Acute Toxicity of Aflatoxin B1in Wethers

THE original objective of this study was the preparation of milligram quantities of aflatoxin M₁. Holzapfel et al.¹ and Masri et al.² had collected sufficient quantities of the toxin from the urine of sheep which had eaten food containing aflatoxin B₁ for structural studies. We administered an exploratory dose of 4 mg of aflatoxin B₁/kg, a conservative value compared with a reported single dose LD₅₀ of approximately 500 mg/kg (ref. 3). This was lethal to our wether. In subsequent correspondence Purchase advised that an (intraperitoneal) dose of 2 mg/kg had killed a Merino sheep, and Masri noted that a repeated oral dose of 0.38 mg/kg per day for seven days was lethal to both a Hampshire ewe and a crossbred western whiteface wether. If the toxin is to be given over a period of time, a sublethal dose must be used. We undertook a toxicological study to satisfy this requirement and now report the results of our LD₅₀ study.