Chicken Gizzard Erosion: Causes of Gizzard Ulcers and Damage

Chicken gizzard erosion is damage to the koilin layer, the tough protective lining inside the gizzard. The gizzard is the muscular part of a chicken's stomach that grinds feed. When that lining becomes rough, thinned, cracked, or ulcerated, the tissue underneath is more exposed to irritation, bleeding, and secondary damage.

This condition is not one single disease. It is a lesion pattern your vet may see when something has injured the gizzard, such as infection, toxins, poor feed quality, or a nutritional imbalance. In chickens, fowl adenovirus has been linked with gizzard erosions, and nutritional problems such as pyridoxine or vitamin B12 deficiency have also been reported. Mycotoxins and other feed-related irritants can contribute as well.

Some birds have only mild changes and few outward signs. Others become thin, weak, off feed, or pass dark droppings if there is bleeding. In backyard flocks, the challenge is that the symptoms often look like many other digestive or flock health problems, so your vet usually needs to look at the whole picture before deciding what is most likely.

Gizzard erosion usually develops when the koilin lining is injured faster than it can repair itself. One important infectious cause is fowl adenovirus, especially strains associated with adenoviral gizzard erosion. These viruses can damage the glands that produce koilin, leading to patchy loss of the protective surface and deeper ulceration.

Feed-related causes are also important. Mycotoxins from moldy grain or poorly stored feed can injure the digestive tract and make birds sick in more than one way at the same time. Some toxic exposures in poultry are reported to cause erosions of the koilin layer. Irritating feed ingredients, rancid fats, or poor feed handling may also worsen gizzard damage.

Nutritional problems can contribute, especially when the diet is unbalanced or homemade rations are not carefully formulated. Merck notes that pyridoxine deficiency has been associated with gizzard erosion in chicks, and vitamin B12 deficiency has also been reported with gizzard erosion among other signs. In real backyard settings, stress, concurrent disease, and low-quality feed can overlap, so there may be more than one cause at the same time.

Less commonly, your vet may also consider abrasive foreign material, medication history, or broader flock management issues. That is why a careful review of feed source, storage, supplements, recent flock additions, and any sudden management changes matters so much.

Your vet usually starts with a history and flock review. They may ask about age of the birds, how many are affected, feed brand and storage, access to moldy bedding or spilled grain, growth rate, egg production, and whether any new birds were added recently. A physical exam can help assess body condition, dehydration, anemia, and whether the problem seems limited to one bird or the whole flock.

Definitive diagnosis often requires seeing the gizzard lining directly. In poultry medicine, necropsy is often the most practical way to confirm erosions, ulcers, koilin loss, or bleeding. If your chicken has died or must be euthanized, your vet or a veterinary diagnostic lab may examine the gizzard and collect samples. PCR or other lab testing may be used if adenovirus is suspected, and feed testing may be recommended if mycotoxins are a concern.

Additional testing depends on the case. Your vet may suggest fecal testing to rule out other causes of weight loss or dark droppings, bloodwork in valuable individual birds, or submission to a state or university diagnostic lab. In the U.S., a basic exam for a backyard chicken often falls around $75-$150, fecal testing may add $25-$100, bloodwork may add $100-$250, and diagnostic necropsy or lab submission commonly ranges from about $35-$150+ depending on the lab and whether flock discounts apply.

Prevention starts with feed quality and storage. Buy fresh feed from a reliable source, store it in a dry rodent-proof container, and avoid feeding anything that smells musty, looks clumped, or shows visible mold. Mycotoxin prevention depends heavily on keeping feed and ingredients dry during storage and transport.

Balanced nutrition matters too. Homemade or heavily supplemented diets can create unintended deficiencies or excesses, especially in growing birds. If you feed anything other than a complete commercial ration, ask your vet or a poultry nutrition professional whether the diet is truly balanced for your flock's age and purpose.

Good flock management also lowers risk. Quarantine new birds, reduce stress, keep housing clean and dry, and watch for patterns such as poor growth, reduced appetite, or multiple birds becoming thin. If one chicken dies unexpectedly, early necropsy can help protect the rest of the flock.

Routine check-ins with your vet are especially helpful for backyard chickens because digestive disease signs are often subtle at first. Catching a feed issue, deficiency, or infectious problem early gives you more treatment options and may reduce losses across the flock.