Associations among the largest follicle, preovulatory estradiol concentrations, and predominant vaginal epithelial cells at the completion of hormonal ovarian stimulation for fixed‐time artificial insemination in goats

Abstract

The objective of the present study was to investigate the association among the largest follicle (LF), preovulatory estradiol (E2), and predominant vaginal epithelial cell at the completion of hormonal ovarian stimulation for fixed‐time artificial insemination (FTAI) in goats. Thirty‐seven crossbred Boer does received gonadotropin‐releasing hormone (GnRH) and intravaginal progesterone (P4)‐releasing devices (day 0). On day 5, P4 devices were removed and does received prostaglandin F2α and equine chorionic gonadotrophin. On day 7, does received GnRH, and FTAI was undertaken. On day 7, does were divided into three groups, i.e. small‐sized (3–3.9 mm; n = 5), medium‐sized (4–4.9 mm; n = 8), and large‐sized (≥5 mm; n = 24) according to the diameter of the ovarian LF; follicular characteristics (number and diameter) were identified, and blood samples and vaginal smears were collected. The average diameters of total antral follicles and LF and the percentage of superficial cell were greatest in large‐sized LF does (p < .01). The average diameters of total antral follicle (r = .68) and LF (r = .71), number of preovulatory follicle (r = .58), and plasma E2 concentrations (r = .61) were positively correlated with the percentage of superficial cells (p < .01). The likelihood of a pregnancy outcome after the FTAI increased by 13.71 times in does with a greater average diameter of antral follicle, 14.18 times with emergence of a large preovulatory follicle, and 36.83 times with a higher percentage of vaginal superficial cells (p < .01). It was concluded that there is a relationship between the cell types of the vaginal epithelium, the diameters of the largest ovarian follicles, and the concentration of E2 in goats subjected to FTAI protocols.