Effects of weaning method and preconditioning period on calf performance, haptoglobin concentrations, feedlot health and performance, and carcass traits

A 2-yr experiment evaluated weaning method and preconditioning period on calf preconditioning and feedlot performance, and carcass traits. Cross-bred steers from the Central (n = 142; BW = 280 ± 34.8 kg) and Hill Farm (n = 149; BW = 232 ± 25.3 kg) Research Stations in Louisiana were stratified by preweaning BW and breed within location into a 2 × 2 factorial arrangement. Treatments included fenceline (began on d 0) or abrupt (began on d 7) weaning and a 21- or 42-d preconditioning period to yield 4 treatments. All calves were supplemented with an 18% CP feed fed at 1.5% of BW beginning at weaning. Blood samples (analyzed for haptoglobin concentrations) and BW were collected from all calves on d 0, 7, 28, and 49. Feedlot performance; morbidity; mortality; and the carcass traits HCW, carcass fat thickness, marbling, LM area, and YG were collected. Calf was the experimental unit. A year effect (P < 0.01) for d 7, 49, shipping, and feedlot entry BW, and a location effect (P < 0.01) for carcass fat thickness, existed. There were no treatment effects (P > 0.10) on preconditioning calf performance, haptoglobin levels, feedlot entry BW, ADG; however, shrink, final BW, days on feed, HCW, and carcass fat thickness were greater (P < 0.01) for the 42-d preconditioned calves. Fenceline weaning did not positively influence postweaning performance; however, a longer preconditioning period did result in an increase in final BW, shrink, HCW, and carcass fat thickness.