Effects of yeast culture on ruminal bacterial fermentation in vitro under high concentrate condition.

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 (P0.05). 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 (P0. 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 (P0. 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 (P0. 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