The effects of a nutritional packet (live yeast, vitamins C and B1, and electrolytes) offered to steers in a calf-fed system on growth performance, nutrient digestion, feeding behavior, carcass characteristics, and ruminal variables.

Effects of a nutritional packet strategically offered to calf-fed system steers on growth performance, nutrient digestibility, feeding behavior, ruminal variables, and carcass characteristics were evaluated. Angus crossbred steer-calves ( N  = 60; body weight [BW] = 234 ± 4 kg) were used in a randomized complete block design (block = BW) and stratified into two treatments: 1) control; and 2) 30 g/steer-daily (dry matter [DM] basis) of a nutritional packet containing (steer-daily basis): Live yeast ( Saccharomyces cerevisiae ; 1.7 × 10 10 CFU), vitamin C (Ascorbic acid, 162 mg), vitamin B1 (thiamin hydrochloride, 400 mg), sodium chloride (2.4 g), and potassium chloride (2.4 g). Animals were offered (electronic feed-bunks [SmartFeed, C-Lock Inc., Rapid City, SD]), a steam-flaked corn-based finishing diet to ad libitum (individual intake), once daily for 233 d. Treatments were offered during the first and last 60 days on feed (DOF). The GLIMMIX procedure of SAS was used, with steer as the experimental unit, treatment and phase (for feeding behavior and digestibility) as fixed effects, and BW-block as a random effect. Steers offered the nutritional packet had 14% less ( P  < 0.01) intake and 18% greater ( P  = 0.01) feed efficiency during the initial 30 DOF. Intake (days 0 to 233) was 6% greater ( P  = 0.02) for steers offered the nutritional packet, while BW gain was not different ( 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 not different ( P  ≥ 0.33). Digestibility of DM, organic matter, and fiber were greater ( P  < 0.01) for steers offered the packet. Steers offered the packet spent 13% less time eating during the first 60 DOF, while during the last 60 DOF a 14% greater meal frequency and 12.3% smaller mean meal size (treatment × phase interaction, P  < 0.02) were observed. Steers offered the packet had a reduced ( P  ≤ 0.01) mean meal duration during both phases. Regardless of treatment, a decreased rumination ( P  ≤ 0.03) and chewing ( P  ≤ 0.01) activities were observed for the last 60 DOF compared to the first 60 DOF. Ruminal papillae area was 30% greater ( P  = 0.02) and the total volatile fatty acid (VFA) tended ( P  = 0.09) to be greater for steers offered the nutritional packet. The nutritional packet offered to calf-fed steers improved feed efficiency during the initial 30 d after arrival, while inducing superior overall intake, nutrient digestibility, dressing percentage, ruminal papillae area, and total ruminal VFA.