Estrual Activity in Open Rambouillet Ewes

THE ewe is generally considered to be seasonally polyestrual in that she exhibits one or more diestrual cycles during a particular season of the year (Frank and Appelby, 1943). However, estrual activity may vary from the monestrual type exhibited by the wild sheep (Asdell, 1946) to the completely polyestrual type of some breeds in certain locations (Roberts, 1921; Kupfer, 1928; Quinlan and Mare', 1931; Hafez, 1952). At the time this study was initiated there was considerable interest in producing falldropped lambs in the Southeastern United States. One of the major difficulties encountered was failure of many of the ewes of most breeds to come into heat during the spring and early summer months so they could be bred for fall lambs. In view of the considerable variation in estrual activity from one geographical area to another and among different breeds in the same area, this study was conducted to ascertain the nature of estrual activity in the Rambouillet ewe under Alabama conditions. The results of a 4-year study are reported herein.