EFFICACY OF LAIDLOMYCIN PROPIONATE TO REDUCE RUMINAL ACIDOSIS IN CATTLE

Three trials were conducted to evaluate the efficacy of laidlomycin pr opionate (LP) to reduce the incidence and severity of ruminal acidosis in cattle fed high-grain finishing diets. In each trial, LP was fed a t 0, 6, or 12 mg/kg of diet DM. In two acidosis-challenge trials, rumi nally fistulated steers were fed (DM basis) a 50% concentrate diet and then fed a 95% concentrate diet at a specific intake (2.75% BW) or st eers were dosed intraruminally with a 100% concentrate diet. Laidlomyc in propionate did not alter ruminal pH or total acid concentrations, b ut in Trial 1 the 6 mg/kg level altered (P <.10) the molar proportions of the acids, increasing total ruminal VFA and decreasing ruminal lac tate. In Trial 3, a finishing trial, LP reduced(P <.10) intake day-to- day variation of individually fed steers during a 13-d adaptation peri od from a 65 to a 100% concentrate diet, suggesting reduced incidence of subacute acidosis. Feed intake was lower (P <.05) during the first 13 d of the trial due to LP but was not affected over the entire trial . Laidlomycin propionate improved feed efficiency (gain/feed) when cal culated on a live weight basis (linear, P =.05) or carcass weight basi s (linear, P = .20). Laidlomycin propionate does not prevent ruminal a cidosis, but it may reduce the severity of ruminal acidosis during ada ptation to a 100% concentrate diet.