ASSOCIATION BETWEEN OVARIAN FOLLICULAR DEVELOPMENT AND OESTRADIOL-17\g=b\SECRETION 3 TO 4 DAYS AFTER OESTRUS IN EWES

A significant increase in oestradiol-17\g=b\(E2) secretion occurs on Day 3\p=n-\4 of the oestrous cycle, i.e. 2\p=n-\3 days after ovulation, in the ewe (Cox, Mattner & Thorburn, 1971; Mattner & Braden, 1972). The present data relate E2 production at that time to the ovarian morphology. Timed collections of ovarian vein blood (Mattner & Thorburn, 1969) were obtained at laparotomy from four control (C) and four progesterone-synchronized (P) 4-yr-old Border Leicester \m=x\Merino ewes at 40, 48, 56 or 64 h after ovulation (32 ewes). Ovulation was accurately timed by endoscopy (Holst & Braden, 1972): each ewe ovulated only one egg. Plasma E2 was assayed by a competitive protein-binding method (Cox et al. 1971; Shutt & Cox, 1972). After the collection of blood, the ovaries were excised and their gross appearance noted. The ovaries from 16 ewes were serially sectioned at 15 \g=m\mand stained with haematoxylin and eosin. Counts were made of all follicles with diameter> 0\m=.\4mm. E2 production varied considerably between ewes, but not significantly between control and progesterone-synchronized ewes or between sampling times. Mean value