Sour crop is one of those poultry issues that can sneak up on you—and often looks a lot like an upper respiratory infection at first glance. While it can carry a distinctive foul smell, that’s not always the case. In fact, many chicken keepers report noticing a gurgling sound before they ever see or smell anything unusual.
I will say—sour crop is the most common issue I see in poultry. I’ve seen it triggered by stress, heat, humidity, sudden rain, changes in feed, wet or mouldy feed and especially too many treats—particularly those high in protein. Chickens have surprisingly sensitive digestive systems, and sometimes all it takes is a small disruption to throw things off. The good news? A lot of the time, they resolve it on their own without any treatment at all.
🍞 Think of the Crop Like Bread Dough
A chicken’s crop is where food is stored before digestion. If conditions are just right (or just wrong), yeast can start to ferment the contents—like proofing yeast in bread dough. It bubbles, foams, and rises. The same idea is happening in their crop.
As gas builds, the contents can bubble up into the throat, causing a very audible gurgling or popping sound, which often sounds extremely alarming to owners. The biggest concern if this isn’t addressed is the risk of aspiration—where fluid enters the airway—potentially leading to a secondary respiratory infection.
The problem? Chickens can’t vomit. So when gas builds up and food ferments, it has nowhere to go.
🔎 What Are the Signs of Sour Crop?
Here’s what you might observe:
- Gurgling noises from the crop or upper throat
- Crop feels squishy or balloon-like, especially in the morning
- Bad breath or sour odor (but not always present!)
- Lethargy or reluctance to eat
- Head shaking or stretching the neck repeatedly
- Liquid coming out of the mouth if gently tipped forward
🧪 The (Not-So-Perfect) Upside-Down Test
Some keepers try gently tipping the chicken forward while securely holding it, to see if fluid leaks out of the mouth. If liquid drains, that can be a sign of a crop issue like sour crop. But this test is not always accurate and can be risky if not done carefully—aspiration is a real danger.
⏰ Early Detection Is Key
Sour crop is much easier to treat if caught early. Left untreated, it can lead to:
- Impacted crop
- Systemic fungal infection
- Severe weight loss or death
If you're unsure, it’s always better to address it sooner rather than later.
🩺 Suspect Sour Crop? Here’s What to Do First
If you think you’re dealing with sour crop, the first and most important step is to separate the bird. Isolation allows you to monitor their intake and output closely without interference—and prevents them from continuing to eat, which can make the issue worse.
1. Pull Feed, but Not Water
You’ll want to remove all feed for the first 12 to 24 hours. This gives the crop time to break down and empty what’s already in there, allowing the gut to settle and reset. Continue to offer clean, fresh water—hydration is still essential.
2. Access and Notate Crop Size, Shape amd Texture
Understand Normal Crop Function: A chicken’s crop gradually fills during the day as they eat and typically empties overnight while they rest. By morning, it should feel flat and soft, almost like an empty balloon.
This is the time to get familiar with how it feels:
- Now: Make a note of its size and texture
- 12 hours later: It should feel smaller
- 24 hours later: It should feel nearly or completely empty
If the crop is not decreasing in size, it may indicate a crop impaction, which can be life-threatening and may require more intensive treatment or even surgical intervention.
🔎 The crop sits on the right side of the bird’s breast, just below the base of the neck. Gently run your fingers along the area—when full, it will feel like a squishy lump. When empty, there’s little to no noticeable bulge.
🚨 At-home impaction treatment should only be attempted by someone with experience. While some have had success treating impactions at home, others have not—and the consequences can be severe. If you choose to skip what is often a much-needed veterinary visit, understand the real risks involved:
- Crop perforation
- Intestinal blockage
- Sepsis
- Death
When in doubt, consult a veterinarian to avoid further harm.
3. Start with Acidified Copper Sulfate
At the beginning of quarantine, one of the tools we rely on here at the farm is Acidified Copper Sulfate, which helps reduce fungal and bacterial overgrowth in the crop. It’s especially useful when treating sour crop without suspected impaction.
