Effect Of Yeast On Selenomonas Ruminantium Utilizing Lactic Acid And Rumen Fermentation Of Sheep

The first objective of this study was to examine the effects of six strains of yeast (Saccharomyces cerivisiae, Candida tropicalis, Pichia burtonii, Candida utilis, Rhodothece glutinis, Geotrichum candidum) on lactate utilization by the predominant ruminal bacterium Selenomonas ruminantium. Six yeasts and one non-yeast group were set, in order to examming the best adding concentration and best action time of yeast, at six concentration level (2g/L, 4g/L, 6g/L, 8g/L, 10g/L, 12g/L) respectively. The pH, acetic acid, propanoic acid and VFAs were detected, in Selenomonas ruminantium culture fluid at Oh, 6h, 12 h, 24 h, 36 h, after adding yeast. The results indicated that lactate uptake can be stimulated by all of the six yeast strains at all of six concentrations levels. When the added yeast was above 10g/L, lactate uptake was decreased, but 12 g/L level still stimulated lactate uptake of Selenomonus ruminantiurn. The yeast also increased the production of acetate, propionate, total VFAs. Because the increase in propionate production was greater relative to acetate, a decrease in the acetate:propionate ratio was observed. By detecting the absorption of lactic acid, production of propionic acid and acetate:propionate ratio, Candida tropicalis, Geotrichum candidum and Candida utilis surpass Saccharomyces cerivisiae, Pichia burtonii, Rhodothece glutinis in promoting lactic acid utilization of Selenomonus ruminantiurn.Twelve sheep with ruminal cannula were used to study the effect of three kinds of yeast culture products on the rumen fermentation. Beerwort yeast medium, Candida tropicalis, Geotrichum candidum and Candida utilis were pour into rumen by cannula, respectively. The pH, concentration of lactic acid, propionic acid and voiatiiisable fatty acids in the ruminal content were measured at Oh, 4h, 8 h, 12h, 24h after adding yeast. The results indicated that, when Candida tropicalis, Geotrichum candidum and Candida utilis were added, the values of pH in the rumen were altered significantly. All three yeast can increase the concentration of lactic acid, propionic acid and voiatiiisable fatty acids, the ratio of acetate to propionate decreased significantly. By detecting the production of propionic acid and acetate:propionate ratio in the rumen, Candida tropicalis surpass Geotrichum candidum and Candida utilis in regulating rumen fermentation of sheep.