Date of this Version
Livestock Science 148 (2012) 282–290; http://dx.doi.org/10.1016/j.livsci.2012.06.024
Studies were conducted to evaluate the effect of early weaning steer calves on BW gain, feedlot performance, and carcass characteristics in two herds located in the Northern Great Plains, USA. Steer calves from predominantly Angus x Hereford dams were stratified within damage and calving date (Fort Keogh Livestock and Range Research Laboratory (LARRL), Miles City, MT, USA; n=354)and randomly assigned to one of three weaning treatments. In addition, steer calves from Angus and Angus x Simmental dams (n=200; Judith Gap (JG), MT, USA) were stratified within breed group by age, calving date, and AI sire. Steer calves either remained with their dams until normal weaning (NW) at approximately 213-d of age or were early weaned at approximately 80-d of age on to one of two early weaning (EW) diets. Steer calves assigned to EW treatments received one of the following diets: (1)17.5% CP (69% RDP and 7.53 MJ/kg NEm); or (2)17.5% CP (57% RDP and 7.69MJ/kg NEm). At time of normal weaning all LARRL steers were gathered and brought into pens at LARRL and held for 22 (2005) or 28-d (2006) before being sold to a commercial feedlot. Sire-identified steers from JG were sent to the University of Illinois for a finishing trial following a 28-d holding period. Steers that were EW were heavier (P<0.01) at time of normal weaning and entered the finishing phase in greater BW (P<0.01) than NW steers in both LARRL and JG studies. Age at harvest was similar for all LARRL steers (P=0.79) regardless of weaning treatment whereas sire-identified JG steers that received EW treatment were harvested at a younger age (P<0.01) than NW steers. Sire-identified steers from JG that received EW treatments received better USDA quality grades (P=0.05; upper 2/3 choice or better) than NW treated steers (P<0.01;lower 1/3 choice). Results from the present studies strongly support the concept that early-weaned steers reach maturity sooner during the finishing phase. However, if early-weaned steers are not identified prior to entrance into the feed yard and harvested at the same time as normal weaned calves of similar genetics and age, the nearly- weaned steers may be subject to undesirable USDA yield grades (4 or greater).