Evaluation of Performance Traits in Brahman Cattle: Blood Parameters, Calf Temperament, Residual Feed Intake, and Bull Reproductive Development

The objectives of these studies were (1) evaluate the relationship between temperament, blood parameters, and performance in Brahman calves (n = 300); (2) evaluate the relationship between residual feed intake (RFI) and reproductive development in Brahman bulls (n = 41). Serum was collected at 24 h and d 21 to 24, and analyzed for total protein (TP) immunoglobulin G (IgG), and cortisol (CS). Calves were weighed at 24 h, weighed and evaluated for temperament using exit velocity (EV) at d 21 to 24, and at 28 d intervals thereafter. Beginning 28 d prior to weaning, and at 28 d intervals through 56 d post-weaning calves were evaluated for pen score (PS) used to calculate temperament score (TS = (EV+PS)/2). The average TS from 28 d prior to weaning and weaning was used to generate temperament groups; calves 1 SD below the mean being calm, those 1 SD above the mean being temperamental and all remaining classified as intermediate. Calf TS influenced WW (P = 0.04) and ADG from birth to weaning (P = 0.03). Serum TP at 24 h affected (P < 0.05) WW and ADG from birth to weaning. Serum IgG at 24 h affected (P = 0.03) WW. Brahman bulls (n = 41) were evaluated for RFI, insulin-like growth factor I (IGF-I), temperament, reproductive development, and ultrasound carcass traits. Serum was collected at d 0 and d 70 of the feeding trial and analyzed for IGF-I. Bulls were classified as efficient, intermediate, or inefficient (RFI classification method I) and as efficient or inefficient (RFI classification method II). Bulls were evaluated for temperament at weaning using TS. Temperament influenced (P < 0.05) IGF-I concentrations at d 0. Reproductive development was not affected (P > 0.05) by TS. Residual feed intake classification did not influence (P > 0.05) age at reproductive milestones. Ultrasound carcass traits were not affected by TS or RFI. Serum TP at 24 h was a viable indicator of future growth performance. Temperamental animals had lower growth rates in both studies. Reproductive development was not affected by RFI. BW at reproductive milestones was lower in temperamental bulls.