).

Phytomolecules can also modulate the immune system of poultry, which can help to prevent E. cecorum infections. For example, some flavonoids and polysaccharides have been found to enhance the immune response of poultry. Fahnani et. al. (2019) found that supplementing broiler chickens with a combination of flavonoids and polysaccharides extracted from the mushroom Agaricus blazei enhanced their immune response.

Overall, phytomolecules have shown promise in supporting the optimum gut health of poultry. Many phytogenic preparations available in the market can be regarded as an important tool to reduce the use of antibiotics in animal production and mitigate the risk of antimicrobial resistance. However, more research is needed to develop an effective combination of active ingredients, as well as strategies for their use in controlling E. cecorum infections in poultry.

Conclusion

In conclusion, the emergence of pathogenic strains of E. cecorum is becoming a major concern for broiler producers globally. This bacterial pathogen can cause significant economic losses in the broiler industry by affecting the overall health and productivity of the birds. Pathogenic E. cecorum infection can lead to clinical signs including diarrhea, decreased feed intake, reduced growth rate, and increased mortality. Proactive measures must be taken to prevent the introduction and spread of pathogenic E. cecorum in broiler flocks. Implementing strict biosecurity protocols and proper disinfection procedures can help reduce the risk of E. cecorum infection. The use of effective antibiotics after receiving the results of the antibiotics sensitivity test is a crucial step in controlling the infection. Phytomolecule-based preparations can be a potential alternative to control the load of E. cecorum by maintaining optimum gut health to minimize economic losses. Moreover, ongoing surveillance and monitoring of pathogenic E. cecorum prevalence in the broiler industry can assist in the timely detection and control of outbreaks.

In summary, the emergence of pathogenic E. Cecorum as a profit killer in the broiler industry warrants careful attention and proactive management practices to minimize its impact.

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Fanhani, Jamile & Murakami, Alice & Guerra, Ana & Nascimento, Guilherme & Pedroso, Raíssa & Alves, Marília. (2016). “Agaricus blazei in the diet of broiler chickens on immunity, serum parameters and antioxidant activity”. Semina: Ciencias Agrarias. 37. 2235-2246.

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Jung, A., and S. Rautenschlein. “Comprehensive report of an Enterococcus cecorum infection in a broiler flock in Northern Germany. BMC Vet. Res. 10:311. 2014.

Jung, A., M. Metzner, and M. Ryll. “Comparison of pathogenic and non-pathogenic Enterococcus cecorum strains from different animal species”. BMC Microbiol. 17:33. 2017.

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Martin, L. T., M. P. Martin, and H. J. Barnes. “Experimental reproduction of enterococcal spondylitis in male broiler breeder chickens”. Avian Dis. 55:273-278. 2011.

Ocaña, A.; Reglero, G. “Effects of thyme extract oils (from Thymus Vulgaris, Thymus Zygis and Thymus hyemalis) on cytokine production and gene expression of OxLDL-stimulated THP-1-macrophages”. J. Obes. 2012, 2012, 104706.

Pannee C, Chandhanee I, Wacharee L. “Antiinflammatory effects of essential oil from the leaves of Cinnamomum cassia and cinnamaldehyde on lipopolysaccharide-stimulated J774A.1 cells”. J Adv Pharm Technol Res. 2014 Oct;5(4):164-70. 

Saeed, M.; Naveed, M.; Arain, M.A.; Arif, M.; Abd El-Hack, M.E.; Alagawany, M.; Siyal, F.A.; Soomro, R.N.; Sun, C. “Quercetin: Nutritional and beneficial effects in poultry”. World’s Poult. Sci. J. 2017, 73, 355–364.

Suyemoto, M. M., H. J. Barnes, and L. B. Borst. “Culture methods impact recovery of antibiotic-resistant Enterococci including Enterococcus cecorum from pre- and postharvest chicken”. Lett. Appl. Microbiol. 64:210-216. 2017.

Thoefner, I. C., Jens Peter. Investigation of the pathogenesis of Enterococcus cecorum after 736 intravenous, intratracheal or oral experimental infections of broilers and broiler breeders. In: 737 VETPATH. Prato, Italy. 2016.

 

By Dr. Ajay Awati, Global Category Manager for Gut Health and Nutrition, EW Nutrition, and Dr. Howard Simmins, InSci Associates

After 30 years of stagnating solutions, in-feed xylanase innovation has finally arrived – with a complete focus on the needs of the broiler feed industry.

It has been over 30 years since xylanase was first introduced in broiler diets in Europe. In the meantime, it has been widely used worldwide with few, if any, major improvements. While the animal feed industry evolved in terms of production landscape, feed processing technologies and use of various by-products, xylanase enzyme technology did not keep pace. In fact, it did not evolve to meet customers’ changing needs and provide that much-needed flexibility of diet formulation for a commercial nutritionist. The wait is over: new in-feed xylanase technology is about to revolutionize broiler nutrition.

Why we need innovative xylanase enzymes for broiler production

Initially, in the 1980s, xylanase was leveraged from industries unrelated to animal production into the feed business. Gut viscosity had been a continuing problem in broiler chickens fed wheat-based diets. It led to an increased risk of enteric disease, generally reducing performance. Xylanase was shown to reduce gut viscosity in wheat-based feed by breaking down soluble arabinoxylans.

As a result, the birds grew as well as if they were fed a low-viscosity corn/soya diet. An additional benefit was lower disease risks from the reduced level of anti-nutritional factors (ANFs) and the multiple negative effects of viscosity in the intestine.

In addition to reducing viscosity, xylanase augments the release in the small intestine of nutrients from previously undigested feedstuffs. The outcome has been the use of an energy matrix value for xylanase, which essentially helps diets through least-cost formulation.

These effects account for the growth of xylanase use in the monogastric feed market. Today, the penetration is above 50%.

Limitations of existing xylanase solutions

Leveraging xylanases from other industries for viscosity reduction in poultry comes with a couple of distinct limitations:

1. Most broiler diets around the globe are based on a corn-soybean formulation, which contains far higher levels of insoluble arabinoxylans than soluble arabinoxylans. In such cases, viscosity is a relatively minor issue compared to the anti-nutritional effect of insoluble arabinoxylans.
2. The reduction of gut viscosity is less relevant in other poultry sectors, such as laying hens and turkeys.

Commercial xylanases would be required to break down insoluble NSPs in which substrate activity may be limited and difficult to predict. Fiber constituents of different cereal grains used in feed are highly variable. By- and co-products derived from cereals contain even more complex fiber components, altered further by the manner of processing that the raw material has undergone.

Additionally, poultry response is highly variable:  For an individual bird, the effectiveness of xylanase depends on the enzyme’s interaction with feed in the gastrointestinal tract (GIT) of the animal, which varies depending on the species and the animal’s age. This may explain why xylanase penetration on the feed market is not as high as that of phytase.

