Effects of the
main mycotoxins on poultry production parameters

We explore with Prof. Milad Manafi (Malayer University, Iran) the consequences of mycotoxin exposure in poultry production.

Milad Manafi

Department of Animal Science, Faculty of Agricultural Sciences, Malayer University, Malayer, Iran.
manafim@malayeru.ac.ir

Chicken meat is healthy and can be produced anywhere. It is among the relatively cheapest animal-source proteins and is not subject to any type of religious restrictions (Manafi et al., 2019).

Food safety and security measures have to be taken up within the food chain from livestock feed to human food.

Producing adequate and available amount of safe feed are important factors to be considered, otherwise, it may lead to food insecurity and malnutrition (Manafi et al., 2018a).

This technical paper reviews the incidence and toxic effects of major mycotoxin in poultry.

Contamination with mycotoxins is among the hidden-potential hazards having a variety of severe adverse health impacts (Manafi y Khosravinia, 2013).

To be more precise, mycotoxins are the secondary metabolites of different fungi (molds) species found on carbohydrate-rich feeds such as peanuts, cottonseed, corn, sorghum, and cereal grains (Manafi et al., 2014a).

There is a range of fungi that can produce different mycotoxins when put together in favorable situations of hot conditions without adequate drying and aeration (Manafi et al., 2012a).

As FAO declared, nearly 25% of the world’s food crops and cereals produced annually are contaminated with mycotoxins, although this figure greatly underestimates the occurrence above the detectable levels (up to 60–80%) (Eskola et al., 2020).

This is to emphasize the importance of the world’s cereal production and distribution from two different angles:

  1. The yield of production
  2. The quality of the product

Aflatoxin contamination of feedstuffs has been reported to be of a wide range from 1 to 900μg/kg in commonly used ingredients as well as mixed feed samples in developing countries (Mohanamba et al., 2007).

Different countries have set down their permissible standard levels for importing and or providing the raw materials to feed their farm animals.

This is crucial to know, as mycotoxin contamination starts right from the production phase and is continued during harvest, transportation, and storage, before reaching the final customer in every corner of the globe.

Developing countries have very strict rules when it comes to this matter, but in certain countries, especially in Africa, a shortage of raw material supply is affecting the permissible level (EUR-Lex., 2021).

As an expert, one should be aware of the variety and content levels of mycotoxins in the feedlot which they receive. Once known, farm nutritionists may think about how to minimize those adverse effects.

It is believed that, apart from acute poisoning and severe liver damages and lesions, these metabolites could be a cause to increase the immune deficiencies and cancer risk in livestock and subsequently be carried on to humankind, leading to genetic mutations when available in food for a long-run (Manafi et al., 2009).

When comes to poultry, currently aflatoxins, ochratoxins, and T-2 toxins are considered to be the most dangerous mycotoxins (Table 1) from food safety and regulatory viewpoints, as well as negatively affecting poultry production parameters (Eskola et al., 2018).

Table 1. Relative toxicity of different mycotoxins
on different livestock species

Aflatoxins

Amongst several types of mycotoxins, aflatoxins are highly toxic, carcinogenic, and cause severe contamination (Manafi, 2012).

Approximately 15 types of aflatoxins have been described, among which “B” and “G” families (aflatoxins B1, B2, G1, and G2) are particularly dangerous to livestock as they have been found in all major food crops, grains, and their derived products utilized for animal and poultry nutrition.

These naturally occurring compounds are produced mainly by the fungi Aspergillus flavus, Aspergillus parasiticus and Aspergillus nomius, leading to serious health consequences through contamination of a wide variety of food such as maize which can be used in animal/poultry feeding (Manafi et al., 2018b).

Among all aflatoxins, aflatoxin B1 (AFB1) is a key toxin that is tightly regulated and monitored in very small quantities (at minor pbb levels) in agricultural commodities to be used by the animal (EUR-Lex., 2021).

Aflatoxicosis, a disease that occurs when large doses of aflatoxins lead to acute poisoning, is life-threatening, usually due to liver damage to the liver. Other adverse effects of aflatoxins are:

  • Poor performance
  • Immunosuppression and Increased susceptibility to infections
  • Increased the susceptibility to other diseases and mortality
  • Drop in egg production and egg weight
  • Decreased hatchability and hatchling weight
  • Increased liver fat and decreased activity of several liver enzymes
  • Changes in organ weights
  • Reduction in serum protein levels
  • Carcass bruising and poor pigmentation

(Manafi et al., 2009; Manafi et al., 2012b; Manafi et al., 2012c; Manafi et al., 2012d; Manafi et al., 2012e; Manafi et al., 2014a; Hedayati et al., 2014a; Manafi et al., 2014b; Hedayati et al., 2014b; Manafi et al., 2014c; Manafi et al., 2015a; Manafi et al., 2016; Manafi et al., 2018b; Manafi et al., 2018c; Manafi, 2018; Eskola et al., 2020).

Although the concentration level, dietary exposure period, sex, species, age, breed, and health status of animals are different factors that affect the level of toxicity in poultry, all avian species, especially younger ones (chicks, goslings, ducklings, and turkey poults) are the most susceptible to AFB1 toxicity (Manafi et al., 2012b; Manafi et al., 2014d).

