Total Production 2023: 144.3 million metric tons for farmed animals

Change from 2022: 2% decrease

Factors Influencing Decrease

Political and Market Pressures: Addressing crises and the shift towards sustainable feed.

Climate and Diseases: Effects of droughts, floods, Avian Influenza (AI), and African Swine Fever (ASF) on raw material supply and animal production.

National Policies: Initiatives for greenhouse gas and nitrate emission reduction.

Consumer Trends: Food price inflation impacting demand.

Production Variability: Different trends across EU Member States, with notable decreases in countries like Germany, Ireland, Denmark, and Hungary, and slight increases in Austria, Bulgaria, Italy, and Romania.

Sector-Specific Trends

Pig Feed: Major decline of nearly 2.5 million tons. Key challenges included:

• Loss of export markets, particularly in Asia
• Negative media impact in Germany
• Significant production drop in Denmark (-13.6%) and Spain (loss of 800,000 metric tons)
• Italy’s ongoing struggle with ASF

Poultry Feed: Increase by 0.9 million tons, yet still 700,000 metric tons below 2021 levels. Challenges included declines in Hungary and Czechia due to reduced broiler production.

Cattle Feed: Decrease of 0.8 million tons from 2022.

2024 key factors

• Animal disease
• Economic instability, persistent food price inflation
• Weather irregularities
• Continued imports of poultry meat from Ukraine
• “Green and animal welfare” policies affecting local production

Summary

The EU’s compound feed production in 2023 faced numerous challenges, leading to an overall decrease. The pig feed sector was most severely hit, while poultry feed showed some recovery. The influence of environmental, economic, and policy factors played a significant role in shaping these trends. Despite the price of feed cereals falling back to the levels seen before Russia’s invasion of Ukraine, these challenges will continue to be felt in 2024.

Source: FEFAC

Judith Schmidt, Product Manager On-Farm Solutions

Improvements in genetics, nutrition, and management continue to enhance dairy cows’ performance. However, being high-performance athletes comes at a cost, putting an extremely high burden on the animals’ energy metabolism. Especially around calving and during the first eight weeks of lactation, dairy cows can experience many stress factors: subclinical hypocalcemia, abomasum displacements, herd composition changes, or lameness. The more stress factors put the cows’ organism under pressure, the more likely they will become sick. A common consequence of stress is the occurrence of metabolic diseases, especially ketosis.

Both in terms of animal health and economic aspects, ketosis is probably the most critical dairy cow disease when also considering the correlated diseases. In this article, we explore the causes and consequences of ketosis and highlight prevention strategies that keep this issue under control.

Ketosis: causes and consequences

How ketosis develops

A restricted feed intake capacity and/or reduced energy concentration in the ration lead to a deficit in the animal’s energy balance. This situation occurs, for instance, at calving when the mother animal focuses her resources on the calf and its care. To compensate for the energy deficit, body fat is broken down for energy production. This process creates free fatty acids that accumulate in the liver and are partially converted into ketone bodies. These ketone bodies are a “transport medium” for energy, which various organs can use as an alternative energy source.

The problem arises when the deficiency lasts too long: more and more body fat is broken down, more and more fatty acids reach the liver, which leads to a fatty liver, and too high an amount of ketone bodies is formed and released into the blood. The ketone bodies in the blood inhibit appetite, resulting in less feed consumption and an energy deficit – the vicious cycle of ketosis begins.

Subclinical ketosis

Subclinical ketosis is defined as the stage of the disease at which an increased level of ketone bodies can be detected in the blood, urine, and milk. Furthermore, signs of hypoglycemia, increased levels of non-esterified fatty acid, and decreased hepatic gluconeogenesis can be seen in the blood. These conditions are typically not detected because there are no clinical signs.

Subclinical ketosis is a problem as it does not cause visible symptoms but leads to an increased incidence of subsequent diseases such as lab stomach displacement, clinical ketosis, and uterine inflammation. In addition, there may be loss of milk and fertility problems. Subclinically ill animals cannot be identified by the farmer by observation alone. Therefore, subclinical ketosis must be detected at an early stage to be able to act at the right time: prophylaxis instead of therapy.

There are several test possibilities to find out if an animal suffers from ketosis:

1. Milk: Milk test for ketosis detection has been available for many years. The results are to be obtained based on a color gamut. In contrast to blood analysis, the milk test does not evaluate exact values but shows a color change of the contained indicator. However, an increased milk cell content of the feeding of poorly fermented silages with a high butyric acid content significantly influences the result. The test often does not adequately reflect the actual conditions.
2. Urine: Another possibility is the examination of urine samples. Urine can be obtained spontaneously or with the help of a catheter. The results can also be read on a color scale of the urine test stripes. Like the milk test, the urine test only distinguishes different concentration ranges, but these are more finely graded than in the milk tests.
3. Blood: The most accurate but also most complex and expensive method is a blood test. It has the advantage that not only ketone bodies but also other parameters such as free fatty acids, minerals, and liver enzymes can be analyzed. In addition, the blood analysis results are evaluated in numbers and are more comparable than the color changes of test stripes. A good alternative is a rapid test by using a rapid test device, which is also used for measuring human blood sugar. A result is displayed with a drop of blood on a test strip within a few seconds.

Clinical ketosis

Depending on why there are elevated ketone body levels in the blood, we distinguish between primary and secondary clinical ketosis. For the primary form of clinical ketosis, the energy deficit itself (due to high performance and/or incorrect feeding) causes the condition. This form mainly occurs in susceptible, high-yielding dairy cows between the second and seventh weeks of lactation (Vicente et al., 2014). Secondary ketosis is caused indirectly by other diseases disease. A cow suffering from, for example, a claw disease might no longer consume a performance-based feed ration, leading to an energy deficit.

Typical symptoms

Typical of metabolic diseases, ketosis leads to a broad spectrum of symptoms. The classic symptoms at the beginning of the disease are a loss of appetite and decreased milk performance. As the disease develops, motor skills may be affected, and the excrement’s consistency becomes firmer and darker in color. The respiratory rate of sick animals increases, and they show dyspnea. Dyspnea is the medical description for breathing difficulties. Affected animals suffer from air shortage, which can occur in different situations. Due to the excretion of ketone bodies via the mucous membranes, the animals’ breath smells more or less strongly of acetone (Robinson and Williamson, 1977).

In addition, the animals undergo rapid and severe weight loss, and their general body conditions deteriorate noticeably. Furthermore, cows suffering from ketosis show increased milk fat content or an increased milk fat/protein quotient. Clinical symptoms include reduced general well-being, apathy, blindness, staggering, persistent “absent-minded” licking of the environment or overexcitability, muscle tremors, and aggressiveness (Andersson, 1984).

Effects on animal health and performance

Even in its subclinical form – if untreated – ketosis will engender health risks and reduced performance, negatively impacting milk yield and cows’ fertility. For clinical cases, typical effects include infertility, udder and hoof problems, and a fatty liver. Ketosis during early lactation is usually associated with fatty liver disease. In severe cases, the liver becomes enlarged and more fragile. It then no longer performs its detoxification function, toxic compounds increase, and the central nervous system is damaged. Anorexia or even a total loss of consciousness, the so-called hepatic coma, might ensue, ending in a complete liver function failure.

Direct economic costs range from high veterinary costs to the total loss of the dairy cow, i.e., approximately € 600 to € 1.000 per cow. Moreover, producers face indirect costs from secondary diseases such as fatty liver disease, increased postpartum behavior such as uterine infections, abomasum dislocations, or claw diseases.

­­Ketosis prevention: feeding and targeted supplementation

Feeding strategy

As part of the preparatory feeding, both dry and pregnant cows should receive rations that lead to an optimal (and not maximum) body condition at the time of calving. Animals with a poorer nutritional status do not have enough body fat reserves to compensate for lack of energy in the first phase of lactation. In more cases, animals have a too high BCS, leading to a risk of difficult births, and the cows have too little appetite at the beginning of lactation. These cows tend to show an excessive mobilization of fat reserves and develop a fatty liver. So prevention of ketosis of the current lactation starts with preventing a too-high BCS in the middle of the previous lactation.

The aim of feeding measures is to keep the lactating cow’s discrepancy between nutrient requirements and nutrient uptake as low as possible when the genetically determined performance potential is exhausted. For this reason, the ration must have a certain minimum energy density (high-quality forage and appropriate concentrate supplements). Also, anything that prevents the cows from ingesting the maximum amount of dry matter should be avoided.

Ket-o-Vital bolus for metabolic support

Another important preventive measure is the specific support of the calving cow’s liver, rumen, and immune system. EW Nutrition’s Ket-o-Vital Bolus was explicitly designed to reduce the risk of ketosis. It contains fast-available glucogenic substances, positively influencing the cow’s energy metabolism. Another advantage the bolus offers is the slow release of the contained cobalt, selenium, niacin, and active yeast:

• Cobalt is a trace element important to form cobalamin, the so-called vitamin B12. It is essential for blood formation and the functioning of the nervous system.
• Selenium protects cells from oxidative damage and ensures an intact immune defense;
• Niacin is a B vitamin that intervenes in energy metabolism and prevents fatty liver syndrome;
• And active yeast supports rumen health, preventing rumen acidosis and increasing feed intake.

The application of the Ket-o-Vital Bolus is profitable and straightforward. Only one bolus per application is required.

Ketosis control: be one step ahead

High-performance dairy cows are at risk of ketosis, which results in involuntary culling, poor health, and performance losses. Advanced feed management practices combined with the targeted use of the Ket-o-Vital bolus offer a solution for preventing this debilitating disease. The bolus protects the cows from clinical and subclinical ketosis, reduces metabolic disorders, increases appetite, and improves health – leading to a quick recovery and ensuring profitable production.

