Evaluation of the effects of live yeast on rumen parameters and in situ digestibility of dry matter and neutral detergent fiber in beef cattle fed growing and finishing diets

Abstract

ABSTRACT Objective This study evaluated the effects of live yeast (LY; Saccharomyces cerevisiae) on rumen parameters and in situ DM digestibility (DMD) and NDF digestibility (NDFD) during 3 consecutive feeding phases: grower (GRW) for 27 d, transition (TRANS) for 14 d, and finisher (FIN) for 14 d. Material and Methods Eight ruminally cannulated cattle (4 steers and 4 heifers) were blocked by sex into 2 pens containing Calan gate feeders and received a control diet (13.7% CP, 42.4% NDF, 88% DM) without LY for 10 d (−10 to −1). Animals were randomly assigned to treatments: control or LY fed every morning (0800 h) at 2.5, 5, or 10 g/d for 55 d. Digestibility was assessed on 9 collection days using in situ nylon bags containing 5 g of diet for GRW, TRANS, or FIN incubated for 48 h. Results and Discussion During the GRW-diet phase, treatment altered DMD and NDFD and tended to affect the rate of degradation and the acetate-to-propionate ratio. During the TRANS-diet phase, treatment affected total gas production, protozoa numbers, DMD, and NDFD. Throughout the FIN-diet phase, treatment affected rate of degradation, VFA concentrations, protozoa numbers, DMD, and NDFD and tended to affect methane and pH. Implications and Applications The LY affected rumen parameters and digestibility, but the dose-response pattern varied depending on the type of diet. The ideal dose of LY might be variable depending on the type of diet, and it might be greater than currently recommended for practical use in farms.