Impact of mycotoxins on poultry – an overview

Mycotoxin, a secondary metabolite produced by fungi, is a prominent global challenge associated with health and performance issues in poultry and financial losses in food production industries. Poultry are susceptible to a wide range of mycotoxins including aflatoxins, ochratoxin, fumonisins, trichothecenes such as deoxynivalenol, and T-2 toxin, and cyclopiazonic acid.

Health implications for people

Mycotoxin in poultry increases mortality rate, reduces productivity, and causes extra management costs including prevention, control, sampling, mitigation, and additional labour. In addition, mycotoxins transmitted to poultry meat and eggs, result in deleterious health effects and major concerns for public health. This article discusses major mycotoxins that present a risk for poultry industry, and control, prevention, diagnosis, and treatment of mycotoxicosis.

Aflatoxins

Aflatoxins, produced by Aspergillus flavus and Aspergillus parasiticus, are found in feed ingredients used for poultry rations. Aflatoxins is the causative agent of “Turkey X Disease” which led to the death of young turkeys in England because of contaminated peanut‐based feed. Aflatoxin metabolites produced in chicken liver accumulate in the egg, meat, and blood. Aflatoxins in poultry are responsible for weight loss, low feed efficiency, reduced egg production and egg weight, enhanced liver fat, alteration in organ weights, decreased serum protein levels, carcass bruising, poor pigmentation, liver damage, low digestibility of starch, protein, and lipids, immunosuppression, disease outbreaks, and vaccination failures

Ochratoxins

Ochratoxins are formed by Aspergillus in hot climates, and Penicillium in temperate climates, even when the temperature is as low as 5ºC. Poultry have a high capacity to excrete ochratoxin which make them less sensitive compared to other species. Ochratoxin-contaminated diets increase the weight and size of the liver and kidneys but reduce the weight and size of lymphoid glands, such as thymus, bursa of Fabricius, and spleen in broilers. In addition, ochratoxin causes lesions in kidneys, liver, bursa of Fabricius, spleen, and thymus, reduces production performance, and results in hematobiochemical disturbances and severe immunosuppression in broilers and layer hens.

Fumonisins

Fumonisins are isolated from Fusarium moniliforme and Fusarium verticillioides cultures and they are identified in 6 different forms (A1, A2, B1, B2, B3, and B4). Fumonisins reduce body weight gain, decrease feed intake, and cause liver damage in chicken, ducks, and turkeys. In chicken, liver alteration includes multifocal liver necrosis and biliary expansion. In turkeys and ducklings, the observed liver changes include diffuse enlargement of liver cells with biliary expansion.

Trichothecenes

Trichothecene mycotoxins are the most potent small-molecule inhibitors of protein synthesis, and they include T2 toxin, HT2 toxin, diacetoxyscirpenol, monoacetoxyscirpenol, neosolaniol, 8- acetoxyneosolaniol, 4-deacetylneosolaniol, nivalenol, 4-acetoxynivalenol, deoxynivalenol or vomitoxin, and 3‐acetyldeoxynivalenol. Trichothecene causes oral lesions, reduction in growth performance, abnormal feathering, reduced egg development and eggshell consistency, regression of the bursa of Fabricius, peroxidative changes in the liver, abnormal blood coagulation, leucopoenia and proteinemia, and immunosuppression. T2 toxin reduces the relative weights of the bursa of Fabricius, thymus, and spleen, and causes swollen liver, friable, and yellowish discoloration in gall bladder, mild haemorrhage and inflammation in the heart, erosion in trachea, and inflammation of the air sacs in broilers. Deoxynivalenol alters main gut functions, decreases villus surface area available for absorption, and affects gut permeability.

Cyclopiazonic acid

Cyclopiazonic acid is an uncommon poultry feed contaminator. Although based on the quantity and duration of ingestion, cyclopiazonic acid causes central nervous system disorders resulting in poor muscle control, paralysis, and muscle spasm. In addition, cyclopiazonic acid increases the weight of the liver, kidneys and forestomach, and decreases the weight of the bursa of Fabricius, thus weakening the immune response after vaccination.

Control and prevention strategies

Control

• Maintaining fresh feed,

• Low humidity (below 11%),

• Proper ventilation in feed storage location,

• Clean equipment,

• Adding fungistatic substances,

• Proper monitoring, storage, and transportation practices,

• An efficient Hazard Analysis and Critical Control Point (HACCP) strategy,

• Changing raw materials at storage locations at regular intervals reduce the risk of mycotoxin formation in poultry feed.

Chemical approach

Furthermore, chemical, biological, enzymatic, and physical decontamination techniques that inactivate mycotoxins without leaving toxic residues or compromising feed properties or palatability can be used to save polluted batches in the manufacturing process.

Chemical approach includes ammoniation, alkaline hydrolysis, peroxidation, ozonation, and the application of bisulphites.

Biological approach

Biological treatment involves using algae and plant ingredients to protect vital organs such as the liver and to improve poultry immune systems.

The enzymatic or microbial detoxification method uses microorganisms such as bacteria, yeast, and fungi or their purified enzymes to transform or break mycotoxins into less or nontoxic compounds. a physical approach tends to eliminate contaminated fractions from bulk material during sorting, milling, dehulling, cleaning, heating, and irradiation.

Diagnosis and treatment

• Mycotoxin exposure, alongside consuming a new batch of feed, causes subclinical disease. Prolonged storage of poor-quality feed ingredients in a substandard location leads to chronic mycotoxin exposure. Impaired production efficiency, mouth ulcers, palate and tongue crusts are signs of mycotoxin exposure.
• Conclusive diagnosis of mycotoxicosis requires detection of the specific toxin which is challenging due to fast and high-volume use of feed ingredients in commercial poultry farms.
• If mycotoxin exposure is suspected, necropsy and a complete feed analysis are required, as well. It is recommended to collect multiple feed samples from various sites including ingredient storage, feed manufacture and transport, and feed bins and feeders to verify the presence of mycotoxins.
• Treatment of mycotoxicosis includes supportive care, probiotic supplementation, and vitamin C and E supplementation. Supportive care involves isolating affected birds from the flock, placing them in a safe, comfortable, warm location with easy access to water and food, limiting stressors and then contacting your veterinarian.

Concluding remarks

Feed is one of the largest costs in poultry industry and low-quality feed and naturally occurring toxic contamination in feedstuffs (e.g., mycotoxins) adversely affects poultry health, welfare, production performance and results in serious economic issues. Application of innovative analytical techniques improves the precise detection of mycotoxins in feed ingredients. In addition, there are various chemical, biological, enzymatic and physical decontamination techniques that can be used to inactivate mycotoxins in feedstuff and, due to the diversity of mycotoxin structures, it is recommended to implement a combination of various decontamination methods. Moreover, an in-depth understanding of the toxicity of end products and the influence on the palatability and nutritional quality of poultry feed is necessary. Finally, further research is required to investigate the stability of toxins in the entire “farm to fork” chain.

Source: A review of the impact of mycotoxin contamination on poultry performances Yemisi Jeff-Agboola University of Medical Sciences, Ondo, Nigeria