What is sour crop in chickens?

It is candidiasis — an opportunistic yeast overgrowth in the crop, primarily Candida albicans, which takes hold when the normal microflora of the digestive tract is disrupted. Merck describes thickened crop mucosa with "whitish, raised pseudomembranes", sometimes with shallow ulcers, and affected birds showing listlessness and loss of appetite. To a keeper it presents as a crop that feels like a squishy water balloon and breath that smells sour or yeasty.

What causes sour crop?

Merck names the predisposing factors explicitly, and they are the useful part because they are what you can actually change: recent administration of antimicrobials, unsanitary drinking facilities, heavy parasitism, and malnutrition — specifically vitamin A deficiency. Young chicks and poults are most susceptible. So a bird who developed sour crop after a course of antibiotics, or who drinks from a waterer with a slimy biofilm inside it, has a cause you can name rather than bad luck.

Should I make my chicken vomit to empty the crop?

No — never. Holding a bird upside down to empty a sour crop is widely recommended and it kills chickens. A bird cannot protect her airway the way a mammal can, and crop fluid running into the lungs causes aspiration pneumonia that is far more lethal than the yeast infection you were trying to treat. If a crop genuinely needs emptying, that is done by a vet. This is the single most dangerous piece of backyard poultry advice in common circulation.

What is the difference between sour crop and impacted crop?

What it feels like, and it is worth being sure which you have. A sour crop is soft, squishy and fluid-filled, like a water balloon, and the breath smells sour. An impacted crop is hard and firm, like a golf ball, and is a physical blockage — usually long grass, hay or bedding — rather than an infection. The test for both is the same: feel the crop last thing at night and again first thing in the morning before she eats. A crop full at night and empty at dawn is working normally. One that is still full at dawn is not emptying, and which of the two it is depends on whether it feels soft or hard.

Can sour crop kill a chicken?

It can, particularly in young birds and particularly when it is secondary to something else. Merck notes that young chicks and poults are the most susceptible, and that heavy parasitism and malnutrition are predisposing factors — so a bird with sour crop is often a bird with another problem underneath. That is the reason to treat it as a vet case rather than a home remedy: the yeast may be the visible symptom of a worm burden, a deficiency, or a course of antibiotics that wrecked her gut flora.

Sour Crop in Chickens

A squishy, foul-smelling crop is a yeast overgrowth — and usually a symptom of something else. Here is how to identify it, what causes it, and the one thing you must never do.

Figures reviewed against published veterinary guidance · Last reviewed August 2026

Never hold a chicken upside down to empty her crop

This is recommended constantly and it kills birds. A chicken cannot protect her airway the way a mammal can, so crop fluid runs into the lungs and causes aspiration pneumonia — far more lethal than the infection you were treating. If a crop genuinely needs emptying, a vet does it. This is the most dangerous advice in common circulation about chickens.

What sour crop actually is

Sour crop is candidiasis — an opportunistic yeast overgrowth, primarily Candida albicans, which takes hold when the normal microflora of the digestive tract gets disrupted. Merck describes the crop developing thickened mucosa with "whitish, raised pseudomembranes", occasionally with shallow ulcers and sloughing tissue, and the bird becoming listless and off her feed.

The word "opportunistic" is the important one. The yeast is normally present and harmless; it becomes a problem when something else lets it take over. Which means sour crop is usually a symptom, not the disease — and treating only the crop leaves the actual cause in place.

Sour crop or impacted crop?

These get confused constantly and they are different problems. The distinction is what it feels like in your hand:

	Sour crop	Impacted crop
Feel	Soft, squishy, fluid — like a water balloon	Hard and firm — like a golf ball
Smell	Sour, yeasty, fermenting	Usually nothing distinctive
Cause	Yeast overgrowth, secondary to something else	Physical blockage — long grass, hay, bedding

The test for both is the same, and it is free. Feel the crop last thing at night, then again first thing in the morning before she eats. A crop full at night and empty at dawn is doing its job — nothing is wrong. A crop still full at dawn is not emptying, and whether it feels soft or hard tells you which problem you have.

The four causes worth checking

Merck names the predisposing factors, and these are the genuinely actionable part of the page — each one is something you can inspect today:

Recent antibiotics. Merck notes candidiasis "commonly develops after administration of therapeutic amounts of various antimicrobials". If she finished a course recently, that is very likely your answer.
Unsanitary drinking facilities. Named explicitly. Put your hand inside the waterer — if it feels slimy, that biofilm is a yeast culture and every bird is drinking from it.
Heavy parasitism. A worm burden or a heavy mite load drags a bird down enough for opportunistic infections to take hold.
Malnutrition, specifically vitamin A deficiency. Worth asking whether the ration is genuinely complete or has drifted toward scratch and scraps — our treat calculator puts the 90/10 rule in ounces.

Merck also notes that young chicks and poults are most susceptible, so sour crop in a brooder is more serious than in an adult hen.

