The Effects of a Novel Brewer's Yeast Product on Ruminal Fiber Fermentation in Vitro.

The objective was to evaluate a novel brewer's yeast product on ruminal fiber fermentation in vitro. The experiment was a completely randomized design and included 4 treatments. Treatments included a negative control (NCON), a commercial brewer's yeast product (Emprove MX; EMX), and a prototype concentrated brewer's yeast (T1R8) fed at low and high inclusions (T1R8-L and T1R8-H, respectively). Inclusions for low and high treatments were 0.0008 and 0.0015 g, respectively, to correspond with 7 and 14 g inclusion in a lactating cow diet. Treatments were evaluated in duplicate flasks in 2 replicated runs for a total of four observations per treatment. Flasks contained 2.5 grams dry matter (DM) of substrate to represent a lactating cow diet (30% haylage, 25% corn silage, 20% corn, 15% canola meal, and 10% soybean hulls), and 150mL of rumen fluid mixture (2 McDougall's buffer:1 rumen fluid ratio). Four F57 sealed Ankom bags were filled with 0.25 grams DM of substrate each to facilitate measuring in vitro DM and neutral detergent fiber disappearance (IVDMD and IVNDFD, respectively). Flasks were incubated at 39℃ for 30 hours with sample aliquots collected at hour 0, 8, 16, and 30 to determine pH and volatile fatty acids (VFA). Data were analyzed using the MIXED procedure of SAS 9.4 with IVDMD and IVNDFD considered a main effect of treatment while pH and VFA were analyzed with effects of treatment, time, and their interaction. No differences in IVDMD were observed (P = 0.31) among treatments. Treatment affected (P = 0.01) IVNDFD with EMX (50.6%), T1R8-L (48.6%), and T1R8-H (50.3%) being greater than NCON (45.7%). A treatment by hour interaction (P < 0.01) was observed for total VFA concentration; EMX (71.8 mM), T1R8-L (72.6 mM), and T1R8-H (66.0 mM) were greater than NCON (47.8 mM) at h 8, but all treatments were not different at h 16. A treatment by hour interaction (P < 0.01) was also observed for acetate and propionate; EMX, T1R8-H, and T1R8-L were greater than NCON at h 8, but all treatments were not different at h 16. At h 30, greater propionate was observed for T1R8-H compared with all treatments. No effects of treatment or treatment by hour (P = 0.89) were observed for acetate:propionate ratio. Although a treatment by hour interaction was not observed for pH (P = 0.12), a treatment effect (P = 0.03) indicated T1R8-L was the greatest with EMX being intermediate, and NCON and T1R8-H being the least. Novel brewer's yeast product T1R8 increased the rate of substrate fermentation in the initial 8 h and increased the extent of fiber degradation after a 30 h in vitro fermentation. [ABSTRACT FROM AUTHOR]