GH10: the next-level xylanase for feed application

A xylanase for feed is required to provide multiple functionalities, of which four are essential:

1. Capacity to break down soluble and insoluble arabinoxylan across a range of typical feedstuffs
2. Rapid activity at optimal pH in the preferred section of the GIT
3. No inhibition in the presence of xylanase inhibitors
4. Comprehensive feed processing thermostability

The GH11 family of xylanases commonly used in feed does not offer these aggregated benefits. They successfully reduce soluble NSPs in wheat-based diets, hence lowering the viscosity level in the broiler GIT. However, they are less effective in the presence of insoluble NSPs in which the arabinoxylan backbone is more complex.

Why GH10 instead of GH11?

The explanation for this can be found in the 3-dimensional structure of the GH11 xylanase. The activity of GH11 xylanases requires 3 or 4 consecutive unsubstituted xylan monomers on the backbone to find an active site. That is why they are hindered by the presence of branches, or side chains, on arabinose backbones. Consequently, they are highly specific, favoring the particularly low-branching wheat backbone.

Xylanases from the GH10 family are entirely different. Although well known, they have not been used in feed yet. The GH10 xylanases require two or fewer consecutive unsubstituted xylan monomers on the backbone to find an active site. Therefore, they can act on xylose residues near branches. This results in both more and shorter xylo-oligomers than found with GH11 xylanases. In simple terms, the GH10 xylanases have a less deep cleft than the GH11 xylanases, providing greater catalytic versatility (Pollet 2010).

Significantly, this potentially allows a broader range of feedstuffs to be incorporated into the complete diet, including co- and by-products, while maintaining performance. Therefore, with GH10, higher levels of cheaper ingredients may be included, with a significant value proposition of further reducing feed costs.

GH10 xylanases generate a range of important prebiotics

As early as 1995, it was proposed that xylanase may affect microbial activity in the gastrointestinal tract through the provision of fermentable oligosaccharides and low molecular weight polysaccharides. These are produced from the hydrolysis of soluble and insoluble arabinoxylans in cereals.

A development of particular interest is that the GH10 xylanases break down the backbone of different fibre components into small xylooligosaccharides (XOS) and arabino-xylanoligosaccharides (AXOS). This action, research shows, has value in supporting the selective growth of fibre-degrading bacteria in the large intestine, conferring positive effects on the host’s health.

The most well-known probiotic strains belong to bifidobacteria and lactobacilli, which have quite different XOS and AXOS utilization systems. Bifidobacterium adolescentis has been shown to consume AXOS and XOS, whereas Lactobacillus brevis utilises only XOS. The outcome is that AXOS releases butyrate, the short-chain fatty acid, which can improve the host’s gut barrier function, as well as reduce Salmonella colonization in broilers. Alongside these health benefits, their presence may improve performance also by reducing FCR. (Courtin et al. 2008; Ribeiro et al. 2018)

As mentioned earlier, the GH10 xylanase requires only two consecutive unsubstituted xylan monomers to cleave the xylan main chain, whereas a GH11 xylanase requires 3 or 4 consecutive unsubstituted xylan monomers. Therefore, the number of potential AXOS and XOS oligomers is higher from the action of the GH10 xylanase. This results in a wider size range of oligomers. The range is valuable as the effect is spread across the large intestine, each oligomer having a different fermentation rate. Consequently, the large intestine’s microbial activity becomes saccharolytic, which potentially reduces the undesirable products of proteolytic degradation, such as phenols and cresols.

Prebiotic combinations will vary depending on the substrate available. However, there is more flexibility in breaking down insoluble NSPs across different feedstuffs using GH10 xylanase compared to GH-11 xylanase.

The future of xylanase: Reducing feed costs through flexible formulation

EW Nutrition’s GH10-based AXXESS XY xylanase, specifically developed for animal feed, has a wide-ranging activity across typical substrates, both in corn-soy and wheat-soy diets. It also allows for a greater proportion of cheaper ingredients, enabling increased flexibility in feedstuff choices and resulting in more stable feed pricing. The activity of the GH10 xylanase in producing oligomers from the breakdown of the arabinoxylan backbone also indicates that it can produce a greater number and diversity of valuable prebiotics that sustain the growth of fiber-degrading microbiota. Consequently, the metabolism of the large intestine is shifted from proteolytic to saccharolytic, which supports the animal’s general health.

The combination of these benefits from using this xylanase results in a bird with a balanced digestive system that is more robust in the face of environmental and health challenges, supporting better performance. Furthermore, this novel enzyme solution gives nutritionists a reliable tool to reduce feed costs by being flexible in diet formulation and opportunistic in using raw materials while maintaining consistency in animal performance. Especially in these times of supply problems and raw material price hikes, such advantages are invaluable.

The naturally thermostable AXXESS XY 1000G is the most advanced xylanase yet. It is a GH10 xylanase that delivers what the industry has been asking for: a fiber-degrading enzyme suited for all poultry feed.

 

References

Courtin, Christophe M, Katrien Swennen, Willem F Broekaert, Quirine Swennen, Johan Buyse, Eddy Decuypere, Christiaan W Michiels, Bart De Ketelaere, and Jan A Delcour. “Effects of Dietary Inclusion of Xylooligo- Saccharides, Arabinoxylooligosaccha- Rides and Soluble Arabinoxylan on the Microbial Composition of Caecal Contents of Chickens.” Journal of the Science of Food and Agriculture 88, no. 14 (2008): 2517–22. https://doi.org/10.1002/jsfa.3373.

Ribeiro, T., V. Cardoso, L.M.A. Ferreira, M.M.S. Lordelo, E. Coelho, A.S.P. Moreira, M.R.M. Domingues, M.A. Coimbra, M.R. Bedford, and C M Fontes. “Xylo-Oligosaccharides Display a Prebiotic Activity When Used to Supplement Wheat or Corn-Based Diets for Broilers.” Poultry Science 97, no. 12 (2018): 4330–41. https://doi.org/10.3382/ps/pey336.

Pollet, Annick. “Functional and Structural Analysis of Glycoside Hydrolase Family 8, 10 and 11 Xylanases with Focus on Bacillus Subtilis Xylanase A,” 2010. https://www.biw.kuleuven.be/m2s/clmt/lmcb/publications/docs/apollet

 

By Dr. Inge Heinzl, Marisabel Caballero, Dr. Twan van Gerwe, and Dr. Ajay Bhoyar – EW Nutrition

Concerns about antibiotic resistance in humans and production animals have prompted a push across the board to reduce antibiotic use, including in livestock rearing. To meet these demands, the industry must keep the pathogenic pressure in production units as low as possible, enabling production with no antibiotics or minimum use of antibiotics.

The 3 essential steps for reducing antibiotics in broiler production

In the following, we discuss experience-based insights and practical advice concerning best practices for broiler meat production with reduced antibiotic use, focusing on the following points:

• Farm biosecurity
• Management of the broiler house, including cleaning & disinfection, and environment & litter management
• Management of the flock, including DOC quality, disease prevention, and nutrition

1. General farm biosecurity

Biosecurity is the foundation for all disease prevention programs (Dewulf et al., 2018). Thus, it is essential in antibiotic reduction scenarios. It includes all measures taken to reduce the risk of introducing and spreading diseases, preventing diseases, and protecting against infectious agents. Its fundament is the knowledge of disease transmission processes.

