Single or Double Inseminations at Fixed-Time Basis on Lambing Rate of Ewes Treated with Porgestogen-Impregnated Intravaginal Sponges during the Non-Breeding Season.

Abstract

Effect of a single or double inseminations at fixed-time basis on lambing rate of ewes treated with 2 different progestogen-impregnated intravaginal sponges during the non-breeding season was investigated in 3 trials (Farms T, H and S). A total of 236 mature Suffolk ewes were treated with either 60 mg medroxyprogesterone acetate (MAP) - or 500 mg progesterone (P) impregnated intravaginal sponge for 9 days and an intramuscular injection of 600 IU PMSG one day before sponge removal. The MAP- and P-treated ewes were inseminated once (36 hr) or twice (30 and 42 hr) with fresh-undiluted semen after sponge removal. The lambing rates in 4 groups were 44.6, 50.9, 46.6 and 50.0% for MAP-single, MAP-double, P-single and P-double inseminations, respectively. There were no significant differences in the lambing rates between the two types of sponges (46.5 and 48.3% for MAP and P sponges, respectively) and between the numbers of insemination (45.6 and 50.4% for a single and double insemination, respectively). The lambing rate in Farm H (33.7%) was significantly lower than those in Farms T (50.0%: p<0.05) and S (61.7%: p<0.01).