References

Vicente, Fernando, María Luisa Rodríguez, Adela Martínez-Fernández, Ana Soldado, Alejandro Argamentería, Mario Peláez, and Begoña de la Roza-Delgado. “Subclinical ketosis on dairy cows in transition period in farms with contrasting butyric acid contents in silages.” The Scientific World Journal 2014 (November 25, 2014): 1–4. https://doi.org/10.1155/2014/279614.

Andersson, L. “Concentrations of blood and milk ketone bodies, blood isopropanol and plasma glucose in dairy cows in relation to the degree of hyperketonaemia and clinical signs*.” Zentralblatt für Veterinärmedizin Reihe A 31, no. 1-10 (1984): 683–93. https://doi.org/10.1111/j.1439-0442.1984.tb01327.x.

Robinson, A. M., and D. H. Williamson. “Effects of acetoacetate administration on glucose metabolism in mammary gland of fed lactating rats.” Biochemical Journal 164, no. 3 (1977): 749–52. https://doi.org/10.1042/bj1640749.

By Si-Trung Tran, SEAP Regional Technical Manager, EW Nutrition

Marisabel Caballero, Global Technical Manager Poultry, EW Nutrition, and
Inge Heinzl, Editor, EW Nutrition

Mycotoxins are secondary metabolites of fungi, commonly found as contaminants in agricultural products. In some cases, these compounds are used in medicine or industry, such as penicillin and patulin. In most cases, however, they are considered xenobiotics that are toxic to animals and humans, causing the disease collectively known as mycotoxicosis. The adverse effects of mycotoxins on human and animal health have been documented in many publications. Aflatoxins (AFs) and deoxynivalenol (DON, vomitoxin) are amongst the most critical mycotoxins affecting milk production and -quality.

Aflatoxins do not only affect cows

Aflatoxins (AFs) are highly oxygenated, heterocyclic difuranocoumarin compounds produced by Aspergillus flavus and Aspergillus parasiticus. They colonize crops, including many staple foods and feed ingredients. Within a group of over 20 AFs and derivatives, aflatoxin B1 (AFB1), B2, G1, and G2 are the most important naturally occurring compounds.

Among the aflatoxins, AFB1 is the most widespread and most toxic to humans and animals. Concern about mycotoxin contamination in dairy products began in the 1960s with the first reported cases of contamination by aflatoxin M1 (AFM1), a metabolite of AFB1 formed in the liver of animals and excreted in the milk.

There is ample evidence that lactating cows exhibit a significant reduction in feed efficiency and milk yield within a few days of consuming aflatoxin-contaminated feed. At the cellular level, aflatoxins cause degranulation of endoplasmic membranes, loss of ribosomes from the endoplasmic reticulum, loss of nuclear chromatin material, and altered nuclear shapes. The liver, as the organ mainly dealing with the decontamination of the organism, gets damaged, and performance drops. Immune cells are also affected, reducing immune competence and vaccination success (Arnold and Gaskill, 2023).

DON reduces cows’ performance

Another mycotoxin that can also reduce milk quality and affect metabolic parameters, as well as the immune function of dairy cows, is DON. DON is produced by different fungi of the Fusarium genus that infect plants. DON synthesis is associated with rainy weather from crop flowering to harvest. Whitlow and co-workers (1994) reported the association between DON and poor performance in dairy herds and showed decreased milk production in dairy cows fed 2.5 mg DON/kg. However, in cows fed 6 to 12 mg DON/kg dry matter for 10 weeks, no DON or its metabolite DOM-1 residues were detected in milk.

Masked mycotoxins hide themselves during analysis

Plants suffering from fungal infestations and thus confronted with mycotoxins convert the harmful forms of mycotoxins into less harmful or harmless ones for themselves by conjugation to sulfates, organic acids, or sugars. Conjugated mycotoxins cannot always be detected by standard analytical methods. However, in animals, these forms can be released and transformed into parent compounds by enzymes and microorganisms in the gastrointestinal tract. Thus, the feed may show a concentration of mycotoxins that is still below the limit value, but in the animal, this concentration is suddenly much higher. In dairy cows, the release of free mycotoxins from conjugates during digestion may play an important role in understanding the silent effects of mycotoxins.

Fusarium toxins, in particular, frequently occur in this “masked form”. They represent a serious health risk for animals and humans.

Aflatoxins first show up in the milk

Masked aflatoxins may also play a role in total aflatoxin contamination of feed materials. Research has harvested little information on masked aflatoxins that may be present in TMR ingredients. So far, metabolites such as Aflatoxin M2 have been identified (Righetti, 2021), which may reappear later in milk as AFM1.

DON-related symptoms without DON?

Sometimes, animals show DON-related symptoms, with low levels detected in the feed or raw materials. Besides sampling errors, this enigma could be due to conjugated or masked DON, which is structurally altered DON bound to various compounds such as glucose, fatty acids, and amino acids. These compounds escape conventional feed analysis techniques because of their modified chemical properties but can be released as their toxic precursors after acid hydrolysis.

Masked DON was first described in 1984 by Young and co-workers, who found that the DON content of yeast-fermented foods was higher than that of the contaminated wheat flour used in their production. The most plausible reason for this apparent increase was that the toxin from the wheat had been converted to a compound other than DON, which could be converted back to DON under certain conditions. Since this report, there has been much interest in conjugated or masked DON.

Silage: masked DON is a challenge for dairy producers

Silage is an essential feed for dairy cows, supporting milk production. Most silage is made from corn and other grains. The whole green plant is used, which can be infected by fungi. Since infection of corn with Fusarium spp. and subsequent DON contamination is usually a major problem in the field worldwide, a relatively high occurrence of this toxin in silage must be expected. The ensiling process may reduce the amount of Fusarium fungi, but the DON formed before ensiling is very stable.

Silage samples show DON levels of concern

It is reasonable to assume that the DON biosynthesized by the fungi was metabolized by the plants to a new compound and thus masked DON. Under ensiling conditions, masked DON can be hydrolyzed, producing free DON again. Therefore, the level of free DON in the silage may not reflect the concentration measured in the plants before ensiling.

A study analyzed 50 silage samples from different farms in Ontario, Canada. Free DON was found in all samples, with levels ranging from 0.38 to 1.72 µg/g silage (unpublished data). Eighty-six percent of the samples contained DON at concentrations higher than 0.5 µg/g. Together with masked DON, it poses a potential threat to dairy cattle.

Specific hydrolysis conditions allow detection

However, in the natural ensiling process, the conditions for hydrolysis of masked DON are not optimal. The conditions that allow improved analysis of masked DON were recently described. This method detected masked DON in 32 of 50 silage samples (64%) along with free DON, increasing DON concentration by 23% in some cases (unpublished data).

Mycotoxins impact humans and animals

Aflatoxins, as well as DON, have adverse effects. In the case of DON, the impact on the animal is significant; in the case of aflatoxin, the possible long-term effects on humans are of higher relevance.

DON has more adverse effects on the animal and its performance

Unlike AFs, DON may be found in milk at low or trace concentrations. It is more associated with negative effects in the animal, altered rumen fermentation, and reduced flow of usable protein into the duodenum. For example, milk fat content was significantly reduced when cows were fed 6 µg DON/kg. However, the presence of DON also indicates that the feed probably contains other mycotoxins, such as zearalenone (ZEA) (estrogenic mycotoxin) and fusaric acid (pharmacologically active compound). All these mycotoxins may interact to cause symptoms that are different or more severe than expected, considering their individual effects. DON and related compounds also have immunosuppressive effects, resulting in increased somatic cell counts in milk. The U.S. FDA has established an action level for DON in wheat and wheat-derived products intended for cows, which is 5µg DON/g feed and the contaminated ingredient must not exceed 40% of the ration.

Aflatoxins decrease milk quality and pose a risk to humans

Aflatoxins are poorly degraded in the rumen, with aflatoxicol being the main metabolite that can be reconverted to AFB1. Most AFs are absorbed and extensively metabolized/hydrolyzed by enzymes found mainly in the liver. This results in the formation of AFM1, a part of which is conjugated to glucuronic acid and subsequently excreted in the bile. The other part enters the systemic circulation. It is either excreted in urine or milk. AFM1 appears within 12-48 hours after ingestion in cow’s milk. The excreted amount of AFM1 in milk from dairy cows usually ranges from 0.17% to 3% of the ingested AFB1. However, this carryover rate may vary from day to day and from one milking to the next in individual animals, as it is influenced by various factors, such as feeding regime, health status, individual biotransformation capacity, and, of course, by actual milk production. Carryover rates of up to 6.2% have been reported in high-yielding dairy cows producing up to 40 liters of milk per day.

In various experiments, AFM1 showed both carcinogenic and immunosuppressive effects. Accordingly, the International Agency for Research on Cancer (IARC) classified AFM1 as being in Group 2B and, thus, possibly carcinogenic in humans. The action level of 0.50 ppb and 0.05 ppb for AFM1 in milk is strictly adhered to by the U.S. Food and Drug Administration (FDA) and the European Food Safety Authority (EFSA), respectively.

Trials show the high adsorption capacity of Solis Max

A trial was conducted at an independent laboratory located in Spain. The evaluation of the performance of Solis Max was executed with the following inclusion levels:

• 0.10% equivalent to 1.0 kg of Solis Max per ton of feed
• 0.20% equivalent to 2.0 kg of Solis Max per ton of feed

A phosphate buffer solution at pH 7 was prepared for the trial to simulate rumen conditions. Each mycotoxin was tested separately, preparing solutions with known contamination (final concentration described in the table below). The contaminated solutions were divided into 3 parts: A positive control, 0.10% Solis Max and 0.20% Solis Max. All samples were incubated at 41°C for 1 hour, centrifuged, and the supernatant was analyzed for the mycotoxin added to determine the binding efficacy. All analyses were carried out by high-performance liquid chromatography (HPLC) with standard detectors.

