Sour Crop and Crop Stasis in our Chickens

INTRODUCTION
The crop is part of the normal anatomy of birds. It is a balloon-like dilation of the esophagus that is located at the base of the neck. It is partially composed of muscle that expands as the bird eats and drinks and then contracts and empties into the lower portion of the digestive tract.

Sour crop is inflammation and infection in the crop of chickens. It will occasionally occur in other birds but is most prevalent in our poultry. In most online poultry references, chicken health handbooks, and poultry magazines, infection is the only aspect of the problem that is discussed. But the root cause of sour crop is a condition called crop stasis.

Crop stasis is partial or complete loss of contractility of the crop. Think of it like a balloon that is inflated and deflated many times - the first several times it is deflated it shrinks back to normal size, but it eventually stretches and loses the ability to collapse when the air is let out.

A normally-functioning crop regularly empties completely several times during the day and overnight. When crop stasis occurs, food and fluid is not completely emptied. Bacteria and yeast overmultiply in the “crop stew” that is left over; this infection, which is secondary to crop stasis, is sour crop. Sour crop snowballs, creating more inflammation in the wall of the crop, which further decreases its ability to contract, making the crop stasis worse.

In short, sour crop only happens secondary to crop stasis.

DIAGNOSIS
Most veterinarians familiar with poultry can usually diagnose sour crop and crop stasis by the bird’s history and our physical exam.

It can be more challenging, and it is sometimes impossible, to diagnose the cause of crop stasis. It is not simply that the balloon (crop) has been filled and emptied too many times. There are a plethora of possible causes that lead to the loss of the contractility in the crop; some of the more common ones we have encountered are:

• Marek’s disease, affecting the nerves to the digestive tract

• Physical obstructions of the digestive tract “downstream” from the crop

• Reproductive tract disease (inflammation of the reproductive tract inflames the digestive tract in contact with it)

• Lead toxicity

TREATMENT
Sour crop can be treated by emptying and flushing the crop, and medicating with antibiotic and antifungal medications. Emptying and flushing the crop can be challenging and usually cannot be safely done at home. Sometimes it can only be done surgically.

Crop stasis is much more difficult (or impossible) to treat, and it is critical to note that treatment for sour crop will ultimately not work unless the bird can be successfully treated for crop stasis. Of the four common causes for sour crop mentioned above:

• Marek’s disease is not treatable.

• Physical obstructions "downstream" in the digestive tract can only infrequently be diagnosed and relieved.

• Reproductive tract disease cannot usually be definitively treated.

• Rarely, lead poisoning can be diagnosed and treated.

At YVC we are always ready and willing to attempt treatment for crop stasis and sour crop, but we are careful to first assess the bird and provide the owner with a prognosis. Treatment is all too often difficult and unsuccessful. Often, the most humane option is euthanasia.

When the affected bird is one member of a flock, we make sure to take into account the health of the entire flock. If we are unsure of the cause of the crop stasis, and the bird passes away or is euthanized, we recommend a necropsy. If we learn the cause of the crop stasis we may be able to prevent it from happening to other birds in the flock.