PSV-B-18 - Effect of Puberty Induction on Embryonic Loss in Precocious Nellore Heifers

Abstract: This study aimed to determine if heifers induced to puberty had damage in reproductive performance compared with heifers that reach puberty naturally. Nellore heifers (n = 210) were weaned at 8 ± 0.7 mo of age were assigned to 42 feedlot pens according to BW (184 ± 1 kg). The diet was compounded by Tifton-85 haylage (18% CP; 55% TDN) ad libitum and supplement (4g/kg of BW; 25% CP; 60% TDN). Puberty and growth were assessed weekly. At 14 mo of age, 46 heifers reached puberty naturally (precocious heifers; PH) and 164 non-pubertal heifers were submitted to puberty induction with progesterone (P4) insert for 10 days and estradiol cypionate (0.5 mg) at P4 removal (puberty induction; PI). After fourteen days, all heifers were submitted to TAI. Heifers were considered pregnant at 20 days (P20) after AI when CL had blood flow < 25% of area (Power-Doppler). Pregnancy rate was also determined at 30 (P30) and 60 (P60) days after AI by embryo detection. Early (P20 – P30) and late (P30 – P60) embryonic loss were determined. Reproductive data were analyzed by GLIMMIX, and BW was analyzed using repeated measures over time (MIXED; SAS 9.3). The PH was heavier than PI from 8 to 16 mo of age, which BW was 296 and 285 ± 3 kg at 14 mo of age, respectively. At beginning of TAI, 88% of PI heifers had a CL. Pregnancy rate was similar (P > 0.05) between treatments, in which pregnancy rate at 20, 30 or 60 days after AI was 65, 47 and 43% for PH and 61, 53 and 48% for PI, respectively. Early (26 vs 14%) and late (9 vs 9%) embryonic loss were similar (P > 0.05) in PH and PI, respectively. In summary, natural or induced pubertal heifers had similar reproductive performance.