Koyun Oositlerinin In Vitro Maturasyonu Sırasında Melatonin İlavesinin Sıcaklık Stresi ve Embriyo Gelişimi Üzerine Etkisi

The aim of this study was to investigate the effect of melatonin administration during in vitro oocyte maturation in sheep on heat stress, with a focus on its impact at the level of embryonic development.One of the most critical stages in in vitro embryo (IVF) production is the oocyte maturation phase, during which the maturation rate of oocytes plays a key role. Stress factors encountered during this stage lead to an increase in reactive oxygen species, causing cellular damage. This study evaluated the embryonic development of sheep oocytes exposed to heat stress and treated with the hormone melatonin. A concentration of 10⁻⁷ M melatonin was added to the maturation medium under different temperature conditions. Oocytes were collected from the ovaries of sheep slaughtered at a local abattoir. Incubation procedures were carried out using specially prepared solutions under appropriate laboratory conditions. Embryonic development was assessed through cleavage, morula, and blastocyst stages. When cleavage rates were compared, the highest rate was observed in group G39M, and the lowest in group G41, with a statistically significant difference (P<0.05). Similarly, the highest morula rate was found in G39M, while the lowest was in G41 (P<0.05). The best blastocyst rates were also observed in G39M. Accordingly, melatonin showed a positive effect on cleavage and morula stages under heat stress; however, a significant reduction was observed at the blastocyst stage (P<0.05).