Oklahoma State University animal scientists evaluated weaning dates of 158 Angus fall-calving cows over a 4 year period. Cows were allowed to nurse their calves for about 210 days (April Weaning) or 300 days (July Weaning). All cows calved in September or October and were weaned in mid-April (April Wean) or mid-July (July Wean). April-weaned young cows had greater re-breeding percentages (98.4% versus 89.3%) than July weaned young cows. However, there was no advantage in the re-breeding performance of April-weaned mature cows compared to July-weaned mature cows (90.2% versus 96.7%). April-weaned cows were heavier and fleshier at calving than July weaned cows.
Calves weaned in July were 90 days older and 204 pounds heavier (642 lb versus 438 lb) when weaned than were the April-weaned calves. The April-weaned calves were allowed to graze native pasture after weaning and weighed 607 pounds in mid July. For most years, it appears more advantageous to delay weaning of calves born to cows 4 years or older to July while maintaining April weaning for cows 3 years of age or younger. On-going drought conditions in some areas of the Southern Plains very well may suggest the earlier weaning date could be considered for all ages of cows. Source: Hudson and co-workers. Journal of Anim. Sci. 2010 vol. 88:1577.