Effects of different weaning management strategies on preconditioning performance, haptoglobin serum levels, feedlot morbidity, and carcass characteristics

Weaning, one of the first major stressors encountered by the calf, has a negative effect on the immune system and increases the likelihood of infection of novel pathogens such as those that cause bovine respiratory disease. Fenceline contact at weaning has been shown to reduce the stress on the calf during the time following maternal separation. Preconditioning programs have been shown to reduce feedlot morbidity and mortality. Combining these two management practices could reduce the length of time calves need to be held in a preconditioning program. A multi-year study was conducted to evaluate if fenceline weaning will allow for a 21-d preconditioning (PRECON) period rather than a 45-d PRECON period. Two-hundred ninety-one cross-bred steer calves from two locations (Central Research Station, Baton Rouge, LA and Hill Farm Research Station, Homer, LA) were used over a two-year period. Both locations were managed independently following the same protocol. Each year, calves were stratified by BW into four treatments: 1. fenceline weaned, PRECON 21 days (FL21); 2. fenceline weaned, PRECON 42 days (FL42); 3. abrupt weaned, PRECON 21 days (S21); and 4. abrupt weaned, PRECON 42 days (S42). Calf was the experimental unit. After the initial 7 d weaning period, all calves were placed on pasture for the assigned PRECON treatment. Calves were fed an 18% CP commercial preconditioning ration at 1.5% of BW during the entire PRECON treatment period. Weight change and ADG were not different (P \u3e 0.05) between all treatments during this period. Steers were transported to and managed by a commercial feedlot in Guymon, OK, until harvest. Morbidity and mortality during the feedlot period were not different (P \u3e 0.05). Entry weight and ADG were not different between treatments, but FL42 and S42 calves were heavier (P = 0.005) and were on feed longer (P \u3c 0.0001) than FL21 and S21 calves. Heavier HCW (P = 0.005) and greater backfat (P = 0.001) were observed in FL42 and S42, but YG, marbling score, and LM area were not different among treatments. These results are indicative that fenceline weaning does not aid in shortening the preconditioning period, and further research is needed to validate these findings