Abstract
The objective of this research is to evaluate the effects of controlled internal drug release (CIDR), sponge impregnated with cronolone (Chronogest) on estrus synchronization and pregnancy during the breeding season in Ossimi sheep. About 18 ewes used in this study were distributed randomly into 3 groups, Group A (Vaginal sponge, n=7) which received the hormonal treatment for 9 days plus an injection of 400 IU of PMSG 48 hrs before the removal of the sponge, Group B (CIDR, n=7) which received the hormonal treatment for 12 days plus an injection of 400 IU of PMSG at the day of removal of CIDR and Group C act as control without any hormonal treatment. Estrus was monitored every 6 hrs for 3 days until the estrus detected by the teaser rams. Natural mating with fertile ram during the estrus. In this study the results showed that the incidence of the estrus was higher in CIDR group than the others. The interval from the device removal to the onset of estrus was longer in the sponge than in CIDR ( 27 - 30 hrs versus 23 - 25 hrs ). Vaginal mucus discharge was observed at a higher level in sponge group than those in CIDR. The duration of estrus was longer in CIDR than in sponge (37 hrs versus 30 hrs), Therefore, the conception rate was higher in the CIDR than sponge group. It was concluded that treatment with CIDR device give high estrus response, short onset to estrus, longer duration and high in conception rate. Along overall CIDR was effective in the efficiency of estrus synchronization.

Key words: CIDR, Estrus, Sheep, Sponge, Synchronization.