Efeito de diferentes momentos de inseminação artificial laparoscópica em programas de transferência de embriões correlacionados com o momento da ovulação em ovinos

Abstract

The unpredictability of results in addition with a variable efficiency on embryo transfer (ET) in sheep can be related to the absence of timing definition on artificial insemination (AI) in ET programs by an asynchrony between ovulations and AI procedures in superovulted animals. The aim of this work, was to identify by laparoscopy the ovarian dynamics of ewes subjected to multiple ovulation embryo transfer program (MOET) and, based upon this knowledge, evaluate two ideal moments of laparoscopic AI, with cooled and frozen semen. In experiment 1, ten females, sheep were used, synchronized with intravaginal progesterone device (CIDR ®) (D0) and Superovulation induction by FSH-p (Folltropin ®), in eight decreasing administration doses every twelve hours, starting at D12. In D15 intravaginal devices have been removed and administered 200IU of equine chorionic gonadrotophin - eCG (Novormon ®, Intervet). The next day, 4μg of buserelin acetate – GnRH - was administered (Conceptal ®, Intervet). After estrous detection, observations of ovarian status laparoscopically were performed at 36, 40, 48, 52 and 56 hours after CIDR removal or until ovulations occurred. In experiment 2, twenty sheep females were used, synchronized and induced with identical protocol of experiment 1 and, after estrous detection, they were divided into four treatments defined as at the time of the Laparoscopic AI based upon removal of intravaginal device and on the type of semen used: T1-36 h/cooled semen; T2-48 h/cooled semen; T3-36 h/frozen semen and; T4-48 h/frozen semen. Five days after laparoscopic AI, collection of the embryos was performed by laparotomy and the recovered structures were evaluated and classified according to IETS (International Embryo Transfer Society) and transferred to recipients that had synchronized estrus by applying intravaginal device impregnated with 60 mg medroxiprogeterona-MAP (Progespon ®), for a period of 15 days, when the device was removed and 400UI of eCG (Folligon ®) was administered subcutaneously and embryos were transferred by semi-laparoscopy. Pregnancy diagnosis was performed by ultrasonography days after ET. There was a higher concentration (90%) of the time of ovulation at 48 hours after the device removal. At Fifty-two hours after device removal, all females from the experiment had ovulated. In the second experiment, no differences were seen in number of structures recovered among treatments with a mean of 11.15 ± 6.35. The number of viable embryos differed statistically between the T2 (8.4 ± 5.5) and T3 (4.0 ± 4.4), showing that cryopreserved sperm cell was not able to accomplishing fertilization when the laparoscopic AI was held at 36 h. It was concluded that females subjected to MOET show a fast follicular growth and ovulations occurred mostly 48 hours after Progesterone device removal. It is possible to suggest a single laparoscopic AI in commercial MOET programs in sheep. It was showed also a numerical superiority, when using cooled semen.