Sonja Eksteen, AFGRI Animal Feeds

Mycotoxins are toxic secondary metabolites produced by moulds, primarily species of Aspergillus, Fusarium, and Penicillium, which commonly contaminate poultry feed ingredients such as maize, wheat, barley, and soybean meal (Mokubedi et al., 2019; Sandu and Swayne, 2024). Mycotoxin contamination represents one of the most significant hidden threats to modern broiler production because contamination often occurs without obvious clinical signs. Consequently, economic losses are frequently associated with reduced growth performance, poor feed conversion ratio (FCR), immunosuppression, increased disease susceptibility, and elevated mortality rates rather than overt toxicity (Olariu et al., 2025; Montayeva et al., 2026).

The influence of mycotoxins on broiler production has become increasingly important as intensive poultry systems rely heavily on high-performance genetics and precision nutrition, leaving little room for reductions in feed quality or nutrient utilization (Olariu et al., 2025). Mycotoxins rarely occur individually under commercial conditions. Instead, broilers are typically exposed to multiple toxins simultaneously, leading to additive or synergistic effects that amplify production losses (Sandu and Swayne, 2024; Montayeva et al., 2026). Recent surveys of South African poultry feed have demonstrated widespread co-contamination with fumonisins, deoxynivalenol (DON), zearalenone (ZEN), and other mycotoxins, highlighting the relevance of this issue for poultry nutrition programs (Mokubedi et al., 2019).

Influence of Mycotoxins on Broiler Performance

Reduced Feed Intake and Growth Performance

One of the earliest and most consistent impacts of mycotoxin exposure is a reduction in feed intake and body weight gain (Olariu et al., 2025). Mycotoxins impair nutrient digestion and absorption, reduce appetite, and damage gastrointestinal tissues, resulting in slower growth rates, lower final body weights, poor flock uniformity, and increased days required to reach market weight (Sandu and Swayne, 2024). The greatest growth depressions are commonly associated with aflatoxins, DON, and T-2 toxin exposure (Olariu et al., 2025; BIŌNTE Technical Department, 2025).

Impaired Feed Conversion Ratio

Feed accounts for approximately 65-75% of broiler production costs; therefore, any factor affecting feed efficiency has a major economic impact. Mycotoxins damage intestinal villi, reduce digestive enzyme activity, and impair nutrient utilisation, causing birds to require more feed to achieve the same weight gain (Montayeva et al., 2026). Even subclinical contamination can negatively affect FCR without obvious clinical symptoms (Sandu and Swayne, 2024).

Immunosuppression and Disease Susceptibility

Among the most important consequences of mycotoxin exposure is immunosuppression. Aflatoxins, ochratoxins, fumonisins, and trichothecenes can reduce the size and functionality of immune organs such as the thymus, spleen, and Bursa of Fabricius (Olariu et al., 2025). Consequently, broilers become more susceptible to bacterial, viral, and parasitic diseases. Exposure to mycotoxins has also been associated with reduced vaccine efficacy and diminished antibody responses following vaccination programs (Olariu et al., 2025; Sandu and Swayne, 2024).

Studies have demonstrated increased susceptibility to coccidiosis, necrotic enteritis, Escherichia coli infections, salmonellosis, and respiratory diseases in mycotoxin-challenged birds (Olariu et al., 2025). In many cases, the combination of disease pressure and mycotoxin exposure produces more severe production losses than either challenge alone (Montayeva et al., 2026).

Organ Damage and Metabolic Dysfunction

Different mycotoxins exhibit different target-organ specificities. Aflatoxins primarily damage the liver, resulting in impaired lipid metabolism, reduced protein synthesis, and decreased detoxification capacity (BIŌNTE Technical Department, 2025). Ochratoxin A mainly affects the kidneys, causing nephrotoxicity and disturbances in water balance (Sandu and Swayne, 2024). Fumonisins impair sphingolipid metabolism and compromise cellular integrity, while DON and T-2 toxin primarily affect the gastrointestinal tract (Olariu et al., 2025). Together, these effects reduce nutrient utilisation and overall production efficiency.

Clinical Signs of Mycotoxicosis in Broilers

Clinical signs vary depending on the specific toxin, level of exposure, duration of exposure, nutritional status, and environmental stressors (Sandu and Swayne, 2024). In many commercial flocks, signs are subtle and difficult to distinguish from management or health challenges.

General Signs

Common indicators of possible mycotoxin exposure include:

• Reduced feed intake
• Poor body weight gain
• Poor FCR
• Increased mortality
• Poor flock uniformity
• Increased disease incidence
• Reduced vaccine responses
• Wet litter
• Increased water consumption
• Feather abnormalities
• Increased condemnations at slaughter

(Sandu and Swayne, 2024; Olariu et al., 2025).

Aflatoxin Exposure

Typical signs include:

• Reduced growth rate
• Reduced feed intake
• Pale combs
• Depression
• Increased mortality
• Enlarged, pale, fatty liver
• Immunosuppression
• Increased susceptibility to secondary infections

(BIŌNTE Technical Department, 2025; Sandu and Swayne, 2024).

