Effect of a hay and a grain diet on the bioavailability of ochratoxin A in the rumen of sheep.

The role of the rumen and its contents in the detoxification of ochratoxin A (OA) was studied in sheep. The first experiment established that very little conversion of OA to alpha ochratoxin (O alpha) occurs systematically; 90 to 97% of the OA and metabolites was recovered as unaltered OA in the urine. Most of the small amount of O alpha recovered was also in the urine. In this experiment, two sheep were fasted and another two fed normally, but feed intake had no significant effect. In the second experiment, two sheep fed hay and two fed grain were dosed with OA at .5 mg/kg of BW into the rumen via a cannula. Recoveries, in urine and feces, accounted for 58 to 70% of the administered OA, but almost all (greater than 97%) was in the form of O alpha. About 76 to 92% of this O alpha was in the urine. Although excretion patterns and pharmacodynamics tended to differ with different diets, one of the sheep fed grain had very low intake and the results were equivocal. In the third experiment, eight sheep (four fed hay, four fed grain) were given a single intraruminal dose of OA (.5 mg/kg of BW). The disappearance of OA from the rumen and the corresponding formation of O alpha was much faster for hay-fed than for grain-fed sheep; the half-lives were .63 and 2.7 h for OA and .9 and 1.9 h for O alpha, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)