Jo Janghoon, Lee Honggu
Department of Animal Science, Purdue University, West Lafayette, IN 47907, USA.
Department of Animal Science and Technology, Sanghuh College of Life Sciences, Konkuk University, Seoul 05029, Republic of Korea.
Animals (Basel). 2025 May 22;15(11):1503. doi: 10.3390/ani15111503.
High relative humidity can increase the risk of heat stress in dairy cows, but its effects in humid continental climates are not well defined. This study evaluated how humidity levels influence dry matter intake, milk yield and composition, physiological response, blood hematology, metabolites, hormones, and heat shock protein gene expression in hair follicles. Sixteen multiparous early-lactating Holstein cows were assigned to four groups in a 2 × 2 factorial design with two temperatures (25 °C and 31 °C) and two humidity levels (50% (LRH) and 80% (HRH)). All cows were housed in climate-controlled chambers. Compared with LRH, HRH at both temperatures reduced dry matter intake, milk yield, milk fat, energy-corrected milk, and 3.5% fat-corrected milk. HRH also increased rectal temperature, heart rate, glucose, blood urea nitrogen, cortisol, and heat shock protein 90 in hair follicles. These results show that HRH, even at moderate temperature, affects dairy cow performance and alters physiological and metabolic functions. These findings emphasize the importance of precise management strategies to reduce the effects of humid heat stress on dairy performance. A comprehensive understanding of these responses is crucial for developing effective, sustainable solutions to ensure the viability of the dairy industry under increasing temperature and humidity.
高相对湿度会增加奶牛热应激的风险，但其在湿润大陆性气候中的影响尚不明确。本研究评估了湿度水平如何影响干物质摄入量、产奶量和乳成分、生理反应、血液血液学、代谢物、激素以及毛囊中热休克蛋白基因的表达。16头经产初产荷斯坦奶牛按照2×2析因设计被分为四组，设置两个温度（25℃和31℃）和两个湿度水平（50%（低湿度，LRH）和80%（高湿度，HRH））。所有奶牛均饲养在气候控制室内。与低湿度相比，两个温度下的高湿度均降低了干物质摄入量、产奶量、乳脂肪、能量校正乳和3.5%乳脂校正乳。高湿度还提高了直肠温度、心率、葡萄糖、血尿素氮、皮质醇以及毛囊中的热休克蛋白90。这些结果表明，即使在中等温度下，高湿度也会影响奶牛的生产性能，并改变生理和代谢功能。这些发现强调了精确管理策略对于降低湿热应激对奶牛生产性能影响的重要性。全面了解这些反应对于制定有效、可持续的解决方案以确保乳制品行业在温度和湿度不断升高的情况下的生存能力至关重要。
