High incidences of pre-weaning mortality continue to limit global sheep production, constituting a major economic and welfare concern. Despite significant advances in genetics, nutrition, and management, the proportion of lamb deaths has remained stable at 15–20% over the past four decades. There is mounting evidence that melatonin can improve outcomes in compromised ovine pregnancies via enhanced uterine bloodflow and neonatal neuroprotection. This review provides an overview of the major risk factors and underlying mechanisms involved in perinatal lamb mortality and discusses the potential of melatonin treatment as a remedial strategy. Supplementing pregnant ewes with melatonin enhances uterine bloodflow and fetal oxygenation, and potentially birthweight and neonatal thermogenic capacity. Melatonin freely crosses the ovine placenta and blood-brain barrier and provides neuroprotection to the fetal lamb during periods of chronic and acute hypoxia throughout gestation, with improved behavioural outcomes in hypoxic neonates. The current literature provides strong evidence that maternal melatonin treatment improves outcomes for lambs which experience compromised in utero development or prolonged parturition, though to date this has not been investigated in livestock production systems. As such there is a clear basis for continued research into the effects of maternal melatonin supplementation during gestation on pre-weaning survival under extensive production conditions.

中文翻译：

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新生儿羔羊死亡率：主要危险因素和褪黑激素的潜在改善作用

断奶前死亡的高发生率继续限制全球绵羊的生产，构成了重大的经济和福利问题。尽管遗传学，营养学和管理学有了重大进展，但在过去的40年中，羔羊死亡的比例一直稳定在15％至20％之间。越来越多的证据表明，褪黑激素可以通过增强子宫血流和新生儿神经保护作用来改善绵羊妊娠结局。这篇综述概述了围产期羔羊死亡率的主要危险因素和潜在机制，并讨论了褪黑激素作为治疗策略的潜力。用褪黑激素补充孕妇的母羊可增强子宫血流量和胎儿的氧合作用，并可能增加出生体重和新生儿产热能力。褪黑激素在整个妊娠期间的慢性和急性缺氧期间可自由穿过羊胎盘和血脑屏障，并为胎儿羔羊提供神经保护，改善缺氧新生儿的行为结果。目前的文献提供了有力的证据表明，产妇褪黑激素治疗可改善子宫发育或长期分娩受到影响的羔羊的结局，尽管迄今为止尚未在畜牧生产系统中进行研究。因此，有一个继续研究母体褪黑激素在妊娠期间在广泛生产条件下对断奶前存活的影响的明确基础。改善缺氧新生儿的行为结果。目前的文献提供了有力的证据表明，产妇褪黑激素治疗可改善子宫发育或长期分娩受到影响的羔羊的结局，尽管迄今为止尚未在畜牧生产系统中进行研究。因此，有一个继续研究母体褪黑激素在妊娠期间在广泛生产条件下对断奶前存活的影响的明确基础。改善缺氧新生儿的行为结果。目前的文献提供了有力的证据表明，产妇褪黑激素治疗可改善子宫发育或长期分娩受到影响的羔羊的结局，尽管迄今为止尚未在畜牧生产系统中进行研究。因此，有一个继续研究母体褪黑激素在妊娠期间在广泛生产条件下对断奶前存活的影响的明确基础。