Ochratoxin A Exposure

Typical signs include:

• Poor growth performance
• Poor FCR
• Increased water intake
• Wet litter
• Enlarged kidneys
• Kidney degeneration
• Reduced immune function

(Sandu and Swayne, 2024).

DON (Vomitoxin) Exposure

Typical signs include:

• Reduced feed intake
• Intestinal irritation
• Reduced nutrient absorption
• Poor growth performance
• Increased gut permeability

(Olariu et al., 2025; Montayeva et al., 2026).

T-2 Toxin Exposure

Typical signs include:

• Oral lesions
• Mouth ulcers
• Necrosis of the tongue and palate
• Severe feed refusal
• Weight loss
• Feather abnormalities

(Sandu and Swayne, 2024; BIŌNTE Technical Department, 2025).

Fumonisin Exposure

Typical signs include:

• Reduced growth
• Poor feed efficiency
• Increased disease susceptibility
• Liver enlargement
• Immunosuppression

(Mokubedi et al., 2019; Olariu et al., 2025).

Prevention and Mitigation Strategies

Feed Ingredient Monitoring

The most effective method of controlling mycotoxicosis is preventing contaminated ingredients from entering the feed manufacturing process. Regular monitoring of maize, wheat, soybean meal, and finished feed through laboratory testing is essential (Mokubedi et al., 2019). South African studies have demonstrated widespread contamination of poultry feed with multiple mycotoxins, emphasizing the importance of routine surveillance programs (Mokubedi et al., 2019).

Proper Grain Storage

Mycotoxin prevention begins with proper storage. Grain moisture content should be maintained below 13-14%, and storage facilities should be adequately ventilated to prevent condensation and fungal proliferation (Sandu and Swayne, 2024). Effective insect and rodent control further reduces opportunities for mould growth and toxin formation (Montayeva et al., 2026).

Mycotoxin Binders

Mycotoxin binders remain one of the most widely adopted nutritional interventions in poultry production.

Examples include:

• Bentonite
• Montmorillonite
• Zeolite
• Hydrated sodium calcium aluminosilicate (HSCAS)

These products bind toxins within the gastrointestinal tract and reduce their absorption into the circulation (Olariu et al., 2025). Clay-based binders are especially effective against aflatoxins (Montayeva et al., 2026).

Yeast Cell Wall Products

Yeast-derived products containing mannan oligosaccharides (MOS) and β-glucans can provide broader-spectrum toxin-binding activity while simultaneously supporting gut health and immune function (Olariu et al., 2025). These products are increasingly utilized in commercial broiler programs.

Biological Detoxification

Certain bacterial and yeast strains can bind or enzymatically degrade mycotoxins. Species of Bacillus, Lactobacillus, and Saccharomyces have demonstrated potential to reduce toxin bioavailability and improve intestinal health (Montayeva et al., 2026). Enzymatic detoxification technologies have shown particular promise against DON, fumonisins, and zearalenone (Olariu et al., 2025).

Nutritional Support

Because mycotoxins induce oxidative stress and inflammation, nutritional interventions can help maintain resilience and immune competence.

Important nutrients include:

• Vitamin E
• Vitamin C
• Selenium
• Zinc
• Methionine
• Choline

These nutrients support antioxidant defense systems, liver function, immune activity, and tissue repair processes (Montayeva et al., 2026; Olariu et al., 2025).

Gut Health Programs

Modern mitigation strategies increasingly focus on gut health. The inclusion of probiotics, prebiotics, organic acids, and butyrate products can improve intestinal integrity, reduce pathogen proliferation, and support immune function during periods of mycotoxin challenge (Montayeva et al., 2026).

References

BIŌNTE Technical Department (2025) Mycotoxicosis in poultry: Clinical signs. Available at: https://www.bionte.com (Accessed: 5 October 2026).

Mokubedi, S.M., Phoku, J.Z., Changwa, R.N., Gbashi, S. and Njobeh, P.B. (2019) ‘Analysis of mycotoxins contamination in poultry feeds manufactured in selected provinces of South Africa using UHPLC-MS/MS’, Toxins, 11(8), pp. 452-469.

Montayeva, N., Nurgaliyev, B., Kereyev, A., Nagimova, G. and Kushmukhanov, Z. (2026) ‘One Health perspective on mycotoxins in poultry production: Ecology, toxicological effects, occupational and environmental exposure, food safety risks, and mitigation strategies (2020-2025)’, Veterinary World, 19(5), pp. 2172-2207.

Olariu, R.M., Fiţ, N.I., Bouari, C.M. and Nadăş, G.C. (2025) ‘Mycotoxins in broiler production: Impacts on growth, immunity, vaccine efficacy, and food safety’, Toxins, 17(6), Article 261.

Sandu, D. and Swayne, D.E. (2024) Mycotoxicoses in Poultry. MSD Veterinary Manual. Available at: https://www.msdvetmanual.com (Accessed: 5 October 2026).