Aflatoxicosis in Chickens: Moldy Feed Liver Toxicity
- Aflatoxicosis is poisoning from aflatoxins, toxins made by certain Aspergillus molds that can grow in feed ingredients such as corn, peanuts, and stored grain.
- In chickens, the liver is the main organ affected. Birds may show poor appetite, slow growth, pale combs, bruising or bleeding, reduced egg production, weakness, or sudden deaths in severe outbreaks.
- See your vet promptly if more than one bird is affected, if feed smells musty or looks caked or moldy, or if birds are weak, bleeding, or dying.
- Early care often starts with removing the suspected feed immediately, supportive care, and testing feed or affected birds to confirm the problem and rule out infections or other toxins.
- Typical US veterinary cost range for a backyard flock workup is about $120-$600 for exam, basic testing, and feed review, with higher costs if lab toxin testing, necropsy, or hospitalization is needed.
What Is Aflatoxicosis in Chickens?
Aflatoxicosis is a poisoning syndrome caused by aflatoxins, toxic compounds produced by certain Aspergillus molds. These molds can grow in feed ingredients before harvest, during storage, or after feed gets damp and warm. In chickens, the toxin mainly targets the liver, but it can also affect immunity, digestion, blood clotting, growth, and egg production.
Chickens are generally more resistant than ducklings or turkeys, but they can still become sick when exposure is high enough or lasts long enough. Backyard flocks may be exposed through moldy bagged feed, wet scratch grains, spoiled treats, or feed stored in humid conditions. Even when mold is not obvious, toxins may still be present.
Some birds develop a sudden, severe illness after eating heavily contaminated feed. Others show a slower decline over days to weeks, with poor body condition, reduced laying, and vague signs that can look like many other flock problems. That is why a careful history, feed review, and veterinary guidance matter.
If you suspect moldy feed, stop offering it and contact your vet. Do not assume birds will recover on their own, especially if several chickens are affected at once.
Symptoms of Aflatoxicosis in Chickens
- Poor appetite or feed refusal
- Slow growth or weight loss
- Lethargy, weakness, or flock unthriftiness
- Pale combs or wattles
- Drop in egg production or poorer shell quality
- Easy bruising, small hemorrhages, or bleeding problems
- Diarrhea or loose droppings
- Ruffled feathers and poor body condition
- Increased illness from other infections due to immune suppression
- Sudden deaths in severe exposure
Signs can be acute or chronic. Mild to moderate exposure may look like a vague flock slump, with reduced feed intake, slower growth, fewer eggs, and birds that never seem to thrive. More severe exposure can cause weakness, bleeding, marked depression, and death.
See your vet immediately if birds are collapsing, bleeding, dying suddenly, or if multiple chickens become sick after a new bag of feed or after feed got wet. Aflatoxicosis can overlap with infectious disease, heavy metal exposure, coccidiosis, and other toxicities, so a veterinary exam is the safest next step.
What Causes Aflatoxicosis in Chickens?
Aflatoxicosis happens when chickens eat feed contaminated with aflatoxins, most often aflatoxin B1. These toxins are produced by molds such as Aspergillus flavus and Aspergillus parasiticus. Common risk ingredients include corn, peanut products, cottonseed products, and other grains or plant-based feed ingredients.
The problem is usually tied to moisture, heat, and storage conditions. Feed stored on damp concrete, in leaky bins, in humid sheds, or for too long is more likely to spoil. Backyard flocks are also at risk when feed is left in troughs long enough to cake, get rained on, or grow mold. A musty smell, clumps, discoloration, or visible mold are red flags, but toxins can be present even when feed looks normal.
Young birds are usually more sensitive than mature birds. Long-term low-level exposure can still hurt flock health by reducing growth, feed efficiency, fertility, hatchability, and immune function. In the US, regulatory action levels for aflatoxin in feed vary by species and use, but feed for immature animals is held to a lower threshold than feed for mature poultry.
It is also important to remember that more than one mycotoxin may be present at the same time. That can make signs less predictable and may worsen the overall effect on the flock.
