Effects of Early Weaning on Cow Performance, Grazing Behavior, and Winter Feed Costs in the Intermountain West1

The objective of this study was to determine the influence of early weaning (EW; approximately 130 d of age) and traditional weaning (TW; approximately 205 d of age) on cow performance, grazing behavior, and winter feed costs in a 2-yr study. Each year, 156 cow-calf pairs were stratified by calf sex, BCS, and age and assigned randomly to 1 of 2 treatments and 1 of 3 pastures. Two cows from each treatment and pasture were fitted with global positioning system collars each year to evaluate grazing behavior. After TW, EW and TW cows were separated and allotted to 1 of 6 pastures based on previous blocking criteria for winter feeding. Cows were fed to attain a similar BCS by 1 mo prior to parturition. Traditional-weaned cows lost 0.8 BCS units and 40 kg BW whereas the EW cows gained 0.1 BCS units and 8 kg BW from EW to TW (P < 0.01). After winter feeding (111 ± 0.4 d), there was no difference between EW and TW cow BCS (P = 0.52). Winter feed costs were $29 greater (P < 0.01) per cow for TW compared with EW. Grazing time, distance traveled, and number of visits to water were unaffected (P > 0.10) by treatment. However, pasture distribution by EW cows tended to be greater than that of TW cows (P = 0.08). Results indicate that EW improved cow BCS entering the winter feeding period, thereby decreasing winter feed costs. Cow grazing behavior was minimally affected by weaning treatment.