Administering the maternal appeasing substance to and cattle placed as yearlings in feedlots with different environmental conditions.

Two experiments evaluated growth performance of finishing cattle placed on feed as yearlings, and receiving the maternal bovine appeasing substance () during stressful management events. In Exp. 1, 240 Angus-influenced yearling steers arrived at the research feedyard on d -1 after a 4-h road transport, and body weight () was recorded upon arrival (411.8 ± 2.5 kg). Steers were ranked by arrival BW and received 1 of 2 treatments during initial processing (d 0): 1) 10 mL of a mBAS (Ferappease; FERA Diagnostics and Biologicals; College Station, TX) or 2) 10 mL of mineral oil (; placebo). Treatments were applied topically to the nuchal skin area (5 mL) and above the muzzle (5 mL). During initial processing, steers were weighed, vaccinated against spp. and respiratory pathogens, dewormed, implanted, and then distributed into 30 drylot pens according to arrival BW and treatment (n = 15 pens/treatment, 8 steers/pen). Steers were reapplied treatments concurrently with reimplanting on d 75. Initial BW was the average BW on d -1 and 0, final BW was the average of BW recorded on d 138 and 139, and steers were slaughtered on d 139. Steers assigned to mBAS had greater (≤ 0.04) ADG, final BW, and hot carcass weight (). Feed intake was greater (≤ 0.05) in mBAS steers, but mostly after reimplanting (treatment × day;  < 0.01). Carcass yield grade, backfat thickness, marbling score, and % Choice or better were greater (≤ 0.05) in mBAS steers. In Exp. 2, Nelore () yearling bulls (n = 2,626) arrived at a feedyard (d 0) after a 96-h road transport, and BW was recorded upon arrival (shrunk BW = 352.9 ± 0.6 kg). Bulls were assigned to receive mBAS or CON as in Exp. 1 during initial processing on d 0 (10 pens/treatment; ~130 bulls/pen) which included deworming and vaccination against spp. and respiratory pathogens. Bulls were on feed for 96.0 ± 1.0 d until slaughter. Bull ADG was calculated using arrival BW considering a 14% shrink and final BW recorded when loading bulls to slaughter. Bulls assigned to mBAS had greater (≤ 0.04) ADG, feed intake, final BW, and HCW. Morbidity and mortality rates due to respiratory disease were less (= 0.02) in mBAS bulls. Collectively, mBAS administration during stressful management events improved growth performance, mainly by increasing feed intake, in finishing cattle placed on feed as yearlings in feedlot systems typical of US (Exp. 1) and tropical regions (Exp. 2).