Oestrous synchronization in ewes: a comparison of prostaglandin F2α tham salt with a progestagen pessary

Abstract

ABSTRACTAn experiment was designed to compare saline, prostaglandin F2α tham salt and progestagen pessaries as agents for oestrous synchronization in mature cyclic ewes maintained under normal husbandry conditions. The effect of these agents on ewe fertility and lambing performance was also assessed.One hundred and sixty Clun Forest ewes were allocated to one of four equal-sized treatment groups and received either two injections of saline given 9 days apart (group A), two injections of 10 mg (group C) or 20 mg (group D) postaglandin F2α tham salt given 9 days apart, or progestagen pessaries left in situ for 12 days (group B). Oestrous response, fertility and lambing performance were monitored thereafter. Oestrus occurred within 3 days of the end of treatment in 0·28, 0·98, 0·58 and 0·83 of ewes in groups A to D respectively, with return rates after a single mating of 0·15, 0·13, 0·25 and 0·33 respectively. There was no difference between treatments in lambing performance. These results indicate that two injections of either 10 or 20 mg prostaglandin F2α given 9 days apart is a less effective means of synchronizing oestrus in sheep than progestagen pessaries.