Results:
The higher concentration of Solis max showed a higher adsorption rate for most mycotoxins. The high dose of Solis Max adsorbed 99% of the AFB1 contamination. In the case of DON, more than 70% was bound. For fumonisin B1 and zearalenone, Solis max showed excellent binding rates of 87.7% and 78.9%, respectively (Figure 1).

Figure 1: Solis Max showed a high binding capacity for the most relevant mycotoxins

Another trial was conducted at an independent laboratory serving the food and feed industry and located in Valladolid, Spain.

All tests were carried out as duplicates and using a standard liquid chromatography/mass spectrometry (LC/MS/MS) quantification. Interpretation and data analysis were carried out with the corresponding software. The used pH was 3.0, toxin concentrations and anti-mycotoxin agent application rates were set as follows (Table 1):

Table 1: Trial set-up testing the binding capacity of Solis Plus 2.0 for several mycotoxins in different contamination levels

Results:

Under acidic conditions (pH3), Solis Plus 2.0 effectively adsorbs the three tested mycotoxins at low and high levels. 100% binding of aflatoxin was achieved at a level of 150ppb and 98% at 1500ppb.In the case of fumonisin, 87% adsorption could be reached at 500ppb and 86 for a challenge with 5000ppb. 43% ochratoxin was adsorbed at the contamination level of 150ppb and 52% at 1500ppb.

Figure 2: The adsorption capacity of Solis Plus 2.0 for three different mycotoxins at two challenge levels

Mycotoxins – Effective risk management is of paramount importance

Although the rumen microflora may be responsible for conferring some mycotoxin resistance to ruminants compared to monogastric animals, there are still effects of mycotoxins on rumen fermentation and milk quality. In addition, masked mycotoxins in feed present an additional challenge for dairy farms because they are not readily detectable by standard analyses.

Feeding dairy cows with feed contaminated with mycotoxins can lead to a reduction in milk production. Milk quality may also deteriorate due to an adverse change in milk composition and mycotoxin residues, threatening the innocuousness of dairy products. Dairy farmers should therefore have feed tested regularly, consider masked mycotoxins, and take action. EW Nutrition’s MasterRisk tool provides a risk evaluation and corresponding recommendations for the use of products that mitigate the effects of mycotoxin contamination and, in the end, guarantee the safety of all of us.

by Inge Heinzl, Editor, and Marisabel Caballero, Global Technical Manager Poultry, EW Nutrition

What is your most crucial key feed performance indicator? We posted this question on an online professional platform and got more than 330 answers from professionals in the industry:

• 55 % of the respondents considered feed efficiency or feed conversion rate (FCR) the key indicator, and
• 35 % listed feed cost / kg produced as their most important indicator.

As feed represents 60-70 % of the total production costs, feed efficiency has a high impact on farm profitability – especially in times of high feed prices. Furthermore, for the meat industry, an optimal FCR is essential for competitiveness against other protein sources. Finally, for food economists, feed efficiency is connected to the optimal use of natural resources (Patience et al., 2015).

In this article, we explain the factors that influence feed efficiency and show options to support animals in optimally utilizing the feed – directly improving the profitability of your operation.

How to measure the feed conversion rate

The FCR shows how efficiently animals utilize their diet for maintenance and net production. In the case of fattening animals, it is meat production; for dairy cows, it is milk, and for layers, it is egg mass (kg) or a specific egg quantity.

The feed conversion rate is the mathematical relation obtained by dividing the amount of feed the animal consumed by the production it provided. The FCR is an index for the degree of feed utilization and shows the amount of feed needed by the animal to produce one kg of meat or egg mass, or, e.g., 10 eggs.

When comparing the FCRs of different groups of animals (e.g., from different houses or farms), some considerations are important:

• Feed consumed is not feed disappeared: Due to differences in feeder design and feeder adjustment, these two values can differ by 10-30 %. If FCR is calculated for economic purposes, the wasted feed must be included, as it causes costs and must be paid by the farmer. However, if FCR is calculated for scientific purposes (e.g., a performance trial), only the feed consumed should be included.
• Even if they are same-aged animals, individuals or groups differ in weight. Hence, they have different requirements for maintenance and also diverging quantity left for production. To avoid mistakes, weight-corrected FCR can be used.
• Nutrient utilization also depends on genotype and sex; thus, comparisons should consider these factors as they also influence weight gain and body composition (Patience et al., 2015).

Many factors influence the FCR

There are internal and external factors that influence feed efficiency. Internal factors originate in the animal and include genetics, age, body composition, and health status. In contrast, external factors include feed composition, processing, and quality, as well as the environment, welfare enrichment, and social aspects.

1. Species

Different species have different body sizes and physiology and, therefore, vary in their growth and maintenance requirements, impacting their efficiency in converting the feed.

Table 1: FCRs of different species

Compared to terrestrial animals, for example, fish and other aquatic animals have a low FCR. Being poikilothermic (animals whose body temperature ranges widely), they don’t spend energy on maintaining their body temperature if the surrounding water is within their optimal range. As they are physically supported by water, they also need less energy to work against gravity. Furthermore, carnivorous fish are offered highly digestible, nutrient-dense feed, which lowers their requirements in quantity. Omnivorous fish, on the other hand, also consume feedstuffs not provided by the producer (e.g., algae and krill), which is not considered in the calculation. Broilers are the only farm animals achieving a similar FCR.

2. Sex, age, and growth phase

Sex determines gene expression related to the regulation of feed intake and nutrient utilization. Males have a better feed conversion and put on more lean meat than females and castrates, which grow slower and easier run to fat.

Young animals have a fast growth rate and are offered nutritionally dense feed; hence, their FCR is lower. When the animal grows and gains weight, its energy requirement for maintenance increases and its growth rate and the feed nutrient density diminish.

Table 2: FCR during different life phases of pigs (based on Adam and Bütfering, 2009)

3. Health and gut health

Health decisively impacts feed conversion. An animal that is challenged by pathogens reduces its feed intake and, thus, decreases growth. Additionally, the body needs energy for the immune defense, the replacement of damaged or lost tissue, and heat production, in case of fever. As many immune components are rich in protein, this is the first nutrient to become limited.

An imbalance in the gut microbiome also impacts feed conversion: pathogenic microorganisms damage tissues, impair nutrient digestion and absorption, and their metabolic products are harmful. Furthermore, pathogens consume nutrients intended for the host and continue to proliferate at its expense.

4. Environment

The environment influences the way the animals spend their maintenance energy. According to Patience (2012), when a 70 kg pig is offered feed ad libitum, 34 % of the daily energy is used for maintenance. For each °C below the thermoneutral zone, an additional 1.5% of feed is needed for maintenance. In heat stress, each °C above the optimum range decreases feed intake by 2%. Therefore, the feed needs to be denser to fulfill the requirement, or the animal will lose weight. Social stress also influences animal performance, especially chronic stress situations. Keeping the animals in their thermoneutral zone and mitigating the impact of stressors means more energy can go towards performance.

5. Feed quantity, composition, and quality

The feed is the source of nutrients animals convert into production. So, it’s natural that its quality and composition, and the availability of nutrients affect feed efficiency.

Better FCR by increasing nutrient density and digestibility

Higher energy content in the diet and better protein digestibility improve FCR. Saldaña et al. (2015) assert that increasing the energy content of a diet led to a linear decrease of the average daily feed intake but improved FCR quadratically. The energy intake by itself remained equal. However, these diet improvements also increase costs, and a cost-benefit analysis should be conducted.

Feed form and particle size play an important role

Feed processing can improve nutrient utilization. Particle size, moisture content, and whether the feed is offered as pellets or mash influence feed efficiency. Reducing the particle size leads to a higher contact surface for digestive enzymes and higher digestibility. Chewning et al. (2012) tested the effect of particle size and feed form on FCR in broilers. They found that pellet diets enable better FCRs than mash diets – one reason is the lower feed waste, another one the smaller feed particle size in the pelleted feed. Comparing the different tested mash diets, the birds receiving feed with a particle size of 300 µm performed better than the birds getting a diet with 600 µm particles.

Richert and DeRouchey (2015) show that pigs’ feed efficiency improved by 1.3 % for every 100 µm when the particle size was reduced from 1000 µm to 400 µm , as the contact surface for the digestible enzymes increased. In weaning piglets of 28-42 days, the increase of particle size from 394 µm to 695 µm worsened FCR from 1.213 to 1.245 (Almeida et al., 2020). There is a flipside to smaller particle size as well, however: high quantities of fines in the diet can lead to stomach ulceration in pigs (Vukmirović et al., 2021).

Non-starch polysaccharide (NSP)-rich cereals worsen FCR

The carbohydrates in feedstuffs such as wheat, rye, and barley are not only energy suppliers, and if not managed well, the inclusion of these raw materials can deteriorate feed conversion. Vegetable structural substances such as cellulose, hemicellulose, or lignin (e.g., in bran), are difficult or even impossible to utilize as they lack the necessary enzymes.

Figure 1: Contents of arabinoxylan and ß-glucan in grain (according to Bach Knudsen, 1997)

Additionally, water-soluble NSPs (e.g., pectins, but also ß-glucans and pentosans) have a high water absorption capacity. These gel-forming properties increase the viscosity of the digesta. High viscosity reduces the passage rate and makes it more difficult for digestive enzymes and bile acids to come into contact with the feed components. Also, nutrients’ contact with the resorptive surface is reduced.

