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Ram-induced growth of ovarian follicles and gonadotrophin inhibition in anoestrous ewes

Atkinson, S. and Williamson, P. (1985) Ram-induced growth of ovarian follicles and gonadotrophin inhibition in anoestrous ewes. Reproduction, 73 (1). pp. 185-189.

Abstract

Summary. Southdown ewes in mid-seasonal anoestrus were exposed to rams for 0 h (control group), 2 h, 24 h, 40 h, 3 days, 10 days or 20 days. Serial blood samples were then taken to determine LH and FSH levels. Ewes with >24 h ram exposure were ovariectomized immediately after bleeding, and all follicles >1 mm diameter were dissected from the ovaries and measured. LH basal concentrations and pulse frequency increased significantly within 2 h of ram introduction, but by 24 h fell, and then remained low. FSH concentrations fell within 2 h of ram introduction and remained low. Control group ewes (isolated) had no follicles >4 mm diameter, whereas all ewes exposed to rams had large follicles, with CL or preovulatory follicles present at 40 h after ram introduction. Ram introduction was also associated with follicle recruitment (antrum formation to <2 mm). Follicular recruitment and development to the large follicle stage therefore occurred during a period of low plasma gonadotrophin levels and suppressed LH pulsing.

Publication Type: Journal Article
Murdoch Affiliation: School of Veterinary Studies
Publisher: Society for Reproduction and Fertility
Other Information: http://dx.doi.org/10.1530/jrf.0.0730185
URI: http://researchrepository.murdoch.edu.au/id/eprint/34034
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