Characterization of the ovarian follicular population in Friesian prepubertal sheep

Abstract

: Folliculogenesis is the process by which immature (primordial) ovarian follicles develop and become preovulatory follicles. In prepubertal females, follicular development up to the antral follicle stage generally occurs in the absence of basal gonadotrophic stimulation. Morphometric analyzes are very useful to quantify the structural follicular changes that occur in the different stages of the reproductive cycle of females (prepubertal, puberty, sexual maturity and senility) as well as in the different stages of the estrous cycle in adult animals. The main objectives of our study were to: a) establish the ovarian follicular dynamics, describing the percentage of follicles of each of the different follicular populations (primordial, transitional, primary, small preantral, large preantral and small antral); b) determine the percentage of atretic antral follicles and the incidence of FMOs, and c) quantify the diameter of the oocyte, nuclear diameter, follicular diameter, thick ness of the granulosa and theca cell layers and determine the average depth of location of the different follicular types. Ten (10) lambs of the Friesian breed were used. On postnatal day 45, bilateral oophorectomy was performed under general anesthesia. The ovaries were dissected, weighed and processed until they were embedded in paraffin to be finally stained. The results obtained in our study allow a better knowledge of the folliculogenesis mechanism and provide information to understand what factors need to be controlled to, for example, produce quality oocytes for In Vitro Fertilization (IVF) and Embryo Transfer (ET) from females. pubertal -MOET- or pre-pubertal -JIVET-, as well as for the implementation of genetic engineering techniques in small ruminants.