Responses of dairy cows to dietary aflatoxin: feed intake and yield, toxin content, and quality of milk of cows treated with pure and impure aflatoxin.

Ten fistulated Holstein cows in midlactation were given daily doses of 13 mg of aflatoxin B1 for 7 days. Six received pure aflatoxin B1; three received an impure preparation that contained aflatoxin B1 plus other aflatoxins and metabolites produced by Aspergillus parasiticus in culture. Toxin was administered to each animal twice daily, one-half of the total dose each time, via the rumen orifice. Morning and evening milks were collected and analyzed for aflatoxin M1. Milk production and feed intake were monitored for 5 days before, every day during, and for 8 days after treatment with aflatoxin B1. Milk contained from 1.05 ppb to 10.58 ppb of aflatoxin M1. None was in milk 4 days after administration of toxin had stopped. Somatic cell counts and standard plate counts from milks of two cows were not affected appreciably by administration of toxin. Fluctuations in feed intake and milk production occurred in all animals during the treatment period with a significant decrease in milk production of those cows receiving 13 mg of impure aflatoxin B1 per day. Differences in results when cows received equal amounts of aflatoxin B1 may be attributable to the type of toxin administered (pure versus impure).