Effects of a multicomponent microbial feed additive containing prebiotics and probiotics on health, immune status, metabolism, and performance of newly weaned beef steers during a 35-d receiving period

We examined the effects of dietary supplementation of a multicomponent blend of prebiotics and probiotics on health, immune status, metabolism, and performance of newly weaned beef steers during a 35-d receiving period. Eighty newly weaned crossbred steers (12-hour postweaning; 206 ± 12 kg of body weight [BW]) from a single source were stratified by BW into four pens (20 steers per pen) such that each pen had similar BW at the beginning of the experiment. The pens were randomly assigned to receive a corn silage-based diet with no additive (CON; two pens; n = 40 steers) or a basal diet supplemented with SYNB feed additive at an average of 28 g/steer/d (SYNB; two pens; n = 40 steers). The SYNB additive is a blend of live Saccharomyces cerevisiae and the fermentation products of S. cerevisiae, Enterococcus lactis, Bacillus licheniformis, and Bacillus subtilis and was supplemented for the first 21 d only. Percentage of steers treated for bovine respiratory disease (BRD) was calculated for each dietary treatment. Daily dry matter intake (DMI) and meal events (meal frequency and duration) were measured. Weekly BWs were measured to calculate average daily gain (ADG). Blood samples collected on days 0, 14, 21, 28, and 35 were used for ex-vivo tumor necrosis factor alpha (TNF-α) release assay following lipopolysaccharides (LPS) stimulation, plasma metabolome analysis, and mRNA expression analysis of 84 innate and adaptive immune-related genes. Compared with CON, supplemental SYNB increased (P ≤ 0.05) ADG, DMI, and meal events during the first 7 d. At d 21, there was no treatment effect (P > 0.05) on final BW, DMI, ADG, and meal events; however, beef steers fed supplemental SYNB had greater (P = 0.02) meal duration. Over the entire 35-d receiving period, beef steers fed supplemental SYNB had greater (P = 0.01) ADG and feed efficiency, tended to have greater (P = 0.08) meal duration, and had lower percentage (35 vs. 50%) of animals treated for BRD and lower percentage of sick animals treated for BRD more than once (7.15 vs. 45%). Whole blood expression of pro-inflammatory genes was downregulated while that of anti-inflammatory genes was upregulated in beef steers fed supplemental SYNB. Beef steers fed supplemental SYNB had lower (P = 0.03) plasma concentration of TNF-α after LPS stimulation. Six nutrient metabolic pathways associated with health benefits were enriched (false discovery rate ≤ 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 thereby extending the SYNB effect by a further 14 days post supplementation.