The application of consistently high biosecurity standards substantially reduces antimicrobial resistance by preventing the introduction of resistance genes into the farm and lowering the need to use antimicrobials (Davies & DWales, 2019).

First of all: everyone must act in concert!

Biosecurity is one of the preconditions for the success of an ABR program, and it is crucial to bring all workers/staff on track through regular training on the best practices and their subsequent rigorous implementation.  The biosecurity plan can only be effective if everyone on the operation follows it – all the time. Farm managers, poultry workers, and other persons entering the facility should adhere to the farm biosecurity measures, 24/24h – 7/7d.

Separation helps to prevent the spread of pathogens

One essential component for biosecurity is implementing a “line of separation” for the farm and each house. It is vital to have a good separation between high and low-risk animals and between areas on the farm that are dirty (general traffic) and clean (internal movements). In this way, it is not only possible to avoid the entrance but also the spread of disease, as potential sources of infection (e.g., wild birds) cannot reach the farm population.

The farm must be well isolated, not allowing the entry or passage of persons who do not work there and animals, including pets.

Inside the farm, the walls of the poultry house form the first line of separation, and the “Two-zone Danish Entry Protocol” constitutes a second line. This system utilizes a bench to divide the anteroom of a poultry house into two sides (outdoor / ‘dirty area’ and indoor / ‘clean area’). At a minimum, footwear should be changed, and hands washed or disinfected when passing over the bench; it is even better when workers have house-specific clothing and hairnets when entering the poultry area.

Figure 1: Safety procedures on the poultry farm – the Danish entry method

The room is divided into “dirty” and “clean” zones.

1. After the entrance from outside, workers/visitors step into a disinfectant boot tray.
2. They take off their street shoes and leave them on the dirty side of the entrance zone.
3. Then, they turn from the dirty to the clean side by swinging their legs without touching the floor.
4. They wash their hands and disinfect them by using the hand.
5. They must put on an overall, cap, mask, and boots of the poultry house.
6. Completely clothed, they can enter the poultry house.
7. When they leave the house, a reversed process must be followed.

Still more needs to be done to prevent the entrance and spread of disease.

Separate materials for each house

For each house, separate materials must be used, keeping a dedicated set of tools and equipment necessary for daily work.

Very important: no materials should be moved from one house to another unless thoroughly disinfected. Crates for bird transport in the case of thinning (partial depopulation of a broiler flock) are an important example.

Practice clean disposal of mortality

First, dead birds’ removal must be frequent (minimum twice a day) as carcasses are a source of infection. The next point is to make sure the route of birds’ disposal is strictly unidirectional, and the buckets or wheelbarrows for the transport of the dead birds do not reenter the poultry house. Finally, the carcasses should remain outside the farm or as far from the buildings as possible until collection, incineration, or composting.

2. Broiler house management

After the general organization on the farm, let’s move on to the poultry houses.

Cleaning and disinfection of the house are the first steps – and check their efficacy!

Cleaning and disinfection are essential components in preventing the persistence and spread of pathogens. Both together aim to decrease microbial numbers on surfaces (and in the air) to a level that will ensure that most -if not all- pathogens and zoonotic agents are eliminated.

Cleaning refers to the physical removal of organic matter and biofilms, so the microorganisms and pathogens are afterward exposed to the disinfectant.

For effective cleaning and disinfection, the all-out/all-in system has proven of value. When birds are collected, all organic material, including feed residues and litter/feces, is removed.

Effective detergents and hot water are used to remove any grease or organic material. Pay special attention to the floors! Also, all surfaces and equipment should be sufficiently cleaned and given final disinfection.

Cleaning is crucial

A study by Luyckx and collaborators (2015) revealed that the mean total aerobic bacterial count on swab samples taken in broiler houses decreases significantly already after cleaning (figure 2). Good cleaning not only strongly reduces microbiological contamination and organic material but also ensures that the subsequent disinfection has a stronger impact on the remaining microorganisms. Consider that all disinfectants, even in high concentrations, are barely effective in the presence of organic material.

Figure 2: % of reduction of bacteria on surfaces after cleaning and after cleaning and disinfection (adapted from Luyckx et al., 2015)

Keep an eye on cleaning & disinfection efficacy

After cleaning and disinfection are complete, it is good practice to check the floors for Total Viable Count (TVC), Salmonella, and E. coli to test the efficacy of the cleaning and disinfection process. Recommended levels of TVC should be less than ten colony forming units per square centimeter (CFU/cm²), and E. coli and Salmonella levels should be undetectable.

When high TVC are found, the cleaning and disinfection procedure must be evaluated, including the products (a rotation is recommended) and their application (e.g., dosage, dilution, water temperature, and exposure time). Also, possible reinfection by vermin or personnel during the downtime must be controlled.

Downtime: After cleaning and disinfection, a down-time time of 10 days allows disease-causing pathogens to die (UC Davis, 2019).

Cleaning and disinfection of the waterline against biofilm

In the waterlines, the build-up of biofilms can be an issue. Biofilm is a sticky film that can be found inside water lines, regulators, and nipple drinkers. It starts when bacteria attach to a surface and produce a matrix of extracellular polymeric substances (EPS), including proteins and sugars, giving the biofilm the stickiness that traps other bacteria and organic matter. It provides the bacteria with protection from the external environment, and thus they multiply and thrive.

Biofilms not only block the water flow, but they can also include pathogenic bacteria. Thus, the waterline must be regularly cleaned and disinfected, not only between flocks but also within each flock.

Between flocks, an effective waterline cleaning should include:

• Application of hydrogen peroxide at high concentration, leaving it in the system for 24-48 hours to remove the biofilm from the pipelines)
• Flush the line to remove the detached biofilm, also activate the nipples with a broom or stick to flush them
• Immediately before the placement of the new chicks, the water lines should be flushed to have fresh drinking water available to the chicks
• The water pressure must be adjusted so that a droplet of water is visible at the end of each nipple, and the drinkers are put to the correct height to stimulate water intake and avoid spilling

During the life of the birds, a water disinfectant should be used to prevent biofilm formation, e.g., hydrogen peroxide in weekly applications or the continuous use of chlorine. Also, flushing is a good practice during the whole cycle to make sure that biofilm is removed and the birds count with fresh drinking water.

To a certain extent, biofilm build-up can be prevented by using organic acidifiers in the water, which improves the sanitizers’ effectiveness and reduces bacterial growth in water lines.

Correct ventilation helps to prevent respiratory diseases

To keep broilers healthy, providing optimal ventilation in the poultry house is crucial. CO₂ and temperature are the most critical parameters. CO₂ should never exceed 2500 ppm and should be monitored continuously, most notably in the early morning before birds increase activity (e.g., eating). Ventilation rates should be adjusted to keep CO₂ below this limit. Draught or cold spots resulting in uneven distribution of birds in the house should be avoided, and causes should be investigated and repaired immediately.