Another disadvantage of NSPs is their “cage effect.” The water-insoluble NSPs cellulose and hemicellulose trap nutrients such as proteins and digestible carbohydrates. Consequently, again, digestive enzymes cannot reach them, and they are not available to the organism.

Molds and mycotoxins impair feed quality, but also animal health

Molds reduce the nutrient and energy content of the feed and negatively impact feed efficiency. They are dependent on active water in the feed and feed ingredients. Compared to bacteria, which need about 0.9-0.97 Aw (active water), most molds require only 0.86 Aw.

Table 3: Comparison of 28-day-old chicks performance fed not-infested and molded corn

Besides spoiling raw materials and feed and reducing their nutritional value, molds also produce mycotoxins which negatively impact animal health, including gut health. They damage the intestinal villi and tight junctions, reducing the surface for nutrient absorption. In a trial with broiler chickens, Kolawole et al. (2020) showed a strong positive correlation between the FCR and the exposure to different mycotoxins. The increase in levels of toxin mixtures resulted in poor FCR. Williams and Blaney (1994) found similar results with growing pigs. The animals received diets containing 50 % and 75 % of corn with 11.5 mg nivalenol and 3 mg zearalenone per kg. The inclusion of contaminated corn led to a deterioration of feed efficiency from 2.45 (control) to 3.49 and 3.23.

Oxidation of fats also affects feed quality

DDGS (distiller’s dried grains with solubles), by-products of corn distillation processes, are often used as animal feed, especially for pigs. The starch content is depleted in the distillation process and thus removed. The fat, however, is concentrated, and DDGS reach a similar energy content as corn.

Pigs also receive fats from different sources (e.g., soybean or corn oil, restaurant grease, animal-vegetable blends), especially in summer. Due to heat, the animals eat less, so increasing energy density in the feed is a possibility to maintain the energy intake.  The high fat content, however, makes these feeds susceptible to oxidation at high temperatures.

The oxidation of feedstuffs manifests in the rancidity of fats, destruction of the fat-soluble vitamins A, D, and E, carotenoids (pigments), and amino acids, leading to a lower nutritional value of the feed.

Use adequate supplements to enhance FCR

The feed industry offers many solutions to improve the FCR for different species. They usually target the animal’s digestive health or maintain/enhance feed quality, including increasing nutrient availability.

1. Boost your animals’ gut health

Producers can improve gut health by preventing the overgrowth of harmful microorganisms and by mitigating the effects of harmful substances. For this purpose, two kinds of feed additives are particularly suitable: phytomolecules and products mitigating the impact of toxins and mycotoxins.

Phytomolecules help stabilize the balance of the microbiome

By preventing the proliferation of pathogens, phytomolecules help the animal in three ways:

1. They prevent pathogens from damaging the gut wall
2. They deter and mitigate inflammation
3. By inhibiting the overgrowth of pathogens, they promote better nutrient utilization by the animal

Only a healthy gut can optimally digest feed and absorb nutrients.

In trials testing the phytogenic Activo product range, supplemented animals showed the following FCR improvements compared to non-supplemented control groups (Figure 2).  Note that phy­tomolecules also have a digestive effect that contributes to the FCR improvements:

Figure 2: FCR improvements for animals receiving Activo

Products mitigating the adverse effects of toxins

Both mycotoxins and bacterial toxins negatively impact gut health. Mycotoxins are ingested with the feed; bacterial toxins appear when certain bacteria proliferate in the gut, e.g., gram-negative bacteria releasing LPS or Clostridium perfringens producing NetB and Alpha-toxin.

Products that mitigate the harmful effects of toxins help to protect gut health and maintain an optimal feed efficiency, as shown with a trial conducted with Mastersorb Gold:

Table 4: Trial design, the impact of Mastersorb Gold on broilers challenged with zearalenone and DON-contaminated feed

Figure 3: Average FCR for broilers, with or without zearalenone and DON challenge, with or without Mastersorb Gold supplementation

2. Improve nutrient utilization

Maximum use of the nutrients contained in the feed can be obtained with the help of feed additives that promote digestion. Targeting the animal, selected phytomolecules are used for their digestive properties. Focusing on the feed, specific enzymes can unlock nutrients and thus improve feed efficiency.

Phytomolecules support the animal’s digestive system

Phytomolecules promote optimal digestion and absorption of nutrients by stimulating the secretion of digestive juices, such as saliva or bile, enhancing enzyme activity, and favoring good GIT motility (Platel and Srinivasan, 2004). FCR improvements thanks to the use of a phy­tomolecules-based product (Activo) are shown in figure 2.

Enzymes release more nutrients from feed

Enzymes can degrade arabinoxylans, for example. Arabinoxylans are the most common NSP fraction in all cereals – and are undigestible for monogastric animals. Enzymes can make these substances available for animals, allowing for complete nutrient utilization.  Additionally, nutrients trapped due to the cage effect are released, altogether increasing the energy content of the diet and improving FCR.

3. Be proactive about preserving feed quality

The quality of feed can deteriorate, for instance, when nutrients oxidize, or mold infestation occurs. Oxidation by-products promote oxidative stress in the intestine and may lead to tissue damage. Molds, in turn, take advantage of the nutrients contained in the feed and produce mycotoxins. Both cases illustrate the importance of preventing feed quality issues. Feed additives such as antioxidants and mold inhibitors mitigate these risks.

Antioxidants prevent feed oxidation

Antioxidants scavenge free radicals and protect the feed from spoilage. In animals, they mitigate the adverse effects of oxidative stress. Antioxidants in pig nutrition can stabilize DDGS and other fatty ingredients in the feed, maintaining nutrient integrity and availability. Figure 4 shows the FCR improvement that a producer in the US obtained when using the antioxidant product Santoquin in pork finisher diets containing 30% DDGS.

Figure 4: FCR improvement in pigs receiving Santoquin (trial with a Midwest pork producer)

In DDGS-free diets, which are more common in poultry production, antioxidants also help optimize FCR, as shown by the results of a comprehensive broiler field study in 2015 (figure 5).

Figure 5: FCR in broilers receiving Santoquin, compared to a non-supplemented control group

Inhibiting molds and keeping feed moisture

To round off the topic of feed quality preservation, one should consider mold inhibitors, which also play an essential role. Used at the feed mill, these products blend two types of ingredients with their different modes of action: surfactants and organic acids. Surfactants bind active water so that the moisture of the feed persists, but fungi cannot survive. Organic acids, on the other hand, have anti-fungal properties, directly acting against molds. Both actions together prevent the reduction of energy in the feed, keeping feed efficiency at optimal levels.

Conclusion

The improvement of feed efficiency ranks as one of the most, if not the most, critical measures to cope with rising feed costs. By achieving optimal nutrient utilization, producers can make the most out of the available raw materials.

The feed industry offers diverse solutions to support animal producers in optimizing feed efficiency. Improving gut health, mitigating the negative impact of harmful substances, and maintaining feed quality are crucial steps to achieving the best possible FCR and, hence, cost-effective animal production.

References

Adam, F., and L. Bütfering. “Wann Müssen Meine Schweine an Den Haken?” top agrar. top agrar online, October 1, 2009. https://www.topagrar.com/schwein/aus-dem-heft/wann-muessen-meineschweine-an-den-haken-9685161.html.

Almeida, Leopoldo Malcorra, Vitor Augusto Zavelinski, Katiucia Cristine Sonálio, Kariny Fonseca da Silva, Keysuke Muramatsu, and Alex Maiorka. “Effect of Feed Particle Size in Pelleted Diets on Growth Performance and Digestibility of Weaning Piglets.” Livestock Science 244 (2021). https://doi.org/10.1016/j.livsci.2020.104364.

Chewning, C.G., C.R. Stark, and J. Brake. “Effects of Particle Size and Feed Form on Broiler Performance.” Journal of Applied Poultry Research 21, no. 4 (2012): 830–37. https://doi.org/10.3382/japr.2012-00553.

Gaines, A. M., B. A. Peerson, and O. F. Mendoza. “Herd Management Factors That Influence Whole Feed Efficiency.” Essay. In Feed Efficiency in Swine, edited by J. Patience, 15–39. Wageningen Academic, 2012.

Kolawole, Oluwatobi, Abigail Graham, Caroline Donaldson, Bronagh Owens, Wilfred A. Abia, Julie Meneely, Michael J. Alcorn, Lisa Connolly, and Christopher T. Elliott. “Low Doses of Mycotoxin Mixtures below EU Regulatory Limits Can Negatively Affect the Performance of Broiler Chickens: A Longitudinal Study.” Toxins 12, no. 7 (2020): 433. https://doi.org/10.3390/toxins12070433.

Patience, J. F. “The Influence of Dietary Energy on Feed Efficiency in Grow-Finish Swine.” Essay. In In Feed Efficiency in Swine, edited by J. Patience, 15–39. Wageningen Academic, 2012.

Patience, John F., Mariana C. Rossoni-Serão, and Néstor A. Gutiérrez. “A Review of Feed Efficiency in Swine: Biology and Application.” Journal of Animal Science and Biotechnology 6, no. 1 (2015). https://doi.org/10.1186/s40104-015-0031-2.

Platel, K., and K. Srinivasan. “Digestive Stimulant Action of Spices: A Myth or Reality?” Indian J Med Res, pp 167-179 119 (May 2004): 167–79. http://www.ncbi.nlm.nih.gov/pubmed/15218978

Richert, B. T., and J. M. DeRouchey. “Swine Feed Processing and Manufacturing.” Pork Information Gateway, September 14, 2015. https://porkgateway.org/resource/swine-feed-processing-and-manufacturing/.

Saldaña, B., P. Guzmán, L. Cámara, J. García, and G.G. Mateos. “Feed Form and Energy Concentration of the Diet Affect Growth Performance and Digestive Tract Traits of Brown-Egg Laying Pullets from Hatching to 17 Weeks of Age.” Poultry Science 94, no. 8 (2015): 1879–93. https://doi.org/10.3382/ps/pev145.

