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In this study, the effects of progestagen + PMSG and melatonin implants on the stimulation of ovarian activity and some of the reproductive parameters were investigated in anoestrus ewes out of the breeding season. Three years old 30 Merino ewes and six rams, were used as material. The ewes were randomly divided into three groups. Eighteen mg melatonin (Regulin, Hoechst) was implanted to ewes in group I (n=10). After 35 days following implantation, leaser rams were introduced and ewes with oestrus symptoms were selected and inseminated. In group II (n=10) vaginal progesterone sponges (30 mg FGA) were inserted for 14 days and 500 IU PMSG was applied on the withdrawal day. After that rams were introduced and ewes in oestrus were inseminated. The ewes in group III (n=i0) were saved as control. Rams were gathered in control group on the same day with the other groups. The ewes and rams were introduced for five days and blood samples were collected once a day from the ewes. Serum progesterone, oestradiol and LH levels were determined by using the R.I.A. technique. The oestrus symptoms were observed after 12 hours following the introduction of rams. The highest oestradiol level was determined on the first day of ram introduction in the treatment groups.
Although oestradiol levels in the control group increased slightly on 2nd, 3rd and 4th days, none of the ewes had oestrus symptoms. Scrum LH values reached the peak levels after 28 and 32 hours following the introduction of rams for groups I and II, respectively. Serum progesterone level reached the value above 1 ng/ml at the 3rd day in group I and at the 2nd day in group II. Serum LH and progesterone levels were at the basal levels during five days following the introduction of rams in the control group. Although no pregnancy was observed in the control ewes (n=10), 90%, 80% oestrus. 90%, 10% pregnancy and 77.7%, 71.4% twinning rates were observed in the melatonin and progestagen + PMSG groups respectively. As a result, the ovarian activities of Merino ewes out of the breeding season can be stimulated with melatonin or progesterone containing vaginal sponges. Also higher pregnancy rates can be provided melatonin applied ewes compared to progesterone treated ewes. In addition, melatonin application is more effective than sponge application in terms of pregnancy rates. In conclusion, in this study melatonin application was found to be more effective than progesterone application in ewes during the non-breeding season. However, both applications would be useful to improve the pregnancy rates in ewes that are in the non-breeding season.