Despite the sector being set for exponential growth, poultry birds are faced with a myriad of challenges such as high susceptibility to diseases and infections, which cause huge losses and economic setbacks.
The poultry sector is one of the fastest growing agricultural sub-sectors especially in developing countries. The sector plays an extremely important role in these economies in terms of ensuring food security and offering proper nutrition.
Factors such as population growth, rise in income levels, and urbanization are set to contribute to the growth of the sector in the future. According to reports by Research and Markets, the sector is expected to grow from US$310.7 billion in 2020 to US$322.55 billion in 2021 at a compound annual growth rate (CAGR) of 3.8%. The market is further expected to hit US$422.97 billion in 2025 with a CAGR of 7%. Despite the sector being set for exponential growth, poultry birds are faced with a myriad of challenges such as high susceptibility to diseases and infections, which cause huge losses and economic setbacks.
One such threat is the ingestion of mycotoxins, which are naturally occurring toxins produced by certain moulds (fungi) and can be found in poultry feed. Some of the moulds that are most common in poultry feed are Aspergillus, Fusarium, and Penicillium. Poultry Science indicates that these fungi produce several mycotoxins such as such as aflatoxins (AF), zearalenone (ZEN), ochratoxin A (OTA), fumonisins (FUM), and trichothecenes such as deoxynivalenol (DON) and T-2 toxin, which are of great concern to the poultry industry. The fore mentioned mycotoxins are commonly prevalent in maize, wheat, soybean meal and barley, feeds which form the bulk of ingredients used in poultry rations.
Prevalence of mycotoxin across the globe
A recent update on the occurrence of mycotoxins in the raw commodities and finished feeds by BIOMIN Mycotoxin, indicated that the most prevalent mycotoxins globally are DON (65%) and FUM (64%), followed by ZEN (48%). The study was based on 96,684 analyses performed between January to December 2020 on 21,709 finished feed and raw commodity samples sourced from 79 countries. Overall, 65% of the samples had at least one mycotoxin above the thresh-hold level. With a threshold level in parts per billion (ppb) of AF-2, ZEN-50, DON-150, T2-50, FUM-500 and OTA-10, risk of contamination in sub-Saharan Africa was flagged as severe as 92 % of the cereal samples tested were found to have been contaminated by DON with a maximum of 917 ppb.
In North America, the case is extreme with DON being one of the main concerns in all species. It was present in 72% of maize samples and in 89% of cereal samples. Average of positives for DON in maize was quite high with 808 ppb and even higher in cereals at 1,721 ppb. Maize in the region was also affected by FUM and ZEN with averages of 2,405 ppb and 323 ppb, respectively. Meanwhile in Central America, nearly all 97% of maize samples tested positive for FUM at an average of 1,820 ppb and a maximum of 24,233 ppb. The by-product maize gluten was highly affected by FUM, ZEN and DON with 100%, 75% and 69% prevalence, respectively. Average contamination was extreme for ZEN with 1,468 ppb. From the analysis, maize in South America is highly contaminated with FUM at 83% and an average of positives of 2,280 ppb. In wheat, DON is the main threat as it was found in 83% of the samples with an average of 1,584 ppb. Soybeans were seen to be highly affected by ZEN with 73% of samples showing presence of the toxin, followed by T-2 (51%) and DON (46%).
The analysis also shifted focus to Europe, revealing that the most prevalent mycotoxin in the region is still DON with 70% of maize samples testing positive for this mycotoxin. DON reached a maximum concentration of as high as 11,875 ppb with ZEN increasing its average contamination in maize to 171 ppb. In Asia Pacific, FUM occurred in 96% of maize, followed by DON in 80% of the samples tested. ZEN is also a risk for animal production as it was present in 68% of the samples analyzed and a maximum of 11,786 ppb was found. In this region Aflatoxin remains a threat for animals. In maize, Aflatoxin was found as high as 2,495 ppb. Meanwhile, in the Middle East, DON increased its prevalence in all samples to 78%.
Heterogeneous sensitivity to mycotoxins
It is important to note that mycotoxin contamination can occur at any point of production and handling of the cereals. According to the Mycotoxins in Poultry report by Ayhan Filazi et al, production of the toxins starts in the farm, during transportation and storage, often under warm and humid conditions. With poultry feed containing various raw materials that are likely to have been produced in varied climatic conditions and handled differently, multiple types of mycotoxins might be found in a single feed. This spells double trouble as the damage caused by mycotoxins is much greater when they are combined than when they occur individually, as they have synergistic or additive effects.
Generally, poultry animals have heterogeneous sensitivity to mycotoxins as different species exhibit varied toxic effects. Ducks, geese, and turkeys seem to be more sensitive to mycotoxicoses than chickens and quails. The effects also depend on the level of contamination, length of time the animal has been consuming the mycotoxin(s), and the bird’s age, sex, and level of stress. To this end the effects range from a slight reaction to death of the bird.
