Fatty liver in adult poultry flocks is commonly caused by the inadequate addition of biotin and/or choline chloride in the feed. This is required for adequate fat metabolism. Excessive amounts of fat accumulate in the liver giving it a characteristic yellow appearance. The liver is very fragile and easily ruptured causing internal bleeding.
Fatty Liver and Kidney Syndrome (FLKS) in young flocks is a manifestation of a failed metabolic process allowing accumulation of fat in the liver and kidneys. Morbidity occurs rapidly in affected chickens and is followed quickly by death, typically with heads extended up and backwards. The underlying cause is a deficiency of biotin.
Clinical signs develop quickly and affected chickens appear depressed and tend to sit in isolation and often die in a sitting position. Affected chickens will usually respond well to medication with biotin delivered via the drinking water.