Treatment, honestly

This is where we part company with most of what you will read. Merck notes nystatin as a treatment used in poultry, but also states plainly that "no approved products are available for the treatment of candidiasis in the US."

So an antifungal is a veterinary conversation, not something to order online and dose by guesswork. We are not going to give you a dose, because there is no approved product to dose and inventing one would be worse than admitting the gap.

What you can do today, safely, without a vet:

Scrub and disinfect every waterer. Not rinse — scrub. This is a named cause and it is entirely in your control.
Separate her somewhere quiet where you can see what she eats and whether the crop is emptying.
Check for parasites — vent, feather bases, and the roosts after dark.
Review the feed. Complete ration in front of her, treats cut right back while she recovers.
Ring a vet, especially for a chick or a bird losing condition.

Notice what is missing: no withholding food for 12 hours, no crop massage schedule, no apple cider vinegar protocol. Those circulate widely and we could not find veterinary sourcing for any of them, so they are not here.

A worked example

A two-year-old hen finished a course of antibiotics for a respiratory infection ten days ago. She has gone quiet, is not interested in her feed, and her crop feels soft and full at eight in the morning. Her breath smells like bread dough.

The morning-full crop confirms it is not emptying; soft and sour rather than hard points at candidiasis rather than impaction. And the cause is sitting right there in the history — Merck names antimicrobial treatment as the leading predisposing factor, and she finished a course last week.

So: separate her, scrub the waterers regardless, and ring the vet who prescribed the antibiotics, because they already know the case and the yeast is a consequence of the treatment rather than a new mystery. Do not turn her upside down.

Sources

The organism, the crop lesions, the predisposing factors and the treatment position are all from the Merck Veterinary Manual entry on candidiasis in poultry, including its statement that no approved products are available for treating candidiasis in the US. No doses appear on this page for that reason. The aspiration warning is a mechanism, not a statistic: a bird cannot protect her airway, so inverting her risks drowning her in crop fluid.

Merck Veterinary Manual — Candidiasis in Poultry
Merck Veterinary Manual — Common Infectious Diseases in Backyard Poultry
UC Davis Veterinary Medicine — Backyard Poultry Health and Disease Identification
University of Florida IFAS Extension — Raising Backyard Chickens for Eggs (AN239)

Frequently asked questions

What is sour crop in chickens?: It is candidiasis — an opportunistic yeast overgrowth in the crop, primarily Candida albicans, which takes hold when the normal microflora of the digestive tract is disrupted. Merck describes thickened crop mucosa with "whitish, raised pseudomembranes", sometimes with shallow ulcers, and affected birds showing listlessness and loss of appetite. To a keeper it presents as a crop that feels like a squishy water balloon and breath that smells sour or yeasty.
What causes sour crop?: Merck names the predisposing factors explicitly, and they are the useful part because they are what you can actually change: recent administration of antimicrobials, unsanitary drinking facilities, heavy parasitism, and malnutrition — specifically vitamin A deficiency. Young chicks and poults are most susceptible. So a bird who developed sour crop after a course of antibiotics, or who drinks from a waterer with a slimy biofilm inside it, has a cause you can name rather than bad luck.
How do you treat sour crop?: Honestly: through a vet, and this is one place where the internet is more confident than the evidence. Merck notes nystatin as a treatment used in poultry but states plainly that "no approved products are available for the treatment of candidiasis in the US" — so an antifungal is a veterinary conversation, not something to order online and dose by guesswork. What you can do immediately and safely is remove the cause: scrub and disinfect every waterer, check for parasites, and review whether the feed is a complete ration or has drifted toward treats.
Should I make my chicken vomit to empty the crop?: No — never. Holding a bird upside down to empty a sour crop is widely recommended and it kills chickens. A bird cannot protect her airway the way a mammal can, and crop fluid running into the lungs causes aspiration pneumonia that is far more lethal than the yeast infection you were trying to treat. If a crop genuinely needs emptying, that is done by a vet. This is the single most dangerous piece of backyard poultry advice in common circulation.
What is the difference between sour crop and impacted crop?: What it feels like, and it is worth being sure which you have. A sour crop is soft, squishy and fluid-filled, like a water balloon, and the breath smells sour. An impacted crop is hard and firm, like a golf ball, and is a physical blockage — usually long grass, hay or bedding — rather than an infection. The test for both is the same: feel the crop last thing at night and again first thing in the morning before she eats. A crop full at night and empty at dawn is working normally. One that is still full at dawn is not emptying, and which of the two it is depends on whether it feels soft or hard.
Can sour crop kill a chicken?: It can, particularly in young birds and particularly when it is secondary to something else. Merck notes that young chicks and poults are the most susceptible, and that heavy parasitism and malnutrition are predisposing factors — so a bird with sour crop is often a bird with another problem underneath. That is the reason to treat it as a vet case rather than a home remedy: the yeast may be the visible symptom of a worm burden, a deficiency, or a course of antibiotics that wrecked her gut flora.