Effect of the addition of cellulolytic bacteria to ruminal bacteria on in vitro fermentation characteristics

Abstract

Background: Digestibility of fiber in the rumen is not due to enzymatic activity of individual bacteria, but rather to their interaction, which complements their enzymatic functioning. Thus, efficiency of fiber digestion depends on the diversity and density of cellulolytic bacteria. Objective: To estimate in vitro production of biogas, methane, and fermentative characteristics of cobra grass (Brachiaria hibrido) inoculated with ruminal bacteria (RB) in coculture with isolated cellulolytic bacteria (ICB) from bovine (ICBbov) or water buffalo (ICBbuf). Methods: ICBbov and ICBbuf were isolated from ruminal cellulolytic bacteria consortia using specific culture media for cellulolytic bacteria. Both were morphologically characterized and a Gram stain was performed. In the in vitro gas production test, the substrate was cobra grass and the inocula were ruminal bacteria (RB), ICBbov, ICBbuf, Coculturebov (RB + ICBbov) and Coculturebuf (RB + ICBbuf). Biogas and methane (CH4) production, as well as dry matter degradation (DMD) and neutral detergent fiber degradation (NDFD) were measured. A completely randomized design was used. Results: The ICB obtained were Gram positive cocci. Accumulated biogas production at 72 h from ICBbov and ICBbuf was on average 42.11% of that produced by RB. The Coculturebov produced 14.24% more biogas than RB. The CH4 production was lower in ICBbov and ICBbuf than in RB, Coculturebov and Coculturebuf . The DMD and NDFD were not different among RB, Coculturebov and Coculturebuf . The ICBbov degraded 37.10 and 96.34% more DMD and NDFD than ICBbuf (p<0.05). Conclusion: The use of ICB from bovine or water buffalo in coculture with RB does not improve in vitro production of biogas, DMD or NDFD with respect to RB alone.