Effects of early weaning on productive and reproductive performance of Nelore heifers.

We aimed to evaluate the effects of early weaning on productive and reproductive characteristics of Nelore heifer progeny. Ninety-four calves from primiparous [PRI] and multiparous [MUL] dams were assigned to one of two weaning strategies; 1) early weaning at 150 days (149 ± 1.97) of age (EW; n=16 from PRI and 31 from MUL); or 2) conventional weaning at 240 days (247±2.41) of age (CW; 16 from PRI and 32 from MUL). All heifers received approximately 5 g/kg of body weight (BW) of creep-feed as fed from 90 days of age until weaning. After weaning, each group of heifers was transferred to a Brachiaria spp. paddock and received 5 g/kg of BW of a protein-energy supplement until 12 mo of age. Then, heifers were confined and fed a diet with a ratio of 79:31 (corn silage: concentrate) for four mo, during which they were submitted to a hormonal protocol to induce puberty and timed artificial insemination (TAI). Reproductive tract score (RTS, 1 to 5 scale: 1 being infantile and 5 being cyclic) and endometrial thickness were determined at 12 mo of age, rump fat thickness (RFT), and body weight (BW) every 28±4 d through the breeding season, and plasma concentrations of IGF-I were evaluated at 12, 14, and 16 mo. At 15.6 mo of age heifers were submitted to a P4/E2 protocol for TAI at Day 0 (D0), and a second TAI was performed at D22 in non-pregnant heifers. Ultrasound was used to determine the presence of corpus luteum on D-10 and dominant follicle (DF) diameter and blood perfusion on D-2 and D0. Data were analyzed using SAS by ANOVA or logistic regression. Though heifers from EW were lighter (P<0.05) than CW at post-weaning time points and CW presented a greater (P=0.002) RFT that EW heifers from 11 to 15 mo, weaning strategy did not affect (P>0.1) BCS at TAI. Concentrations of IGF-I did not differ (P>0.1) between heifers weaned at 150 or 240 days. The proportion of pubertal heifers, endometrium tone and thickness, and RTS at 16 mo did not differ (P>0.1) between EW and CW groups. The diameter of DF on D-2 and D0 and follicular blood perfusion on D0 were greater (P<0.05) for heifers in the CW group than EW group, but P/AI at first and second TAI did not differ (P>0.1) between groups. In conclusion, early weaning in Nelore heifers moderately reduces post-weaning growth but does not affect puberty and reproductive performance before the breeding season when submitted to confinement.