176 Weaning weight trends in the U.S. beef cattle industry

Abstract

Abstract The objective of this study was to characterize the trend over time for weaning BW in commercial cow/ calf operations in the U.S. beef cattle industry. The first data set contained weaning BW data from four enterprise analysis programs from 1991 to 2015. The second data set included mean forecasted delivery BW of sale lots of beef calves sold through Superior Livestock Auction (SLA) from 1995 to 2016. The SLA data were evaluated for two regions, North Central/Rocky Mountain region (NC) and South Central region (SC) and were restricted to sale dates and projected delivery dates approximating those associated with spring-calving operations. The third data set included mean actual and adjusted weaning BW of commercial cow/calf operations participating in the Alabama Beef Cattle Improvement Association (BCIA) from 1983 to 2017. Adjusted annual weaning BW reported from the American Angus Association and American International Charolais Association were used to evaluate trend over time for bull calves from 1995 to 2016. There was a significant linear increase (0.5 kg per yr; P = 0.01) for weaning BW reported by the Kansas Farm Management Association. Projected delivery BW for NC implanted and non-implanted calves increased (P < 0.01) and plateaued in 2006 and 2007, respectively. In contrast, projected delivery BW for non-weaned SC implanted and non-implanted calves increased (P < 0.01) linearly over time. Adjusted and unadjusted weaning BW reported to the Alabama BCIA increased until 1998 and 1995, respectively. The phenotypic trend for Angus and Charolais bulls was a polynomial regression equation (P < 0.01) with declining rate of change in weaning BW. Substantial variation in the trend over time for weaning BW in commercial cow/ calf operations exists within region and record program. Furthermore, weaning BW is substantially more variable in Southern states. Environmental limitations to continued progress in this trait are evident