PSLBII-13 Bioinformatics of rumen fluid from steers fed alfalfa-bermudagrass mixtures in the Deep South

Abstract When harvesting high-quality, high-water content forages like legumes, there is often a greater percentage of nutritive loss due to the drying process. Alternative feeding strategies like baleage provide a way to mitigate these losses. However, there is not much adoption of baleage in the Deep South. Therefore, our objective was to assess the influence of conserved forage type on rumen metabolomes of beef cattle systems in the Deep South. Three treatments including bermudagrass (Cynodon dactylon) hay, alfalfa (Medicago sativa) baleage, and alfalfa-bermudagrass baleage were supplied to four fistulated steers with a calculated daily forage allowance based on intake, body weight, and feed refusals. Each diet was allocated to one of three periods in which all four animals received the same diet due to potential feed spoilage. Each period had a 21-d adaptation period followed by a 5-d collection period to analyze rumen fluid, total fecal weight, feed intake, feed refusal, and total urine. This study integrated 16S RNA sequencing and LC-MS-based metabolomics to evaluate rumen bacterial diversity and metabolome of beef steers. Sequencing data from the rumen fluid samples were then analyzed using QIIME2. Bermudagrass hay had a reduced alpha diversity compared with alfalfa baleage (Shannon: H = 5.19, P = 0.02). Additionally, we saw a change in beta diversity (P < 0.001), measured using the unweighted UniFrac distance, between conserved forage types and distinct clustering in the PCoA analysis. The most abundant taxa in all microbial communities were from the orders Lachnospirales, Bacteroidales, and Oscillospirales. Previous analysis in this study evidenced that baleage had an increased dry matter digestibility (DMD; P = 0.02). The increase in DMD was associated with the increase in diversity of the metabolome which could influence animal health and performance. Thus, baleage can serve as a beneficial conserved forage type that mitigates the losses of high-quality forages and diversifies the gut microbiome of ruminant animals.