Regression of the ovary may result in leakage of free yolk into the abdomen (yolk peritonitis); this rarely causes death, except when yolk material migrates through the air sacs to the lung and causes foreign body pneumonia. Free yolk is seen in many cases of acute illness, injury, or forced molt. Regression of the ovary is frequently caused by low body weight, deliberate reduction of feed, overcrowding, or lack of feeder space.
Infectious diseases known to cause regression of the ovary include:
It can also result from severe stress, which is often accompanied by feather molt, emaciation, and dehydration.