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Fatty Liver (Photo: BIOMIN / Filipe Ribeiro)

Fatty liver

Birds afflicted with fatty liver syndrome present general obesity (on the average 20% overweight) with enlarged, fat-infiltrated livers, which are soft and easily damaged. Variable low mortality (2-5%) may be observed, caused by internal liver hemorrhage. In that case, birds will be found suddenly dead with pale head skin.

Fatty liver syndrome is a non-infectious condition that affects laying or breeding hens, especially caged animals. Some strains appear to be more susceptible than others, higher producing hens are the most susceptible within a flock and outbreaks of the problem are often associated with hot weather and a period of extensive egg laying.

Usually, the cause is related with high calorie intake (high energy diets or incorrect energy: protein ratios) but other factors, such as intake of the hepatotoxic aflatoxin or mismanagement of layer birds must not be disregarded.

In case exposure to mycotoxins is to blame, commonly known as lean bird fatty liver, livers are yellowish with petechial hemorrhages but not swollen; microscopic lesions of centrilobular necrosis and bile duct hyperplasia are present, but no excessive abdominal fat is found.

Depending on the potential cause for fatty liver, different corrective actions are proposed (see tables below).


Potential causeChecklistCorrective action
Aflatoxin B1
  • Young animals: Fibrosis of liver leads to hardening of the organ.
  • Older animals: Hepatic lipidosis, with softening of the organ.
  • Pale friable livers seen at slaughter.
  • Histopathology of the liver
  • Origin of raw materials from supplier/region with history of Afla contamination.
  • Check average contamination levels.
  • Positive for Afla in raw materials (ELISA) or feed (HPLC).
  • Prevent mold growth, purchase clean raw materials.
  • Avoid contamination of feed bins or feed/water lines by stale, wet or moldy feed.
  • Add an effective mycotoxin deactivator in the feed.


Potential causeChecklistCorrective action
Energy: protein balance

Excessive energy in diets can cause lipidosis and fatty liver problems.

  • Carbohydrate level in diet.
  • Energy-protein ratio in diet.
  • Avoid high carbohydrate diets, especially in summer.
  • Adopt proper energy-protein ratio.
Poor quality fat in the diet

Peroxides can impair the liver activity, creating fatty liver.

Quality of fats in term of peroxide value, rancidity and free fatty acids.
  • Avoid low quality fats.
  • Use low quality fats in the grower/finisher phases.
  • Replace animal fats with vegetable fats.
Choline / biotin deficiency

Pale friable livers seen at slaughter.

AA scale at feed mill.Increase level of synthetic amino acids in the diet.


Potential causeChecklistCorrective action
Viral hepatitis
(IBH – Viral inclusion body hepatitis)

Adenovirus causes yellow/hemorrhagic liver and focal necrosis. Symptoms include immunosuppression, diarrhea, anorexia, depression, ruffled feathers, especially in the region of head and neck.

  • Necropsy: Macroscopic lesion in the enlarged, dystrophic liver with yellowish color and crumbly texture; enlarged kidneys.
  • Histopathology: Detection of intranuclear inclusion bodies.
  • Isolation of serotype I or II or III from the lesions by serological assays.
  • Use inactivated vaccines (exist only for group I).
  • Check the breeding stock and eliminate the affected birds.


Potential causeChecklistCorrective action
Full fed broilers at slaughter

High lipid concentrations in the blood at slaughter can lead to paler livers.

 Fast birds before slaughter.
Hormone status

An over-stimulation of egg production may lead to excessive levels of estrogen in blood that facilitate fat storage in the liver and occurrence of fatty liver, especially in layers and breeders.

Management of laying birds (excessive estrogen stimulation).
  • Improve management of laying birds.
  • Correct lighting program.

Find this handy checklist and more in our Science & Solutions special issue.