Vukmirović, Đuro, Radmilo Čolović, Slađana Rakita, Tea Brlek, Olivera Đuragić, and David Solà-Oriol. “Importance of Feed Structure (Particle Size) and Feed Form (Mash vs. Pellets) in Pig Nutrition – A Review.” Animal Feed Science and Technology 233 (2017): 133–44. https://doi.org/10.1016/j.anifeedsci.2017.06.016.

By Dr. Inge Heinzl, Editor, EW Nutrition 

For a long time now, IgY technology has been used to provide clear benefits in diagnostics, human medicine, and animal production. To give you a deeper insight into this topic, in the following, we will show you some steps of production, the benefits, and the applications of IgY.

IgY – what is it?

A short time later, Klemperer (1892) documented that the serum antibodies were also transferred into the egg. For this purpose, he did a similar trial with hens but collected the eggs. He fed mice a solution containing the egg yolk, and afterward, he infected them with tetanus. All mice with a higher dosage of egg yolk remained healthy, the others receiving a low dosage or no egg yolk died.

IgY production is a non-invasive and highly effective process

The “usual” production of antibodies in mammals includes pain and stress-causing procedures such as immunization, bleeding, and sacrifice. The only stress factor in producing egg antibodies is the hyper-immunization with the pathogen or parts of it; the rest -collecting the eggs- is non-invasive (Ikemori et al., 1993). The European Centre for the Validation of Alternative Methods (ECVAM) ), one of Europe’s health and consumer protection institutes, strongly recommends egg immunoglobulins as an alternative to mammalian antibodies (Schade et al., 1996).

IgY production is also advantageous in terms of quantitative and qualitative output. Usually, one egg (with 15 mL of yolk) contains about 100-150 mg IgY  (Pereira et al., 2019). Assuming that a hen lays about 300 eggs per year, one bird can produce between 30 and 45 g IgY in this period. After the isolation of the IgY from the egg yolk and the extraction from the remaining proteins, a final purification step that includes chromatography could achieve IgY with >90 % purity (Morgan et al., 2021).

Hyperimmunized hens provide more effective IgY

The targeted confrontation of the animal with specific pathogens or antigens leads to the production of specific antibodies. In a field trial with piglets, Kellner et al. (1994) compared three groups of piglets suffering from diarrhea on day 1 of the test. One group received egg powder originating from hens hyperimmunized with diarrhea-causing pathogens, the second group egg powder from regular eggs, and the third didn’t receive any egg powder. The following results they achieved in one of two farms. The trial shows that, after applying egg powder with specific antibodies, the animals completely recovered within three days. In the group receiving egg powder of regular eggs, still, 9.1 % suffered from severe diarrhea and in the control group without any egg powder, only 27.3 % recovered.

Figure 1: Comparison of eggs originating from regular and hyperimmunized hens

Preconditions for and benefits of industrially produced IgY

A process must meet specific requirements to be suitable for industrial production. In the case of IgY production, the crucial preconditions are that…

• hens produce antibodies also against pathogens non-specific to them
• the antibodies produced and transferred to the egg also are effective in mammals (Yokoyama et al., 1993)
• due to their phylogenetic distance from mammals, hens can produce antibodies even against structurally highly conserved proteins, which is not always possible in rabbits, guinea pigs, and goats (Gassman and Hübscher, 1992).

Industrially produced IgY can target specific pathogens, e.g., enteric bacteria or viruses, respiratory pathogens, SARS-COV-2, etc. As the antibodies act not only in birds but also in other animals, such as mammals including humans, they can be used to prevent disease or support persons/animals in the case of illness. If the technique is mastered, the production of IgY is not complicated. IgY is safe for animals and humans.

Concerning the economic benefits of IgY production, it can be said that it is a cost-effective method due to the high concentration of IgY in the egg yolk and the relatively simple process of the purification of the antibodies. Additionally, feeding and handling are easier and more cost-effective for hens than for many other animals.

Not all IgY products are the same

There are different methods of IgY production. One possibility is to hyperimmunize the hens simultaneously with multiple antigens. This method seems to be convenient but does not deliver standardized products concerning the content of immunoglobulins.

The other possibility is the immunization of different groups of hens, each with one antigen (e.g., Rotavirus, Salmonella, E. coli). The content of immunoglobulins is determined, and the different egg powders are mixed. The result is an IgY product with standardized amounts of specific immunoglobulins.

Where can we use IgY?

There are different application areas for IgY or IgY products. In human medicine, egg immunoglobulins can be used against the toxin of rattlesnakes or scorpions, or Streptococcus mutans bacteria, causing dental caries (Gassmann and Hübscher, 1992) Egg immunoglobulins are important for diagnostic tests such as radioimmunoassay (RIA) and enzyme-linked immunoassay (ELISA).

A further application area is animal nutrition. Young animals, such as calves or piglets, but also young dogs or cats, are born with immature immune systems. If they, additionally, are deprived of maternal colostrum in adequate quantity and/or quality, they suffer from immunity gaps during their first weeks of life and are susceptible to pathogens in their environment.

Antibiotics have been used prophylactically for a long time to protect young animals in this critical phase. With increasing antibiotic resistance, this procedure is not allowed anymore.

Products based on egg immunoglobulins against enteric pathogens, e.g., support young animals against newborn or weaning diarrhea (e.g., Yokoyama et al., 1992; Ikemori et al., 1992; Ikemori et al., 1997, Yokoyama et al., 1998).

IgY – a fascinating technology that should be better recognized

IgY technology is an animal-friendly technology with high output. Its various applications make IgY a helpful tool for human medicine as well as animal production. To get the best results, attention must be paid to quality, meaning, a.o. the standardization of the products.

IgY is an optimal tool to help young animals such as calves and piglets cope with pathogenic challenges in early life. Consequently, IgY technology enables us to limit (preventive) antimicrobial use in critical periods of animal rearing and, therefore, reduce antimicrobial resistance.

References:

Gassmann, M., and U. Hübscher. “Use of Polyclonal Antibodies from Egg Yolk of Immunised Chickens .” ALTEX – Alternatives to animal experimentation 9, no. 1 (1992): 5–14.

Ikemori, Yutaka, Masahiko Kuroki, Robert C. Peralta, Hideaki Yokoyama, and Yoshikatsu Kodama. “Protection of Neonatal Calves against Fatal Enteric Colibacillosis by Administration of Egg Yolk Powder from Hens Immunized with K99-Piliated Enterotoxigenic Escherichia Coli.” Amer. J. Vet. Res. 53, no. 11 (1992): 2005–8. https://doi.org/PMID: 1466492.

Ikemori, Yutaka, Masashi Ohta, Kouji Umeda, Faustino C. Icatlo, Masahiko Kuroki, Hideaki Yokoyama, and Yoshikatsu Kodama. “Passive Protection of Neonatal Calves against Bovine Coronavirus-Induced Diarrhea by Administration of Egg Yolk or Colostrum Antibody Powder.” Veterinary Microbiology 58, no. 2-4 (1997): 105–11. https://doi.org/10.1016/s0378-1135(97)00144-2.

Ikemori, Yutaka, Robert C. Peralta, Masahiko Kuroki, Hideaki Yokoyama, and Yoshikatsu Kodama. “Research Note: Avidity of Chicken Yolk Antibodies to Enterotoxigenic Escherichia Coli Fimbriae.” Poultry Science 72, no. 12 (1993): 2361–65. https://doi.org/10.3382/ps.0722361.

Kellner, J., M.H. Erhard, M. Renner, and U. Lösch. “Therapeutischer Einsatz Von Spezifischen Eiantikörpern Bei Saugferkeldurchfall – Ein Feldversuch.” Tierärztliche Umschau 49, no. 1 (January 1, 1994): 31–34.

Klemperer, Felix. “Ueber Natürliche Immunität Und Ihre Verwerthung Für Die Immunisirungstherapie.” Archiv für Experimentelle Pathologie und Pharmakologie 31, no. 4-5 (1893): 356–82. https://doi.org/10.1007/bf01832882.

Pereira, E.P.V., M.F. van Tilburg, E.O.P.T. Florean, and M.I.F. Guedes. “Egg Yolk Antibodies (Igy) and Their Applications in Human and Veterinary Health: A Review.” International Immunopharmacology 73 (2019): 293–303. https://doi.org/10.1016/j.intimp.2019.05.015.

Schade, R., C. Staak, C. Hendriksen, M. Erhard, H. Hugl, G. Koch, A. Larsson, et al. “The Production of Avian (Egg Yolk) Antibodies: IgY,” 1996. https://www.researchgate.net/publication/281466059_The_production_of_avian_egg_yolk_antibodies_IgY_The_report_and_recommendations_of_ECVAM_workshop_21.

Schade, R., C. Staak, C. Hendriksen, M. Erhard, H. Hugl, G. Koch, A. Larsson, et al. “The Production of Avian (Egg Yolk) Antibodies: IgY. The Report and Recommendations of ECVAM Workshop 21.” ATLA (Alternatives to Laboratory Animals) 24 (1996): 925–34. https://doi.org/https://www.researchgate.net/publication/281466059_The_production_of_avian_egg_yolk_antibodies_IgY_The_report_and_recommendations_of_ECVAM_workshop_21.

Yokoyama, H, R C Peralta, R Diaz, S Sendo, Y Ikemori, and Y Kodama. “Passive Protective Effect of Chicken Egg Yolk Immunoglobulins against Experimental Enterotoxigenic Escherichia Coli Infection in Neonatal Piglets.” Infection and Immunity 60, no. 3 (1992): 998–1007. https://doi.org/10.1128/iai.60.3.998-1007.1992.

