Direct-Fed Microbials Alter Ruminal in vitro Gas Production and Fermentation with a High-Concentrate Diet

Abstract

By simulating the rumen environment, the in vitro gas production technique allows characterization of DFM mediated changes in the rumen. Previous in vitro gas production experiments have focused primarily on the effects of providing Saccharomyces cerevisiae or combinations of yeast and various Lactobacilli strains and have produced variable results on the impact on gas production and the formation of endpoint fermentation end products [10][11][12]; however, there is limited data on the impact of bacterial DFM on in vitro gas production [2]. This study was designed to differentiate between immediate (in vitro, addition to fermentation vessel) and adaptive (in vivo, consumed for 28 d) effects of LAB containing DFM on ruminal in vitro fermentation of high concentrate substrates, as indicated by alterations in gas production and fermentation end products. Materials and Methods Experimental design and treatmentsAll procedures were approved by the University of Kentucky Institutional Animal Care and Use Committee. Twelve ruminally cannulated Angus steers (initial body weight 385 ± 35 kg) were used in a split-split plot design experiment (Figure 1). The whole plot consisted of steer and dietary DFM provision; the subplot consisted of the in vitro fermentation vessel and media DFM, and within sub-plot