Any mycotoxin present in feed is delivered straight to the gastrointestinal tract (GIT) of the bird, which is the most important organ for converting feed into energy. The GIT is also the biggest immune organ in the body system. Once compromised from exposure to mycotoxins, the bird suffers from immunosuppression which would lead to increased susceptibility to infectious diseases, reactivation of chronic infections, potential secondary reactions, and increased use of drugs coupled with ineffectiveness of vaccination programs. Further to that, mycotoxins exposure can cause reduced feed intake, retarded growth, oral lesions, abnormal feathering, organ damages (mainly kidney and liver), carcinogenicity, teratogenicity, decreased egg production, poor feathering and excessive mortality at high dietary concentrations, among other ailments
Detection modes of mycotoxins
These symptoms and lesions can be used to clinically diagnose the presence of mycotoxins in a feed although most are not just straightforward. Valid determination of mycotoxins and their metabolites is a crucial step in any intervention, mitigation, or remediation strategy to cope with the deleterious effects of the toxins to livestock. According to Mycotoxin Site, the most widely used method of detecting the disease-causing agents in animal feed are either antibody-based assays or chromatography techniques.
ELISA is one of the most commonly used enzyme-linked immunosorbent antibody-based assay as it is affordable. However, its limit of detection for many mycotoxins often exceeds 0.2 ppm. In pursuit for higher precision, focus has shifted to use of Liquid chromatography coupled to a tandem mass spectrometry detector (LC-MS/MS) for the analysis of mycotoxins and their metabolites at very low concentrations and from complex biological samples. The advanced technique, detect hundreds of mycotoxins simultaneously in a sample. Other types of chromatographic techniques include: High-performance liquid chromatography (HPLC) and Gas chromatography and Mass spectrometry (GC/MS). HPLC and GC/MS have a detection limit of less than 0.05 ppm but requires expensive equipment and technical support, making LC-MS/MS to be the most suitable technique for use.
Diverse counteractive strategies
Once the poultry feed has been put under test to determine the presence and level of mycotoxins contamination, its confirmation calls for decontamination approaches which are technologically diverse and based on chemical, biological and physical strategies.
Managing mycotoxin exposure should start at harvest by removing heavily contaminated grains where possible. The heavily contaminated grains are considerably lighter than non-contaminated ones and thus can be removed with a grain separator that uses air flow to raise and separate very light kernels from the undamaged grain. However, in the case of purchase of mixed feed or ground grain, other methods will be needed in order to effectively deal with the mycotoxin load. A report by PennState Extension, calls for adoption of dilution of the affected feed with uncontaminated portions. However, this strategy demands for multiple sampling and mycotoxin analysis to determine the concentration of mycotoxin in every batch of feed, reducing the practical efficiency of this method for feed manufacturers. As an additional tip, prior to diluting affected raw materials, organic acids could be sprayed on them. This will kill most of the fungal contamination and will limit the mycotoxin production once the contaminated material has been diluted.
Other physical processes aimed to eliminate mycotoxin contamination include controlling temperature and humidity using aeration especially in storage units as they serve as the main breeding grounds. It is also advisable to use fungal inhibitors and protection against damage caused by insects and rodents.
If mycotoxin contamination is still an issue after attempted use of physical inhibitors, mycotoxin binders could be another option to reduce the impact of the toxins on poultry. The inclusion of binding agents or “enterosorbents” in the diet has been given considerable attention as a strategy to reduce foodborne exposures to mycotoxins. Potential mycotoxin binders include activated carbon; aluminosilicates (e.g., clay, bentonite, montmorillonite, zeolite, phyllosilicates); and complex indigestible carbohydrates (e.g., cellulose, polysaccharides in the cell walls of yeast and bacteria) as well as some synthetic polymers. It is important to note that the process of mycotoxin binding only starts when the animal ingests the feed. Due to this delay, even the most effective binding agent will not mitigate the initial toxic effect immediately after feed ingestion.
Although this approach successfully eliminates the risk of certain mycotoxins such as Aflatoxin, it does not work comprehensively on all of the mycotoxins relevant to the poultry industry, especially not against trichothecenes mycotoxins since their structures are not suitable for adsorbing by binders. To this end biotransformation using microbes and enzymes is the most effective strategy. It provides reliable protection against mycotoxins, biodegrading them into non-toxic metabolites. Also, the technique is fast, specific and irreversible.
In addition to biotransformation, a bioprotection strategy is also important. A variety of feed additives are available that contains plant and algae extracts suitable to provide protection of vulnerable organs such as the liver and overcome the immune suppression caused by mycotoxins.
A combination of different strategies can counteract the negative effects of mycotoxins in poultry more completely, especially in cases of multi-mycotoxin contamination. Overall, mycotoxins still impose a great risk for the poultry sector and alternative approaches for the prevention are still being sought by researches around the world.