223 Impacts of Active Dry Yeast (Saccharomyces cerevisiae) on Gut Permeability in Finishing Beef Cattle

Abstract

Abstract The objectives of this study were to examine the impacts of active live yeast (Saccharomyces cerevisiae) as a dietary feed additive on dry matter intake, feed sorting, gut permeability, ruminal pH and volatile fatty acids (VFA) concentration, as well as fecal pH and VFA concentration in cattle fed a high-grain finishing diet and subjected to a ruminal acidotic challenge. Fifteen Hereford X Charolais heifers were blocked by BW into three blocks. Heifers were randomly assigned within block to one of two dietary treatments; CON (no additive), or YST (3 g· animal-1· day-1 of active live S. cerevisiae) added to a steam-flaked corn diet (83% steam-flaked corn, 8% wheat straw, 5% soybean meal protein mix, 4% vitamin and minerals on a DM basis). The experimental timeline was as follows: 30 d adaptation (ADPT), 5 d baseline (BASE), 5 d ruminal acidosis challenge (CHAL), and three subsequent 5 d recovery phases (REC1, REC2, and REC3). On day 2 of each phase and days 2 and 4 of CHAL, 179 mM Cr-EDTA and 360 mM Co-EDTA were infused into the omasum and rumen, respectively, as gut permeability markers. Within each phase, in-dwelling pH probes were used to capture reticulo-ruminal pH every 5min for 96 consecutive hours, rumen fluid and fecal grab samples were collected once for every 3 h in a 24 h period, and blood was collected at 2, 4, 12, and 24 h after each Co and Cr infusion. Dry matter intake and feed sorting were measured daily for each animal. Statistical analysis was conducted using PROC GLIMMIX in SAS as a randomized complete block design with block, treatment, and phase as fixed effects and animal as a random effect. Ruminal acidosis was successfully induced using this method, as suggested by the statistically significant reduction in minimum pH and increase in pH range in the CHAL phase compared with other phases of the experiment (P ≤ 0.02). Recovery from the ruminal acidosis challenge was detected within the REC1 phase when comparing minimum pH (CHAL 5.25 vs. REC1 5.54; P = 0.001). Additionally, the sorting behavior of some particle sizes was significantly impacted by phase (P ≤ 0.01). Overall, the addition of yeast to the diet did not impact feed intake, sorting behavior, spot ruminal and fecal pH, volatile fatty acid concentrations in ruminal fluid or feces, or the uptake of Cr-EDTA and Co-EDTA. These results suggest that adding live S. cerevisiae yeast at this dose in a high-grain finishing diet does not impact feed intake, gut permeability, or the production of VFA when ruminal acidosis is induced.