The Effects of Early Weaning on Cow Performance and Grazing Behavior in the Intermountain West
Our objective was to determine the influence of early weaning (EW) and traditional weaning (TW) on cow performance and grazing behavior in a 2 yr study. In addition, cow winter feed costs were compared. Each year, 156 cow/calf pairs (78 steer calves and 78 heifer calves) were used in a randomized complete block design. Cows were stratified by calf sex, BCS, and age and assigned randomly to one of two treatments (TRT) and one of three 810-ha pastures. Two cows from each TRT and pasture were fitted with global positioning system collars each year (6 cows/TRT/yr) to evaluate grazing behavior. The EW calves were removed from dams at approximately 130 d, while TW calves grazed with their dams until approximately 205 d of age. All cows were removed from pastures following TW and placed in six separate 25 ha pastures. The same cow groups (blocks) remained intact; however, EW and TW cows were separated and randomly allotted to pastures. All cows were fed to attain a similar BCS (minimum of 5) by approximately 1 mo prior to calving. The TW cows lost 0.8 BCS and 40 kg while the EW cows gained 0.1 BCS and 8 kg from EW to TW (P < 0.01). After winter feeding (approx. 110 d), there was no difference between EW and TW cow BCS (P = 0.52). However, winter feed costs were $29 greater (P < 0.01) for TW compared with EW cows. Grazing time, distance traveled, and number of visits to water were unaffected (P > 0.10) by TRT. However, the proportion of each pasture visited by EW cows tended to be greater than that of TW cows (P = 0.08). Results indicate that EW improves cow BCS entering the winter feeding period, thereby, decreasing winter feed costs. Cow grazing behavior was minimally affected by weaning treatment.
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