Submitted to: Journal Dairy Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: February 26, 2011
Publication Date: July 10, 2011
Citation: Mohammed, R., Stevenson, D.M., Beauchemin, K.A., Weimer, P.J., Muck, R.E. 2011. Changes in rumen bacterial community composition following feeding of silage inoculated with a commercial silage inoculant. Journal of Dairy Science. 94(E-Supplement 1):390. Technical Abstract: Some silage inoculants yield an increase in milk production without increasing fiber digestibility, possibly through altering the rumen microflora. We hypothesized that silage treated with a commercial inoculant (Lactobacillus plantarum, LP) would improve milk production and would alter rumen bacterial community composition (BCC) compared to silage without inoculant (Ctrl). Eight rumen-cannulated Holstein cows were allotted to two diets (Ctrl- or LP-treated silage) in a double cross-over design with four 28-day periods. Diets were formulated to contain (per kg DM) 300 g NDF and 161 g CP, and contained (g/kg DM): alfalfa silage, 500; corn silage, 250; high-moisture shelled corn, 176, soy hulls, 50; plus minerals and vitamins. Ruminal digesta were collected just before feeding on the last three days of each period, and were separated into solid and liquid phases. Microbial DNA was extracted from each phase, amplified by polymerase chain reaction (PCR) using domain-level bacterial primers, and subjected to automated ribosomal intergenic spacer analysis (ARISA) for comparison of BCC. Correspondence analysis of the 266 peaks in the ARISA profile across the 192 samples revealed that the first two components contributed 6.8% and 4.2% to the total variation in the profile. Data points representing the liquid and solid phases clustered separately, indicating that these phases differed in BCC. Treatment effects were not apparent from the ARISA profiles. However, the relative population size (RPS) of LP, determined by quantitative PCR, was greater in treated silage compared to the Ctrl (P<0.01). Data points corresponding to certain individual cows clustered separately, and the most distinctive bacterial communities were those associated with milkfat-depressed cows. The RPS of one bacterial species, Megasphaera elsdenii, was greater in fat-depressed cows. However, mean RPS of M. elsdenii did not differ between the treatments. The results indicate that a silage inoculant can affect rumen bacterial composition beyond elevating the population of the specific microbial inoculant.