Incorrect ventilation often is the reason for respiratory diseases and the need for antibiotic treatment. No matter if natural or power ventilation is used, proper monitoring of the system is indispensable to ensure the well-functioning of the equipment and, therefore, appropriate air quality (Neetzon et al., 2017).

Litter management to keep diseases in check

Effective litter management is another step on the road to keeping the birds healthy. Dryness of litter and ammonia level at bird’s level are two significant key success factors in raising broilers. Dry litter preserves the footpads, so litter material should have a good moisture-absorbing capacity (e.g., chopped straw, wood shaving, rice husks, sunflower husks). When using build-up litter, litter sanitation and treatments need more attention.

Litter treatment (with acidifying or binding substances) and adequate ventilation are the most practical measures to control ammonia and improve littler quality (Malone, 2005). Keep litter temperature at 28 – 30°C (82.4 – 86°F), and use only litter tested or certified to have a TVC <10 CFU/g.

3. Flock management

The basis: healthy, high-quality day-old chicks

To produce good-quality day-old chicks, the parent flocks (PS) must be of good health status. PS should be free from vertically transmitted diseases such as Mycoplasma and Salmonella and be vaccinated/protected against important diseases:

• Salmonella pullorum/Salmonella Gallinari should be assessed in PS by RPA serology in week 25-30, at least 60 samples per flock.
• Mycoplasma gallisepticum should be checked by RPA/ELISA serology on a regular basis, preferably at least monthly, with a minimum of 30 samples per flock.

Parent flock vaccination leads to the production of maternal antibodies that help prevent horizontal infection (from the broiler farm environment) in chicks at an early age. This type of prevention is the primary function of some vaccinations, such as against Gumboro disease.

An essential part of the broilers’ life occurs already in the hatchery. Single-stage incubation is recommended, and all floor eggs and dirty nest eggs should be excluded to assure the best day-old chick quality.

Comfortable conditions bring chicks to eat

The brooding phase needs special attention; it is about welcoming the chicks and making them comfortable in the house environment. For this, enough litter needs to be provided, the environment must be managed, and feed and water must be supplied.

At least 24 hours before chick placement, the house and floor temperature are increased to a minimum of 34°C and 28°C, respectively. Proper ventilation and lighting are also essential. These conditions need to be monitored and adjusted after the placement so the chicks feel comfortable and start feed and water consumption. Checking chick behavior is crucial during the first hours after placement.

Upon the placement of the chicks, it is recommended to have pre-starter crumble feed available on top of brooder paper underneath the drinking line. To stimulate early feed and water consumption, gently place the chicks onto that paper. The target is to have 100 % of chicks with crop filled within 48 hours of chick placement.

Reduce the stocking density

In general, high stocking density may restrict bird movement, interfere with airflow, and increase litter moisture and microbial growth, including pathogens, which potentially impairs broiler health, welfare, and performance.

When reducing antibiotics, increase the space per bird by 0.05 ft²/46 cm² per bird compared to your current conventional program. A lower stocking density helps keep litter moisture at a minimum, which reduces the shedding of cocci oocyst and pathogenic bacteria over the population.

Feed and water access must be granted to all animals at every moment. The number of chickens per feeder or drinker depends on the type of equipment used.

Consistent observation of the flock

To recognize emerging health issues, producers should critically observe the behavior of birds every day. On which points should they focus?

• First, when entering the house, birds’ behavior and response to the poultry worker should be observed with attention. Note the spread of birds throughout the house.
• Note birds’ drinking and eating behavior. Feed and water intake should be recorded daily, always at the same hour.
• The quality of the fresh fecal droppings should be judged. Any changes in the fecal droppings (loss of consistency) can help notice emerging disease and take measures against it.

Especially during and after feed change, attention to changes in the usual feces consistency is necessary.

Vaccination and judicious antibiotic use are crucial

Carefully consider vaccination programs for broilers. Unnecessary vaccinations impact the immune system, possibly resulting in reduced performance and, in some circumstances, make the birds more susceptible to other diseases. Hence, the vaccination program must be diligently attuned (Neetzon et al., 2017).

• The disease background of the parent farm as well as the broiler farm where the chicks will be placed are essential factors for the vaccination program
• If possible, vaccine strains that are the least immunosuppressive should be chosen
• If coccidiostats are not permitted, an effective vaccination against coccidiosis is required and must be done as early as possible
• All vaccinations must be given using a standard operating procedure that minimizes bird discomfort and optimizes the vaccine, and always administer vaccines following the advice from the manufacturer

After the vaccination, it is essential to monitor the effects of vaccination stress and take preventive measures to avoid any issues with broiler performance in terms of weight gain and mortality.

Use antibiotics with discernment

As we aim to reduce antibiotics, they should be limited to pure therapeutic use, only if other disease-prevention measures have not been successful, and mortality or disease symptoms make the treatment necessary. Before the treatment, the disease must be diagnosed by a qualified veterinarian. The diagnosis should be preferably followed up by isolation of the disease-causing bacteria, classification, and susceptibility testing before the antibiotics are applied.

Small-spectrum antibiotics that are less likely to cause antimicrobial resistance (AMR) should be preferred. Broad-spectrum antibiotics or antibiotics that are likely to cause AMR can only be used after susceptibility testing has demonstrated resistance to a first-choice antibiotic. The treatment effect must be evaluated by daily monitoring of disease symptoms, mortality, water, feed intake, and body weight gain.

Thinning – things to consider

If thinning (partial depopulation) is practiced, it should be done with the highest bio-security measures. Producers must ensure that the equipment used in the catching process is thoroughly cleaned before entering the house, and bird-catching personnel takes the same measures as farm personnel when entering the farm and the house. These policies will help to minimize the introduction of infectious agents.

Keep the feed withdrawal period for this process as short as possible to avoid flightiness, which can induce skin lesions (some regions catch birds in low light intensities to avoid flightiness). A short feed withdrawal period also prevents over-consumption of feed in a short amount of time, possibly disrupting feed passage in the gut and leading to bacterial imbalance and dysbacteriosis in the remaining birds. After thinning, feed and temperature must be adapted to the lower number of animals.

Provide your birds with high-quality water for drinking

Water is the most important nutrient for broilers. It plays an essential role in digestion and metabolism, thermoregulation, and waste elimination.

Several factors affect water quality: temperature, pH, bacteria, hardness, minerals, and total dissolved solids. These parameters should be analyzed at least twice per year. If necessary, corrective actions should be taken, e.g., a filtration to remove minerals, the addition of chlorine for disinfection, or the addition of organic acids to drop the pH.

Before each cycle, the water must be tested for total aerobic + enterobacteria, compared to reference values: Total plate count (TPC) should be < 1000 CFU/ml, and E.coli, Enterobacteriaceae, yeast, and molds at undetectable levels. The section about cleaning and disinfection of the waterline provides insights and practical advice about water sanitation and microbiological analysis.

Nutrition & feeding – a pillar for antibiotic reduction

Nutrition and feeding in ABR broiler production are not only about providing nutrients for growth but also about the effects of the feed on gut health. Gut health is essential for animals’ overall health, welfare, and productivity, even more so in antibiotic reduction scenarios.

