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 x 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. (c) 2006 Elsevier B.V. All rights reserved.