Effect of dietary inclusion of concentrated separator by-product and weaning management on performance of newly received feedlot steers

During the fall of two consecutive years, 260 newly received cross-bred steers (266.8 kg±1.6 kg initial body weight (BW)) were used to evaluate effect of concentrated separator by-product (CSB; de-sugared molasses) and weaning management on dry matter intake (DMI), growth, feed efficiency, and health. Steers were stratified by weight, and allotted randomly to treatment in a completely randomized design. Treatments were arranged in a 2×2 factorial; factors were dietary inclusion of CSB (0 or 5%, dry matter (DM) basis) and weaning management (weaned on the day of shipping, SHIP; and weaned 3–5 weeks prior to shipping, WEAN). The control diet contained 50% alfalfa-brome hay, 44% corn, and 6% supplement, while the diet with CSB contained 50% alfalfa-brome hay, 40.5% corn, 5% CSB, and 4.5% supplement (DM basis). Water was added to the diet without CSB at 6.3% of the as fed weight (equal to as fed level of CSB) to minimize differences in diet acceptability due to dustiness. Diets were formulated to contain a minimum 13.5% crude protein (CP) 0.7% Ca, 0.32% P, and 1.4% K (DM basis). Steers were fed for 27 days in year 1 and 28 days in year 2. Performance data were analyzed across years using the GLM procedure of SAS and health data were analyzed across years using χ2. Steers fed 5% CSB gained 19% faster (P=0.07) during days 1–14 and consumed 10% more feed throughout the trial (P=0.006). WEAN steers were heavier (P<0.001) and consumed more feed (P<0.001). WEAN steers gained faster during the first 2 weeks (P=0.02) and SHIP steers were more efficient during the second 2 weeks (P=0.03). No effect of dietary CSB addition on morbidity (P=0.24) or mortality (P=0.93) occurred. Fewer WEAN steers (P=0.06) were treated for signs of bovine respiratory disease (BRD) complex compared with SHIP steers. Addition of 5% CSB to diets fed to newly received feedlot calves increases DMI and calves weaned 3–5 weeks prior to shipping are healthier and consume more feed.