Feed should be of the highest quality – in all respects

High feed quality is necessary to provide the animal with the required nutrients and achieve their optimal utilization. Also important is the absence, limitation, or management of harmful substances and pathogens. High quality, therefore, includes:

• Form and composition of the final feed
• Nutritional value of the raw materials
• Management of harmful substances.

From reception and storage of the raw materials to the dispatch of the finished feed, the feed mill management emphasizes their quality assurance system, which is decisive in this connection.

First measure: quality assurance at the feed mill level

The feed mills producing for operations with no or reduced use of antibiotics must have a quality assurance (QA) and/or a good manufacturing program (GMP) in place that guarantees the production of consistently good quality feeds.

Proper raw material management and processing of feeds are necessary to achieve the lowest possible microbial-pathogen load, including:

• An effective rodent and wild birds control
• Disinfection of all the vehicles entering the feed mill
• Proper storage and utilization of raw materials (e.g., first in-first out use, silo management)
• Periodic thorough cleaning of milling equipment, premises and storage areas, and the monitoring of these activities
• Standard operating procedure and quality assurance systems that guarantee feed safety and quality

Check the quality of the raw materials and the final feed

Digestion, absorption, and gut health depend on the quality of the feed ingredients. To provide the best preconditions for healthy growth, producers should avoid raw materials of a reduced and/or inconsistent quality. For this purpose, each raw material batch should be analyzed for its specific quality parameters. Quality parameters to consider are:

• Physical ones, such as color, odor, particle size, and general appearance
• Chemical ones, such as nutritional composition and specific parameters. For example, grains should be analyzed for mycotoxins and antinutritional factors; fats and oils need to be analyzed for free fatty acids (FFA), unsaturated/saturated (US) ratio, iodine value (IV), but also the peroxide value (PV) as oxidized fats have a lower energy value, and their intake is related to enteric diseases
• Biological ones, including yeasts, molds, and enterobacteria

Also, the finished feed should be monitored by analyzing every batch concerning composition compared to values in the feed formulation, as well as physical, chemical, and microbiological quality parameters.

Clean storage on the farm prevents feed spoilage

As in the feed mill, keeping the farm facilities clean is of the highest importance. Warehouses, silos, bins, feeders, etc., should be emptied, cleaned, and disinfected after each flock; this avoids the formation of feed aggregates that can lead to mold growth and mycotoxin contamination; also, insects, bacteria, and parasites can remain in those residues.

Adapt feed formulation and feeding to the feeding phase

The value of phase feeding

Having the correct number of dietary phases to meet animal demands and avoid excess nutrients provides better intestinal health and thus aids production animals in ABR scenarios. The feeding phases should be designed to prevent abrupt changes in nutrition and raw material inclusions, possibly leading to dysbacteriosis.

Feeding for gut health

When feeding broilers in antibiotic reduction scenarios, extra care should be taken when formulating diets. The challenge is to achieve the same performance as conventional management at an optimum cost.

• Don’t waste nutrients: Improve feed digestibility, and at the same time, reduce the dangers of antinutritional factors coming from different ingredients by using suitable exogenous enzymes.
• Keep an eye on fiber: Moderate levels of insoluble fibers with adequate structure and composition can be included to promote gizzard development and function. This measure leads to a better modulation of gut motility and feeds passage into the intestine. Additionally, it promotes gut health, resulting in higher nutrient digestibility.
• Be careful with protein: Excess of undigested protein in the hindgut may lead to the proliferation of Clostridium perfringens; then, subclinical challenges of necrotic enteritis may occur. Moreover, the excess of nitrogen may increase feces moisture content, leading to wet litter. The optimization of the diets based on digestible amino-acid profiles and the use of synthetic amino acids decrease or eliminate the minimum requirements of crude protein, avoiding its excess.

Which feed form?

The feed form depends on the age or feeding phase: starter feeds can be offered as coarse mash, but preferably as crumble or mini-pellets (< 2 mm diameter) and grower and finisher diets as 3 – 4 mm pellets.

When using pelleted diets, quality is also the most crucial criterion. Poor pellet quality and thus the excess of fine particles increase feed passage rate, resulting in poor gizzard development and compromised gut health.

A high-quality pelleted feed can withstand – without much breakage – the handling that occurs after processing, such as transportation, storage, and farm management. Pellet quality can be measured by the Pellet Durability Index (PDI) obtained by simulating the impact and shear forces in a known quantity of feed for a determined amount of time. After this time, the sample is sieved, and the fines are separated, weighed, and compared with the initial sample

The PDI should be measured in the feed mill and compared to a standard. Later, it is also recommended to measure the PDI on the farm, and the producer should take corrective actions if the pellets cannot maintain their quality.

Additionally, it should be known that coarse ground grains stimulate gizzard development and function. So, about 30 % of the feed should consist of particles between 1-1.5mm (post pelleting) in all feeding phases.

Broilers’ selection criteria for feed are form, color, size, and consistency

Broilers’ selection criteria for feed are form, color, size, and consistency. They prefer feed that is easy to pick, such as crumbles or pellets. 

Feed additives can support antibiotic reduction

The feed additive industry provides broiler farms and integrations with various solutions to make production more manageable and efficient.

A healthy start is half the battle

Let’s start with the chicks. The early introduction of beneficial bacteria into the intestinal tract has proven helpful for gut health optimization. This colonization can be achieved with the administration of suitable probiotics preparation at the hatchery. Multi-strain probiotic preparations effectively initiate healthy microbiome development for optimum gut health. For these challenges, support is offered through EW Nutrition’s VENTAR D and ACTIVO LIQUID, phytomolecule-based products for the feed and the waterline, respectively.

Maintain gut health

Gut health is one of the essential preconditions for efficient growth. Only a healthy gut guarantees efficient digestion and absorption of nutrients. Several approaches are recommended to maintain gut health:

• Promotion of beneficial and reduction of pathogenic gut flora: here, solutions can come in the shape of products based on phy­tomolecules that can be applied with the feed (VENTAR D) or the water (ACTIVO LIQUID)
• Management of bacterial toxins and mycotoxins: for this topic, products mitigating the toxins’ negative impact on the birds (Product range of MASTERSORB and SOLIS) are offered

Protect your feed

When feed is stored, there is always the risk of bacteria, mold, or yeast overgrowth. Oxidation of feed ingredients, such as fats and oils, reduces their nutritional value. These issues can be prevented by applying:

• Acidifiers that have antimicrobial effects due to their pH-decreasing effect, which, later on, improves the feed digestibility and stabilizes the GIT flora (ACIDOMIX, FORMYCINE, and PRO-STABIL)
• Antioxidants preserving ingredients susceptible to oxidation, such as fats and oils (AGRADO, SANTOQUIN, and STABILON)

Improve pellet quality

Moisture retention during the conditioning process influences pellet quality: higher moisture retention entails a higher starch gelatinization resulting in higher digestibility, pellet binding, fewer fines, and a higher PDI. Surfactants (for example, SURF•ACE) are compounds that can reduce the surface tension between the water and the feed, improving moisture absorption during the conditioning process.

