172 Effect of period of insertion of a progesterone-releasing device and pro-oestrus length on follicular and luteal characteristics and pregnancy rates to fixed-time AI in Bos indicus heifers
G. A. Bo A B , A. Cedeño A C , R. Maingón D , J. P. Cedeño D , H. Gamboa C , J. Avellan C , J. Bravo C , C. Rivera C and I. Macias CA Instituto A. P. de Ciencias Básicas y Aplicadas, Universidad Nacional de Villa María, Villa del Rosario, Córdoba, Argentina;
B Instituto de Reproducción Animal Córdoba (IRAC), Paraje Pozo del Tigre, Gral. Paz, Córdoba, Argentina;
C Laboratorio de Biotecnología de la Reproducción Animal, Escuela Superior Politécnica Agropecuaria de Manabí (ESPAM), Calceta, Ecuador;
D Agrícola El Naranjo, San Vicente, Manabí, Ecuador
Reproduction, Fertility and Development 32(2) 213-213 https://doi.org/10.1071/RDv32n2Ab172
Published: 2 December 2019
Abstract
An experiment was designed to evaluate the effect of the length of insertion of a progesterone (P4)-releasing device and the length of pro-oestrus on follicular and luteal characteristics and pregnancy rates to AI (P/AI) in Bos indicus heifers treated with oestradiol/P4-based treatments. Bos indicus beef heifers (n = 374), 22-26 months of age, with a corpus luteum (CL) or at least one follicle ≥8 mm in diameter and with a body condition score between 2.5 and 3.5 (1-to-5 scale) were synchronised using three treatments for fixed-time AI (FTAI). On Day 0, all heifers received 2 mg of oestradiol benzoate (Sincrodiol, Ourofino) and an intravaginal device with 1 g of P4 (Sincrogest, Ourofino). The P4 device was removed on Day 6 in heifers in the J-Synch 6 group (n = 120) and on Day 7 in heifers in the J-Synch 7 group (n = 105) and conventional group (n = 165). All heifers received 500 μg of cloprostenol (Sincrocio, Ourofino) and 300 IU of equine chorionic gonadotrophin (SincroeCG 6000UI, Ourofino) at the time of P4 device removal. Furthermore, heifers in the conventional treatment group received 0.5 mg of oestradiol cypionate (SincroCP, Ourofino) at the same time. In addition, all heifers were tail-painted for oestrus detection (CeloTest, Biotay). Heifers that had lost ≥50% of the tail paint by 70-74 h (J-Synch groups) or 48-52 h (conventional group) after device removal were FTAI at that time. Heifers not showing oestrus by 70-74 h (J-Synch groups) or 48-52 h (conventional group) received 10 μg of gonadotrophin-releasing hormone (Sincroforte, Ourofino) at the same time and were FTAI 8 h later. All heifers were also examined using ultrasonography (Mindray DP50 Vet) every 12 h from the time of device removal to determine the time of ovulation, 6 days after ovulation to determine the diameter of the CL, and 28 days after FTAI for P/AI determination. Data were analysed using the MLGM procedure (InfoStat) for normal data families (follicular dynamics) and binary data family (P/AI). The results are shown in Table 1. The diameter of the dominant preovulatory follicle and the CL did not differ among groups (P > 0.12). However, the interval from device removal to ovulation was longer in heifers in the J-Synch groups than in heifers in the conventional group (P < 0.05). Furthermore, P/AI was not different among groups. In conclusion, although the J-Synch protocols delayed the interval from P4 device removal to ovulation, the three protocols evaluated in the present study were equally effective in Bos indicus heifers.
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