Want to learn more about what it does and how else we use it? Check out our full write-up:
👉 Acidified Copper Sulfate: A Powerful Ally in Poultry Health
🍎 A Note on Apple Cider Vinegar: Some poultry owners try adding apple cider vinegar (with the mother) to the water as a first response. While many have reported success with this natural remedy, I personally haven’t found it effective in treating sour crop within my own flock. In my experience, Acidified Copper Sulfate has been a far more effective and reliable choice for managing this condition—especially when symptoms are more than mild.
4. Follow Up with Electrolytes and Probiotics.
❗️After 24-48 hour treatment period, follow up with Merrick’s Blue Ribbon Poultry Electrolyte & Probiotics for several days to help restore gut health and support recovery. ❗️
Is it Contagious?
Sour crop is not contagious in the way bacterial or viral diseases are, but that doesn’t mean your other birds are completely in the clear.
Here’s how to think about it:
❌ Not Contagious Like a Virus
Sour crop itself is a yeast (fungal) overgrowth, typically caused by Candida albicans. It develops inside the crop when the normal balance of bacteria and yeasts is disrupted — often due to things like:
- Poor diet (too much sugar or soft/stale feed)
- Antibiotic use
- Impacted or slow-moving crop
- Underlying illness or weak immune system
This means one bird’s sour crop won’t “spread” directly to another bird by casual contact.
⚠️ But Be Cautious — Shared Risk Factors Matter
Even though it’s not contagious, other birds in the flock could still get sour crop if they’re exposed to the same conditions that caused it, such as:
- Moldy or fermented feed
- Dirty waterers or feed containers
- Overcrowded or unsanitary living conditions
- Stagnant water or wet litter
- Long periods of fasting followed by gorging
Think of it like this: not contagious, but definitely “environmentally repeatable.”
✅ What You Should Do
If one bird has sour crop:
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Check your feed and storage conditions (avoid dampness, spoilage).
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Clean all feeders and waterers thoroughly.
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Review their diet — too much bread, scratch grains, or treats high in sugar/starch can contribute.
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Isolate the sick bird during treatment, mostly so you can monitor intake/output and avoid pecking.
🥣 What to Feed After Treatment
Once the crop has started to empty properly and your bird is no longer showing signs of fermentation or bloating, it’s time to reintroduce food gradually.
For the first 24 hours, offer small, frequent portions of easily digestible food. This helps reduce the risk of overwhelming the crop while supporting the bird’s recovery.
✅ Suggested Easily Digestible Foods for Poultry:
- Moistened crumble feed (soaked in warm water until soft)
- Boiled egg yolk, mashed
- Scrambled eggs (plain, no seasoning or oils)
- Plain oatmeal (cooked and cooled)
- Unflavored yogurt (small amounts only—contains beneficial bacteria)
- Cooked plain white rice (soft and slightly mushy)
Feed very small amounts 3–4 times over the course of the day, gradually increasing portion size as long as the crop continues to empty properly each morning. By day two or three, most birds can begin transitioning back to their regular diet, assuming all signs are improving.
🚨 When to Call the Vet
If your hen continues to decline—shows no improvement, or the crop remains full and hard despite treatment—it may be time to seek a veterinary consultation. A vet can provide additional diagnostics, antifungal medications, or even surgical intervention in severe or impacted cases.
Whenever possible, we strongly recommend seeking out a licensed Avian Veterinarian, particularly one affiliated with a specialty or exotic animal practice. While many general veterinarians are more than willing to see poultry, not all have in-depth experience treating them.
This isn’t to discredit general vets—it simply highlights how different and complex avian medicine can be. Birds process illness, medications, and nutrition differently than dogs and cats. Having a vet who is specifically trained in avian health can make all the difference.
If you're unsure where to find one, the Association of Avian Veterinarians offers a helpful searchable directory to locate an avian-experienced vet near you.
📌 Disclaimer
We are not veterinarians, nor do we claim to be. This blog post is intended to educate and inform, and may include opinions based on multiple chicken keepers and/or our personal experience raising poultry through multiple generations. While that experience has provided us with valuable insight, it does not replace the expertise of a licensed veterinarian.
Every flock and every bird is different. Diagnosing poultry health issues requires a trained eye, and we strongly encourage you to consult with a qualified veterinarian—especially when symptoms persist, worsen, or involve complications like crop impaction. Seeking the guidance of a professional is always the best course of action when your bird’s health is in question.