本试验研究添加不同活性和不同浓度的酵母培养物在高精料日粮的发酵体系中对混合瘤胃细菌发酵的影响。采用二因子设计，进行体外厌氧发酵，发酵结束采集样品，测定乳酸、挥发性脂肪酸及酶活浓度。结果表明，发酵24 h后各处理pH均随着酵母培养物添加量的增加而升高。活性组各处理乳酸浓度均显著低于灭活组（P<0.05），灭活组与活性组中各处理之间淀粉酶酶活均差异显著（P<0.05），且各处理均随着酵母培养物添加量的增加而逐渐降低。活性组中各处理乙丙比均显著低于灭活组，而TVFA浓度均显著高于灭活组（P<0.05），发酵系统中NH₃-N浓度均随着酵母培养物添加量的增加而逐渐降低。结果提示，在高精料日粮条件下添加酵母培养物可改善瘤胃环境，改变瘤胃发酵类型。

This study was to investigate the effects of yeast culture from different activities and concentrations on  in vitro fermentation of rumen bacteria under high concentrate condition. In vitro anaerobic fermentation technique was used in this study, and samples were collected after 24 h fermentation for determination of lactate, VFA concentration and some enzyme activities. The results showed that pH value of culture supernatant of each treatment increased as the concentration of yeast culture increased in both the autoclaving and the non autoclaving groups. The concentration of lactic acid in the culture supernatant of every non autoclaving group was lower than that of the autoclaving group (P<0.05). The CMCase activity of the culture supernatant of each treatment of the autoclaving group was higher than that of the nonautoclaving group (P<0.05). The amylase activity of the culture supernatant of each treatment decreased significantly as the concentration of yeast culture increased in both the autoclaving and the non autoclaving groups (P<0.05). The ratio of acetate to propionate of the culture supernatant of every treatment of the non autoclaving group was significantly lower than that of the autoclaving group, but the TVFA was higher (P<0.05). The concentration of NH₃-N of the culture supernatant of each treatment decreased significantly as the concentration of yeast culture increased in both the autoclaving and the non autoclaving groups (P<0.05). It was concluded that addition of yeast culture could change the fermentation pattern of rumen and improve the fermentation characteristic under high concentrate condition.