Increase of ruminal fiber digestion by cellobiose and a twin strain of Saccharomyces cerevisiae live cells in vitro

This experiment was designed to investigate the effects of different concentrations of cellobiose (CB) or a twin strain of Saccharomyces cerevisiae live cells (YST) (20, 40 and 60 mg/60 mL), and CB + YST (60 + 20, 60 + 40, 60 + 60 mg/60 mL) on mixed ruminal microorganism fermentation in vitro. Ruminal fluid was collected from a cow, mixed with phosphate buffer (1:2) and incubated (60 mL) anaerobically at 38°C for 24 h with or without supplement plus 400 mg (dry matter [DM] basis) substrate (hay plus concentrate, 1.5:1). The medium pH numerically decreased with CB and CB + YST, but was unchanged with YST. The total volatile fatty acid and proportion of propionate increased (P < 0.05) in all cases. The proportion of acetate decreased (P < 0.05) with CB and CB + YST, but increased (P < 0.05) with YST and that of butyrate increased (P < 0.05) with CB and CB + YST, but decreased (P < 0.05) with YST. Ammonia‐N decreased (P < 0.05) with CB and CB + YST, but was unchanged with YST. The number of protozoa was unchanged, and that of cellulolytic bacteria increased (P < 0.05) in all cases. Total gas production increased (P < 0.05) in all cases. Methane decreased, hydrogen was unchanged by YST and both gases were unchanged by CB and CB + YST. The in vitro disappearance of DM and neutral detergent fiber increased (P < 0.05) by 11.2% and 8.9%, 9% and 8.5%, and 12.1% and 10.2% in the case of CB, YST and CB + YST, respectively. Therefore, the dietary supplementation of CB and/or YST may improve ruminal fermentation and digestibility.