EN
No offspring have yet been obtained in horses either from oocytes collected from preantral follicles or other ones maturing in vitro. The available literature does not provide any detailed description of the ovary with respect to distribution and morphology of the ovarian follicles. The purpose of the study was to define the location and histomorphology of preantral follicles in the mare ovary in order to find if it is then possible to isolate and cultivate it. The investigations were carried out on some histological samples of longitudinal and transversal sections of mare ovaries which were collected from a 6-year-old anoestrus mare at 10 minutes after slaughter. From among 821 preantral follicles, wihich were located and evaluated, 567 came from transversal sections and 256 from the longitudinal ones. The preantral follicles were found in all parts of the ovary stroma. In a single histological preparation from a transversal section an average number of 70,5 preantral follicles were found and in a longitudinal one there were 84.7 preantral follicles the size of 35.2 and 45 µm, respectively. The follicles mostly occured singly (54.7%) or in groups of 2 to 7 (45.3%). Among all the preantral follicles 31.2% were defined as artretic, 30.6% were found in the group of the primordial ones and 63.6% in the secondary ones. The percentage of artretic follicles increased with the stage of follicular development. Isolation of the follicles from ovary, their culture and in vitro maturation still remains a problem. The present study indicates that samples collected from any part of the ovarian stroma can be used for this purpose.