Mitigating the effect of trichothecene mycotoxins in layer diets
The health and performance impact of trichothecene mycotoxins in laying hen feed can be quite severe. This is why reducing its adverse effects on health, performance, and egg quality should be top of mind. This article discusses mitigation strategies tailored to laying hens to reduce these negative impacts.
Trichothecenes, a major class of mycotoxins, are comprised of a diverse range of compounds such as T-2 toxin, fumonisin B1, and deoxynivalenol (DON). The presence of trichothecenes in the diet of laying hens poses significant adverse effects on health, performance and food safety due to the inhibition of protein synthesis, disruption of cell membranes and induction of oxidative stress.
Trichothecene mycotoxins
Trichothecenes are a structurally diverse group of mycotoxins produced by Fusarium, Myrothecium, Trichoderma, and Stachybotrys fungi. Trichothecenes serve as the core structure for over 200 naturally-occurring derivatives with a wide range of toxicological effects. These mycotoxins are divided into 4 main types: Type A, Type B, Type C, and Type D. Trichothecenes contaminate cereal grains such as wheat, barley, maize and rice and they are stable in poultry diets during feed processing and resistant to degradation by heat and pH.
Factors including chemical structure, dose, duration of exposure and the susceptibility of bird species affect the toxicological effects of trichothecene mycotoxins. Type A trichothecenes include T-2 toxin and HT-2 toxin as the most toxic members of the trichothecene family. Type B trichothecenes include DON and type C and type D are less common in poultry feed.
Metabolism in laying hens
It is essential to understand the metabolism of mycotoxins to evaluate toxicological effects, develop effective management strategies and ensure the safety of poultry products for human consumption. Trichothecenes metabolism in laying hens is a complex process affected by route of exposure, dose, duration of exposure, age, genetics, nutritional status, the presence of underlying diseases and stressors such as heat stress or transportation. Trichothecenes undergo extensive metabolism in the gut tract and liver to create metabolites with altered chemical and biological properties.
Impact on health and performance
Acute exposure to high doses of trichothecenes leads to feed refusal, diarrhoea, haemorrhagic lesions in the gut tract, impaired nutrient absorption, weight loss and lower growth performance in laying hens. Chronic exposure to lower doses of trichothecenes can result in immunosuppression and increased susceptibility to infectious diseases such as coccidiosis, infectious bronchitis, and Newcastle disease, thus leading to economic losses for producers and reduced welfare for laying hens.
Consuming feed contaminated with trichothecenes leads to the deposition of toxin residues in eggs, thus reducing egg safety for human consumption. In addition, trichothecenes contamination of eggs impacts their quality attributes, reduces albumen consistency, and increases susceptibility to eggshell fractures. Eggshell fractures reduce the aesthetic appeal of eggs, increase the risk of microbial contamination and spoilage and reduce shelf life.
Another adverse effect of trichothecenes is alteration of the colour and viscosity of egg yolks and albumen, which makes them less appealing to consumers and reduces the marketability of eggs. Furthermore, trichothecenes contamination of eggs causes off-flavours and odours that reduce their sensory quality and consumer acceptance.
Mitigation strategies
Implementing mycotoxin mitigation strategies is crucial for safeguarding health, welfare, egg safety and the economic viability of laying hen operations. Effective strategies include a multi-dimensional approach that considers both pre-harvest and post-harvest factors.
The pre-harvest mitigation approach focuses on reducing the risk of mycotoxin contamination in feed ingredients. This approach is implemented through proper agricultural and crop management techniques such as crop rotation, tillage practices and weed control. In addition, selecting resistant crops and planting them at optimal times decreases their vulnerability to mycotoxin contamination.
Proper ventilation, temperature, and moisture in feed storage facilities prevent fungi growth and mycotoxin production in grains and feed ingredients. Furthermore, feed ingredients need to be sampled and analysed regularly to identify contaminated batches.
The post-harvest mitigation approach reduces the impact of trichothecene-contaminated feed on laying hens’ health, performance and egg quality. Physical methods including sorting, cleaning and thermal processing remove contaminated feed ingredients; however, these methods may not be effective in eliminating heat-stable compounds such as T-2 toxin. Chemical methods include the application of detoxification agents such as activated carbon, bentonite clay and hydrated sodium calcium aluminosilicate that bind to mycotoxins in the gut tract of laying hens and prevent their absorption. Furthermore, mycotoxin-degrading enzymes and microbial biotransformation products are used to detoxify contaminated feed ingredients.
Dietary supplementation with antioxidants such as vitamin E, vitamin C and selenium reduces oxidative stress and inflammation induced by mycotoxins. Dietary supplementation with minerals, yeast cell walls, mannan oligosaccharides and beta-glucans improve gut health, nutrient absorption and resilience to mycotoxin exposure.
Another post-harvest mitigation strategy includes biosecurity measures that prevent the introduction and spread of mycotoxin-producing fungi in laying hen production systems. These biosecurity measures involve cleaning and disinfecting feed storage areas, equipment and facilities to reduce the risk of fungi growth and mycotoxin contamination, and to prevent cross-contamination of feed batches.
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