Yokoyama, Hideaki, Robert C. Peralta, Kouji Umeda, Tomomi Hashi, Faustino C. Icatlo, Masahiko Kuroki, Yutaka Ikemori, and Yoshikatsu Kodama. “Prevention of Fatal Salmonelosis in Neonatal Calves, Using Orally Administered Chicken Egg Yolk Salmonella-Specific Antibodies.” Amer. J. Vet. Res. 59, no. 4 (1998): 416–20. https://doi.org/PMID: 9563623.

Yokoyama, Hideaki, Robert C. Peralta, Sadako Sendo, Yutaka Ikemori, and Yoshikatsu Kodama. “Detection of Passage and Absorption of Chicken Egg Yolk Immunoglobulins in the Gastrointestinal Tract of Pigs by Use of Enzyme-Linked Immunosorbent Assay and Fluorescent Antibody Testing.” American Journal of Veterinary Research 54, no. 6 (1993): 867–72. https://doi.org/PMID: 8323054.

Zhang, Xiao-Ying, Ricardo S. Vieira-Pires, Patricia M. Morgan, Rüdiger Schade, Xiao-Ying Zhang, Rao Wu, Shikun Ge, and Álvaro Ferreira Júnior. “Immunization of Hens.” Essay. In IGY-Technology: Production and Application of Egg Yolk Antibodies. Basic Knowledge for a Successful Practice., 116–34. Cham, Switzerland: Springer Nature, 2021.

Zhang, Xiao-Ying, Ricardo S. Vieira-Pires, Patricia M. Morgan, Schade Rüdiger, Patricia M. Morgan, Marga G. Freire, Ana Paula M. Tavares, Antonysamy Michael, and Xiao-Ying Zhang. “Extraction and Purification of IgY .” Essay. In IGY-Technology: Basic Knowledge for a Successful Practice, 135–60. Cham: Springer International Publishing AG, 2021.

Zhang, Xiao-Ying, Ricardo S. Vieira-Pires, Patricia M. Morgan, Schade Rüdiger, Patricia M. Morgan, Xiao-Ying Zhang, Antonysamy Michael, Ana Paula M. Tavares, and Marga G. Freire. “Extraction and Purification of IgY (Chapter 11).” Essay. In IGY-Technology: Basic Knowledge for a Successful Practice, 135–60. Cham: Springer International Publishing AG, 2021.

Diarrhea is a protective measure of the organism 

In general, diarrhea is characterized by more liquid being secreted than being resorbed. However, diarrhea is not a disease but only a symptom. Diarrhea has a protective function for the organism: the higher liquid volume in the gut increases motility, and pathogens and toxins are more readily excreted. 

Diarrhea can occur for several reasons. It can result from inadequate nutrition but also the reaction to an infection by pathogens such as bacteria, viruses, and protozoa.  

Where does the fluid come from? 

Depending on how the accumulation of fluid in the gut is generated, there are different kinds of diarrhea:  

• In the case of secretory diarrhea, as the name says, the fluid accumulation comes from an increased secretion into the gut caused by toxins activating enzyme systems. The gut mucosa can no longer resorb this higher amount of liquid.  
• When the animals suffer from malabsorptive diarrhea due to destroyed enterocytes and shortened villi, the enzyme activity and absorption capacity are reduced. Less liquid can be absorbed and has to be excreted via the gut.  
• When inflammatory diarrhea occurs, the gut mucosa is damaged. Higher amounts of mucus, protein, and blood are released into the gut lumen.  

Due to multiple infections, diarrhea often is a mixture of different forms. 

Multiple causes can be responsible 

For the occurrence of diarrhea, different causers can be a possibility. Besides infectious pathogens, also the feed must be considered.  

1. Bacteria often produce toxins

E. coli is a common agent of the gut microflora and in general it is harmless. However, E. coli can also be the cause of different types of diarrhea, depending on the virulence factors. Virulence factors of E.coli are, e.g., fimbria for the attachment to intestinal receptors or the ability to produce toxins influencing the secretion of ions and liquids. Example: enterotoxic E. coli (ETEC) F5 and F41 occurring during the first days of life. 

In general, Salmonella plays a secondary role in calf diarrhea. Of the Salmonella serovars, mainly S. Typhimurium and S. Dublin are found in calves. Salmonella produces enterotoxins that attack the intestinal wall.

Clostridia infections belong to the most expensive ones in cattle farming globally. In herbivores, clostridia are part of the normal flora of the gastrointestinal tract; only a few types can cause severe disease. In calves, the necrotizing toxin-producing Clostridium perfringens can lead to enterotoxaemia manifesting in acute bloody diarrhea.

2. Viruses cause lesions in the gut 

Rotavirus, which occurs mainly during the 5th -15th day of life, is the most common viral pathogen causing diarrhea in calves and lambs. If more enterocytes are destroyed than regenerated by the organism, the resorption surface in the gut decreases. With increasing age, animals develop immunity against this pathogen. 

Coronavirus usually attacks calves at the age of 5 – 21 days (mainly correlated with the decreasing concentration of antibodies in maternal milk). They cause similar lesions in the intestine as rotavirus but additionally lead to necrosis of the crypts in the large intestine. The digestive and absorptive function is lost, resulting in reduced reabsorption of fluids. 3 to 20 % of diarrhea arising in calves is caused by Coronavirus.  

3. Protozoa can lead to malabsorptive diarrhea 

Cryptosporidium parvum (mainly 1-2 weeks after birth) belongs to the coccidia and is presumed to be the most common pathogen to cause diarrhea (prevalence up to more than 60 %) in calves. Cryptosporidium is transmitted via oocysts found in feces and on the farm equipment. Cryptosporidia destroy the microvilli in the gut, the function of the gut mucosa is reduced, the resorption area decreases. Consequence: loss of enzyme activity and, therefore, an insufficient breakdown of sugar and protein, resulting in malabsorption.  

4. Calves need their special feed

In general, raw materials which cannot be well digested by the calf (mainly soya products, often used in milk replacers) or which cause allergy can cause diarrhea in calves. Also, antibiotics can lead to an imbalance of the intestinal flora, destruction of the villi, and malabsorptive diarrhea. 

Trial shows promising results in the field 

A field study with the egg powder-based product Globigen Dia Stop was conducted with 16 calves suffering from diarrhea. They were fed twice daily 50 g of Globigen Dia Stop stirred into the milk replacer.  

Result (fig. 1): already one day after the first application of Globigen Dia Stop, 50 % of the calves recovered. After seven days, all calves overcame diarrhea. On average, one calf needed 2,4 treatments to show a full recovery from diarrhea (≙ 1,25 treatment days). 

Egg immunoglobulins support against diarrhea 

Egg immunoglobulins can effectively support calves in their fight against diarrhea. Immunoglobulins can act against bacteria, parasites, and viruses, not only against bacteria as antibiotics do. With egg immunoglobulin-based products, the farmer has a tool at his disposal that is easy to handle and does not require a withdrawal period. As there is no danger of the generation of resistance, these products are ideal for reducing the use of antibiotics in animal production. 

Article initially published in NutriNews

Undersupply with immunoglobulins lowers later performance

In 2015, the Ludwig Maximilian University of Munich examined the immunoglobulin supply of 1,242 newborn calves. This study showed that more than half of the calves were undersupplied: 23% severely (<5mg IgG / ml blood serum) and 36% slightly undersupplied (5-10mg IgG/ml). The supply situation was only satisfactory in 41% of the calves (> 10 mg IgG/ml).

Undersupply results in higher susceptibility to disease, higher mortality, and lower daily weight gain. This entails increased rearing costs. Besides, only healthy calves can achieve their full potential as adult animals. For example, when a calf experiences even mild diarrhea, it is expected to produce 344 kg less milk the first lactation (Welsch, 2016). Possible causes of diarrhea are infectious factors such as viruses (rota, coronaviruses), bacteria (E. coli) and parasites (cryptosporidia), but also non-infectious factors such as poor husbandry and feeding errors.

Survey confirms: Calves lack sufficient amounts of immunoglobulins

In December 2020, EW Nutrition conducted a telephone survey among 55 dairy cattle consultants and veterinarians from Spain, Germany, France, Poland, and Great Britain to review calves’ passive immunity.

This survey confirmed that calves lack sufficient amounts of immunoglobulins: 69.1% of respondents thought that calves were undersupplied. 76.4% of them saw a clear connection between early-occurring diarrheal diseases and calves’ insufficient passive immunity. Respondents came to these conclusions even though more than half of them thought that colostrum quality had not deteriorated during the last years (56.4%).

Immunoglobulins from the egg help calves against diarrhea

Egg immunoglobulins offer one way to support calves in case of diarrhea. Chickens form antibodies (IgY from “Immunoglobulins in Yolk”) against all disease pathogens they encounter and release them into the egg as an immunological starting aid for the chick. It does not matter whether the disease is relevant to poultry or cattle.

These antibodies can be used to improve poor-quality colostrum or to support the calf during acute diarrhea. Studies show that egg immunoglobulins act in calves’ intestines, where they can bind and block diarrhea pathogens (Ikemori et al., 1992).

IgY add value to colostrum

A feeding study with 39 female newborn calves took place on an 800-cow dairy farm in Brandenburg, Eastern Germany. The objective was to examine whether the IgY-containing complementary feed Globigen Colostrum effectively supports calves during the first critical period. For the experiment, all calves were given high-quality colostrum (4L within 2 hours after birth). During the first 5 days of life, the 19 calves in the test group additionally received 100g of the complimentary feed stirred into the colostrum (day 1) or the mixed colostrum (days 2 – 5).

