Effects of administration on performance and carcass traits of finishing feedlot cattle.

This study evaluated the effects of administration at the beginning of the feedlot period on performance of bulls. On d 0, 383 Nellore bulls (initial shrunk body weight 384 ± 29.2 kg; initial age = 24 ± 2 mo) were assigned to treatments in a randomized complete block design. Treatments consisted of 1) 14 d adaptation diet and transition to a finishing diet (), 2) CONT plus oral administration of 20 mL of Lactipro-NXT () on d 0 of the study (), 3) CONT diet, consisting of 6 d of adaptation diet plus oral administration of 20 mL of Lactipro-NXT on d 0 of the study (), and 4) No adaptation diet and oral administration of 20 mL of Lactipro-NXT on d 0 of the study (). Experimental period lasted 119 d. No treatment effects were observed for any of the performance parameters evaluated herein ( ≥ 0.15). Nonetheless, a treatment × wk interaction was observed for DM, NE, and NE intakes ( < 0.0001). For all these parameters, MEG-0 and MEG-6 had a reduced intake vs. MEG-14 and CONT in the first wk of the study ( ≤ 0.05). For the carcass traits, no effects were observed for HCW ( ≥ 0.24), whereas MEG-6 had a greater REA when compared with MEG-0 and MEG-14 (quadratic effect; = 0.04) and MEG-administered bulls tended to have a greater BFT vs. CONT ( = 0.08). In summary, administration at the beginning of the feedlot period did not improve performance, whereas reducing the length of the adaptation period for 6 d improved REA of finishing bulls.