Aflatoxin carryover and clearance from tissues of laying hens.

A feeding trial was conducted to determine the levels of aflatoxins deposited in the tissues of hens fed a diet contaminated with 3310 micrograms AFB1/kg and 1680 micrograms AFB2/kg for 4 wk. At the end of aflatoxin feeding, the livers were pale, enlarged and haemorrhagic and the ovaries were significantly smaller than those from control hens and contained only small ova. Only a small fraction of the aflatoxins consumed was deposited in the tissues, either as the original compounds or as their metabolites, which were widely distributed in all tissues. The highest levels of aflatoxins were detected in the gizzard, kidneys and liver, with average total concentrations of less than 3 micrograms/kg. The lowest residue levels were detected in the breast, blood serum and leg, with breast muscle having a total concentration of less than 0.1 microgram/kg. Two days after removal of the contaminated feed, aflatoxin residues in all tissues had decreased markedly, with no aflatoxins being detected in the heart or spleen. No aflatoxin residues were detected in the breast, leg, gizzard and ovaries of hens killed 8 days after withdrawal, or in the kidneys and blood at 16 days. However, one of seven hens had measurable amounts of AFB2 in the liver 32 days after withdrawal. Although few residues were detected in most tissues after 8 days on the aflatoxin-free diet, variation existed between tissues and between individual hens in the amount of time required to achieve tissue clearance.