337 - Effects of Dietary Supplementation of Saccharomyces Cerevisiae-based Microbial Additive Containing Fermentation Products on Health, and Performance of Weaned Beef Steers During a 35-d Receiving Period

Abstract: We examined the effects of dietary supplementation of Saccharomyces cerevisiae-based microbial additive containing fermentation products of multiple micro-organisms on health and performance of newly weaned beef steers during a 35-d receiving period. Crossbred beef steers (n = 80; 12-hour post-weaning; 206 ± 12 kg of BW) were stratified by BW into 4 pens (20 steers per pen) such that each pen had similar BW at the beginning of the experiment. The steers were assigned to receive a corn silage-based diet with no additive (CON; 2 pens) or a diet supplemented with a blend of live S. cerevisiae and the fermentation products of S. cerevisiae, Enterococcus lactis, Bacillus licheniformis, and B.  subtilis at an average of 28 g/steer/d for the first 21 d (SYNB; 2 pens). Percentage of steers treated for bovine respiratory disease (BRD) was calculated for each dietary treatment. Daily DMI and weekly body weights were measured. Blood samples collected weekly were analyzed for mRNA expression of 84 immune-related genes and plasma metabolome. Compared with CON, supplemental SYNB increased (P ≤ 0.05) average daily gain (ADG) and DMI during the first 7 d. During the first 21 d, there was no treatment effect (P > 0.05) on final BW, DMI, and ADG. Over the entire 35-d receiving period, beef steers fed supplemental SYNB had greater (P = 0.01) ADG and had reduced percentage (35 vs. 50%) of animals treated for BRD. Whole blood expression of pro-inflammatory genes was downregulated while that of anti-inflammatory genes was upregulated in beef steers fed supplemental SYNB. Six nutrient metabolic pathways of great health benefits were enriched (FDR ≤ 0.05) in beef steers fed supplemental SYNB. This study demonstrated that dietary supplementation of SYNB during the first 21 d of arrival reduced BRD morbidity, improved the performance, immune, and metabolic status of beef steers over a 35-d receiving period.