Leyva-Corona José C, Angulo-Valenzuela Norberto I, Laborin-Escalante Blanca M, Gastelum-Delgado Miguel A, Silva-Avila N Jahzeel, Luna-Nevárez Pablo, Aragón-López Carlos E, Sánchez-Castro Miguel A, Morales-Pablos Marcela I
Departamento de Ciencias Agronómicas y Veterinarias del Instituto Tecnológico de Sonora, 5 de febrero 818, 85130, Obregón Sonora, Mexico.
Facultad de Agronomía, Universidad Autónoma de Sinaloa, 80260, Culiacán, Sinaloa, Mexico.
Trop Anim Health Prod. 2023 Apr 26;55(3):174. doi: 10.1007/s11250-023-03569-5.
Ovine reproductive behavior depends on annual photoperiodic cycle and its impact on endogenous melatonin secretion. In this regard, exogenous melatonin administration previous to the physiological anestrus period could modify the reproductive performance of sheep in the northwest of Mexico. Two independent studies were performed to evaluate such hypothesis in hair sheep implanted with melatonin prior to the anestrus season in latitudes 24° and 25° of Mexico. Study 1 involved 15 rams assigned to one of three treatments receiving 0mg (n=5), 18mg (n=5), or 36mg (n=5) of melatonin subcutaneously. Study variables were measured monthly since implantation (d0) and included testosterone concentration, scrotal circumference, mass motility, individual motility, and sperm concentration. Study 2 included 50 ewes assigned to one of two treatments receiving 0mg (n=25) or 18mg (n=25) of melatonin subcutaneously. In ewes, progesterone concentration and the frequency of females in anestrus were measured during the implantation (-30d), as well as at the beginning (0d) and at the end (45d) of the mating period, while pregnancy rate was determined by ultrasonography 45d after. Continuous variables were analyzed using a mixed effects model considering treatment, time, and the treatment by time interaction as fixed effects. Animal nested within treatment was the random effect. Binary variables were analyzed using the chi-square test. In males, melatonin improved testosterone and sperm concentrations (P<0.05), while in females, a 28% higher pregnancy rate was observed in implanted ewes (P<0.05). Therefore, melatonin enhanced reproductive parameters in both sexes and its exogenous administration previous to the anestrus season in northwest Mexico could be more effective in rams.
绵羊的繁殖行为取决于年度光周期及其对内源性褪黑素分泌的影响。在这方面，在生理乏情期之前给予外源性褪黑素可能会改变墨西哥西北部绵羊的繁殖性能。进行了两项独立研究，以评估在墨西哥北纬24°和25°的乏情季节之前给毛用绵羊植入褪黑素的这一假设。研究1涉及15只公羊，分为三组接受皮下注射0毫克（n = 5）、18毫克（n = 5）或36毫克（n = 5）褪黑素的处理之一。自植入（第0天）起每月测量研究变量，包括睾酮浓度、阴囊周长、总活力、个体活力和精子浓度。研究2包括50只母羊，分为两组接受皮下注射0毫克（n = 25）或18毫克（n = 25）褪黑素的处理之一。在母羊中，在植入期间（-30天）以及交配期开始（第0天）和结束（第45天）时测量孕酮浓度和处于乏情期的母羊频率，而在45天后通过超声检查确定妊娠率。连续变量使用混合效应模型进行分析，将处理、时间以及处理与时间的交互作用作为固定效应。嵌套在处理中的动物为随机效应。二元变量使用卡方检验进行分析。在雄性中，褪黑素提高了睾酮和精子浓度（P<0.05），而在雌性中，植入褪黑素的母羊妊娠率高出28%（P<0.05）。因此，褪黑素提高了两性的繁殖参数，在墨西哥西北部乏情季节之前给予外源性褪黑素对公羊可能更有效。
