PSII-8 Different nutritional management strategies post-weaning in growth and reproductive performance of Nellore heifers

Abstract

Abstract The objective of this study was to evaluate different nutritional management strategies (drylot vs. supplementation on pasture) to optimize growth and reproductive performance of Nellore heifers submitted to the fixed-time artificial insemination (FTAI) at 14–15 mo. On d0, 126 weaned Nellore heifers (152±22 kg of BW; 240±28 days of age) were stratified by BW and age, and randomly assigned to receive: (1) high-concentrate-based diet (62.2% TDN, 12.0% CP of DM of diet) ad libitum in feedlot from d 0 to 246 (FDL; 6 pens and 7 heifers/pen); (2) fixed supplementation at 1% of BW on Brachiaria pastures from d0 to 246 (PAS10; 6 pastures; 7 heifers/pastures and 4 ha/pasture); and (3) increasing supplementation on Brachiaria pastures at 0.8% of BW from d 0 to 80 and 1.2% of BW from d 81 to 246 (PAS812; 6 pastures; 7 heifers/pastures and 4 ha/pasture). Supplement offered to heifers on pasture consisted of corn, soybean meal, urea, and minerals (78% TDN, 22% CP of DM at dry season and 79% TDN, 20% CP of DM at rainy season). Final pregnancy rate was determined on d238. Heifer BW on d160 was greater (P < 0.01) for FDL vs. PAS10 and PAS812 (264 vs. 251 and 253±10.1 kg, respectively). Overall ADG from d0 to the start of breeding season (d160) and BW on d246 were greater (P < 0.01) for FDL vs. PAS10 and PAS812 (0.72 vs. 0.62 and 0.64±0.02 kg/d, and 325 vs. 310 and 316 ±10.3 kg, respectively). Heifer BW on d160 and 246 and ADG from d0 to 160 did not differ between PAS10 and PAS812 (P ≥ 0.33). Final pregnancy rates did not differ (P = 0.75) among treatments. Therefore, growth performance, but not pregnancy rates following FTAI, was enhanced for Nellore heifers developed in drylot vs. pasture systems and submitted to FTAI at 14–15 mo.