174 DEVELOPMENT AND IN VITRO PRODUCTION OF PREPUBERTAL NELORE HEIFERS LONG-ACTING PROGESTERONE EXPOSED

Abstract

Ovum pick-up (OPU) and aspirated oocytes produced by in vitro production (IVP) are obtained at random stages of the oestrus cycle and are exposed to different concentrations of oestradiol, progesterone, LH and FSH. These factors may influence the oocyte developmental competence of in vitro embryos. The studies with young females aroused the interest of the investigated for decades and showed that one of the advantages working with young animals would be the amount of follicles that develop are best quality when comparing with pubertal animals. However some studies have shown a reduction in the competence of prepubertal oocytes can be partly attributed to the smaller size of the oocyte, differences in protein synthesis and energy metabolism, delayed migration of cytoplasmic organelles and reduced activity of some enzymes. The aim of this study was to evaluate the influence of injectable long-acting progesterone in embryonic development of prepubertal Nelore females. The OPU and treatments were carried out on the farm João Martins, in the county of Guatapará, São Paulo, Brazil, and laboratory stages of production in vitro embryo, the Department of Preventive Veterinary Medicine and Animal Reproduction, UNESP-Jaboticabal. They were select 21 heifers, Nelore, prepubertal of 127 animals. The selection was based on age, bodyweight, and absence of corpus luteum. The selected animals were aged 18 to 20 months and not pregnant with average bodyweight was 268 kg. The donor oocytes were divided into 3 experimental groups crossover design as follows: Group (P0, n = 21), animals in this group received 2 placebo oily solution applications (1 mL), interval of 7 days beginning 14 days (Day 14) before the first aspiration (Day 0); Group (P7; n = 21): the animals received a placebo solution oily application (1 mL), 14 days (Day 14) and progesterone (P4) injection (150 mg) 7 days (Day 7) before aspiration; Group (P14, n = 21), animals in this group received 2 injections P4 applications (150 mg) with an interval of 7 days, the first 14 days (Day 14) and the second 7 days (Day 7) before aspiration. There were a total of 3 OPU an interval of 28 days. After the first follicular aspiration groups were divided again so that all the animals go through all treatments. After confirming the homoscedasticity (BoxCox) and normal (Cramér-von Mises test) data, was conducted the analysis of variance (ANOVA). The Tukey test was used for comparisons of mean variables. The groups P0, P7, and P14 had an average of 4.04, 5.03, and 4.43 embryos produced by session. To assess embryonic development, it was observed that the treated groups (P7 and P14) and control (P0) produced a greater amount of expanded blastocyst, 3.40 ± 3.74, 2.57 ± 2.67 and 3.14 ± 3.41, respectively (P > 0.05). It was observed differences (P < 0.05) in the early blastocyst production in the treated groups produce a greater amount. The use of long-acting injectable progesterone improved did not delay embryo development in vitro but did not alter the production of embryos from prepubertal Nelore heifers.