Efeito do método de sincronização da onda folicular na resposta superovulatória em bovinos

Abstract

Although the bovine embryo transfer is a technique widely used around the world, the variability of donor response to superovulatory treatment is still an important limitation. The objective of this study was to evaluate the effect of the synchronization method of follicular wave on superovulatory response of bovine embryo donors. For this, seven Girolando cows and five Girolando heifers previously selected (depending on the reproductive history, sanitary conditions, nutritional and reproductive tract without anatomical abnormalities) were randomly assigned to three treatments according to the synchronization of follicular wave before the superovulation: i) synchronization with GnRH ii) synchronization with progestagen implant and application of estradiol benzoate iii) without synchronization (based on estrus detection - Control Group). After submitted to the treatment for synchronization of follicular wave, the donors were superovulated with eight decreasing FSH doses, applied twice daily by deep intramuscular injection (IM) with intervals of 12 hours for each application, with a total dose of 133 mg for each animal. The first insemination was conducted 12 hours after application of ovulation inducer (GnRH) and the second insemination conducted 12 hours after the first. The superovulatory response was measured with an ultrasound device (MINDRAY D2200 VET) to quantify the number of corpus luteum present in the ovaries on the day of embryo flushing and also assessed the number and quality of embryos recovered. It was observed that animal category and crossbred influenced the superovulatory response (p <0.05). The heifers showed a higher response to superovulatory treatment (100% of response in all treatments) when compared to cows had showed 85.7%, 57.1% and 57.1% of superovulatory response to estrus based group, GnRH and P4+EB, respectively. The genetic group (crossbred) also showed influence on superovulatory response (p <0.05) since the 3/8 animals responded better than 3/4animals. The treatments for follicular wave emergence synchronization did not show differences for superovulatory response (p>0.05), recovered structures and viable structures. So, we conclude that the treatments for follicular wave synchronization with GnRH or P4+BE can be used in Girolando donors with same efficiency of estrus based group. Besides, we conclude also that Girolando heifers have better superovulatory response than cows as well as 3/8 crossbred donors.