Sexual behaviour responses of the ovariectomized ewe to oestradiol benzoate, and their persistent reduction after exposure to phyto-oestrogens

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Abstract
Characteristics of estrous behavior were recorded for 14 control ovariectomized ewes treated with 15, 25 or 40 .mu.g estradiol benzoate (OB), and for 24 ovariectomized ewes, 11 of which were infertile after prolonged intake of estrogenic clover, which were each treated successively with 0, 10, 15.6 and 24.3 .mu.g OB. Squatting by the ewe and Flehmen by a ram after sniffing the ewe were not associated with estrogen treatment. Looking over the shoulder was a sign exhibited by most ewes treated with 10 .mu.g OB, but not by ewes that did not receive estrogen. There were no differences between clover-affected and control ewes for these responses. Active soliciting by the ewe, standing for mounting, and being mounted by the ram, were behavioral responses closely associated with doses of OB greater than 15 .mu.g. Tail fanning and kicking by the ewe were less closely associated with higher doses of OB. All of these responses were slightly but significantly diminished in clover-affected ewes, either in incidence, duration or by a later time to onset. Prolonged exposure to plant estrogens may cause persistent desensitization of the hypothalamus of the ewe to estrogen.