DIFFERENCES IN DEVELOPMENT OF BOVINE OOCYTES RECOVERED BY ASPIRATION OR BY MINCING

This experiment was performed to clarify relationships between conditions of bovine ovaries and developmental capacity of the follicular oocytes recovered from them and to compare two methods of oocyte collection, aspiration and mincing. Follicular oocytes with surrounding intact, unexpanded cumulus recovered by follicular aspiration or by mincing of tissue from 24 pairs of ovaries were matured and fertilized in vitro. The number of follicular oocytes recovered from pairs of ovaries averaged 32.1 +/- 3.2, but the number recovered varied greatly among the 24 pairs of ovaries (range, 7 to 71). The overall rate of development to the blastocyst stage was 18% (137/771), and the average number of blastocysts produced from a pair of ovaries was 5.7 +/- 1.1 (range, 0 to 17). No relationships were found between the presence of corpora lutea or large follicles and the proportion of oocytes capable of reaching the blastocyst stage in vitro. However, a positive correlation was observed between the number of oocytes obtained from each pair of ovaries and subsequent in vitro development; the correlation was especially high for oocytes obtained by aspiration. These data suggest that the developmental capacity of bovine follicular oocytes after in vitro maturation and fertilization is correlated to the number of antral follicles aspirated from the pair of ovaries.