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

Abstract

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.