Effect of Melatonin Supplementation on Reproductive Performance, Hormonal Profile and Antioxidant Status in Sheep Under Subtropical Conditions

Limited information is available regarding the role of melatonin in regulating seasonal reproductive activity and oxidative stress in sheep under subtropical climatic conditions. Therefore, the present study evaluated the effect of melatonin administration on reproductive performance, hormonal profile, and antioxidant status in ewes during breeding and non-breeding seasons. A total of 48 clinically healthy multiparous ewes (2–5 years old) were equally divided into breeding and non-breeding season groups (n = 24 each). During each season, animals were allocated into four treatment groups: Group I (control; corn oil @ 1 mL/animal, s/c, n = 6), Group II (melatonin @ 10 mg/animal, s/c, n = 6), Group III (melatonin @ 20 mg/animal, s/c, n = 6), and Group IV (melatonin @ 40 mg/animal, s/c, n = 6). Melatonin administration significantly improved estrus response and conception rate during both seasons. During the breeding season, estrus response was observed in 33.33%, 100%, 100%, and 66.67% of animals in Groups I, II, III, and IV, respectively, whereas during the non-breeding season, estrus response was 0%, 83.33%, 100%, and 33.33%, respectively. Similarly, conception rates during the breeding season were 50%, 100%, 100%, and 66.67%, respectively, while corresponding values during the non-breeding season were 0%, 80%, 100%, and 50%. Serum estrogen concentration increased significantly (p < 0.05) in Groups II and III, particularly on day 7 during the breeding season and on day 14 during the non-breeding season. Progesterone concentration increased significantly (p < 0.05) on day 30 following 10 and 20 mg melatonin treatment during both seasons. Antioxidant enzyme activities, including glutathione peroxidase, superoxide dismutase, and catalase, were significantly enhanced following melatonin treatment. In conclusion, subcutaneous administration of melatonin improved reproductive performance, hormonal profile, and antioxidant status in sheep under subtropical conditions, with 20 mg melatonin/animal producing the most favorable responses, particularly during the non-breeding season.