GENETIC VARIATION IN THE SECRETION OF OESTROGEN IN THE EWE

Abstract

A.R.C. Animal Breeding Research Organisation, The King's Buildings, West Mains Road, Edinburgh, EH9 3JQ and †M.R.C. Unit of Reproductive Biology, Department of Obstetrics and Gynaecology, University of Edinburgh, Edinburgh, EHI 2QW (Received 12 May 1977) It has been suggested that the sensitivity of ewes to the negative and positive feedback effects of oestrogen can be related to the rate of ovulation of the breed (Land, 1976; Land, Wheeler & Carr, 1976), and may be associated with different patterns of oestrogen secretion as inferred by Land, Thompson & Baird (1972). However, no apparent differences between the concentrations of oestrogens in jugular venous plasma from ewes with differing rates of ovulation have been reported (Bindon, Blanc, Pelletier, Terqui & Thimonier, 1975; Scaramuzzi & Land, 1976). The pulsatile nature of the ovarian secretion of oestradiol (Baird, Swanston & Scaramuzzi, 1976) and the fact that the concentrations of oestrogen in peripheral plasma are so