This research paper addresses the hypothesis that intensive cooling management during the summer improves the secretion of metabolic hormones in dairy cows. To test this hypothesis, we characterized the effect of different cooling managements on the different ghrelin isoforms and leptin secretion of 20 Israeli-Holstein dairy cows during 5 weeks during heat stress. The cows were divided into two groups: one was exposed to 5 cooling sessions per day (5 CS) and the other to 8 cooling sessions per day (8 CS). Blood was collected and leptin and ghrelin isoforms level were radioimmunoassayed. Analysis of the interaction between coolings and the week of the experiment showed that the 8 CS group consumed more food and produced more milk, although neither difference was statistically significant. In addition, the 8 CS group exhibited higher blood levels of acyl-ghrelin and leptin as compared to the 5 CS group. Conversely, the blood levels of total ghrelin were lower in the cows exposed to 8 CS as compared to cows from the 5 CS treatment. Furthermore, a significant correlation was found only between total ghrelin levels and the weeks, but not with other parameters examined. We further compared digestibility as well as stress parameters between the groups. We found that the 8 CS group cows ruminated and lay down more hours during a day and simultaneously had better activity time. No significant difference was detected between groups in milk yield and digestibility parameters. Our results suggest that intensive cooling management during the hot season influences the levels of metabolic hormones in the circulation and helps to mitigate the detrimental effect of heat stress on dairy cow welfare and production.

中文翻译：

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降温管理对热应激期间奶牛干物质摄入量、代谢激素水平和福利参数的影响

这篇研究论文提出了这样一个假设，即夏季强化降温管理可以改善奶牛代谢激素的分泌。为了验证这一假设，我们描述了不同冷却管理对 20 头以色列-荷斯坦奶牛在热应激期间 5 周内不同生长素释放肽异构体和瘦素分泌的影响。奶牛分为两组：一组每天进行 5 次降温（5 CS），另一组每天进行 8 次降温（8 CS）。收集血液并放射免疫测定瘦素和生长素释放肽同种型水平。对冷却和实验周之间的相互作用的分析表明，8 CS 组消耗更多的食物并产生更多的牛奶，尽管两者的差异都没有统计学意义。此外，与 5 CS 组相比，8 CS 组表现出更高的血液中酰基生长素释放肽和瘦素水平。相反，与 5 CS 处理的奶牛相比，暴露于 8 CS 的奶牛的总生长素释放肽的血液水平较低。此外，仅在总生长素释放肽水平和周数之间发现了显着相关性，但与检查的其他参数无关。我们进一步比较了各组之间的消化率和压力参数。我们发现，8 头 CS 组奶牛在一天中反刍和躺下的时间更长，同时活动时间也更长。产奶量和消化率参数组间未检测到显着差异。