Increase in rumen fibrolytic bacteria and the improvement of fiber degradability of ensiled total mixed ration assessed by in vitro rumen culture

Abstract

Effect of ensiling total mixed ration (TMR) on the improvement of fiber degradability in response to change in rumen fibrolytic bacteria was evaluated by an in vitro rumen culture technique. The TMR for dairy cattle consisted of 45% of roughage and 55% for concentrates on a dry matter basis and it was ensiled for 40 days in summer. An in vitro ruminal incubation experiment was conducted using rumen fluid with pre-ensiled or the ensiled TMR samples in anaerobic fermentation bottles for 6 and 24 h. The methane production (p=0.02) and total short chain fatty acids production (p=0.01) in the endiled TMR culture were higher than that in the pre-ensiled TMR culture. Copy numbers of two of three major fibrolytic bacteria (Ruminococcus albus and Ruminococcus flavefaciens) in the culture were higher at 24 h culture of the ensiled TMR (p=0.007 for R. albus, p=0.002 for R. flavefaciens) than that of pre-ensiled TMR, whereas Fibrobacter succinogenes numbers seemed to increase earlier than did the other two species. Our results suggest that the ensiling process for TMR may affect activities three rumen fiber-degrading bacteria, followed by improved fiber degradation in the in vitro rumen culture.