Effects of types of vaginal sponge impregnated with progestogen on estrus induction and lambing rate in seasonally anestrous ewes.

Abstract

For out-of-seasonal breeding, types of vaginal sponges and progestogens were compared in two field trials. The materials used were as follows; I) 60 mg medroxy-progesterone acetate (MAP)-impregnated sponge (supplied by the Upjohn International, Australia), II) 500 mg progesterone-impregnated empty-MAP sponge, and III) 500 mg progesterone-impregnated self-made sponge. The sponge was inserted in the vagina for 12 (Trial 1) and 9 days (Trial 2). A 600 IU PMSG was injected intramuscularly in ewes at the time of sponge removal, and a synthetic LH-RH (Conceral, 100 μg) was also given in ewes at the time of estrus detection. In trial 1, the proportion of estrous ewes within 5 days after treatment was satisfactory (94-100%) with no significant differ-ences among the groups. The mean time of induced estrus was significantly (P<0.05) earlier in the ewes treated with 500 mg progesterone-impregnated sponges than that with MAP sponges. The lambing rates were 85, 60 and 57% for groups I, II and III, respectively. However, they were not significantly different. In trial 2, the proportion of estrous ewes was generally low (68-88%) with no significant differences among the treatments. The lambing rates of the ewes mated following the sponge removal were also low (31-33%). However, there were no significant differences among the types of sponges and progestogens used. The present results indicate that the self-made vaginal sponge impregnated with 500 mg progesterone has similar effects to the MAP sponge for estrus induction and lambing rate in ewes treated during the non-breeding season.