Associative effects of rice straw supplemented with different level of alfalfa hay on rumen fermentation of goats

In order to determinate the associative effects of different diet on rumen fermentation, 9 healthy and half sib Chengdu Ma goats with similar weighs (41.3±1.2) kg and fitted with permanent ruminal cannulas were randomly divided into three groups and fed with the different diets which was rice straw (RS) supplemented with 25%(MSL25), 50%(MSL50) and 75%(MSL75) alfalfa hay (Medicago sativa, MSL), respectively. pH of these three mixed forages fluctuated between 6.53 and 6.93. The concentration of NH3-N, total volatile fatty acids(VFAs), rumen microbial protein (MCP) were 73.56～132.23 mg·dL-1, 9.42～43.27 mg·dL-1 and 69.45～107.28 mmol·L-1, respectively, which nonlinearly increased with increasing levels of MSL. Compared with MSL25, the multiple-factors associative effects index (MFAEI) of MSL75 and MSL50 were 1.21 and 1.03, respectively, which indicated that 50% was the optimal proportion of alfalfa hay supplemented to the rice straw in this trail. There was no significant improvement on fiber usage when MSL supplementary proportion was over 50%.