Published in Scientific Papers. Series A. Agronomy, Vol. LIX
Written by Carol MOFFAT, Anya WESTLAND, Lancelot BUTTERS
Sheep breeding can be manipulated by several methods and is hugely dependant on the use of hormones to modify the physiological events involved in reproduction. This study aims to investigate the use of the “ram effect” by teasing the ewes for different timescales to synchronise breeding, induce oestrus, to improve conception and pregnancy rates during the breeding season. During the 17 day pre-breeding synchronisation period 126 ewes were assigned to three treatments and a control. Treatment group one was exposed to a vasectomised ram for 17 days (n=30). Treatment group two were exposed to an entire ram for two days (n=30). Treatment group three were exposed to an entire ram for four days (n=31). The control were not exposed to either a vasectomised or an entire ram (n=35). This study found a significant difference (P=0.002) in conception rates in ewes exposed to an entire ram for four days in that they conceived less than expected in the first half of cycle one compared to the other treatments and control. It was also found that ewes had conceived significantly more than expected when exposed to an entire ram for four days for the second half of cycle one compared to the other treatments and control (P=0.043). In conclusion in this study it was found that the ram effect is not effective at inducing oestrus during the breeding season. The synchronicity of the ewes was achieved; however other factors may have influenced this study including flushing, photoperiod, and the female effect.
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