EFFECTS OF YUCCA-SCHIDIGERA EXTRACT ON FEED-UTILIZATION BY EQUINE WEANLINGS

Reports in the literature suggest that dietary supplementation with water soluble extract of Yucca shidigera can reduce biological ammonia emissions from livestock in confinement. Because a reduction in environmental ammonia in equine housing facilities would benefit both human and animal health, the effects of Y. shidigera extract(YSE) on equine nitrogen metabolism were examined in this experiment. The addition of 100 ppm Y. shidigera extract to a 75% hay, 25% grain, lysine-deficient feed resulted in a significant increase in fecal nitrogen excretion by weanling Thoroughbreds and therefore a decrease in the apparent digestibility of dietary nitrogen. The proportion of fecal nitrogen that was water soluble increased (p < .01), suggesting that the saponins in the Yucca extract bound free ammonia within the large intestine and prevented its reabsorption and recycling. When a live yeast culture(YC) preparation was also added (20 g/day), the apparent digestibility of dietary nitrogen increased 30% (p < .01) compared to the unsupplemented basal feed and 56% (p < .01) compared to the feed supplemented with Y shidigera extract. When added together, YSE and YC supplementation resulted in additive effects on dietary nitrogen processing. These data suggest that the efficiency of utilization of a relatively inadequate, lysine-deficient feed can be increased by supplementation with live yeast culture. Concurrent use of Y shidigera extract may also decrease ammonia release into the environment, without adversely affecting nitrogen utilization.