2023-11-032023-11-032022-12https://hdl.handle.net/2346/96558The effects of a nutritional packet strategically offered to a calf-fed system on growth performance, carcass characteristics, nutrient digestibility, feeding behavior, and ruminal characteristics were evaluated. Angus crossbred steer-calves (n = 60; body weight = 234 ± 4 kg) were assigned to a randomized complete block design (block = body weight) and stratified into 2 treatments: a) control (no packet, finely-ground corn used as carrier only); and b) 30 g (DM basis)-/steer-daily of a nutritional packet [live-yeast (Saccharomyces cerevisiae; 8.7 Log CFU/g), Vitamin C (159 mg/steer-daily of Ascorbic acid), Vitamin B1 (394 mg/steer-daily of Thiamine hydrochloride), NaCl (2.4 g/steer-daily), and KCl (2.4 g/steer-daily)]. Animals were offered [electronic feed-bunks (SmartFeed/C-Lock Inc.)] a steam-flaked corn-based finishing diet ad libitum, once daily for 233 d. Treatments were offered during the first (phase 1) and last (phase 2) 60 d on feed. Digestibility assessments took place within both phases. The GLIMMIX procedure of SAS was used, in which the model used steer as the experimental unit, treatment as fixed effect, and body-weight block as random effect. Steers offered the nutritional packet had 14% less (P < 0.01) intake and 18% greater (P = 0.01) gain efficiency during the initial 30-d on feed. Overall intake (d0 to 233) was 6% greater (P = 0.02) for steers consuming the nutritional packet, while ADG (1.56 vs. 1.61), and gain efficiency (0.204 vs. 0.198) for control and packet, respectively, were unaffected (P ≥ 0.44). Greater (P = 0.02) dressing percent (61.1 vs. 62) for steers offered the packet was observed, while other carcass variables were unaffected (P ≥ 0.33). Digestibility of DM, OM, NDF, ADF, and hemicellulose were increased (P < 0.01) for steers consuming the packet on average by 2.4, 2.4, 8.3, 10, and 7.5% respectively, for both digestibility phases. Regardless of treatment, a decreased rumination (P ≤ 0.03) and chewing (P ≤ 0.01) activity-variables were observed for phase 2 compared to phase 1. Steers consuming the packet spent 13% less time eating during phase 1 only (P < 0.01), and had a 14% increase in meal frequency (P = 0.02) and 12.3% reduction in mean meal size, kg of DM (P < 0.01) in phase 2 only. Steers consuming the packet also had a reduced mean meal duration in both phase 1 (P = 0.01) and phase 2 (P = 0.01). Average papillae area was increased (P = 0.02) by 30% and the total VFA tended (P = 0.09) to increase by 8% for steers consuming the packet at time of slaughter. Calf-fed steers improved gain efficiency during the initial 30 d after feedlot arrival, while superior intake, dressing percentage, nutrient digestibility, total VFA, ruminal papillae area, and eating behavior appear to last until cattle harvest.Application/pdfencalf-feddigestibilityelectrolyteslive-yeastvitamin B1vitamin CThesisAccess is not restricted.