PSIX-6 Effects of a live yeast product on ruminal bacterial diversity and metabolome of beef cattle

Abstract

Abstract This study utilized 16S ribosomal ribonucleic acid (rRNA) sequencing and liquid chromatography-mass spectrometry (LC-MS)-based metabolomic profiling to evaluate the effects of a live yeast product on ruminal bacterial diversity and metabolome of beef steer. Eight rumen-cannulated Holstein steers were assigned randomly to 1 of 2 treatment sequences in a study with two 25-d experimental periods and a crossover design. The steers were fed 50% concentrate-mix and 50% red clover hay ad libitum. Dietary treatments were (1) control (CON; basal diet) and (2) yeast (YEA; basal diet plus 15 g/d of live yeast product; PMI, Arden Hills, MN, USA). Bacterial diversity was examined by sequencing of the V3-V4 region of the 16S rRNA gene. Metabolome analysis was performed using an ultra-performance LC-MS system. Relative abundance of bacteria was analyzed using the GLIMMIX procedure of SAS and a model that included the effects of treatment, period, and their interaction. Significant differences were declared at P ≤ 0.05. Differential metabolites were filtered using significance estimate of P ≤ 0.10 using Metaboanalyst 4.0. Pearson correlation was used to examine associations between the relative abundance of ruminal bacteria and rumen metabolites. Yeast supplementation increased (P ≤ 0.05) the relative abundance of Ruminococcaceae NK4A214, Christensenellaceae R-7, Ruminococcaceae UCG-010, Ruminococcus 2, and Ruminococcaceae UCG-005, Candidatus saccharimonas, Anaerovorax, and Lachnospiraceae. Yeast supplementation increased (P ≤ 0.10) the concentrations of 4-cyclohexanedione and β-d-glucopyranoside, and decreased concentrations of threonic acid, xanthosine, deoxycholic acid, lauroylcarnitine, methoxybenzoic acid, and pentadecylbenzoic acid. Bacteroidales BS11, Christensenellaceae R-7, and Candidatus saccharimonas showed positive correlations with metabolites involved in amino acid biosynthesis and metabolism of energy substrates; the functions of these bacteria are not fully understood in relation to the mode of action of yeast. This study confirms the usefulness of LC–MS-based metabolomics in deciphering the mode of action of live yeast in the rumen.