The development of embryos from bovine oocytes cultured in vitro : relation to ovarian activity and steroidogenesis in follicular fluid, maturation media and culture media
The present study was undertaken to examine the effect of ovary type on in vitro production of embryos. Experiment 1 examined the effect of the presence or absence of a corpus luteum and/or large follicle(s) on an ovary, on the development of oocytes to embryos at the blastocyst stage. Experiment 2 investigated whether the ovary type used as the source of granulosa cells in culture (as supplementary cells and for monolayers), affected in vitro production of embryos at the blastocyst stage. The concentrations of progesterone, oestradiol-17B and testosterone in follicular fluid (experiments 1 and 2) "spent" maturation and culture media (experiment 2) in relation to embryonic production were also examined. Ovaries obtained from heifers at presumed random stages of the oestrous cycle were grouped into treatments CL, LF and N as described below: CL:-Ovaries with a corpus luteum at stages II and III of the oestrous cycle (Ireland et al., 1980). Ovaries with follicles>12 mm diameter were excluded. LF:-Ovaries with a large follicle>12 mm diameter (excluding cystic follicles). N:-Ovaries with follicles <12 mm diameter and/or a newly formed or regressing corpus luteum. The number of oocytes matured, inseminated and cleavage rates on a per oocyte recovered basis were not significantly different among the three ovarian treatments, nor for the three monolayer types.