Avaliação de parâmetros reprodutivos com o uso de gonadotrofina coriônica humana (hCG) e deslorelina em um programa de transferência de embrião equino

Abstract

Embryo transfer (ET) is one of the most prominent techniques in the expansion of horse breeding, enabling the production of more products of a single mare per year, thus increasing the number of animals with high genetic value. The hormonal control of ovulation can be used as a tool to optimize the reproductive parameters and reduce the costs in an ET program. This study compared the effectiveness of lower doses than those traditionally used of Deslorelin and hCG, evaluating the time between ovulation and induction, the recovery rates and embryo attachment. The study was conducted at the Department of Animal Reproduction and Evaluation of UFRRJ. We conducted follow-up of 85 estrous cycles of Breton Postier and Mangalarga Marchador mares, when the mares presenting an ovarian follicle ≥ 35 mm, they were divided randomly into one of three treatments: G1 (n = 32) - treatment with 1000 IU (1.0 ml iv) of hCG (Chorulon ® - Intervet Schering-Plough Animal Health), G2 (n = 28) - treatment with 0.75 mg (0.75 ml iv) Deslorelin (Botupharma) and G3 (n = 28) - Treatment with 1.0 ml saline iv. Twenty four hours after application, ultrasound evaluation of ovarian was held every six hours up to ovulation. The donors were inseminated the day after induction and embryo collection took place in nine days after ovulation. The recovered embryos were immediately transferred to recipients previously synchronized, these pregnancy diagnosis was performed at 15 and 30 days old embryo. Data regarding the time between ovulation and induction and characteristics of follicular development were analyzed using analysis of variance (ANOVA), and the averages of these data were analyzed when needed by the Tukey test. The data regarding the percentage of mares ovulated in different periods, were analyzed using the Qui-quadrado (χ2) 5%. In the case of embryo recovery rate, the data were analyzed using the Fisher exact test, however in relation to pregnancy rate was not possible to perform statistical analysis due to low sample size. The percentage of ovulation in up to 36 hours for G1, G2 and G3 were 34.4%, 13.3% and 8.7%, between 36 and 42 hours were 62.5%, 56.7% and 8.7%, from 42 to 48 hours were 0%, 20% and 13%, more than 48 hours were 3.1%, 10% and 69.6% respectively. Having thus a significant difference between treated and control groups (p <0.05). The embryo recovery rate was 75% (6/8) in G1 and G2, and 44.4% (4/9) in group G3, there was no significant difference between groups (p> 0.05). The rate of pregnancy at fifteen days old embryo was 69.2% (9/13). Thus the lower doses commonly used with inducing agents in question, were effective in promoting ovulation within 48 hours, but the use of these didn't result in significant improvement in the rates of embryo recovery.