Annual reproductive rhythm and ovulation rate in four fat-tailed sheep breeds

Abstract
Karakul, Mehraban, Naeini and Bakhtiari sheep were checked twice a day for oestrus using aproned rams and were laparotomized within 5 to 16 h of the end of every second oestrous period. Oestrus was observed for 12 monthly periods commencing on 21 April.The Mehraban breed with 1 -6 oestrous periods per month was less seasonal in its breeding activity (PPv. 1·28 oestrous periods per month). Seasonal variation in the sexual activity of the ewes was observed (PPPPPv. 0·43, P<001).