{"id":218534,"date":"2024-07-15T14:09:58","date_gmt":"2024-07-15T12:09:58","guid":{"rendered":"https:\/\/ew-nutrition.com\/mycotoxins-poultry-external-signs-can-give-hint-2\/"},"modified":"2025-03-28T09:38:07","modified_gmt":"2025-03-28T08:38:07","slug":"mycotoxins-poultry-external-signs-can-hint","status":"publish","type":"post","link":"https:\/\/ew-nutrition.com\/us\/mycotoxins-poultry-external-signs-can-hint\/","title":{"rendered":"Mycotoxins in poultry \u2013 External signs can give a hint"},"content":{"rendered":"

Part 3: Bone disorders and foot pad lesions<\/h4>\n

By Dr. Inge Heinzl, Editor, and Marisabel Caballero, Global Technical Manager Poultry<\/span><\/em><\/p>\n

 <\/p>\n

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<\/a><\/span>; Rath, N.C. & Durairaj, 2022<\/a><\/span>; Suchacki et al., 2017<\/a><\/span>).<\/p>\n

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.<\/p>\n

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.<\/p>\n

Mycotoxins affect bones in different ways<\/h2>\n

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.<\/p>\n

Inadequate bone mineralization and strength \u2013 Rickets and layer cage fatigue<\/h3>\n

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:<\/p>\n

    \n
  1. Decrease in the availability of the nutrients necessary for mineralization. This can occur if the digestibility of these nutrients deteriorates<\/li>\n
  2. Impact on the Ca\/P ratio\u2014A ratio of 1 \u2013 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.<\/li>\n
  3. Impact on the Vitamin D receptor, affecting its expression or the transporters for Ca and P.<\/li>\n<\/ol>\n

    Aflatoxins<\/span> 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)<\/a><\/span> 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: \u00a0Bai et al. (2014)<\/a><\/span> feeding diets contaminated with 96 (starter) and 157\u00a0\u00b5g Aflatoxins (grower) per kg of feed to broilers and Han et al. (2008)<\/a><\/span> saw no impact on cherry valley ducks with levels of 20 and 40 \u00b5g AFB1\/kg diet.<\/p>\n

    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 \u00a0Zhao et al. (2010)<\/a><\/span>: They<\/span> 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)<\/a><\/span> showed decreased Ca in the tibia and reduced tibial break strength.<\/p>\n

    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)<\/a><\/span> 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.\u00a0 Paneru et al. (2024)<\/a><\/span> could confirm this downregulation of the Vit D receptor and additionally of the Ca and P transporters in broilers with levels of \u226575 ppb AFB1. They also saw a significant reduction in tibial bone ash content at AFB1 levels >230\u00a0ppb, 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.<\/p>\n

    \"Figure\"
    \nFigure 1: Increasing doses of AFB1 (<2 ppb \u2013 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).<\/span><\/p>\n

    All experiments strongly suggest that aflatoxins harm bone homeostasis. Additional liver damage, oxidative stress, and impaired cellular processes can exacerbate bone health issues.<\/strong><\/p>\n

    Trichothecenes<\/span> 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.<\/p>\n

    For instance, when T-2 toxin <\/strong>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 \u2013 2 to 0.85, 0.66, and 0.59 (P<0.05) (Gu et al., 2023<\/a><\/span>). 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.<\/p>\n

    Other studies show that serum P levels decreased in broilers fed DON-contaminated feed with levels of only 2.5 mg\/kg (Ke\u00e7i et al., 2019<\/a><\/span>). 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)<\/a><\/span>: After their trial with broilers<\/span>, 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 Ke\u00e7i 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.<\/p>\n

    In line with trichothecenes effects in Ca and P absorption, Ledoux et al. (1992)<\/a><\/span> 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.<\/p>\n

    Ochratoxin A <\/span>(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 \u00b5\/g, and Duff et al. (1987)<\/a><\/span> report similar results also in turkey poults.<\/p>\n

    A further mycotoxin possibly contributing to leg weakness is cyclopiazonic acid<\/span> 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<\/a><\/span>). Tran et al. (2023) also showed this fact with multiple mycotoxins.<\/p>\n

    The co-occurrence of different mycotoxins in the feed \u2013 the standard in praxis \u2013 increases the risk of leg issues. A trial with broiler chickens conducted by Raju and Devegowda (2000)<\/a><\/span> showed a bone ash-decreasing effect of AFB1 (300 \u00b5g\/kg), OTA (2 mg\/kg), and T-2 toxin (3 mg\/kg), fed individually but an incomparable higher effect when fed in combination.<\/p>\n

    Impairment of bone growth – tibial dyschondroplasia (TD)<\/h3>\n

    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 Sokolovi\u0107 et al. (2008)<\/a><\/span>, 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.<\/p>\n

    T-2 toxin:<\/span> 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)<\/a><\/span> found that T-2 toxin decreased cell viability, alkaline phosphatase activity, and glutathione content (P\u2009<\u20090.05). 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.<\/p>\n

    Gu et al. (2023)<\/a><\/span> 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<\/a><\/span>; Gao et al., 2010<\/a><\/span>; Ukwu et al., 2014<\/a><\/span>; Yu et al., 2022<\/a><\/span>), their slowdown indicates lower growth performance.<\/p>\n

    Fumonisin B1<\/span> 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<\/a><\/span>). Possible explanations are the reduced viability of chondrocytes, as found by Chu et al. (1995<\/a><\/span>) 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<\/a><\/span>).<\/p>\n

    Bacterial chondronecrosis with osteomyelitis lameness (BCO) can be triggered by DON and FUM<\/h3>\n

    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.<\/p>\n

    In their experiment with DON <\/span>and FUM<\/span> in broilers, Alharbi et al. (2024)<\/a><\/span> showed that these mycotoxins reduce the gut\u2019s 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.<\/p>\n

    The increase in uric acid leads to gout<\/h3>\n

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

    One of these mycotoxins is T-2 toxin<\/span>. With the trial mentioned before (Yangzhou goslings, 21 days of exposure), Gu et al. (2023)<\/a><\/span> 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.<\/p>\n

    Huff et al. (1975)<\/a><\/span> applied Ochratoxin<\/span> to chicks at 0, 0.5, 1.0, 2.0, 4.0, and 8.0 \u00b5g\/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 \u00b5g\/g and higher. At 4.0 and 8.0 \u00b5g\/g doses, uric acid increased by 38 and 48%, respectively (see Figure 2). Page et al. (1980)<\/a><\/span> also reported increased uric acid after feeding 0.5 or 1.0 mg\/kg of Ochratoxin A to adult white Leghorn chickens.<\/p>\n

    \"Figure\"Figure 2: Effect of Ochratoxin A on plasma uric acid (mg\/100 ml) (according to Huff et al., 1975)<\/span><\/p>\n

    Foot pad lesions \u2013 a further hint of mycotoxicosis<\/h2>\n

    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<\/a><\/span>). Here are some examples of the adverse effects of mycotoxins leading to intestinal disorders and diarrhea:<\/p>\n