Effects of feeding a yeast culture product on performance, blood biomarkers, rumen fermentation, and rumen bacteria species in peripartal dairy cows

Feeding yeast culture fermentation products has been associated with improved feed intake and milk yield in transition dairy cows. The objective of this study was to evaluate the effects of a commercial yeast culture product (Cellerate Culture Classic HD (YC); Phibro Animal Health, Teaneck, NJ) on performance, blood biomarkers, and rumen fermentation and bacterial population in dairy cows during the transition period until 50 DIM. Forty Holstein dairy cows were enrolled in a randomized complete block design from −30 to 50 DIM and blocked according to expected calving day, parity, previous lactation milk yield, and genetic merit. At −30 DIM cows were assigned to either a basal diet plus 114 g/d of ground corn (CON; n = 20) or basal diet plus 100 g/d of ground corn and 14 g/d YC (n = 20), fed as a top-dress. Cows received the same close-up diet from −30 until calving (0.63 Mcal/kg DM and 12.3% CP) and lactation diet from calving to 50 DIM (0.73 Mcal/kg DM and 15.6% CP). Blood samples were collected at −30, −15, 7, 14, and 30 DIM to evaluate biomarkers of muscle body mass, metabolism, and oxidative stress. Rumen fluid (~50 mL) was sampled via esophageal tubing on −59, −30, 5, and 30 DIM for analysis of ammonia, VFA, and bacterial populations via qPCR amplification. Data were analyzed using the MIXED procedure of SAS. There was a trend (P ≤ 0.13) for increased milk yield (+2.5 kg/d), ECM (+3.2 kg/d), and ECM/DMI (+0.13) for cows fed YC than CON. A trend (P = 0.10) for lower NEFA in YC than CON cows was observed. A trend (P = 0.08) for a Diet × Time was observed for butyrate percentage, where lower (P = 0.03) butyrate was observed in YC than CON at 5 DIM. Rumen bacteria associated with improved feed efficiency such as Megasphaera elsdenii was greater (P = 0.05) in YC cows compared with CON while Prevotella albensis was greater (P = 0.01) in YC compared with CON cows at 30 DIM. These results suggest that feeding YC to transition dairy cows can affect rumen fermentation by altering rumen bacteria populations, which helps explain the observed improvements in milk yield and milk yield efficiency