PSVIII-B-6 - Effect of Yeast on Rumen Ph and Redox Potential in Ruminally-cannulated Dairy Cows

Abstract: Yeast products are used worldwide to stabilize the anaerobic rumen environment in dairy cattle. Multiparous lactating ruminally fistulated dairy cows (n = 4; ±150 DIM) were used in an 84-d 4×4 Latin square design to evaluate the effect of yeast on rumen pH and redox potential (eH). Periods were 21 d with 16 d used for treatment acclimation and HOBO pH and Temperature Data Loggers were placed in the rumen cranial sac on d 16 and removed on d 17 after a period of 24 hr for data collection. Cows were housed in a single pen and individually fed a basal dairy diet (CON) with no yeast culture or probiotics formulated for high milk yield targeting 5% feed refusals using a Calan Broadbent feeding system. Cows were randomly assigned to 1 of 4 treatments in period 1: CON, 14 g Diamond V XPC (XPC), 5 g Phileo-Lesaffre Actisaf HR+ (HR+), and HR+ 5 g Phileo-Lesaffre Safmannan (HR+Saf). Feed was delivered twice daily. Treatments were top-dressed at 0630 hr to ensure treatment consumption. Data were analyzed using GLIMMIX procedure of SAS 9.4. Significance was determined at P ≤ 0.05 and tendencies were considered at P ≤ 0.15. A treatment by time interaction occurred for rumen pH (P = 0.02). All yeast treatments were different than CON (P < 0.01), with no differences between yeast treatments (P > 0.52). A treatment by time interaction for eH (P = 0.04) occurred. Yeast eH was less than CON (P < 0.01). Redox potential decreased for HR+ compared to XPC (P = 0.04), while HR+Saf tended to decrease eH compared to XPC (P = 0.11). Over time, eH increased after feedings (P < 0.01). Data indicated that adding yeast to a dairy diet promoted an anaerobic environment, increasing rumen efficiency in lactating dairy cattle.