Effects of Facultative Anaerobic Cellulolytic Bacteria and Nitrogen-fixing Bacteria Isolated from Cow Rumen Fluid on Rumen Fermentation and Dry Matter Degradation in Vitro

The purpose of the paper was to study the effects of cellulolytic bacteria （CB） mixed with nitrogen-fixing bacteria （NFB）onfermentationinvitro.NineCBstrainsandsevenNFBstrainswereisolatedfromrumenfluidofthreeHolsteincows.Basedon higher activity of cellulose or nitrogenase, three CB types CB-2（KT725624）, CB-5（KT725623） and CB-6（KT725622） and one NFB type NFB-3（KT735054） were screened out, respectively. Two parts were included in this study. The first part explored the optimal mixed ratio of CB to NFB through inoculating filter paper medium with the bacteria of 2×10~5 cfu·mL^-1. According to CMCase and FPase activities in the medium, the ratio of 4 to 1 was proven to be more effective. In the second part, rumen fermentation in vitro was conducted at 4:1 of CB to NFB, aiming at studying the effects of mixed bacteria. Six groups were classified, namely, control group（no bacteria）, Group 1 （CB-2+NFB-3）, Group 2 （CB-5+NFB-3）, Group 3 （CB-6+NFB-3）, Group 4 （NFB-3） and Group 5 （CB-6）. All the experimental groups had the same amount of bacteria (4×10~6 cfu·mL^-1) in the fermentation liquid. Samples were collected at 2, 4,8, 12 and 24 h of incubation. Compared with the groups with CB or NFB alone, gas production, dry matter degradability and bacterial protein expressions in the mixed groups increased. However, NH3-N concentration decreased and p H was stable. Meanwhile, related values among three mixed groups were significantly different; values in Group 2 were the best.