Effects of melatonin on reproductive performance, plasma progesterone and malondialdehyde concentrations during breeding season in ewes

Abstract

Abstract Melatonin, synthesized in the pineal gland, affects the hypothalamus, leading to the release of gonadotropins during the transition period in sheep and goats. Melatonin regulates the production of prolactin in lactotrophic cells and of follicle-stimulating hormone and luteinizing hormone in gonadotropic cells. Melatonin may also provide better reproductive performance through its positive effects on reproduction, such as improving oocyte quality, favoring embryo implantation, reducing oxidative stress, and protecting the offspring by increasing progesterone levels. Melatonin applications in sheep are generally carried out during anoestrus and transition periods. In this study, the effect of exogenous melatonin used with different methods on estrus onset, fertility, plasma progesterone, and malondialdehyde (MDA) concentration will be examined during the breeding season in sheep. For this purpose, the ewes were assigned to three groups: Group I (MEL): Subcutaneous administration of 18 mg of melatonin (Regulin, Ceva-Türkiye) Group II (MELPRO): Subcutaneous administration of 18 mg melatonin (Regulin, Ceva-Türkiye) + Intravaginal sponge containing 20 mg of flugestone acetate for 9 days (Choronogest CR- France) + As soon as the sponge is removed, intramuscular PGF2α (250 µg cloprostenol, Senkrodin-Vetaş-Türkiye) Group III (CON): 1 ml of physiological saline was administered subcutaneously for the placebo effect. As a result, in ewes, only exogenous melatonin administration during the natural breeding season causes a short delay in the time to first estrus. Melatonin increases progesterone concentration on day 17 of gestation in the natural breeding season. The positive reproductive effects of melatonin may increase the multiple birth rate and litter size.