Fatty liver hemorrhagic syndrome (also referred to as fatty liver syndrome), a disease

Disease

A disease is an abnormal condition affecting the body of an organism. It is often construed to be a medical condition associated with specific symptoms and signs. It may be caused by external factors, such as infectious disease, or it may be caused by internal dysfunctions, such as autoimmune...

 in chickens and other birds, affects only hens (females). Birds with this disease have large amounts of fat deposited in their liver and abdomen. This often results in an enlarged liver

Liver

The liver is a vital organ present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...

 that is easily damaged and prone to bleeding. In some cases the disease is fatal, usually as a result of blood loss from an internal hemorrhage in the liver. The hemorrhage often occurs when a hen is straining to lay her egg. Fatty liver hemorrhagic syndrome is "the major cause of mortality in laying hens."

Causes

Excessive dietary energy

Food energy

Food energy is the amount of energy obtained from food that is available through cellular respiration.Food energy is expressed in food calories or kilojoules...

 intake is believed to be the cause of fatty liver hemorrhagic syndrome. Heredity may also play a role, but it is not the entire cause for the disease. Birds housed in cage

Cage (enclosure)

A cage is an enclosure made of mesh, bars or wires, used to confine, contain or protect something or someone. A cage can serve many purposes, including keeping an animal in captivity, capturing, and being used for display of an animal at a zoo.-History:...

s will more likely be affected because they are unable to exercise to burn off the extra dietary energy. Walking hens are less likely to develop this problem. The disease is observed most often in birds that appear to be healthy and in a state of high egg production. As a result, death can occur quite unexpectedly.

Symptoms

Affected birds are usually overweight

Overweight

Overweight is generally defined as having more body fat than is optimally healthy. Being overweight is a common condition, especially where food supplies are plentiful and lifestyles are sedentary...

and may also have pale combs. Generally, however, the disease has few or no symptoms prior to the bird's death.