Ruminal fermentation and nitrogen metabolism in sheep fed a silage-based diet supplemented with Yucca schidigera or Y. schidigera and nisin

Three ruminally cannulated Cheviot wethers (55.8 ± 5.8 kg BW) were used in a 3 × 3 Latin square design to determine effects of supplementing Yucca schidigera, with or without nisin, on ruminal fermentation patterns and N metabolism. The wethers were fed twice daily (08:00 and 16:00 h) with a basal diet consisting of timothy silage and a concentrate (85:15 on a dry matter (DM) basis). Dietary treatments were basal diet (control), basal diet plus 240 ppm (DM) of Y. schidigera per day (YS), basal diet plus 240 ppm (DM) of Y. schidigera and 6 mg/kg BW0.75 of nisin per day (YN). Results showed that YS and YN supplemented diets had lower (P<0.05) rumen ammonia N concentrations compared to the control diet. The molar proportion of acetate was lower (P<0.05) in sheep receiving the YS and YN diets compared to the control diet, and molar proportions of butyrate and iso-acids were higher (P<0.05). Urinary N was lower (P<0.01) for YS and YN diets versus the control diet, and microbial N supply and efficiency of microbial N synthesis were higher (P<0.05) in sheep fed the YS diet versus those fed the YN and control diets. Results indicate that Y. schidigera can be used to modify rumen fermentation in order to decrease ruminal ammonia concentrations and reduce urinary N excretion thereby reducing the environmental impact of ruminant production systems.