Abstract
This experiment compared performance and health responses of feedlot cattle consuming different feed additives during a 45-d receiving period. Angus-influenced steers (n = 256) were purchased from a commercial auction yard, and road-transported (12 h) to the experimental feedyard on d -1. Upon arrival, body weight (BW) was recorded and steers were ranked by BW into 1 or 18 drylot pens (14 or 15 steers/pen). Pens were randomly assigned to receive RAMP® from d 0 to d 45 with the inclusion of: 1) Rumensin + Tylan (Elanco Animal Health; Greenfield, IN; 360 mg and 90 mg per animal/daily, respectively; RT), 2) Rumensin + Celmanax + Certillus (Church and Dwight Co., Inc., Princeton, NJ; 18 g and 28 per animal/daily, respectively; RCC), or Celmanax + Certillus (18 g and 28 per animal/daily, respectively; CC). Feed intake during the initial 21 d of the experiment was greater (P ≤ 0.05) in CC vs. RCC and RT. No treatment effects were detected for steer BW gain and feed efficiency (P ≥ 0.41). Total incidence of steers treated for respiratory disease did not differ between treatments (77.9, 82.3, and 80.0%, respectively, P = 0.77). Removal of steers from the experiment due to extreme morbidity of mortality was greater (P = 0.02) in RT vs. CC, and intermediate for RCC (22.4, 7.0, and 12.9%, respectively). Accordingly, total liveweight per pen on d 45 was greater (P ≤ 0.05) for CC and RCC vs. RT (3.79, 3.61, and 3.20 ton, respectively). Inclusion of CC into a receiving diet improved initial feed intake compared with ionophore-containing diets, but without changing steer performance. Moreover, CC and RCC resulted in improved health responses during the 45-d receiving period compared with the traditional RT receiving diet. These results suggest that CC ingredients improved intake and immunocompetence of receiving cattle.