PSXVI-22 The influence of Propionibacteria on in vivo rumen fermentation characteristics and in vitro lactic acid clearance rate in fistulated steers fed moderately high concentrate diets

Abstract

Abstract Six steers fitted with ruminal cannulae were used in a crossover design to examine the impact of direct fed microbial (DFM) supplementation on in vivo rumen fermentation characteristics and in vitro lactic acid clearance. Steers were fed a moderately high concentrate -1∙day-1 of 4.45x 1010 CFU/g of Propionibacteria acidipropionici). Treatments were administered daily, directly into the rumen via the cannula as a single bolus dose at the time of feeding. Rumen contents were sampled two h post-feeding daily and analyzed for short chain fatty acids (SCFA). On d 7 and 14, rumen fluid was collected from all steers and subjected to an in vitro lactic acid clearance challenge. Lactic acid and SCFA concentrations were determined at 3, 6 and 9 h post incubation. After d 14, all cattle received the basal diet for 21 d. On d 22, treatment crossover was implemented and the experiment repeated. Animal was considered the experimental unit and data were analyzed as a crossover design using Proc Mixed in SAS. In vivo propionic acid concentrations were greater (P < 0.05) and total SCFA tended (P < 0.06) to be greater in rumen fluid from steers receiving DFM. D- and total lactic acid concentrations were lesser (P < 0.05) at 3 h post in vitro incubation for steers receiving DFM. D-, L+, and total lactic acid concentrations were similar between treatments at all other timepoints. In vitro propionic acid and total SCFA concentrations were greater (P < 0.05) and acetic acid concentrations lesser (P < 0.05) in steers receiving DFM. These data indicate that the DFM Propionibacteria acidipropionici, alters in vivo and in vitro rumen fermentation characteristics.