The effect of melatonin and progestagen sponge administrations separately and together on the reproductive performance at the onset of the breeding season were investigated in Kıvırcık ewes. On June 22, to 40 anoestrous and non-lactating ewes were administrated melatonin (Regulin) implants. On July 14, progestagen (Synchron) sponges were inserted in 20 of these ewes and in 20 other ewes. They were removed 14 days later and on the day of removal the ewes were given 600 I.U. pregnant mare's serum gonadotrophin (PMSG). The other 20 ewes served as controls. Rams were introduced on July 28. The lambing percentages of the ewes in the melatonin, progestagen + PMSG, melatonin + progestagen + PMSG and control groups were 85% , 90% , 95% and 75% and the twinning rates were 52.9% , 73.7%, 61.1% and 43.6%, respectively. Lambing days after ram introduction were 156 ± 6.24, 153 ± 6.07, 155 ± 7.33 and 164 ± 12.03 days in the melatonin, progestagen + PMSG, combined and control groups, and lambings were more condensed on 17.66 ± 3.51 days in the treatment groups and 33.07 ± 2.25 days in the control group. The mean numbers of live born lambs per ewe were 1.47 ± 0.51, 1.44 ± 0.51, 1.47 ± 0.61 and 1.43 ± 0.50, respectively. We conclude that melatonin and progestagen treatments separately and together at the onset of the breeding season may advance and condense the rates of lambing and the breeding season can be controlled by these treatments. In addition, melatonin treatment may be a viable alternative to traditional hormonal techniques using progestagen and PMSG.

The effect of melatonin and progestagen sponge administrations separately and together on the reproductive performance at the onset of the breeding season were investigated in Kıvırcık ewes. On June 22, to 40 anoestrous and non-lactating ewes were administrated melatonin (Regulin) implants. On July 14, progestagen (Synchron) sponges were inserted in 20 of these ewes and in 20 other ewes. They were removed 14 days later and on the day of removal the ewes were given 600 I.U. pregnant mare's serum gonadotrophin (PMSG). The other 20 ewes served as controls. Rams were introduced on July 28. The lambing percentages of the ewes in the melatonin, progestagen + PMSG, melatonin + progestagen + PMSG and control groups were 85% , 90% , 95% and 75% and the twinning rates were 52.9% , 73.7%, 61.1% and 43.6%, respectively. Lambing days after ram introduction were 156 ± 6.24, 153 ± 6.07, 155 ± 7.33 and 164 ± 12.03 days in the melatonin, progestagen + PMSG, combined and control groups, and lambings were more condensed on 17.66 ± 3.51 days in the treatment groups and 33.07 ± 2.25 days in the control group. The mean numbers of live born lambs per ewe were 1.47 ± 0.51, 1.44 ± 0.51, 1.47 ± 0.61 and 1.43 ± 0.50, respectively. We conclude that melatonin and progestagen treatments separately and together at the onset of the breeding season may advance and condense the rates of lambing and the breeding season can be controlled by these treatments. In addition, melatonin treatment may be a viable alternative to traditional hormonal techniques using progestagen and PMSG.