On the occurrence of oestrus in pregnant Barki and Merino ewes

Abstract

The incidence of oestrus in pregnant ewes has been reported previously by Williams et al. (1956) and Bichard et al. (1974). However, their investigations were not designed specifically to study such a phenomenon and the number of animals employed was small. None of the factors affecting oestrus occurrence was investigated. Under experimental conditions, vasectomized or aproned rams are sometimes used after the removal of fertile rams to detect embryonic failure in pregnant ewes. It is of interest to check on the validity of this method. This study was carried out to obtain an estimate of the incidence of oestrus in early pregnancy using relatively large numbers of fat-tailed Barki and imported Hungarian Merino ewes and to investigate the effect of year, breed of ewe and age of ewe on its occurrence.