Effect of Saccharomyces cerevisiae on the synchronization of organic matter and nitrogen degradation kinetics and microbial nitrogen synthesis in sheep fed Berseem hay (Trifolium alexandrinum)

The effect of baker’s yeast (baker’s Saccharomyces cerevisiae; BSC) on the degradation kinetics of organic matter (OM) and nitrogen (N) in Berseem hay (Trifolium alexandrinum, BH) was studied using three cannulated sheep in an in situ trial. Two levels of BSC were added to BH, the treatments were: (1) BH; (2) BH + 11.25 g of BSC (LBSC); and (3) BH + 22.5 g of BSC (HBSC). The degradation rate of (OM) was accelerated significantly (P < 0.05) in response to BSC supplementation and the values were 0.065, 0.071 and 0.075 h−1, for BH, LBSC and HBSC, respectively. Meanwhile, degradation rate ofNwas not affected by BSC. The synchronization index (SI) was calculated from the ratio between hourly release of N and OM in the rumen, and the values were 0.59, 0.61 and 0.72 for BH,LBSCand HBSC, respectively.Asignificant (P < 0.01) correlationwas found between daily microbial nitrogen synthesis (DMNs) and SI, resulting in the following equation, DMNs = 3.6+20.3SI (±5.7) (r = 0.80; S.E. = 0.38). Results of the present study showed that the addition of HBSC to BH improved the release of energy in the rumen to be available for microbial growth as long as the N release was not affected. © 2003 Elsevier B.V. All rights reserved.