88 Impacts of Body Condition Score at Initiation of the Breeding Season on Reproductive Performance and Overall Productivity of Bos Taurus and B. Indicus Beef Cows

Abstract

Abstract Responses of Bos taurus (BT) and B. indicus (BI) beef cows were compared according to their body condition score (BCS) at initiation of breeding season. Cows were assigned to an estrus synchronization + AI protocol and classified as BCS < 5.0 (LBCS, BT, n = 158; BI, n = 248) or BCS ≥ 5.0 (HBCS; BT, n = 173; BI, n = 122). Pregnancy status was verified via transrectal ultrasonography at 30 and 40 d after AI for BI and BT cows, respectively. All BT cows were exposed to natural service for 50 d (beginning 18 d after AI), and all non-pregnant BI cows were immediately exposed to natural service for 60 d. Pregnancy rates to AI did not differ (P ≥ 0.16) between HBCS or LBCS cows (60.9 vs. 53.5% for BT; 37.0 vs. 31.4% for BI; respectively). Pregnancy rates to natural service were greater (P = 0.03) in HBCS BT cows compared with LBCS (82.7 vs. 67.9%; respectively) but did not differ in BI cows (78.9 vs. 71.5%; respectively). Calving rate was greater (P < 0.03) in HBCS cows, which also calved earlier (P < 0.01) compared with LBCS (93.7 vs. 85.1% in BT, 83.6 vs. 73.3% in BI; respectively). HBCS Cows weaned more (P ≤ 0.05) calves compared with LBCS, which were older (P ≤ 0.04) (215 vs. 211 d in BT, 219 vs. 209 d in BI; respectively) and heavier (P ≤ 0.09) at weaning (258 vs. 252 kg in BT, 213 vs. 203 d in BI; respectively). Lastly, kg of calf weaned/cow was greater (P ≤ 0.03) in HBCS cows compared with LBCS (221 vs. 200 d in BT, 159 vs. 129 d in BI; respectively). Therefore, HBCS cows had greater reproductive efficiency and overall productivity, and this was observed in both BT and BI.