Abstract

The pattern of ovarian follicular development in Booroola x Romney ewes (6-7 y) with an ovulation-rate >/-3 (F+ ewes) differed from that in Booroola x Romney ewes (6-7 y) with an ovulation-rate <3 (++). The difference was not due to variations in the number of ovarian follicles (>/-1 mm diameter) or in the proportion of healthy follicles which were similar for both genotypes. It arose because follicles in F+ ewes produced oestradiol and reached maturity at a smaller diameter than in ++ ewes. During a prostaglandin induced follicle phase, the secretion rate of oestradiol from ovaries with 3 presumptive preovulatory follicles in F+ ewes was similar to that from ovaries with only 1 such follicle in ++ ewes. Moreover, the total number of granulosa cells (i.e. the oestrogen-secreting cells) in 3 preovulatory follicles from F+ ewes was similar to that in 1 such follicle in ++ ewes. In F+ ewes, the presumptive preovulatory follicles reached 4.6

JF, Smith, KS MacLean, LT McGowan, and IR Potts

Proceedings of the New Zealand Society of Animal Production, Volume 44, , 25-28, 1984