182 Custom Bovine Heifer Development to Advance Onset of Puberty in a Limited-Resource Beef Cow-Calf Operation

Abstract

Abstract Age at puberty in bovine heifers is controlled largely by genetic and environmental factors, among which nutrition has a major influence. This study evaluated the utility of cool-season forages for heifer development in a limited-resource beef cow-calf system. Beef heifer development was evaluated at 4 time periods: Period 1 (Birth-Weaning) heifers sucked dams until weaning, Period 2 (Weaning-Puberty) heifers grazed natural pastures and supplements in Fall and Winter, Period 3 (Puberty-Breeding) heifers grazed cool-season forages, Period 4 (Breeding-Pregnancy) heifers were maintained on Spring and Summer forages. The supplements were fed at a rate of 0.45 kg/68.2 kg. calf BW and consisted of a 1:1 ratio of cracked corn and commercial grower pellets. Cool-season pasture consisted mainly of Rye grass and clovers. Hay, water, and minerals were provided free choice. Heifer body weights were obtained at quarterly intervals. They were synchronized with two doses of prostaglandin F (PGF) 2α, 14 days apart before bull introduction on June 1st. Pregnancy was confirmed by ultrasonography at the end of breeding in August. The growth trajectory was evaluated by mixed procedures of SAS. A stair-step pattern of body weight gain was observed from birth to pregnancy. There was rapid growth pre-weaning, average daily gain (ADG) = 0.95 ± 0.0.17kg ∙heifer-1∙day-1. Limited growth during the juvenile period (ADG = 0.24 ± 0.17kg∙heifer-1∙day-1) and compensatory growth during the pre-pubertal period (ADG = 1.32 ± 0.17kg∙heifer-1∙day-1). These preliminary results indicate that limited-resource beef cow-calf producers should utilize winter forages to leverage compensatory growth in their heifer development programs. Funded by FAMU World Class Scholars Program and NIFA CBG # 2021-38821-34599