BOVINE OOCYTE RETRIEVAL - WHICH FOLLICLES TO PUNCTURE

Recent literature describing techniques for in vitro culture of immatu re oocytes to the blastocyst stage has focused on the optimal criteria required for selection of follicles and oocytes mainly recovered from slaughterhouse ovaries. The problem of follicle selection before punc ture is discussed on three levels. First, the importance of the physio logical status of the donor animal is explained, the most important pa rameters being stage of the estrous cycle, body condition, age and bre ed. Second, the possibility of follicular selection at the ovarian lev el is highlighted. For this purpose, follicles are categorized based o n macroscopic and morphological appearance, on histological and ultras tructural examination of the follicular wall and the cumulus oocyte co mplex (COC) and on the different hormonal micro-environment in the fol licular fluid. Finally, the most important parameters in the assessmen t of follicle and oocyte health are described in relation to the subse quent developmental capacity. The importance of the metabolic coupling between the cumulus cells and the oocyte is illustrated at the macros copic and ultrastructural levels. In conclusion, the practical consequ ences and implications of follicular selection prior to transvaginal o ocyte retrieval in living donor animals are discussed.