Abstract:

【Objective】An experiment was designed to explore the effect of Yucca schidigera saponin and tea saponin mixture and different concentrate/forage ratios In vitro on rumen fermentation and rumen fiberolytic bacterial activity.【Method】A 2×4 two factorial design of experiment was adopted: one factor was adding or without saponins (0.3% tea saponin and 0.03% Yucca schidigera extract), the other was four different concentrate/forage ratios (20﹕80, 40﹕60, 50﹕50, and 60﹕40).【Result】The results showed that the mixed saponins reduced pH and the group whose concentrate/forage ratio was 20﹕80 had significant effect (P＜0.05). Concentrations of acetate, propionate, butyrate and total VFAs were increased by addition of the mixed saponins, however, from the molar ratio of VFAs it was found that the proportion of propionate and butyrate were decreased while the proportion of propionate was increased, so the acetate/propionate ratio descended. The mixed saponins increased ruminal bacterial protein yield whereas the yield of ruminal protozoal protein was decreased, and the ratio of bacterial protein/ protozoal protein was significantly increased (P＜0.05) compared with the control group. The relative amount of Fibrobacter succinogenes was extremely higher by addition of the mixed saponins whose concentrate/forage ratio was not 20﹕80. And the mixed saponins increased the relative amount of Ruminococcus flavefaciens and Ruminococcus albus except that the concentrate/forage ratio was 40﹕60.【Conclusion】Results indicate that this mixed saponins have effects on microbial fermentation and fibroliytic bacteria activities, and that the effects depend on the ratio of concentrate to rughage in the substrate.

Key words: Yucca schidigera, tea saponin , rumen fermentation, fibrolytic bacteria