The animal material of the project is composed of 120 Chios x Kivircik (F1) sheep. The sheep were purchased from 3 different enterprises dealing with migrating sheep production and a new flock was composed. While, purchasing the animals, attention was paid to the fact that they were aged 3-4 had given birth at least once and display the phenotypic traits of Chios x Kivircik crossbred sheep and a homogenous flock was composed. No studies had been carried out on the material so far. The ewes were not given additional feed and they only grazed. The ewes were divided into 4 groups at the beginning of August, which is the mating season for the region. The experiment was composed of 4 groups, namely, control group, the group with only sponge insertion (for 14 days), group with sponge + 400 IU PMSG and group with sponge + 500 IU PMSG.