Date of this Version
The Professional Animal Scientist 25 ( 2009 ):273–282
A 2-yr study was conducted using 200 long yearling steers/yr (436 ± 30 kg) to determine the effect on performance and economics of sorting by BW at feedlot entry and feeding 200 mg/steer of Optaflexx (OPT) daily for the last 28 d. At feedlot entry, steers were allotted into 1 of 4 treatments in a 2 × 2 factorial arrangement: sorted or unsorted with or without OPT. Sorted steers were placed into 1 of 3 groups—1) heavy steers (32%; 468 kg), 2) medium steers (44%; 432 kg), or 3) light steers (24%; 399 kg)—and were fed for 97, 118, or 132 d, respectively. Initial BW for unsorted steers averaged 436 kg and steers were fed 111 d. There were no sorted × OPT interactions (P > 0.10) and feeding OPT did not affect steer performance (P > 0.10). Sorted steers were fed more days than unsorted steers (114 vs. 111) and were not statistically different in final BW (645 vs. 640 kg; P = 0.15) or hot carcass weight (406 vs. 403 kg; P = 0.14). Sorting increased LM area (P < 0.01), fat thickness (P = 0.02), and percentage of YG 4 carcasses or higher (P < 0.01). From this study, we concluded there were no benefits to sorting long yearling steers by initial BW or feeding OPT to long yearling steers for the last 28 d of the feeding period.