Besides that, moist steam in the pelleting process penetrates better and has a higher antimicrobial effect leading to lower production of bacterial and mycotoxins. The possible reduction of the pelleting temperature protects the nutrients.

ABR in broiler production is practicable – by observing some rules

As shown above, antibiotic-reduced broiler production needs many aspects to be considered and a lot of measures to be taken. All of these measures seek to keep animals healthy and avoid antibiotic use. Maintaining gut health is crucial, as only a healthy gut performs well, achieves the optimal utilization of nutrients, and increases growth performance.

Maintaining a successful production unit with no or reduced antibiotic use requires a holistic approach in which best practices must be assured at all levels of the production chain. The feed additive industry provides a broad range of solutions to support animal production through this challenging task. The objective could not be more critical: lowering antibiotic resistance to assure the future of animal and human health.

 

References:

Davies, Robert, and Andrew Wales. “Antimicrobial Resistance on Farms: A Review Including Biosecurity and the Potential Role of Disinfectants in Resistance Selection.” Comprehensive Reviews in Food Science and Food Safety 18, no. 3 (2019): 753–74. doi.org/10.1111/1541-4337.12438

Dewulf, Jeroen, and Van Filip Immerseel. “General Principles of Biosecurity in Animal Production and Veterinary Medicine.” Essay. In Biosecurity in Animal Production and Veterinary Medicine: From Principles to Practice. Wallingford, Oxfordshire, UK: CABI, 2019. doi.org/10.1079/9781789245684.0063.

Luyckx, K.Y., S. Van Weyenberg, J. Dewulf, L. Herman, J. Zoons, E. Vervaet, M. Heyndrickx, and K. De Reu. “On-Farm Comparisons of Different Cleaning Protocols in Broiler Houses.” Poultry Science 94, no. 8 (2015): 1986–93. doi.org/10.3382/ps/pev143.

Kreis, Anna. “Broiler Feed Form, Particle Size Assists Performance.” Feed Strategy, September 20, 2019. https://www.feedstrategy.com/poultry-nutrition/broiler-feed-form-particle-size-assists-performance/.

Malone, B. “Litter Amendments: Their Role and Use.” University of Delaware – Agriculture & Natural Ressources – Fact Sheets and Publications. University of Delaware, November 2005. https://www.udel.edu/academics/colleges/canr/cooperative-extension/fact-sheets/litter-amendements/

Neetzon, A. M., Pearson, D., Dorko, N., Bailey, R., Shkarlat, P., Kretschmar-McCluskey, V., Van Lierde, E., Cerrate, S., Swalander, M., Vickery, R., Bruzual, J., Evans, B., Munsch, G., & Janssen, M. (2017, October). Aviagen Brief. Aviagen – Information Library. https://en.aviagen.com/assets/Tech_Center/Broiler_Breeder_Tech_Articles/English/AviagenBrief-ABF-Broiler-EN-17.pdf.

UC Davis Veterinary Medicine. “‘All out All in’ Poultry Management Approach to Disease Control. A Guide for Poultry Owners.” Poultry-UC ANR, March 2019. https://ucanr.edu/sites/poultry/files/301023.pdf

 

What can the right phytogenic feed additive deliver for broiler producers?

It is essential to improve broiler gut health, as only healthy birds will perform and allow producers to be profitable. Producers can maintain flock performance through preventive management measures, a consistent hygiene concept, and the use of high-quality feed. For unproblematic flocks, the same measures also positively affect profit, generating a healthy return on investment (ROI).

What affects your return on investment?

In broiler production, the cost of feed is highest, with a share of 60 – 70 % of the total production costs. The proportion tends to be higher in markets that rely on importing feed raw materials (Tandoğan and Çiçek, 2016).

Let us take an example: With a compound feed price of 300 € / t as the basis, an increase of 10 € / t results in a profit reduction of 0.016 € / kg live weight. On the other hand, an improvement in feed conversion from 1.60 to 1.55 results in a financial advantage of 0.015 € / kg live weight. The best possible feed efficiency is always desirable to keep production costs low.

Another risk factor for high-yield broiler production lives in the poultry intestines: the most significant “invisible” losses result from subclinical necrotic enteritis (Clostridium perfringens). This disease worsens the feed conversion on average by 11 % (Skinner et al., 2010). In the previous example, this would reduce feed efficiency from 1.60 to 1.78 points and reduce the contribution margin by 0.054 € / kg live weight. In addition,  a live weight reduction of up to 12 % can be observed (Skinner et al., 2010). It is, therefore, critical to stabilizing gut health to reduce the risk of subclinical necrotic enteritis.

Practice prevention for a secure return on investment

The prophylactic use of antibiotics in compound feed was a well-known reality for decades. With the EU-wide ban on the use of antibiotic growth promoters, the occurrence of multi-resistant bacteria, and a globally increased demand for antibiotic-free chickens, producers now have had to cut down on antibiotic use.

For this reason, a lot of research has been conducted into alternative measures for maintaining good broiler health. Studies have confirmed that setting up a comprehensive hygiene concept to reduce the formation of biofilms on stable surfaces and reduce the recirculation of pathogens is a solid basis. At every production stage, irregularities can be detected through a meticulous control of performance parameters and illness symptom-centered health monitoring. Diseases can either be avoided or at least recognized earlier through targeted measures, and treatment can be carried out more efficiently.

A thorough hygiene concept and careful monitoring at every production stage are key to ensuring broiler performance.

Feed additives for intestinal stabilization

Hygienically impeccable compound feed is the wish of every animal producer to promote the development of a balanced intestinal flora. However, the quality of the available raw materials is subject to fluctuations and can therefore not be 100 % anticipated. Consequently, producers are now commonly balancing these uncertainties by using feed additives, which positively influence the intestinal flora. These products must prove their positive effects in scientific studies before they can be used in practice.

An effective solution: Encapsulated phytogenic feed additives

Studies have found that certain phytomolecules, which are secondary plant metabolites, can support broiler gut health. By stimulating digestive enzyme activities and stabilizing the gut microflora, feed utilization improves, and broilers are less prone to developing enteric disorders (Zhai et al., 2018).

The encapsulation of these naturally volatile substances in a high-performance delivery system is critical for the success of a phytogenic feed additive. This protective cover, which is often a simple coating, provides good storage stability in many cases. However, in addition to the high temperatures, mechanical forces also act on these coatings during pelleting. The combination of pressure and temperature can break the protective coating of the product and lead to the loss of active substances.

A complete solution: How Ventar D maximizes your ROI

Because of the difficulties mentioned, the use of modern delivery system technologies is therefore necessary. EW Nutrition has many years of experience in the development of phytogenic products. Due to an original, innovative delivery system technology, Ventar D can offer high pelleting stability for optimal improvement of animal performance.