Result: The daily weight gain for the test group was 18% higher than in the control group (+ 151g). This resulted in 13% higher weaning weights (see above).

Three calves in the control group had mild diarrhea; in the test group, only one calf. However, antibiotics did not have to be used to treat the diarrhea.

IgY to reduce neonatal diarrhea

The IgY-based product Globigen Calf Paste was tested on two dairy farms in Russia. These trials focused on reducing neonatal diarrhea, which occurs in the first 2 to 3 weeks of life. The product, a 30ml oral syringe with a dosing ring, was administered at a rate of 10ml per day for the first three days of life. On the first farm in the Belgorod region, the trial and control groups consisted of 11 calves each. On the 10^th day of life, the diarrhea incidence per group was checked: while 73% of the calves in the control group had diarrhea, requiring antibiotics, only 1 calf of the trial group had diarrhea, and no antibiotic treatment was needed. On the second farm in the Moscow region, where the groups encompassed 20 calves each and observations took place on the 5th day of life, results were similar: 75% of the control animals suffered from diarrhea, but just 3 calves in the trial group showed signs of diarrhea.

IgY support calves with acute diarrhea

In another trial, carried out with 38 calves on a dairy farm with 550 cows in North Rhine-Westphalia, Western Germany, the dietetic feed supplement Globigen Dia Stop was tested. This product is also based on egg immunoglobulins.

Only calves showing newborn diarrhea were used for this experiment. When diarrhea occurred, the 21 calves in the test group received 50g Globigen Dia Stop twice a day in addition to their milk drink. The diseased calves in the control group (17 calves) were given a rehydration solution, stirred into water, twice a day.

If the diarrhea could not be stopped after four days in the calves of either group, the animals were treated by a veterinarian.

Result: In the test group, 100g (+ 20%) and thus significantly higher daily gains were achieved, which led to a 9% higher weaning weight. Furthermore, over 40% fewer calves had to be treated with antibiotics in the Globigen Dia Stop group than in the control group. (see above)

Conclusion: Egg immunoglobulins support gut health

The results of these studies indicate that the administration of egg antibodies (IgY) to calves supports intestinal health and has a positive effect on calves’ performance. Globigen supplementation can likely reduce diarrhea incidence and severity, especially in the critical first phase of the calves’ life – thus ensuring high performance in the long term.

Amongst naturally occurring mycotoxins, the five most important ones are aflatoxin, ochratoxin, deoxynivalenol, zearalenone, and fumonisin. Their incidence varies with the different climates, the prevalence of plant cultures, the occurrence of pests, and the handling of harvest and storage. Worldwide, farmers faced various and sometimes extremely high mycotoxin contamination in their feed materials in 2021. In the following, we show the major challenges in five main regions.

Asia faced high aflatoxin contamination

In Asia, high temperatures and humidity favor Aspergillus growth in grains. As a result, 95 % of the samples in South Asia and three-quarters of the samples in the China and the SEAP region (Indonesia, Philippines, Vietnam) showed aflatoxin contamination. The average contamination being higher than the threshold for all farm animals represents an increased risk for their health and performance.
In China and the SEAP region, also DON and T-2 were highly prevalent. Showing an incidence of more than 60%, they pose a severe risk when combined with aflatoxin.

Fumonisins afflicted the LATAM region

In Mexico, Central and South America, fumonisin contamination prevailed with an incidence of almost 90% at average levels that can be considered risky for swine and dairy. Together with incidence levels of around 60% found for DON and T2, fumonisin may act synergically in the animals, raising the risk for health and performance.
The Fusarium species linked to these mycotoxin contaminations occur in the grains on the field. Amongst others, insect damage, droughts during growing, and rain at silking favor their development.

Trichothecenes prevailed in North America

Contamination with trichothecenes (DON and T2) is the rule in the United States. The interaction of these mycotoxins is at least additive. The damage they cause to the gut opens the door to dysbiosis and disease, decreasing performance and profitability.
Also in this case, the responsible molds for the contamination are Fusarium species that develop when grains are in the field. As with fumonisins, the molds are favored by insect damage, moderate to warm temperatures and rainfall.

Fusarium toxins contaminated grain in the MEA region

Fusarium toxins such as Fumonisin, DON, and T2 prevail in the region of Egypt, Jordan, and South Africa. In combination, these mycotoxins have additive effects at the intestinal level, which increases the risk of dysbiosis in poultry.

A challenging year with long-term repercussions

Since mycotoxin contamination affects animal health, measures must be taken to provide the best protection. Besides improving agricultural practices in the field, smart in-feed solutions and mold inhibitors can be used in stored grain. These measures help producers preserve feed quality after a troubled year for crops around the world.

Singapore – November 1, 2021 – EW Nutrition has successfully passed an external audit conducted by the Cattle Council of Australia (CCA) and achieved Pasturefed Cattle Assurance System (PCAS) certification for three products: Activo Premium, Mastersorb Gold, and Prote-N. 

The PCAS is a certification program that enables grassfed cattle producers to prove claims relating to pasturefed or grassfed production methods. EW Nutrition also achieved two optional modules under the PCAS Standards relating to the freedom from antibiotics and hormone growth promotants (HGPs). As a certified supplier, EW Nutrition is able to provide feed products to the industry to support pasturefed or grassfed production methods. 

“We are pleased to receive the certification for our solution offerings in Australia. The qualification of these products is a testament of our commitment to work together with the industry to mitigate the impact of antimicrobial resistance. By pursuing our objectives in animal nutrition, our work contributes to increasing the efficacy of human healthcare.” said David Sherwood, Commercial Director Oceania with EW Nutrition. 

The PCAS certified products are: 

Activo Premium
Activo Premium contains standardized amounts of selected phytomolecules. 

Mastersorb Gold
Mastersorb Gold is part of EW Nutrition’s Toxin Risk Management Program, which also includes services, on-site advice, and expert consultancy. 

Prote-N
Prote-N is a slow-release source of nonprotein nitrogen (NPN). 

About EW Nutrition 

EW Nutrition offers animal nutrition solutions to the feed industry. The company’s focus is on gut health, supported by other product lines. EW Nutrition researches, develops, produces, sells and services most of the products it commercializes. In 50 countries, key accounts are served directly by EW Nutrition’s own personnel.  

For more information, please visit https://ew-nutrition.com. 
For more information about PCAS, please visit https://pcaspasturefed.com.au/  

Contact: 

Zack Mai
Marketing Manager, EW Nutrition South East Asia/Pacific
Phone no.: +65 6735 0038
Email: zack.mai@ew-nutrition.com 

by Technical Team, EW Nutrition

The world demand for milk has seen a sharp rise. Today, we have just over 1 billion dairy cows in the world producing about 1.6 billion tons of milk per year. However, OECD and FAO estimate that numbers will rise up to 1.5 billion dairy cows in 2028, for a total milk production of 2 billion tons . This increase will come at a tremendous cost in terms of global warming: Each day, dairy cows can produce 250 to 500 litres of methane, a powerful greenhouse gas (Johnson and Johnson, 1995).

Climate change is not the only reason for zootechnical production to adopt methane reduction strategies. Methane emissions represent an important energy loss for dairy cows, which negatively impacts production performance. In this article, we review why methanogenesis in dairy cows arises, and how the use of phytogenic product Activo Premium can help achieve efficient energy use and reduced climate impact.

Less methane: environmental, regulatory, and business pressures

Methane (CH₄) is considered one of the gases that, together with CO₂ (carbon dioxide) and N₂O (nitrous oxide), traps heat in the atmosphere and, thus, causes global warming. While methane is generated in multiple industries, including the energy and waste sectors, much of the methane present in the atmosphere derives from livestock activities and, in particular, from ruminant farms.

About 28% of total methane emissions derive from agriculture sector and enteric fermentations (digestive processes in which feed is broken down by microorganisms) are responsible for about 65% of the total methane coming from zootechnical sector (Knapp et al., 2014). For this reason, in recent years, strategies for mitigating methane emissions in dairy cows have aroused great interest among researchers and environmentally-conscious consumers.

Regulators have also caught on: In October 2020, the European Commission presented its strategy for reducing methane emissions in Europe. Reductions are essential to achieve the Commission’s climate objectives for 2030 and climate neutrality by 2050. For the livestock sector, the Commission seeks to develop an inventory of innovative mitigating practices by the end of 2021, with a special focus on methane from enteric fermentation.

Uptake of mitigation technologies will be promoted though Member States’ and the Common Agricultural Policy’s “carbon farming” measures. Carbon-balance calculations at farm level are to be encouraged through digital tools; and the Horizon Europe strategic plan 2021-2024 will likely include targeted research on effective reduction strategies, focusing on technology, dietary factors, and nature-based solutions such as phytogenic products.

Even aside from environmental concerns, consumers demands, and regulatory steps, there is a critical business case for dairy producers to lower methane emissions. Given the ever-increasing global demand for dairy products, farmers and other operators in the sector more than ever try to maintain and indeed improve production to maximize yields, both economically and in terms of finished products. Problematically, methane production in the rumen represents a great loss of energy for the animal.

On average, about 6% of the total energy ingested by a dairy cow is transformed into methane, every single day (Succi and Hoffmann, 1993). The less methane a cow produces, the more metabolizable energy (ME) she gets out of her gross energy (GE) intake. A better ME/GE ratio translates into higher net energy of lactation (NEl). Energy losses from methanogenesis thus directly decrease the energy nutritionist can consider as usable during rationing.

Before we review the current research on how an adequate manipulation of the diet and of the rumen environment can mitigate these energy losses, we need to ask ourselves, why is methane formed in the rumen at all?

