Abstract

In ruminants, the role of melatonin in the control of reproductive seasonality is well reported, but it is still little known about its action on milk traits and on the immune system. The aim of this study was to assess the effect of melatonin on milk yield and composition, somatic cell count (SCC), some cytokine blood concentration and reproductive resumption in sheep. One hundred lactating sheep were allocated to two groups (of 50 sheep each), M (treated with melatonin) and C (controls), and exposed to the rams for 50 d. Time period in days from ram introduction to lambing (TRIL) and litter size were recorded. Every 15 d, from 1 March to 30 April, the individual daily milk yield was registered and milk composition and SCC, were analysed. The levels of Interleukin 2 and 6 (IL-2 and 6) and tumour necrosis factor-alpha (Tnf-α) were evaluated every 15 d. The highest fertility rate (p < .01) and the shortest TRIL (p < .05) was recorded in M group. Milk yield and composition were similar between groups. The somatic cells decreased continuously in the treated ewes (p < .01) and increased continuously in untreated ewes (p < .05). IL-2 and IL-6 increased in M group, although no statistical differences were found between groups. Melatonin administration improved reproductive efficiency, did not affect milk yield and composition and decreased somatic cells. This last effect could help to maintain healthy mammary gland and encourage farmers to reduce the use of drugs against mastitis.

• Highlights

• Melatonin is involved in different physiological processes, such as the control of reproductive seasonality, milk production and the immune response.

• Melatonin administration in Sarda sheep did not modify milk yield and composition, decreased SCC and advanced reproductive resumption in spring.

• Melatonin could be used to strengthen the sheep immune response in order to reduce the use of drugs for both therapeutic and preventive purposes against mastitis.

摘要

在反刍动物中，褪黑激素在控制繁殖季节中的作用已被广泛报道，但对它对乳汁性状和免疫系统的作用仍知之甚少。这项研究的目的是评估褪黑激素对绵羊产奶量和成分，体细胞计数（SCC），某些细胞因子血药浓度和生殖恢复的影响。将一百只哺乳的绵羊分为两组（每组50只绵羊），M（用褪黑激素处理）和C（对照），并暴露于公羊50 d。记录了从种公羊到产羔（TRIL）的天数，以及垫料的大小。从3月1日至4月30日，每15 d记录一次每日的牛奶产量，并分析牛奶成分和SCC。每15天评估一次白细胞介素2和6（IL-2和6）以及肿瘤坏死因子-α（Tnf-α）的水平。最高生育率（ M组记录 到最短的TRIL（p <.01）（p <.05）。两组之间的牛奶产量和组成相似。体细胞在处理过的母羊中连续减少（p  <.01），而在未处理过的母羊中连续增加（p  <.05）。M组IL-2和IL-6升高，但两组之间无统计学差异。褪黑激素的给药改善了生殖效率，不影响牛奶的产量和组成，并减少了体细胞。最后的效果可能有助于维持健康的乳腺，并鼓励农民减少对乳腺炎的药物使用。

• 强调

• 褪黑素参与不同的生理过程，例如控制繁殖季节，产奶量和免疫反应。

• 在Sarda绵羊中服用褪黑激素不会改变牛奶的产量和组成，降低SCC并在春季提高生殖能力。

• 褪黑激素可用于增强绵羊的免疫反应，以减少用于治疗和预防乳腺炎的药物。