A review of black organs (acquired visceral melanosis) in livestock

Summary

​Acquired Visceral Melanosis (AVM, black liver) is a naturally occurring black pigmentation of the liver, often with concurrent lung and kidney discolouration. AVM typically affects livestock grazing specific pasture types in Australian, the Falkland Islands and Norway. Affected stock appear healthy and the condition is observed as an incidental finding at slaughter.
Generally regarded as a benign condition, AVM became the subject of investigation following rejection of sheep carcasses at slaughter in the Middle East.

Microscopic, electron microscopic and biochemical studies were performed to characterise the black pigment in ovine livers from Australia, Norway and the Falklands with similar changes detected in each case, indicating the pigment is the same or closely related in each case.

The pigment has previously been identified as melanin, lipofuscin or a combination of the two. While the pigment has several light microscopic and chemical similarities to melanin, it appears to be a distinct compound.
Feeding trials to assess effects of eating affected livers were performed on rats without ill-effects attributable to the pigment or significant absorption of the pigment, detected.

The study furthers identification of the pigment and supports a lack of detrimental effect when affected tissue is included in a diet.