Impact of Relative Humidity on Heat Stress Responses in Early-Lactation Holstein Cows

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, horm...

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Main Authors: Janghoon Jo, Honggu Lee
Format: Article
Language:English
Published: MDPI AG 2025-05-01
Series:Animals
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Online Access:https://www.mdpi.com/2076-2615/15/11/1503
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author Janghoon Jo
Honggu Lee
author_facet Janghoon Jo
Honggu Lee
author_sort Janghoon Jo
collection DOAJ
description 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.
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spelling doaj-art-ff8500a76c2a4aadb327c9ec45fb9dda2025-08-20T02:23:01ZengMDPI AGAnimals2076-26152025-05-011511150310.3390/ani15111503Impact of Relative Humidity on Heat Stress Responses in Early-Lactation Holstein CowsJanghoon Jo0Honggu Lee1Department of Animal Science, Purdue University, West Lafayette, IN 47907, USADepartment of Animal Science and Technology, Sanghuh College of Life Sciences, Konkuk University, Seoul 05029, Republic of KoreaHigh 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.https://www.mdpi.com/2076-2615/15/11/1503dairy cowheat stressmilk energyrelative humidity
spellingShingle Janghoon Jo
Honggu Lee
Impact of Relative Humidity on Heat Stress Responses in Early-Lactation Holstein Cows
Animals
dairy cow
heat stress
milk energy
relative humidity
title Impact of Relative Humidity on Heat Stress Responses in Early-Lactation Holstein Cows
title_full Impact of Relative Humidity on Heat Stress Responses in Early-Lactation Holstein Cows
title_fullStr Impact of Relative Humidity on Heat Stress Responses in Early-Lactation Holstein Cows
title_full_unstemmed Impact of Relative Humidity on Heat Stress Responses in Early-Lactation Holstein Cows
title_short Impact of Relative Humidity on Heat Stress Responses in Early-Lactation Holstein Cows
title_sort impact of relative humidity on heat stress responses in early lactation holstein cows
topic dairy cow
heat stress
milk energy
relative humidity
url https://www.mdpi.com/2076-2615/15/11/1503
work_keys_str_mv AT janghoonjo impactofrelativehumidityonheatstressresponsesinearlylactationholsteincows
AT honggulee impactofrelativehumidityonheatstressresponsesinearlylactationholsteincows