PSVI-3 Effects of dietary supplementation of multi-species direct-fed microbial products on energy status, apparent nutrient digestibility, and rumen metatranscriptome of beef steers

Abstract

Abstract This study evaluated the effects of two different multi-strain direct-fed microbial products on energy status, nutrient digestibility, and ruminal metatranscriptome of beef steers. Nine rumen-cannulated Holstein steers were assigned to 3 treatments arranged in a 3 × 3 Latin square design with three 21-d periods. Dietary treatments were (1) CON (basal diet without additive), (2) PROB (basal diet plus 19 g/d of Commence), and (3) SYNB (basal diet plus 28 g/d of RX3). Commence is a blend of S. cerevisiae, Enterococcus lactis, Bacillus subtilis, Enterococcus faecium, and L. casei. RX3 is a blend of S. cerevisiae and the fermentation products of S. cerevisiae, Enterococcus lactis, Bacillus licheniformis, and Bacillus subtilis. Rumen fluid (for metatranscriptomics analysis) and blood samples (for analysis of plasma glucose and non-esterified fatty acid) were collected on d 21 of each period. From d 16 – 20, TMR and fecal samples were collected daily to determine apparent total tract digestibility of nutrients using indigestible neutral detergent fiber (iNDF) method. The data were analyzed using the GLIMMIX procedure of SAS. The model included the effects of treatment, period, and random effects of cow and square. There were no effects on DMI and non-esterified fatty acid. Compared with CON, steers fed either additives had greater (P = 0.02) plasma glucose concentrations. Results of metatranscriptome analysis revealed no differentially expressed functional genes among the treatments. Apparent total-tract digestibility of nutrients were also similar among treatments. These results demonstrated that supplemental PROB and SYNB improved the plasma glucose concentration, but had no effects on the functional capacity of the ruminal microbiome and apparent digestibility of nutrients in beef steers.