Reduced reproductive performance of lactating cows during the summer is associated mainly with intensive genetic selection for high milk production, which places a great load on the thermoregulatory mechanism. In the last decades, a big effort has been made to explore the mechanism by which heat stress compromises fertility. The data gained so far revealed that the effect of thermal stress on the female reproductive tract is multifactorial in nature. Based on this understanding, new strategies to mitigate the effect of heat stress have been developed. The review summarizes some of the physiological responses of the cow to elevated temperature and discusses its limitations to maintain normothermia. The review emphasizes that cooling is the predominant strategy used today to alleviate the effects of heat stress. Findings from the Israel dairy herd indicate that efficient cooling management can improve milk production during the summer to a similar level of the winter, expressed by summer to winter ratio of 0.98. However, cooling as a singular approach cannot eliminate the decline in reproduction. Nonetheless, an efficient cooling system is a prerequisite for any other strategy. The review suggests additional hormonal treatments to improve reproductive performance during the summer. Given the complexity of heat stress effects on reproduction, comprehensive reproductive management during the summer is suggested, that is combining two or more strategies in a programme, might be more beneficial.

中文翻译：

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降温是缓解热应激对奶牛影响的主要策略。

夏季泌乳奶牛繁殖性能下降主要与高产奶的密集遗传选择有关，这对体温调节机制造成了很大的负担。在过去的几十年里，人们付出了巨大的努力来探索热应激损害生育能力的机制。迄今为止获得的数据表明，热应激对女性生殖道的影响本质上是多因素的。基于这种理解，已经开发出减轻热应激影响的新策略。这篇综述总结了奶牛对高温的一些生理反应，并讨论了它在维持正常体温方面的局限性。该评论强调，冷却是当今减轻热应激影响的主要策略。来自以色列奶牛群的研究结果表明，有效的冷却管理可以将夏季的牛奶产量提高到与冬季相似的水平，夏冬比为 0.98。然而，冷却作为一种单一的方法并不能消除繁殖的下降。尽管如此，高效的冷却系统是任何其他策略的先决条件。该评论建议在夏季进行额外的激素治疗以改善生殖性能。鉴于热应激对生殖影响的复杂性，建议在夏季进行全面的生殖管理，即在一个计划中结合两种或多种策略，可能更有益。然而，冷却作为一种单一的方法并不能消除繁殖的下降。尽管如此，高效的冷却系统是任何其他策略的先决条件。该评论建议在夏季进行额外的激素治疗以改善生殖性能。鉴于热应激对生殖影响的复杂性，建议在夏季进行全面的生殖管理，即在一个计划中结合两种或多种策略，可能更有益。然而，冷却作为一种单一的方法并不能消除繁殖的下降。尽管如此，高效的冷却系统是任何其他策略的先决条件。该评论建议在夏季进行额外的激素治疗以改善生殖性能。鉴于热应激对生殖影响的复杂性，建议在夏季进行全面的生殖管理，即在一个计划中结合两种或多种策略，可能更有益。