Yeast infections in chickens, commonly called sour crop or thrush, are treated by clearing the yeast overgrowth with antifungal medication while supporting the bird’s recovery with dietary changes and crop massage. The yeast responsible is usually Candida, a fungus that normally lives in small numbers in a chicken’s digestive tract but multiplies out of control when something disrupts the balance of healthy gut bacteria.
Most backyard chicken keepers can manage a mild case at home, but moderate to severe infections often need veterinary-prescribed antifungals. The key is catching it early and understanding what caused the imbalance in the first place.
How to Identify Sour Crop
The simplest diagnostic test takes about ten seconds. First thing in the morning, before your chicken has eaten anything, feel her crop. A healthy crop will be empty and flat, almost hard to find. You should be able to move it around freely with your fingers. A chicken with sour crop will still have a full, squishy crop in the morning because food isn’t moving through properly. The crop feels like a water balloon rather than a golf ball (a hard, immovable crop points to an impaction, which is a different problem requiring different treatment).
The hallmark sign is smell. Sour crop produces a distinctly foul, fermented odor, often noticeable when you pick the bird up or when she opens her beak. In more advanced cases, you may see a fine white film inside the mouth or along the esophagus. This is the Candida colony spreading upward from the crop. Other signs include lethargy, loss of appetite, weight loss, and sometimes regurgitation of sour-smelling liquid.
What Causes Yeast Overgrowth
Candida is an opportunistic organism. It’s already present in your chicken’s gut and only becomes a problem when something knocks the normal bacterial population out of balance. The most common trigger is antibiotic use. Broad-spectrum antibiotics kill beneficial bacteria alongside harmful ones, leaving a gap that yeast fills quickly. If you’ve recently treated a bird for a bacterial illness, yeast overgrowth is a known secondary risk.
Other causes include dirty waterers (especially in warm weather when standing water breeds microorganisms), vitamin A deficiency, heavy parasite loads, and diets too high in sugar or simple carbohydrates like bread. Anything that slows crop motility, such as eating long grass or fibrous material that partially blocks the crop, can also create conditions where yeast thrives.
First Steps: Isolation and Crop Emptying
Separate the affected bird from the flock and place her in a warm, quiet space with clean water. This reduces stress and lets you monitor her food and water intake closely. Withhold food (not water) for 12 to 24 hours to let the crop empty as much as possible. A crop full of fermenting material is essentially feeding the yeast, so you want to clear it before starting treatment.
Gentle crop massage can help move stagnant contents along. Hold the bird upright and use your fingers to softly knead the crop in a downward motion toward the body several times a day. Do not tip the bird upside down to try to empty the crop manually. This risks aspiration, where liquid enters the airway and lungs, which can be fatal.
When you reintroduce food, offer small amounts of soft, easily digestible options like plain scrambled eggs, moistened layer feed, or plain yogurt. Avoid bread, scratch grains, and treats until the crop is functioning normally again.
Over-the-Counter Antifungal Options
For mild to moderate cases, many chicken keepers use miconazole, the same antifungal sold as a vaginal suppository for humans. Use a generic brand without propylene glycol, which can be harmful to birds. The typical protocol is to give one-quarter of a suppository orally for bantam breeds or one-third for standard-sized birds, once daily for a minimum of three days. Combine this with crop massage several times a day to help distribute the medication and move contents through.
Apple cider vinegar is a widely used preventive measure and mild treatment for early-stage cases. It works by lowering the pH of the crop environment, making it less hospitable to yeast. The recommended dilution is about 20 milliliters of raw, unfiltered apple cider vinegar per liter of drinking water (roughly a 2% solution). Use plastic waterers only, since the acid corrodes metal. This is best thought of as a supportive measure rather than a standalone cure for an established infection.
Copper Sulfate Water Treatment
Copper sulfate, sometimes called bluestone, is an older but effective treatment used by poultry producers for crop mycosis. Mississippi State University Extension recommends dissolving half a pound of copper sulfate and half a cup of vinegar into one gallon of water to create a stock solution, then dispensing that stock at a rate of one ounce per gallon for the actual drinking water. A simpler method is dissolving one ounce of copper sulfate and one tablespoon of vinegar directly into 15 gallons of water. Either version serves as the bird’s sole water source during treatment.
This approach works best as a follow-up after the crop has been partially cleared. Copper sulfate is effective but can irritate the digestive tract at incorrect concentrations, so measure carefully.
Veterinary-Prescribed Antifungals
When home treatment doesn’t resolve the infection within a few days, or if the bird is visibly declining, a veterinarian can prescribe nystatin or fluconazole. Nystatin is the standard first-line antifungal for poultry candidiasis. For flock-level treatment, it can be added to feed at 110 milligrams per kilogram of feed, given once daily for 7 to 10 days, or mixed into drinking water for five days. Your vet will determine the appropriate dose for an individual bird.
Fluconazole is typically reserved for stubborn infections that don’t respond to nystatin. It’s given orally, usually twice daily. Fungal infections are notoriously slow to clear, and treatment with fluconazole can take weeks or even months in resistant cases. Your vet will likely start at a standard dose and may reduce it once the bird improves.
Preventing Recurrence
The most effective long-term prevention targets the conditions that allow Candida to take over. Clean and refill waterers frequently, especially during summer. Standing water in warm conditions is one of the most common sources of yeast exposure. Scrub waterers with a dilute bleach solution at least weekly.
If your birds have recently finished a course of antibiotics, follow up with a probiotic supplement to rebuild healthy gut bacteria. Lactobacillus strains, particularly Lactobacillus acidophilus and Lactobacillus reuteri, compete directly with harmful organisms for space and nutrients in the gut lining. Poultry-specific probiotics are available at feed stores, but plain yogurt with live active cultures also works as a short-term source. Research on broiler chickens has shown that Lactobacillus strains given early in life significantly shape gut microbiota development, reducing colonization by harmful organisms.
Ensure your flock’s diet includes adequate vitamin A, which supports the health of the mucosal lining throughout the digestive tract. Leafy greens, carrots, and sweet potatoes are good supplemental sources. Keep pastures mowed to prevent chickens from eating long, fibrous grass that can slow crop motility. And resist the urge to offer sugary or starchy treats like bread, which essentially feeds yeast in the crop.
A bird that has had sour crop once is somewhat more likely to develop it again, especially if the underlying cause (like a stretched or pendulous crop) hasn’t been resolved. A pendulous crop hangs visibly in front of the bird and doesn’t empty efficiently, creating a chronic environment for yeast. Birds with this condition may need ongoing management, including smaller, more frequent meals and periodic apple cider vinegar in their water.