Obtaining follicular fluid through ovum pick up to determine steroidal concentrations of preovulatory follicles in donkeys

Abstract

There is currently no evidence of reference values for steroid hormones in the follicular fluid of the species Equus asinus during the estrous cycle. The present study aimed to determine the hormonal concentrations of estradiol and progesterone in the follicular microenvironment to establish a better understanding of the role they play in the donkey and their importance in reproductive physiology of this species.. The study was carried out at the FMVZ-UNAM Equine Reproduction Clinic authorized by the Institutional Sub-committee for the Care and Use of Experimental Animals (SICUAE.MMVZ-2020/4-2). Seven Creole donkeys aged between 3 and 9 years, clinically healthy, weighing between 128 and 206 kg and with a body condition of 3 on a scale of 0 to 5, were used. In order to identify preovulatory follicles with a diameter from 27 to 38 mm (depending on the specimen), each donkey was monitored by ovarian palpation and transrectal ultrasonography. Each follicle was standardized based on its size and previous records over three estrous periods where the optimal follicular diameter was observedprior to ovulation. Subsequently, the follicular fluid was recovered using the transvaginal ultrasonography-guided follicular aspiration technique and stored at -20°C until determination of hormones by ELISA (Estradiol ELISADRG, EIA-2693 and Progesterone ELISA DRG, EIA-1561). Prior to the analysis of each sample, follicular fluid was diluted in PBS 0.1M, pH 7.2 from 1:1000 to 1:10,000. Each sample was measured in duplicate. A total of 70 follicular aspirations were obtained during 10 estrous cycles from each donkey, with an average interval of 15 to 17 days. data in Table 1 represent the mean ± standard error of the mean of 10 observations per animal. The results show for first-time concentrations of estradiol and progesterone in the donkeys, which will serve as a reference in subsequent studies.