PSIX-13 The Impact of Saccharomyces Cerevisiae Fermentation Product on in-Vitro Rumen Fermentation Characteristics, gas Production, and Ruminal Microbiome Composition

The objective of this experiment was to evaluate the effect of Saccharomyces cerevisiae products (NaturSafe) on in-vitro rumen fermentation characteristics and microbial diversity. Three crossbred feedlot steers fitted with rumen cannulae were adjusted to a moderately high-concentrate diet for 28-d. On d-29, 1 L of rumen fluid was collected from each steer and composited. A set of vaccine bottles (n=5/treatment/time + blanks and controls) containing 0.5 g of basal diet plus dietary treatments were filled with 30 ml of rumen fluid-McDougall’s buffer solution (1:1), sealed, and placed in a 39°C water bath. Treatments consisted of 1) Control (no added NaturSafe); 2) NaturSafe-dry (9 g/animal/day equivalent); 3) NaturSafe-dry (12 g/animal/day equivalent); 4) NaturSafe-liquid (14 g/animal/day equivalent); 5) NaturSafe-liquid (21 g/animal/day equivalent); and NaturSafe-liquid (28 g/animal/day equivalent). Samples were collected at 0, 6 and 12 h post-fermentation. No treatment effect on any fermentation parameters was found at 6 h. At 12-h post-incubation, dry matter digestibility (DMD) (P < 0.04) and molar proportions of propionic acid (P < 0.03) were greater for treatments containing NaturSafe compared with control. Molar proportions of acetic acid (P < 0.07), percent CH4 (P < 0.08), and NH3-N (P < 0.06) tended to be lesser and percent CO2 tended (P < 0.07) to be greater for NaturSafe treatments compared with controls. Microbiome 16S rRNA analysis results suggest that microbial communities differed (P < 0.05) between 6 and 12 h post-incubation. Incorporating NaturSafe into fermentation vessels revealed an inverse correlation with NaturSafe concentration and microbial diversity (P = 0.08) and that the overall microbial diversity was altered (P < 0.03) by NaturSafe concentration. The microbial community was not affected by additive type. These data suggest that NaturSafe alters fermentation characteristics and microbial community diversity toward improved rumen efficiency while reducing environmental impact.