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Sour Crop

Thrush, Yeast Infection, Moniliasis, Candidiasis, Candida Infection

Sour crop, a common name for candidiasis or candida infection, is caused by fungi of Candida species, which are yeasts. The most common pathogens belonging to this group are Candida albicans, C.tropicalis, C.glabrate, and C.krusei. Candida species are a normal part of a healthy chicken's microflora. Factors such as prolonged or inappropriate antibiotic use, corticosteroids, malnutrition, stress, underlying illness, and/or excessive use of disinfectants can predispose chickens to sour crop.

Clinical Signs of Sour Crop

The most common clinical signs observed in chickens with sour crop include:
  • Changes in behavior
  • Delayed crop emptying, which after a period of time can lead to the development of a foul smell coming from the chicken's mouth.
  • Regurgitation
  • Reduced appetite
  • Depression/lethargy
  • White patches or plaques (oral lesions) on the inside of their mouth and/or under the tongue.
  • Abnormal droppings, often appear brownish and watery
  • If chicks are affected, may show stunted growth
Chickens with candidiasis can sometimes be concurrently infected with other diseases, which can complicate or confuse clinical signs observed.

Sour Crop Vs Canker

Candidiasis (Thrush)Canker
Body areas affectedOral cavity, esophagus, and cropOral cavity, esophagus, and crop
Pathogen typeYeastProtozoan parasite
Pathogen speciesCandida albicansTrichomonas gallinae
Oral lesion appearancePatches of raised, whitish, dead epithelial debris. The top white pseudomembranes can be wiped off. Sticky, yellowish-white 'canker-like' masses of caseous, necrotic material.
More likely to occur followingProlonged antibiotic therapy, concurrent disease, infestation with internal or external parasites, or stressful event.Pigeons and doves sharing the same water or feed source.
TreatmentTreat the primary cause, antifungals, strengthen immunity, crop flushMetronidazole, thyme extract

Treatment for Sour crop

In very mild or early cases of sour crop, all that may be needed is a change in diet and the use of natural remedies, such as apple cider vinegar added to the water. However, once the condition has progressed to a severe infection (once the bird has stopped eating and drinking and is showing obvious lethargy or depression), a trip to your veterinarian is needed.

In severe cases, if the chicken is unable to empty their crop, they may need it emptied and flushed (a procedure that should only be done by a veterinarian, as if it is done wrong, can be fatal to the bird). Concurrent supportive care may be needed as well, in the form of IV fluids, to help restore the natural balance of microorganisms in the crop. Your veterinarian will usually prescribe one of three types of antifungal medications---Nystatin, Ketaconazole, or Itraconazole. There are a variety of different herbs and nutraceuticals that can be given concurrently to help strengthen their immune system.

Clinical Signs

Delayed crop emptying (full crop)
Oral lesions inside mouth
Excessive beak rubbing
Sour odor from mouth
Loss of appetite
Weight loss
Roughened feathers
Yellowish-green diarrhea


  • History
  • Clinical signs
  • Physical exam
  • Wet or Gram's-stained smears
  • Crop washings


Supportive careIsolate the bird from the flock and place in a safe, comfortable, warm location (your own chicken "intensive care unit") with easy access to water and food. Limit stress. Call your veterinarian.
Fennel teaHas proved a good initial natural product to get the crop moving( purchase fennel tea bags)Bird Vet Melbourne
Crop FlushYour veterinarian will usually empty out and flush the chicken's crop contents and obtain a sample to run a laboratory test on in order to verify the specific organism. Following this procedure, supportive care is needed in order to prevent dehydration and help to restore the natural balance of the crop.Bird Vet Melbourne
AntifungalsNystatin (300 KIU/kg) administered orally is the drug of choice, however in some cases your veterinarian may recommend Ketoconazole (10-30 mg/kg) or Itraconazole.

This medication is only effective for oral or topical use only, for it must come into direct contact with the yeast to be effective.
K Marx; D McCluggage
Strengthen immunityAloe vera, Chinese herbal tea combinations, Larch arabanogalactans, or Lactalbumins.D McCluggage
Apple cider vinegarAdd 1 tablespoon of apple cider vinegar to each gallon of water and use as drinking water for 3 to 4 days. It may help in chickens with mild cases.D McCluggage; Bird Vet Melbourne; G Damerow



  • Avoid prolonged or excessive use of antibiotics in chickens.
  • Maintain good sanitary conditions
  • Do not put sick or injured chickens back out into the flock until they have fully recovered and immune system is restored.
  • Feed a balanced diet
  • Do not feed chickens spoiled food
  • Change water sources daily
  • Do not excessively use disinfectants
  • Administer apple cider vinegar every other month in drinking water at a rate of 5 mL per L of water.

Scientific References

Good Overviews


Risk Factors

  • Antibiotics
  • Corticosterioids
  • Chickens with scissors beak
  • Young chicks
  • Older chickens
  • Chickens with weakened immune systems, such as when recovering from an illness or injury
  • Stress
  • Excessive or inappropriate use of disinfectants
  • Malnutrition

Case Stories