The effect of the presence of the ram on the ovarian activity of the ewe.

Abstract

Observations were made on the effect of the presence of the ram when introduced to Merino ewes in the transition from the "non-breeding" to the "breeding" season in the Roseworthy environment. These observations showed that the primary effect was to stimulate ovulation without oestrus ("silent heat") in the majority of those ewes which had not already commenced cyclic breeding activity. This effect occurred within 6 days of joining the rams with the ewes. It is concluded that this mechanism explains the "lag and peak" incidence of oestrus previously observed under these conditions (Underwood, Shier, and Davenport 1944; Thompson and Schinckel 1952; Schinckel 1954).