Impact of Sorting Prior to Feeding Zilpaterol Hydrochloride on Feedlot Steers

Crossbred yearling steers (n = 1000; 755 ± 23 lb) were utilized to evaluate effects of sorting and feeding zilpaterol hydrochloride (Zilmax®) on feedlot performance, carcass characteristics, and economics. Treatments were: unsorted negative control (–CON); unsorted Zilmax fed positive control (+CON); and three treatments where the heaviest 20% of steers within the pen were identified at beginning (EARLY), 100 days from harvest (MIDDLE), or 50 days from harvest (LATE) and marketed 28 days earlier. Dry matter intake was not different. Gain and G:F were improved by feeding Zilmax. Carcasses from the +CON and steers sorted EARLY, MIDDLE, and LATE were 61, 56, and 53 lb heavier than –CON, respectively. Fat depth and marbling were lower for +CON compared to –CON, but feeding Zilmax with any of the sorting treatments improved marbling to equal –CON