In particular, the positive influence of the phytogenic feed additive Ventar D on intestinal health under increased infection pressure was assessed in multiple studies. In two studies carried out in the United Kingdom, birds were challenged by being housed on used litter harvested from a previous trial. Moreover, increasing levels of rye were introduced into the diet, adding a nutritional challenge to provoke an increased risk of intestinal infections in the broilers. The use of 75 g of Ventar D per t compound feed increased the EPEF (European Production Efficiency Factor) by 4.1% and feed efficiency from 1.63 to 1.60.

With Ventar D use at 100 g / t compound feed under comparable conditions, EPEF increased by 8.9 %, and feed efficiency improved by 5 points (0.05), compared to a non-supplemented control group (NC).

Another study was carried out in the USA. In addition to performance parameters, data on intestinal health were also recorded. In the group fed with Ventar D (100 g / t compound feed), 50 % fewer necrotic enteritis-related lesions of the intestinal wall were found after 42 days. Compared to the group fed with Ventar D, the broilers of the control group showed a performance decrease of 11.8 % with an 8% lower final fattening weight and a 3 points poorer FCR.

Based on the results of the above studies, the ROI for Ventar D due to the improvement in feed efficiency by 3 and 5 points could be 1:3.5 and 1:6.5, respectively. Similarly, the net returns for using Ventar D could be 0.007 and 0.013 € / kg live weight, given the 3 and 5 points improvements in feed efficiency. The ROI for Ventar D use could be even higher thanks to additional benefits such as improvements in litter condition and foot pad lesions, reduced veterinary cost, etc., depending on the prevailing challenges.

The future of feeding is here

The first study results for Ventar D underscore that, if combined and delivered right, phytomolecules can transform broiler performance from inside the gut. Ventar D’s stable delivery system ensures a constant amount of active molecules in targeted intestinal sites and, therefore, supports a favorable intestinal flora. With Ventar D supplementation, subclinical intestinal infections due to C. perfringens or other enteric bacteria can be very well kept in check, ensuring improved broiler productivity and production profitability.

 

References

Skinner, James T., Sharon Bauer, Virginia Young, Gail Pauling, and Jeff Wilson. “An Economic Analysis of the Impact of Subclinical (Mild) Necrotic Enteritis in Broiler Chickens.” Avian Diseases 54, no. 4 (December 1, 2010): 1237–40. https://doi.org/10.1637/9399-052110-reg.1.

Tandoğan, M., and H. Çiçek. “Technical Performance and Cost Analysis of Broiler Production in Turkey.” Revista Brasileira de Ciência Avícola 18, no. 1 (2016): 169–74. https://doi.org/10.1590/18069061-2015-0017.

Zhai, Hengxiao, Hong Liu, Shikui Wang, Jinlong Wu, and Anna-Maria Kluenter. “Potential of Essential Oils for Poultry and Pigs.” Animal Nutrition 4, no. 2 (June 2018): 179–86. https://doi.org/10.1016/j.aninu.2018.01.005

by Predrag Persak, Regional Technical Manager North Europe, EW Nutrition

The main sustainability challenge for broiler production lies in securing enough high-quality, nutritious, safe, and readily available food at a reasonable cost. At times, feed ingredients have to be included that are not nutritionally ideal and might compromise one’s broilers’ health and wellbeing. However, counteracting this threat with prophylactic antibiotics is not acceptable: We must minimize the use of antibiotics to mitigate antimicrobial resistance. The way forward is to go beyond static and linear nutritional value-to-price thinking. A dynamic nutritional strategy focusing on the interdependencies between ingredients, gut, microbiome, and digestion, enables sustainable ABF broiler production.

Sustainable ABF broiler production requires a dynamic, gut health-oriented nutritional strategy

Sustainability vs. ABF production – is there a trade-off?

The United Nations’ 1987 Brundtland report offers a clear definition of sustainability as “development that meets the needs of the present without compromising the ability of future generations to meet their own needs.” “Ability” includes the availability of resources – and in broiler production, which is one of the most efficient livestock productions, resources have always been a top priority. As a constantly evolving industry, broiler production has been quick to adopt sustainability into its management strategies. The use of the resource that is antibiotics, however, poses particular challenges.

Humans and animals depend on antibiotics to fight microbial infections. It is essential to maintain their efficacy so that future generations can lead healthy lives. Antibiotic efficacy is under threat from the development of antimicrobial resistance, which emerges from overuse and misuse in both human and veterinary medicine. Across the globe, broilers are still raised with the assistance of antibiotics. Either for disease therapy, to prevent disease occurrence, and still, in some parts of the world, to enhance performance. Driven by regulatory and consumer demands, broiler production with minimal or no use of antibiotics is rapidly gaining importance.

The challenges of antibiotic-free broiler production

ABF systems encounter numerous challenges since production requirements change drastically. Stock density must be lower; it takes longer to reach the desired weight; and more feed is needed to produce the same amount, with a higher risk of morbidity and mortality (Cervantes, 2015). The latter can result in more birds needing treatment with medically important antimicrobial drugs. All those challenges need to be overcome by adopting suitable strategies related to nutrition, genetics, management, biosecurity, welfare, and food safety.

As animal nutritionists, our focus lies on nutrition, feed, feed materials, additives, feed processing, feeding, and their (positive or negative) influence on the sustainability of ABF broiler production. However, we cannot look at these dimensions of production as a separate process. They are linked in the whole food chain and are affected by changes that happen in other related parts. An obvious example is feed production, which has an enormous impact on the overall sustainability of ABF broiler production:

• Due to raw material shortages, diets are becoming ever more complex, containing more single feed ingredients. For some of them, we need a better understanding of their impact on ABF broiler production (e.g., sunflower, rapeseed, beans, lupins).
• The nutritional composition of raw materials changes due to limitations in fertilizer use, and variability within the same raw material group is expected to increase.
• New food waste-reducing feed materials can enhance feed security but also require nutritional profiling to integrate them into diets.
• Local feed material production in humid and warm environments can introduce various pathogens into the feed/food chain.
• Increases in known and the emergence of new antinutrients and feed components that impair animal health, performance, and feed efficiency.
• Sustainability-driven pesticide reduction raises concerns about mycotoxins contaminating feed ingredients.
• Nutrient reduction to support gut health and, primarily, lower the excretion of nitrogen and phosphorous, negatively affects growth, nutritional standards, and the ability to freely select feed materials to include in broiler diets.
• The value (of which price is also part) of raw materials will be compromised, due to availability and nutritional variability.

Mycotoxin contaminated-feed can damage production animals’ performance, health, and welfare

When striving for a sustainable ABF broiler production approach, the possibility for errors becomes higher, while the error margin becomes smaller. The solution lies in helping the animals to mitigate the impact of stressors by focusing on the interaction of ingredients, gut, microbiome, and digestion. It is a holistic approach centered on gut health. Keeping the intestines BEAUTIful will help you produce in challenging conditions without the use of antimicrobials.

