Effects of Yucca Shidigera extract on feed utilization by equine weanlings

Summary 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 A reduction in ambient ammonia in equine housing facilities may be desirable from several health perspectives. Environmental ammonia is noxious to both animals and man, and may provoke respiratory irritation and compromise. 6. , 29. Soluble compounds extracted from Yucca shidigera have recently been reported to reduce airborne ammonia concentrations in livestock production facilities when added directly to manure or incorporated into livestock feeds. 3. , 29. Althohgh free ammonia production may increase in the presence of a water soluble extract of Y. shidigera, ammonia in digesta and fecal materials apparently binds to the steroid saponins (sarsapogenin, smilagenin, hecogenin) found in the extract. 19 The most convenient method for introducing saponins into equine waste would be via the feed. Dietary saponins are apparently neither absorbed nor metabolized by ruminants or nonruminants, 7. , 10. , 27. although their ingestion may be associated with improved feed utilization and rates of growth. 18. , 27. However, it is not clear whether increased production efficiency resulted from metabolic effects attributable to saponins or from a reduction in animal stress accompanying a reduction in ambient ammonia concentrations. In the equine, growth efficiency is dependent on effective reutilization of a portion of the cecal and colonic ammonia derived from the hydrolysis of urea secreted into the intestine 11 Significant binding of ammonia to saponins within the cecum and colon could impair nitrogen economy and be detrimental to growing horses. On the other hand, increased urease hydrolysis of recycled urea could compensate for a saponin-induced reduction in the free ammonia content ofdigesta. Live yeast culture preparations may stimulate urease activity in young horses; 13. , 14. combined supplementation with both saponins and yeast culture might maintain efficient utilization of dietary nitrogen and tissue growth while reducing ammonia emissions. This experiment was undertaken to determine whether supplementation with Y. shidigera extract (YSE) affects the digestibility of dietary nutrients, the production of fecal ammonia, the efficiency of utilization of dietary nitrogen or growth in young horses. In order to ease the detection of any responses, particularly in the absence of any dose-response data, nitrogen-replete but lysine-deficient diets were used. The possibility that supplemental live yeast culture (YC) added with the saponins-emiched extract might beneficially interact with any effects of the saponins was also examined.