Feedlot performance and tissue residues of cattle consuming diets containing aflatoxins.

A comparative slaughter feeding trial was conducted using crossbred Hereford-Angus steers. Cottonseed meal known to be contaminated with aflatoxins was fortified with long-grain rice cultures of Aspergillus flavus to produce complete rations that contained 0, 60, 300 and 600 ppb aflatoxin B1 (AFB1). Forty steers, weighing approximately 250 kg were randomly assigned to four equal treatment groups. Animals were housed in individual pens and fed the assigned contaminated ration ad libitum for 155 d. On d 156 all animals were placed on the control ration for 14 d. Animals were weighed and blood samples collected every month for clinical chemistry analysis. Liver, muscle and fat biopsies were collected at 6-wk intervals. These samples were stored in liquid N2 prior to analysis for aflatoxin M1 and B1 content. Separate liver samples were taken for histopathological examination. Aflatoxin was withdrawn from the diet 2 wk prior to slaughter. After 1 wk of withdrawal liver, muscle and fat samples were collected and assayed for AFB1 and aflatoxin M1 (AFM1). Liver samples also were taken for histopathological examination. Growth rates and feed intakes in the 60 and 300 ppb aflatoxin treatments were not significantly different from controls. The 600-ppb treatment group had a decrease in feed intake and rate of gain. Rations containing 60 and 300 ppb of aflatoxin had no significant influence on blood components and enzyme patterns. The 600-ppb treatment caused a slight, but consistent, increase in serum glutamic oxaloacetic transaminase and alkaline phosphatase.(ABSTRACT TRUNCATED AT 250 WORDS)