Keep the broiler gut BEAUTIful and resilient to stress

The BEAUTIful formula captures the six areas producers need to target for supporting broiler gut health:

Barrier

If it’s working correctly, the effective gatekeeper knows what gets in and what stays out. When the barrier function is compromised due to stress, pathogens can cause infections, disrupt health, and negatively impact broiler immunity. Necrotic enteritis, femoral head necrosis, and bacterial chondronecrosis with osteomyelitis (BCO) are common diseases that affect today’s broiler production (Wideman, 2015). As the source of nutrients, feed serves as a modulator of various physiological functions in the intestinal tract, including intestinal barrier function.

Enzymatic digestion

The gut is where endogenous and exogenous enzymes perform their hydrolysis functions to break down complex nutrients into the parts that can be used either by the intestinal tissue itself or for the whole animal. One part of hybrid enzymatic digestion is the fermentation by commensal microbes, in which complex materials form end-products of high biological values (such as short-chain fatty acids, SCFA).

Absorption

Maintaining the gut’s resorptive capacity is essential to secure the total intake of digested nutrients. Otherwise, pathogenic bacteria might use the excess nutrients to grow, form toxins, and affect the birds’ health and productivity.

United microbiome

The intestine of a broiler chicken is colonized by more than 800 species of bacteria and other inhabitants, such as viruses and simple organisms that are still unknown. By competitive exclusion and secretion of bacteriocins (volatile fatty acids, organic acids, and natural antimicrobial compounds), commensal bacteria keep the host safe from an overgrowth of dangerous bacteria (e.g., Salmonella, Campylobacter, and Clostridium perfringens). The fine-tuned diversity in the intestinal flora and balance in all interactions between it, the host, and the ingesta are needed for birds to stay healthy and perform well.

Transport

Birds’ digestive tract volumes are smaller than those of mammals with similar body weight. This means that they achieve more efficient nutrient digestion in a shorter retention time, averaging between 5 and 6 hours. Passing the small intestine usually takes around 3 hours, of which 1 hour is spent in the duodenum and jejunum. Transport times are affected by the feeding system and the extent to which material enters the caeca. Reflux of material from the distal to the proximal small intestine is an important feature that helps digestion and maintenance of a healthy gut.

Immunity

The intestinal microbiota is critically important for the development and stimulation of the immune system. The intestine is the key immunological organ, comprised of myeloid and lymphoid cells, and a site for producing many immune cell types needed to initiate and mediate immunity. Together with the microbiome, dendritic cells induce antigen-specific responses and form immunoglobulin A, which works in the intestinal lumen.

Natural gut health solution for sustainable ABF broiler production

In practice, supporting broiler gut health requires a holistic approach that includes natural feed additive solutions. Phytomolecules are compounds that certain plants develop as defenses mechanisms. Phytomolecules-based solutions should feature prominently in sustainable ABF broiler production approaches due to their advantageous properties:

Enhance digestion, manage variability

Sustainability necessitates efficient resource utilization. Digestion support needs to be a priority to use the available feed in its entirety. This is particularly important if antibiotics use needs to be minimized: a maximum of nutrients should be utilized by the animal; otherwise, they feed potentially harmful bacteria, necessitating antibiotic treatments. Enhancing digestibility is the focus when we are dealing with variable feed materials or feed changes that represent stress to the animal. Selected phytomolecules have proven efficient at improving performance due to enhanced digestion (Zhai et al. 2018).

Work on microbiome and pathogens

The antimicrobial activity of certain phytomolecules can prevent the overgrowth of pathogens in the gastrointestinal tract, thereby reducing dysbacteriosis (Liu et al., 2018) and specific diseases such as necrotic enteritis. Studies on broilers show that they also reduce the adhesion of pathogens to the wall of the intestine. Certain phytomolecules even possess antimicrobial characteristics against antibiotic-resistant pathogens.

Keep gut integrity

Phytomolecules help maintain tight junction integrity, thus preventing leaky gut (Li et al., 2009). As a result, the potential flow of bacteria and their toxins from the gut lumen into the bloodstream is mitigated. Their properties thus make phytomolecules a promising alternative to the non-therapeutic use of antibiotics. 

Trial results: Phytomolecules enhance broiler gut health

To test the efficacy of phytomolecules, we conducted a large-scale field study in Brazil, under practical conditions. The focus was on growth performance, and no growth-promoting antibiotics were used. Lasting 5 months, the trial involved more than 2 million broilers. The birds were divided into a control and a trial group, with two repetitions per group. Both groups were fed the standard feed of the farm. The trial group additionally received 100g of Activo per MT in its finisher feed for 3 weeks. The study clearly shows that Activo supplementation improves performance parameters (daily weight gain, average total gain, and improved feed efficiency), which resulted in a higher production efficiency factor (PEF):

• Activo groups had a 3 % higher average daily weight gain and reached their slaughtering age earlier
• The final weight of Activo groups was about 2.5 % higher than in the control group
• With a 2 points better feed conversion, the animals of the Activo group achieved a 13.67 points higher PEF

Figure 1: Broiler performance results, Activo vs. non-supplemented control group 

Conclusion

Antibiotic-free broiler production is a challenging endeavor: producers need to maintain animal welfare and keep up efficiency while making farming profitable. Over time, these challenges will affect producers even more as sustainability requirements increase across all parts of the broiler production chain. On top of that, coccidiostats, which are essential for efficient broiler production, are increasingly being questioned, which will require concerted research into feed additive solutions.

To make sustainable ABF broiler production the norm, it is unavoidable to adopt suitable strategies related to nutrition, genetics, management, biosecurity, welfare, and food safety. Effective, scientifically and practically proven tools already exist: Thanks to their positive impact on intestinal health, phytomolecules reliably support sustainable broiler production without antibiotics.

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References

Cervantes, Hector M. “Antibiotic-Free Poultry Production: Is It Sustainable?” Journal of Applied Poultry Research 24, no. 1 (2015): 91–97. https://doi.org/10.3382/japr/pfv006.

Li, Y., H.Y. Cai, G.H. Liu, X.L. Dong, W.H. Chang, S. Zhang, A.J. Zheng, and G.L. Chen. “Effects of Stress Simulated by Dexamethasone on Jejunal Glucose Transport in Broilers.” Poultry Science 88, no. 2 (2009): 330–37. https://doi.org/10.3382/ps.2008-00257.

Liu, ShuDong, MinHo Song, Won Yun, JiHwan Lee, ChangHee Lee, WooGi Kwak, NamSoo Han, HyeunBum Kim, and JinHo Cho. “Effects of Oral Administration of Different Dosages of Carvacrol Essential Oils on Intestinal Barrier Function in Broilers.” Journal of Animal Physiology and Animal Nutrition 102, no. 5 (2018): 1257–65. https://doi.org/10.1111/jpn.12944.

Wideman, Robert F. “Bacterial Chondronecrosis with Osteomyelitis and Lameness in Broilers: a Review.” Poultry Science 95, no. 2 (2016): 325–44. https://doi.org/10.3382/ps/pev320.

Zhai, Hengxiao, Hong Liu, Shikui Wang, Jinlong Wu, and Anna-Maria Kluenter. “Potential of Essential Oils for Poultry and Pigs.” Animal Nutrition 4, no. 2 (2018): 179–86. https://doi.org/10.1016/j.aninu.2018.01.005.