Influence of Long and Short-term Progesterone Administration on Estrous Synchronization and Reproductive Performance in Ewes During May Season

Estrous synchronization is a promising management device to get better reproductive proficiency, particularly in ruminants. However, limited information is available about the influence of long and short-term progesterone administration on estrous synchronization and reproductive performance in ewes during May season, particularly in Egypt. In this study, a total of 144 ewes have been utilized for estrous synchronization and reproductive performance in ewes during May season. Ewes were separated into six groups with different treatments as follows: G1, control (natural mating), G2, ewes were treated with 20 mg Cronolone vaginal impregnated sponges (Flurgestone acetate, FGA). The sponge was remained intravaginal for 11 days. Each ewe was intramuscularly (i.m.) injected with 500 international unit (IU) Pregnant mare serum gonadotrophin (PMSG) on the day of sponge withdrawal (day 11), G3, ewes were treated with intra-vaginal sponges. The sponge was remained intra-vaginal for 11 days, on day 10, each ewe was injected with 25 mg ultra-short progesterone (P4) (1 ml Lutone). Each ewe was injected i.m. with PMSG (500 IU) on day 11. G4 ewes were treated with intra-vaginal sponges. The sponge was remained for 11 days. Teaser ram was introduced to treated ewes after sponge withdrawal. The 5th group (G5), ewes were treated with intra-vaginal sponges. The sponge was remained intravaginal for 11 days. On day 10, each ewe was injected with 25 mg P4 (1 ml Lutone). Teaser ram was introduced to treated ewes after sponge withdrawal. The 6th group (G6), the same treatment of G2, but the sponge was inserted intra-vaginal only for 6 days. Each ewe was i.m. injected with 500 IU pregnant mare's serum gonadotropin (PMSG) on day 6. Synchronization was better in G2, G3 and G6, respectively and all short-term group animals came into estrus. In addition, onset of estrus and its duration differs significantly among groups. Reproductive performance also showed a significant difference among groups and the short-term group has the highest fertility rate. Given the above information, our data concluded that progestagens synchronized estrus (long term or short term) and administration of PMSG (500 IU) at sponge withdrawal improves the reproductive efficiency of artificially inseminated crossbred ewes.