Effects of live yeast cell supplementation to high concentrate diets on the toxicokinetics of ochratoxin A in sheep.

Previous studies have indicated that high concentrate feeding reduces the ruminal degradation of the mycotoxin ochratoxin A (OA) to the less-toxic ochratoxin alpha (Oalpha) in ruminants. This is due to a pH-induced decrease in ruminal protozoa and subsequent increasing transfer of OA into the systemic circulation. The present study investigated whether stabilization of rumen pH by the live yeast cell supplementation to high concentrate diets affects the toxicokinetics of OA in sheep. Sheep were fed diets consisting of 70% concentrates and 30% grass silage (dry matter basis) supplemented without or with live yeast cells (Saccharomyces cerevisiae CNCM I-1077). After an adaptation period of 3 weeks, animals were given a single dose of OA (2.46 mg) in the form of contaminated wheat. Even though live yeast cells accelerated the recovery of ruminal pH from the decrease in pH induced by feeding, no effect on ruminal degradability and systemic availability of OA was recorded. Based on in vitro studies, live yeast cells and extracts of live yeast cell walls have been suggested as a mycotoxin-binding agent. However, supplementation with live yeast cells had no effect on the excretion pattern of OA in sheep, indicating that binding of OA to yeast components may be limited in ruminants. With respect to the toxicokinetics of OA, our results are in agreement with earlier results demonstrating that the hydrolysis of OA in the gastrointestinal tract of sheep is substantially less than previously described, especially if OA is ingested in combination with concentrate-rich diets. Our study demonstrates that feeding a live yeast cells product, registered as a feed additive for improving zootechnical performance, had no impact on the toxicokinetics of OA under the chosen conditions.