Decreased lambing rate is one of the main obstacles in the development of sheep rearing, which causes great economic losses to sheep farmers. The aim of the present study was to evaluate the effect of polyunsaturated fatty acids (PUFAs), including oils containing omega-6 and omega-3 fatty acids in the pre-breeding diet on folliculogenesis, blood metabolites and reproductive parameters in Shall ewes. For this purpose, 25 ewes were allocated to 3 experimental groups so that the control group had 9 animals and the two other groups (group fed calcium salt of soybean oil and group calcium slat of flaxseed oil) each had 8 animal. The energy and crude protein levels in the experimental diets were somewhat identical. The estrous cycles of all ewes were synchronized with insertion of intravaginal sponges containing progesterone in a 13 d period and one day before the removal of sponges, all ewes were injected 400-IU eCG intramuscularly. The growth and activity of ovarian follicles were monitored from 4 days before until 1 day after sponge removal using ultrasonography. Blood samples were taken from the jugular vein during the monitoring of ovarian follicles and also 12 days after the onset of estrus to evaluate the concentration of various blood metabolites. At the beginning of the study, all ewes were fed at the level of maintenance for 3 weeks as the adaptation period, and then all animals received the flushing diets for 4 weeks. Results showed that the experimental diets affect the population of medium size follicles at one day after sponge removal. In other words, the diets containing PUFAs oils (source of omega-6 and omega-3) had higher (P 0.05) medium size follicles compared to the control group. Blood triglyceride concentration was higher (P 0.01) in the group fed omega-6 source than those of the two other groups. The blood cholesterol and HDL were different (P 0.01) between the treatments, so that the highest concentrations were observed in omega-6 fatty acids, omega-3 fatty acids, and the control group, respectively. Although the concentration of blood progesterone was not different between the experimental groups, however, the orthogonal contrasts showed calcium salts of oils increased (P 0.01) the blood progesterone concentration at 12 d after the onset of estrus. Birth weight of lambs was not affected by the experimental diets, but sex and number of lambs affected the lambs' birth weight (P 0.01), so that female lambs and multiple lambs had lower weight. In general, it was concluded that using the calcium salts of PUFAs in flushing diet may have a positive effect on blood metabolites, hormones and the reproductive performance of Shall ewes. Keyword :Sheep, Flushing, Twinning, Follicular growth, Fatty acid, Omega-6, Omega-3
