Effects of progesterone in synchronization of estrus and fertility in Shal ewes in nonproductive seas

Synchronization of estrus let to insemination and husbandry as a work plan proportionate with other require activities that reduces estrus diagnosis time consuming conduct and reproductive season. About 80 Shal ewes 2-4 years old that all have had calving last year and lactate lambs were divided into four groups of 20 lambs per treatment (three treatment groups and one control group) and they were examined. They were inoculated with CIDR in three groups in May (anestrous season). CIDRs were remained in vagina of the treatment groups ewes for 10, 12 and 14 days and then they were removed. All experiment groups were fertilized with a healthy and fertile ram. Twenty four hours after CIDR withdrawal, the half of the ewes was injected 100 mg GnRH-IV. Occurrence of estrus in the control group was 12 and in experimental groups was 70, 90 and 80 percent, respectively. Estrus incidence in the groups treated with CIDR showed significant difference compared to control group (p<0.01) but there was no significant differences in incidence of estrus in experimental groups (P≥0.05). The pregnancy rate in experimental groups ewes that was received GnRH compare to control group was significantly higher (P<0.05). It was concluded that the occurrence of estrus using CIDR in non- reproductive season for 10, 12 and 14 days was associated with the onset of good estrus and use of GnRH has good effect on fertility in treatment groups.