ARS | Publication request: EFFECTS OF SEASON OF CALVING AND WEANING AGE ON COW AND CALF PRODUCTION THROUGH WEANING

Submitted to: Research Update for Fort Keogh Livestock and Range Research Laboratory
Publication Type: Popular Publication
Publication Acceptance Date: October 1, 2002
Publication Date: January 15, 2003
Repository URL: http://www.larrl.ars.usda.gov
Citation: GRINGS, E.E., SHORT, R.E., HEITSCHMIDT, R.K. EFFECTS OF SEASON OF CALVING AND WEANING AGE ON COW AND CALF PRODUCTION THROUGH WEANING. RESEARCH UPDATE FOR FORT KEOGH LIVESTOCK AND RANGE RESEARCH LABORATORY. p. 30-31. 2003.

Interpretive Summary: Decisions to optimize economic outcomes in cow/calf beef production systems are complicated because of the hundreds of variables that affect the economic and biological outcomes of the system. Also, these variables change dramatically over time (mainly seasonally and annually but at times the changes can be daily) and the optimal integration of decisions is almost always regional and even site specific due to unique aspects of regional ecosystems and individual ranches or production systems. Two of the most basic decisions that a cow/calf producer must deal with are 1) when should cows be bred and 2) when should the calves be weaned so that calving and weaning occur at the optimal times during the year. Research in other regions of the U. S. have shown season of calving affects amount and costs of inputs as well as production such as calf weaning weights and rebreeding percentages. There are also effects of age at weaning on cow/calf performance. This experiment is being conducted to better understand the economic and biological variables associated with season of calving and weaning age in a Northern Great Plains environment. The data reported here include only animal performance traits measured from calving to weaning from the first year of a three-year study. There were small but significant effects of season of calving on birth weight of calves, but these effects did not have any consistent pattern as calving season changed from early to late. Weaning weight of calves on a constant date was decreased as calving season became later. This decrease was partially caused by differences in chronological age, but also involved was the effect of season of calving on calf age-constant weights and calf gains. As calving season became later, age-constant weights decreased which was caused by a reduction in calf gains from birth to weaning. Calf gains from 1st to 2nd weaning (Weaning 2 - Weaning 1) also decreased as calving season became later with the largest decrease being in the June calvers.

Technical Abstract: A herd of crossbred cows that were mainly crosses of Red Angus, Tarentaise, and Charolais, but also included some Hereford, Angus, Limousin, Piedmontese, and Simmental, were randomly assigned to one of three calving seasons (February, April, or June) and one of two weaning ages (early and late) within each SOC. There were small but significant effects of season of calving on birth weight of calves, but these effects did not have any consistent pattern as calving season changed from early to late. Weaning weight of calves on a constant date was decreased as calving season became later. This decrease was partially caused by differences in chronological age, but also involved was the effect of season of calving on calf age-constant weights and calf gains. As calving season became later, age-constant weights decreased which was caused by a reduction in calf gains from birth to weaning. Calf gains from 1st to 2nd weaning (Weaning 2 - Weaning 1) also decreased as calving season became later with the largest decrease being in the June calvers.