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Investigating the effects of different soybean products on rumen microbial populations in dairy cows using in vitro fermentation.

M. Leibstein



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Investigating the effects of different soybean products on rumen microbial populations in dairy cows using in vitro fermentation.
M. Hennessy1, J. Bender1, M. Leibstein*2, B. Vecchiarelli1, N. Indugu1, S. Garapati3, J. Toth2, L. Baker1, D. Pitta1. 1University of Pennsylvania School of Veterinary Medicine Kennett Square, PA, 2Oceanside High School Oceanside, NY, 3Drexel University Philadelphia, PA.

While several soybean (SB) products are commonly included in dairy cow rations, their specific effects on rumen microbial populations are not well understood. This study examined 9 diets: a basal diet made up of corn silage, haylage, and corn; the basal diet plus either SB meal, SB hulls, SoyPlus, raw SB, or roasted SB; and the basal diet plus a combination of either SB meal and SoyPlus, SB meal and SB hulls, or SB hulls and SoyPlus. Three dairy cows from farm A were sampled for rumen contents and these samples were combined and added as an inoculum to fermentation vials containing feed and artificial buffer, purged with CO2, and incubated at 37�C for 6h with slow agitation. The same procedure was carried out with 3 dairy cows from farm B. Samples were collected before (0h) and after (6h) incubation and separated into liquid and solid fractions. These samples were extracted for DNA, PCR-amplified for the V1-V2 region of the 16S rDNA bacteria gene, sequenced on an Illumina platform, and analyzed for bacterial diversity. At the community level, weighted Unifrac distance-based analysis revealed differences in communities between ruminal fractions and time of incubation (P < 0.05). Within each fraction, at 6h, differences in bacterial communities were influenced by source of rumen inoculum, diet, and interaction between inoculum and diet (P < 0.05). Comparison of individual bacterial taxa between fractions using ANCOM revealed that the solid fraction had lower amounts of Succinivibrionaceae and higher amounts of Oribacterium (P < 0.05) whereas the liquid fraction contained higher amounts of Veillonellaceae and lower amounts of Clostridium (P < 0.05) in all diets with soybean products compared with the control diet despite differences in the source of ruminal inoculum. In vitro-based microbial analysis revealed that soybean products may influence bacteria involved with soluble carbohydrate and protein breakdown with no effects on fiber-digesting bacteria. However, the causality behind these effects of soybean products on ruminal microbiota needs to be investigated using in vivo experiments.

Keywords: microbiome, proteolytic bacteria, ANCOM.