Chicken Mycotoxicosis: Feed Toxins Affecting the Gut, Mouth, and Liver

Chicken mycotoxicosis is illness caused by mycotoxins, which are toxic chemicals made by certain molds growing in feed ingredients. In poultry, the most important toxins include aflatoxins, ochratoxins, fumonisins, zearalenone, and trichothecenes such as deoxynivalenol (DON) and T-2 toxin. These toxins may be present even when feed does not look dramatically moldy, so a bag that seems only slightly stale or dusty can still be a problem.

The effects depend on the toxin, dose, and how long your flock has been exposed. Some birds develop mouth irritation, ulcers, and feed refusal, especially with trichothecenes. Others show diarrhea, poor weight gain, weak immunity, lower egg production, or liver injury, which is common with aflatoxins. Merck notes that mycotoxins can also interact with infections, nutrition problems, medications, and vaccines, which is one reason signs can look confusing.

For pet parents, the key point is that mycotoxicosis is usually a feed and environment problem first, then a medical problem second. Your vet will often want to evaluate the birds and the feed source at the same time. Early removal of the suspected feed can make a meaningful difference, but chickens with severe dehydration, liver damage, or extensive mouth lesions may still need hands-on veterinary care.

Mycotoxicosis happens when chickens eat feed or grain contaminated by molds that produce toxins. These molds may grow before harvest in the field or after harvest during storage, especially when grain is exposed to moisture, heat, insect damage, or poor ventilation. Aflatoxins are classically associated with Aspergillus species, while several trichothecenes and DON are associated with Fusarium molds.

Backyard flocks are at risk when feed is stored in humid sheds, metal cans with condensation, open bags, or bins that are not cleaned between batches. Wet scratch grains, spoiled treats, moldy bread, damp litter contamination, and old feed left through seasonal weather swings can all contribute. Even if only part of a bag looks clumped or musty, toxins may be distributed more widely than the visible mold.

Different toxins target different organs. Aflatoxins are well known for liver damage and immune suppression. Ochratoxins can contribute to poor feed conversion, diarrhea, and production losses. Trichothecenes, including T-2 toxin, are especially irritating to the mouth and upper digestive tract and can cause necrosis and ulceration. More than one mycotoxin may be present at the same time, which can make illness more severe and signs less predictable.

Diagnosis usually starts with a careful history. Your vet will ask about recent feed changes, storage conditions, moisture exposure, flock size, how many birds are affected, and whether signs started after opening a new bag or grain source. Because mycotoxicosis can look like infection, parasites, vitamin deficiencies, or chemical poisoning, diagnosis is often a process of ruling out other causes while investigating the feed.

A hands-on exam may be followed by oral examination, body condition assessment, fecal review, and bloodwork in valuable birds when practical. If a bird dies or is euthanized, necropsy can be very helpful. Merck notes that diagnosis requires detection and quantification of the specific mycotoxin, so your vet may recommend submitting a feed sample for aflatoxin or mycotoxin screening and, in some cases, tissue testing through a veterinary diagnostic laboratory.

In real-world flock medicine, your vet may make a presumptive diagnosis when the pattern fits: several birds exposed to the same feed, compatible signs, no better explanation, and improvement after the feed is removed. That said, lab confirmation matters when losses are ongoing, when food safety is a concern, or when you may need documentation for a feed complaint.

Prevention starts with feed storage. Keep feed in a cool, dry, well-ventilated area, off the floor, and protected from rain, condensation, rodents, and insects. Buy amounts your flock can use within a reasonable time, rotate stock so older feed is used first, and clean bins before adding a new batch. If feed smells musty, feels damp, looks clumped, or shows visible mold, do not feed it.

Use reputable feed sources and pay extra attention after drought, crop stress, insect damage, or humid storage conditions, because these increase mycotoxin risk. Merck also notes that monitoring crop and storage conditions and testing suspect feed are important prevention tools. If your flock has had a prior problem, ask your vet whether keeping a sample from each new feed batch is worthwhile in case testing is needed later.

Do not rely on home remedies alone to make contaminated feed safe. Some adsorbent products have partial benefit for certain toxins, but Merck notes that efficacy is variable and that the FDA has not licensed any product for use as a mycotoxin binder in animal feeds in the US. In practice, the safest prevention plan is good storage, fast turnover, prompt disposal of suspect feed, and early veterinary input when several birds become sick together.