Ruminants are relatively resistant to the acutely toxic effects of
ochratoxin A, due to extensive degradation of
ochratoxin A to its less toxic metabolite
ochratoxin alpha by rumen microorganisms. However, most estimates of the degradation capacity for
ochratoxin A in ruminants are based on in vitro studies. In the current study, the metabolism of
ochratoxin A was investigated over a period of 29 days, feeding various doses of the
mycotoxin (0, 9.5, 19.0, and 28.5 mug
ochratoxin A/kg
body weight) to sheep. Animals were fed diets consisting of 70% concentrates and 30% grass silage. Significant concentrations of undegraded
ochratoxin A were detected in serum of sheep at all levels of
ochratoxin A tested. Serum concentrations of
ochratoxin A slightly accumulated with time of exposure and were linearly dependent on the administered dose of
ochratoxin A. Furthermore, a constant proportion (6-8%) of the dose was excreted in the urine. The results of this study indicate that even at moderate to low levels of
ochratoxin A in the diet, considerable amounts of the
mycotoxin are absorbed by ruminants and may accumulate in tissues. Therefore, feeding of
ochratoxin A-contaminated feedstuffs to ruminants does not seem to be a reliable means for using these feedstuffs.