Figura 1. Factores y efectos asociados a la exposición a las aflatoxinas en las aves de corral.

Ochratoxins

Ochratoxins are a group of naturally occurring foodborne mycotoxins found in a wide variety of agricultural goods worldwide, including staple food crops, cereal grains, dried fruits, and nuts.

They are produced by some Aspergillus species (mainly A. ochraceus, A. carbonarius and A. niger) and some Penicillium species, especially P. verrucosum (Manafi et al., 2011).

Ochratoxins represent three secondary metabolite forms (A, B, and C), among which Ochratoxin A is the most prevalent fungal toxin of its family.

Ochratoxin A is known to have nephrotoxic, teratogenic, immunosuppressive, and hepatotoxic effects in many animal species.

Its possible carcinogenic effects on humans, which could be caused through the consumption of toxins accumulated in animal meat, are also reported by scientists (Scudamore, 1996).

Ochratoxin A also inhibits protein synthesis and lipid peroxidation. The latter could be related to oxidative damage which impairs the overall quality and safety of animals (Stander et al., 2000).

Consumption of ochratoxin A by poultry may lead to:

  • Decrease in farm productive performance
  • Subcutaneous hemorrhage
  • Immunosuppression
  • Increased age-specific pathological lesions
  • Increased relative weight of the liver, kidney, spleen, pancreas, proventriculus, gizzard, heart
  • Increased mortality
  • Poor feed conversion efficiency
  • Reduced relative weight of the Bursa of Fabricius

(Giambrone et al., 1985; Gibson et al., 1989; Scudamore, 2005; Martins et al., 2008; Manafi et al., 2009; Manafi et al., 2011)

The effects of ochratoxin A in poultry have been found to be quite pronounced in younger animals (Dortant et al., 2001).

In birds, the kidney is the main and primary organ affected, and a marked decrease in the percentage of circulating lymphocytes and a significant increase in the percentage of inflammatory cells (monocytes and heterophils) are also reported (Moura et al., 2004).

Figura 2. Efectos asociados a la ocratoxina en las aves de corral.

T-2 toxin

Reported in many parts of the world, trichothecenes are produced as secondary metabolites (T-2 toxin being the earliest investigated and amongst the most toxic members of this family), mainly by fungi of the genus Fusarium of which the most important species are F. sporotrichioides, F. langsethiae, F. acuminatum and F. poae, commonly found in various cereal crops (wheat, corn, barley, oats, rye, etc.) but also in soy meal (Manafi et al., 2015b).

Routinely, the high-pressure liquid chromatography (HPLC) is used to detect the T-2 toxin in a wide range of feed and food.

These compounds are generally very stable and are not degraded during storage/milling and high temperatures of cooking/processing of food.

The toxicity and deleterious effects of T-2 toxin vary based on numerous factors, such as the administration route, the exposure time, the administered dosage, and the age, sex, and overall health of the animal (Hossam et al., 2013).

T-2 toxin is believed to increase oxygen radical production hence resulting in direct cell injury (Manafi et al., 2012f).

Studies indicating that T-2-toxin ingestion in high doses by poultry through the contaminated grain, hay, and straw causes:

  • Lipid peroxidation
  • High fever
  • Muscle and skin necrosis, as well as bacterial infections of the necrotic tissues
  • Enlarged lymph nodes
  • Delayed ovulation
  • Decreased sperm motility and increased sperm morphological abnormalities
  • Inhibition of protein, DNA, and RNA synthesis
  • Cytotoxicity
  • Immunomodulation
  • Lesions in the digestive tract, organs, and skin
  • Neural disturbances and nervous disorders
  • Declined performance and production parameters due to feeding refusal
  • Bloody diarrhea, bone marrow, buccal lesions, serous hemorrhagic inflammation
  • Dystrophy in liver, kidney, heart, brain and peripheral ganglia of the vegetative nervous system

(Kalantari et al., 1989; Zian et al., 2011; Kachuei et al., 2014; Krska et al., 2014; Drakulic et al., 2016; Yuan et al., 2016)

Preliminary, the liver is one of the first target organs where the enzymes help metabolize drugs that pass through the liver. The decrease in its activity could lead to an increase of unmetabolized drugs in the plasma, which can pose a dangerous risk for the animal’s health (Goossens et al., 2013).

The increased elevation of glutathione disulfide and 3-hydroxybutyrate suggests that the T-2 toxin promotes an anti-oxidative response in organ systems and helps with free radical generation.

Figura 3. Factores y efectos asociados a la exposición a la toxina T-2 en aves de corral.

CONCLUSIONS

Concentrations of mycotoxins in the feed are usually low and their immunosuppressive effects and secondary infections often make diagnosis difficult.

If at the onset of the disease, a change in the diet leads to health and performance improvements in animals, this may point to mycotoxin poisoning.

Although it is difficult to predict the effect of multiple toxins, certain studies confirm that presence of combined mycotoxins in animal feed show more severe impacts on livestock health and productivity.

Monitoring and controlling all the feed ingredients which are to be used for poultry diets is not always practical and could seriously compromise the world food supply, due to very large quantities, however, regular control of grain and feed samples is a valuable preventive measure and it is only accurate if representative samples are tested in the laboratory.

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