Evaluation of the maternal bovine appeasing substance administered at arrival and time of reimplant on feedlot performance and carcass characteristics of yearling beef steers

Evaluate the effects of the maternal bovine appeasing substance (mBAS) on feedlot performance, health outcomes, hair cortisol concentrations, and carcass characteristics for northern US-origin yearling beef steers. Crossbred steers (n = 1,754; initial BW = 424 kg, SD = 25 kg) were received on 7 ar-rival dates to a commercial Nebraska feedyard, gate sorted into 20 pens, and pens were randomly assigned to receive (1) 10 mL of mBAS (FerAppease, FERA Diagnostics and Biologicals) or (2) 10 mL of mineral oil placebo (CON). Treatments were applied topically to the poll and muzzle (5 mL at each site) at initial processing and reimplant. A subset of 5 steers per pen (n = 100) were randomly select-ed for hair sampling at arrival and d 14 to assess cortisol. Steers were fed a high-moisture, corn-based finishing diet for 167 d on feed before harvest. Dry matter intake and ADG did not differ between treatments. Carcass-adjusted G:F tended to improve for mBAS on a deads-in basis. Hot carcass weight, LM area, and marbling score were similar, though dressing percent tended to be greater with mBAS. Quality grade and yield grade distributions did not differ between treatments. Administering mBAS did not affect treatment frequency for illness, overall mortality rate, or hair cortisol concentrations. Topical mBAS ap-plication at arrival and reimplant did not influence growth, health, or cortisol, but may modestly improve carcass-ad-justed feed efficiency in yearling steers.