Effects of lubabegron dose and duration on calculated cumulative ammonia gas emissions and growth performance by feedlot steers during the last 28, 56, or 84 days of the feeding period

Objective

Our objective was to characterize the effects of lubabegron (Experior 10; Elanco Animal Health, Greenfield, IN) on ammonia gas emissions, growth and carcass merit, and animal mobility of feedlot steers.

Materials and Methods

Crossbred beef steers were used in a randomized complete block with a 4 × 3 factorial arrangement of dietary lubabegron concentrations. (LUB; 0, 1.5, 3.5, or 5.5 mg/kg of DM) and duration of feeding (28, 56, or 84 d before slaughter). Blocks were slaughtered after an equal time on feed.

Results and Discussion

Calculated cumulative ammonia gas emissions per kilogram of hot carcass weight decreased after 28 d (linear) as LUB increased and responded quadratically after 56 and 84 d (LUB × duration). Steer DMI (LUB × duration) decreased linearly as LUB increased after 28 and 56 d. Final shrunk BW and ADG (LUB × duration) increased (linear) as duration increased and increased (quadratic) as LUB increased. The increase in G:F (LUB × duration) as LUB increased was linear within each duration, with an increasingly smaller magnitude as duration increased. Steer G:F increased linearly as duration increased when 0, 1.5, and 3.5 mg/kg of DM was fed. Steer DP (LUB × duration) increased quadratically as duration increased and linearly as LUB increased. Marbling score (LUB × duration) decreased quadratically as LUB increased when fed for 84 d and decreased linearly when 1.5 or 3.5 mg/kg of DM was fed. Average YG decreased (LUB × duration) linearly as LUB increased. Neither LUB nor duration altered the distribution of mobility scores at lairage before slaughter.

Implications and Applications

Feeding lubabegron resulted in lesser calculated ammonia emissions per kilogram of output, ≤0.3 kg/d lesser DMI, up to 19 kg more hot carcass weight, and leaner carcasses with a lesser marbling score after 56 d and did not alter health status or animal mobility after transport to slaughter.