Effects of Saccharomyces cerevisiae fermentation products and subacute ruminal acidosis on feed intake, fermentation, and nutrient digestibilities in lactating dairy cows

Abstract

Effects of Saccharomyces cerevisiae fermentation products (SCFP) and subacute ruminal acidosis (SARA) on rumen and hindgut fermentation, feed intake, and total tract nutrient digestibilities were determined in 32 lactating Holstein cows between weeks 4 and 9 of lactation. Treatments included control, 14 g·d−1 Diamond V Original XPC™ (SCFPa; Diamond V, Cedar Rapids, IA, USA), 19 g·d−1 NutriTek® (SCFPb-1X; Diamond V), and 38 g·d−1 NutriTek® (SCFPb-2X; Diamond V). During weeks 5 and 8, SARA challenges were conducted by switching from a 18.6% to a 27.9% dry matter (DM) starch diet. This reduced the rumen and feces pH. The durations of the rumen pH below 5.6 during these challenges averaged 175.0, 233.8, 246.9, and 79.3 min·d−1 for the control, SCFPa, SCFPb-1X, and SCFPb-2X treatments, respectively. Hence, SARA was not induced under the SCFPb-2X treatment. The feces pH during the SARA challenges was lowest during SCFPb-2X, suggesting this treatment shifted fermentation from the rumen to the hindgut. The SARA challenges reduced the total tract digestibility of DM, neutral detergent fiber digestibility (NDFd), and phosphorus, but tended to increase that of starch. The SCFPb-2X treatment increased the NDFd from 52.7% to 61.8% (P < 0.05). The SCFPb-2X treatment attenuated impacts of SARA.