Submitted to: Professional Animal Scientist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/23/2007
Publication Date: 2/1/2008
Citation: Merrill, M.L., Bohnert, D.W., Ganskopp, D.C., Johnson, D.D., Falck, S.J. 2008. Effects of early weaning on cow performance, grazing behavior, and winter feed costs in the intermountain west. Professional Animal Scientist. 24:29-34. Interpretive Summary: In late summer and early fall, cow/calf pairs grazing sagebrush rangelands usually loose weight due to poor forage quality. Cows may be able to sustain or gain weight on poor forage if calves are weaned early to eliminate the cow=s need to produce milk for their young. We studied the effects conventional weaning (late October) and early weaning (early August) on cow performance, grazing behavior, and subsequent winter feed costs. Early weaned cows gained 18 pounds in late summer and fall while traditionally weaned cows lost 88 pounds over the same period. Early weaned cows ranged across more of their pasture than traditionally weaned cows, but grazing time, distance traveled and the number of visits to water were the same between treatments. To recover from their earlier weight loss, winter feed costs were $29 more per cow for traditionally weaned cows than early weaned cattle. Results suggest that over winter feeding costs may be reduced by early weaning, and that early weaned cattle will enter the winter feeding period in better condition than conventionally weaned cows. These findings should benefit ranchers or beef producers who wish to reduce over winter feedings costs .
Technical Abstract: Our objective 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 one of two treatments (TRT) and one of three pastures. Two cows from each TRT 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 one of six 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 and 40 kg while the EW cows gained 0.1 BCS and 8 kg 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 TRT. However, pasture distribution 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.