Efficacy of laidlomycin propionate to reduce ruminal acidosis in cattle

Three trials were conducted to evaluate the efficacy of laidlomycin propionate (LP) to reduce the incidence and severity of ruminal acidosis in cattle fed high-grain finishing diets. In each trial, LP was fed at 0, 6, or 12 mg/kg of diet DM. In two acidosis-challenge trials, ruminally 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 steers were dosed intraruminally with a 100% concentrate diet. Laidlomycin propionate did not alter ruminal pH or total acid concentrations, but in Trial 1 the 6 mg/kg level altered (P < .10) the molar proportions of the acids, increasing total ruminal VFA and decreasing ruminal lactate. In Trial 3, a finishing trial, LP reduced (P < .10) intake day-to-day variation of individually fed steers during a 13-d adaptation period 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 calculated on a live weight basis (linear, P = .05) or carcass weight basis (linear, P = .20). Laidlomycin propionate does not prevent ruminal acidosis, but it may reduce the severity of ruminal acidosis during adaptation to a 100% concentrate diet.