Different estrous induction protocols during non-breeding season in Assaf ewes

Abstract

This experiment was conducted to investigate the effect of pregnant mare serum gonadotrophin (PMSG) levels and the progestagen method on estrus response, onset and duration of estrus, lambing rate and litter size. A total of 20 Assaf ewes were used in the experiment, which was conducted during April, a month that is considered as non-breeding period in Palestine. Ewes were treated with intravaginal sponges containing 60 mg medroxyprogesterone acetate (MAP). Seven days later, sponges were removed and 10 new sponges were inserted to 10 of the experimental ewes. Following withdrawal of sponges at day 14, 5 ewes from each treatment groups were injected intramuscularly with a pregnant mare serum gonadotrophin (PMSG) at level of 300 or 600 IU. The results showed that level of PMSG and progesterone application methods had no significant effects on the tested parameters. This finding indicated that low level of PMSG can be applied for estrus synchronization. Results showed that using one sponge followed by a 300 IU dose of PMSG could induce estrus successfully with low cost comparing to application of two sponges and high doses of PMSG.