Animal physiology: how methane is formed in the rumen

Ruminants’ digestion of vegetal ingredients is linked to their rumen’s symbiotic bacterial, protozoan, and fungal flora. This microbiota has all the enzymatic properties necessary for the digestion (or rather pre-digestion) of ingested forage, including some cellulose fractions that monogastric animals cannot use.

In the rumen, the main products deriving from bacterial fermentation are volatile fatty acids and methane. The main volatile fatty acids are acetic acid, propionic and butyric acid, which are mainly absorbed and used by the animal. Meanwhile, methane helps to maintain the oxidative conditions in the rumen’ anaerobic environment, but also represents an energy loss (Czerkawski, 1988).

Methanogenesis is carried out by methanogenic bacteria and archae in the rumen (Guglielmelli, 2009). They use molecular hydrogen and carbon dioxide as a substrate for the synthesis of methane, according to the following equation:

4 H₂ + CO₂ → CH₄ + 2 H₂O

A few other chemical reactions contribute to methanogenesis, but they all have one thing in common: they require hydrogen ions in the rumen fluid to form methane from CO₂. This gives us the first “point of attack” for reducing methane formation: the diet.

Increase the share of propionic acid

Propionic acid is in competition with methanogens in using hydrogen ions to reduce glucose molecules:

C₆H₁₂O₆ (glucose) + 4 H → 2 C₃H₆O₂ (propionic) + 2 H₂O

It is clear that if propionic fermentations are stimulated through the diet at the expense of the pathways leading to acetate and butyrate (where hydrogen ions are transferred to the rumen environment), the availability of hydrogen for the reduction of CO₂ by methanogenic bacteria decreases.

Diets with a high level of concentrates, and low levels of neutral detergent fibre, yield more propionic acid and less acetic and butyric acid. Set aside lower methane emissions, this increase in energy is desirable during peak lactation: the energy gap that follows from the decrease in ingestion by the animal requires diets with a high amount of substrate for gluconeogenesis. Furthermore, the greater production of propionate sequesters H₂ in the rumen environment and, consequently, less CO₂ is reduced to methane.

Optimize the protozoa count

Most methane-producing bacteria live in symbiosis with most of the protozoan species, they are located on the surface of the protozoan. It follows that optimizing the population of protozoa present in the rumen (through dietary measures) leads to a lower methanogenesis (Patra and Saxena, 2010). Naturally, a minimum amount of protozoa must be maintained to avoid excessively reducing ruminal motility (regular contractions that mix and move the rumen content), which is important for feed digestibility.

Diet is not enough: feed additives to reduce methane production

Dietary measures alone cannot considerably reduce daily methane production. In the past, antibiotic growth promoters belonging to the ionophores family were commonly administered in the EU. These antibiotics increase efficiency and daily weight gain by promoting gluconeogenesis through greater production of propionic acid in the rumen and a consequent reduction in emitted methane (Piva et al., 2014).

The emergence of bacterial forms resistant to growth-promoting antibiotics have forced the EU to ban these molecules to safeguard consumer health. Fortunately, certain feed additives can also help reduce methanogenesis and generate energy saving – without the danger of resistance.

Secondary plant extracts or phytomolecules feature relevant properties, including bactericidal, virucide, and fungicide effects. As we have seen, it is critical to encourage certain fermentations at the expense of others and possibly reduce the organisms directly and indirectly responsible (bacteria and protozoa) for methanogenic fermentations.

Activo Premium: reduce methane and preserve energy

Phytogenic product Activo Premium contains a targeted phytomolecules mix capable of influencing the rumen microbiome in this manner:

Figure 1: Anti-methanogenic properties of selected phytomolecules. Based on Lourenço et al. (2008) and Supapong et al. (2017)  

Activo Premium is a blend of phytomolecules that maximizes production results for both high- and low-energy diets. Studies show that Activo Premium’s effects on the on the rumen microbiome reduce the ratio of acetic to propionic and butyric acid and decrease the energy losses due to methane production.

Field trial: Activo Premium improves rumen fermentation processes

A trial at the University of São Paul, Brazil, sought to evaluate the impact of Activo Premium on rumen fermentation and methane emissions. Nine rumen-cannulated sheep (55 ± 3.7 kg of body weight) were divided into 3 groups, and randomly distributed in a triple 3×3 Latin square design. The animals were fed their experimental diets for 22 days (the sampling period) in the following 3 set-ups: one control group (basal diet without additives); one group receiving a basal diet with 200 mg of Activo Premium per kg of dry matter intake; and one group receiving a basal diet with 400 mg of Activo Premium per kg of dry matter intake.

Figure 2: Ratio of acetate to propionate (p = 0.03)

Figure 3: Protozoa count (p = 0.06; x 10⁵ / ml) and methane production (p < 0.01; l per kg of dry matter). Based on Soltan et al. (2018)

As shown in figures 2 and 3, Activo Premium favourably modifies the ratio of volatile fatty acids and reduces the protozoa count, which, as to be expected, results in reduced methane emissions.

Rumen simulation trial: the more Activo Premium added, the less methane produced

A trial was conducted at the University of Hohenheim (Germany) sought to evaluate the methane-reducing effects of different inclusion rates of Activo Premium, using a continuous long-term rumen simulation technique (Rusitec). Four different inclusion levels of Activo Premium (0, 2.1, 4.2, and 8.4 mg/d) were added to a diet with a ratio of concentrates to roughages of 80% to 20%, respectively.

Five consecutive Rusitec runs with one replication of each of the four inclusion schedules were performed. The run lasted for 14 days; 7 days were used for adaptation and the later 7 days for sampling. The fermenters were heated to 39°C. During the sampling period, total gas production and methane concentration of the total gas produced were measured every 24 h.

Figure 4: Methane emission (ml / day) for increasing inclusion rates of Activo Premium

In this trial with a rumen simulation system, Activo Premium significantly reduced methane volume (Figure 4): from 231 ml/d for the diet without any Activo Premium to 172 ml/d for the highest inclusion rate of Activo Premium.

Activo Premium: reduce methane emissions, support your profits and our planet

Both in vivo and in vitro trials have shown with high statistical reliability that Activo Premium can positively modulate rumen fermentations. The strategic combination of phytomolecules appears highly effective as a natural dietary supplementation option to modulate ruminal fermentation and decrease methane emissions. Adding Activo Premium to dairy cows’ diet will likely contribute significantly to reducing their methane emissions and optimizing their energy balance – improving animal performance while curbing the climate change impact, a win-win for everyone.

References

Czerkawski, J. W. “Effect of Linseed Oil Fatty Acids and Linseed Oil on Rumen Fermentation in Sheep.” The Journal of Agricultural Science 81, no. 3 (1973): 517–31. https://doi.org/10.1017/s0021859600086573

Guglielmelli, Antonietta (2009) Studio sulla produzione di metano nei ruminanti: valutazione in vitro di alimenti e diete. [Tesi di dottorato] (Unpublished) http://www.fedoa.unina.it/3960/

Johnson, D.E., and K.A. Johnson. “Methane Emissions from Cattle.” Journal of Animal Science 73, no. 8 (August 1995): 2483–92. https://doi.org/10.2527/1995.7382483x

Knapp, J.R., G.L. Laur, P.A. Vadas, W.P. Weiss, and J.M. Tricarico. “Invited Review: Enteric Methane in Dairy Cattle Production: Quantifying the Opportunities and Impact of Reducing Emissions.” Journal of Dairy Science 97, no. 6 (2014): 3231–61. https://doi.org/10.3168/jds.2013-7234

Lourenço M., P. W. Cardozo, S. Calsamiglia, and V. Fievez. “Effects of Saponins, Quercetin, Eugenol, and Cinnamaldehyde on Fatty Acid Biohydrogenation of Forage Polyunsaturated Fatty Acids in Dual-Flow Continuous Culture fermenters1.” Journal of Animal Science 86, no. 11 (November 1, 2008): 3045–53. https://doi.org/10.2527/jas.2007-0708.

Patra, Amlan K., and Jyotisna Saxena. “A New Perspective on the Use of Plant Secondary Metabolites to Inhibit Methanogenesis in the Rumen.” Phytochemistry 71, no. 11-12 (August 2010): 1198–1222. https://doi.org/10.1016/j.phytochem.2010.05.010.

Piva, Jonatas Thiago, Jeferson Dieckow, Cimélio Bayer, Josiléia Acordi Zanatta, Anibal de Moraes, Michely Tomazi, Volnei Pauletti, Gabriel Barth, and Marisa de Piccolo. “Soil Gaseous N2O and CH4 Emissions and Carbon Pool Due to Integrated Crop-Livestock in a Subtropical Ferralsol.” Agriculture, Ecosystems & Environment 190 (2014): 87–93. https://doi.org/10.1016/j.agee.2013.09.008

Soltan, Y.A., A.S. Natel, R.C. Araujo, A.S. Morsy, and A.L. Abdalla. “Progressive Adaptation of Sheep to a Microencapsulated Blend of Essential Oils: Ruminal Fermentation, Methane Emission, Nutrient Digestibility, and Microbial Protein Synthesis.” Animal Feed Science and Technology 237 (March 2018): 8–18. https://doi.org/10.1016/j.anifeedsci.2018.01.004.

Supapong, C., A. Cherdthong, A. Seankamsorn, B. Khonkhaeng, M. Wanapat, S. Uriyapongson, N. Gunun, P. Gunun, P. Chanjula, and S. Polyorach. “In Vitro Fermentation, Digestibility and Methane Production as Influenced by Delonix Regia Seed Meal Containing Tannins and Saponins.” Journal of Animal and Feed Sciences 26, no. 2 (2017): 123–30. https://doi.org/10.22358/jafs/73890/2017

Succi, Giuseppe, and Inge Hoffmann. La Vacca Da Latte. Milano: Cittá Studi, 1993.