How Is Aflatoxicosis in Chickens Diagnosed?
Your vet diagnoses suspected aflatoxicosis by combining the history, flock pattern, exam findings, and testing. A recent feed change, damp storage, visible mold, or several birds getting sick at once can raise concern. Because the signs are not specific, your vet will also consider infections, nutritional problems, parasites, and other toxins.
Testing may include a physical exam of affected birds, bloodwork in valuable individuals, and necropsy if a bird has died or needs humane euthanasia for diagnosis. The liver may appear enlarged, pale yellow, fatty, congested, or hemorrhagic. Your vet may also recommend histopathology to look for liver cell injury and related changes.
Feed testing is often one of the most useful steps. A sample of the suspected ration can be sent to a diagnostic or feed laboratory to measure aflatoxin levels. If possible, bring the original bag, lot information, and a representative sample from the feed actually offered to the flock.
A confirmed diagnosis often depends on putting several pieces together rather than relying on one test alone. That is another reason to involve your vet early, before the feed is discarded and before more birds are exposed.
Treatment Options for Aflatoxicosis in Chickens
Spectrum of Care means you have options. Here are treatment tiers at different price points.
Budget-Conscious Care
- Immediate removal and disposal of suspected feed
- Replacement with fresh, dry feed from a new source
- Clean, dry feeders and waterers
- Warmth, reduced stress, and close flock monitoring
- Basic veterinary guidance by phone or office visit
- Isolation of the weakest birds for easier observation and access to feed and water
Recommended Standard Treatment
- Veterinary exam and flock history review
- Feed assessment and recommendation to stop suspected ration
- Necropsy of a deceased bird or diagnostic sampling when appropriate
- Feed sample submission for aflatoxin testing
- Supportive care plan such as fluids, nutritional support, and management changes as directed by your vet
- Treatment of secondary problems if present, such as dehydration or concurrent disease
Advanced / Critical Care
- Hospitalization for valuable or severely affected birds
- Injectable or tube-administered fluids and intensive supportive care as directed by your vet
- Serial bloodwork to monitor liver injury and clotting concerns when available
- Histopathology and comprehensive laboratory testing
- Management plan for larger flock outbreaks or breeding stock
- Consultation with a poultry specialist or diagnostic laboratory
Cost estimates as of 2026-03. Actual costs vary by location, clinic, and individual case.
Questions to Ask Your Vet About Aflatoxicosis in Chickens
Bring these questions to your vet appointment to get the most out of your visit.
- Do my chickens' signs fit aflatoxicosis, or are there other likely causes we should rule out first?
- Should I bring a feed sample, the bag label, and lot number for testing?
- Would necropsy or lab testing help confirm liver damage or toxin exposure in this flock?
- Which birds need to be seen right away, and which can be monitored at home?
- What supportive care is appropriate for my flock size and setup?
- How long should I watch for delayed effects on growth, egg production, or fertility?
- Do I need to worry about other mycotoxins or a secondary infection at the same time?
- What feed storage changes would most reduce the risk of this happening again?
How to Prevent Aflatoxicosis in Chickens
Prevention starts with feed quality and storage. Buy feed from a reliable source, check bags for damage, and avoid buying more than your flock can use while it is still fresh. A practical rule for backyard flocks is to avoid storing feed too long, especially in hot weather. Keep it in a clean, dry, rodent-proof area and off concrete floors so it does not wick up moisture.
Use containers that stay dry and protect feed from rain, condensation, and pests. Clean feeders regularly so old feed does not cake in corners. If feed smells musty, looks clumped, feels damp, or shows visible mold, do not feed it. Throw it out and clean the storage area before opening a new bag.
Good flock management also helps. Offer only what your birds will eat in a reasonable time, and do not let wet feed sit in troughs. Rotate stock so older feed is used first. If you keep a larger flock or have had a prior mycotoxin problem, your vet may discuss whether feed testing or commercial mycotoxin-control strategies make sense for your situation.
Most importantly, never try to "use up" suspicious feed. With aflatoxins, the safest choice is to stop exposure early and involve your vet if any bird seems off.