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 present in many cases of acute illness, injury, or forced molt.
Regressed follicles in a hen.
Courtesy of Dr. Rodrigo Espinosa.
While disease can trigger regression of the ovary, other frequent causes include low body weight, deliberate decrease of feed, overcrowding, and lack of feeder space (see and photographs).
Regressed follicles and an overstimulated ovary in a hen.
Courtesy of Dr. Rodrigo Espinosa.
Infectious diseases known to cause regression of the ovary include the following:
Ovary regression can also result from severe stress, which is often accompanied by feather molt, emaciation, and dehydration.
