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ARS Home » Plains Area » Miles City, Montana » Livestock and Range Research Laboratory » Research » Publications at this Location » Publication #147414
Title: EFFECTS OF CALVING DATE AND WEANING AGE ON COW AND CALF PRODUCTION IN THE NORTHERN GREAT PLAINS

Author
item Grings, Elaine
item SHORT, ROBERT - RETIRED ARS
item Heitschmidt, Rodney

Submitted to: Western Section of Animal Science Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 4/1/2003
Publication Date: 6/1/2003
Citation: GRINGS, E.E., SHORT, R.E., HEITSCHMIDT, R.K. EFFECTS OF CALVING DATE AND WEANING AGE ON COW AND CALF PRODUCTION IN THE NORTHERN GREAT PLAINS. WESTERN SECTION OF ANIMAL SCIENCE PROCEEDINGS. 2003. v. 54. p. 335-338.

Interpretive Summary: Rangeland forage quality in the Northern Great Plains is of high quality in May and June when temperature and precipitation conditions are optimal for growth of native cool-season forages. Forage quality declines rapidly in late summer, creating a long period when nutritional quality may be limiting to maximal beef production. Understanding the relative performance of cattle born during different seasons of the year is important to optimizing economic returns. Additionally, the choice of calving seasons may influence the most appropriate time of weaning. The objective of this study was to evaluate the effect of calving during late winter (February), early spring (April), and late spring (June) and the effect of two times of weaning within each season on cow and calf performance. Weaning occurred at about 6- and 8-mo of age for the February and April calves and at 4- and 6-mo of age for the June calves. Environmental conditions varied throughout the study periods, affecting forage quantity and quality along with winter feed needs. Weaning weights adjusted to 190-days of age were less for June calves than for February and April calves. Weaning weight adjusted to a constant date (October 19) declined as calving season advanced, due both to younger age and a lighter age-constant weight for the June calves. This greater decline for calves weaned later in the year is likely due to a combination of both forage quality and temperatures. February cows gained weight between weanings, whereas April and June cows lost weight, and weight loss was greater for June than April cows. Choice of calving season can have large effects on outputs from rangeland-based beef operations in the Northern Great Plains. Careful consideration of all goals is required in choosing the optimal calving time for a specific enterprise.

Technical Abstract: A 3-year study evaluated late winter (Feb), early spring (Apr), and late spring (Jun) calving systems (CS) on beef cow and calf performance. Crossbred cows were randomly assigned to 1 of 3 CS (avg n/CS/yr = 148) and 1 of 2 weaning times (Wean 1, 2) within each CS. Feb and Apr calves were weaned at 6- and 8-mo of age; Jun calves were weaned at 4- and 6-mo of age. Breeding by natural service occurred in a 32-d period that included estrus synchronization. Early weaned steers were housed in feedlots while half of the early weaned heifers grazed improved pastures and half were housed in feedlots. Early weaned calves were weighed on approximately the same day as late weaning. Weaning weight of calves adjusted to a constant date (October 19) was decreased (P < 0.01) as calving time became later (273, 229, and 181 kg for Feb, Apr, and Jun calves, respectively). Jun calves (203 kg) were lighter (P < 0.01) than Feb (224 kg) and Apr (221 kg) calves at 190 d of age. A CS x Wean interaction (P < 0.01) occurred for calf gains between Wean 1 and 2. Gains for early weaned calves averaged 0.71, 0.56, and 0.56 and for late weaned calves averaged 0.75, 0.47, and 0.56 kg/d for Feb, Apr, and Jun, respectively. Between weanings, suckled cows gained less (Feb: Wean 1, 23.0 kg vs Wean 2, 6.0 kg) or lost more than non-suckled cows in all herds (P < 0.01). Cow weight change between Oct (Wean 1) and Dec (Wean 2) did not differ for Apr and Jun (-1.7 kg) non-suckled cows, but loss was greater for suckled Jun (-35.0 kg) than Apr (-15.4 kg) cows (CS x Wean interaction, P < 0.01). Time of weaning did not affect (P > 0.10) subsequent year's cow or calf performance at weaning. Pregnancy rates (87.9%) were not affected (P > 0.10) by CS. Season of calving and weaning age have significant impacts on outputs from rangeland-based beef cattle operations.