Metabolism and excretion of ochratoxin A fed to sheep

Hydrolysis of the mycotoxin ochratoxin A (OA) to ochratoxin alpha (O alpha) by microorganisms within the gastrointestinal tract leads to the excretion of OA as the nontoxic alpha form. The O alpha form is the principal means for the detoxification of OA. In the current experiment, three groups of fo ur sheep were fed diets consisting of 70% concentrates and 30% hay (dry mat ter basis, energy to supply 1.1 times the requirement for maintenance) for 4 wk with three dietary concentrations of OA (0, 2, or 5 mg/kg of concentra te feed). The OA content did not affect feed intake or nutrient digestibili ty. In a preliminary experiment, an OA dose of 20 mg/kg of concentrate feed greatly reduced feed intake. After 1, 2, 3, and 4 wk of the trial, signifi cant concentrations of OA were detected in the serum of the animals fed 2 o r 5 mg of OA/kg feed. This suggested that even at a dosage of 2 mg of OA/kg of concentrate feed, considerable amounts of OA were not degraded by rumin al and intestinal microorganisms. The analysis of the feces and urine sampl es reflected these findings; OA and O alpha were found in significant conce ntrations, escaping fermentation in the rumen and in the hindgut. The curre nt experiment demonstrates that OA hydrolysis in the gastrointestinal tract of sheep is substantially less than previously described, especially if OA is ingested in combination with concentrate-rich diets.