Article

High temperature-humidity index is negatively associated with milk performance and quality in Korean dairy system: Big data analysis

Dongseok Lee1, Daekyum Yoo1, Hyeran Kim2, Jakyeom Seo1,*
Author Information & Copyright
1Department of Animal Science, Life and Industry Convergence Research Institute, Pusan National University, Miryang 50463, Korea.
22Animal Nutrition and Physiology Team, National Institute of Animal Science, RDA, Wanju 55365, Korea, Wanju 55365, Korea.
*Corresponding Author: Jakyeom Seo, Department of Animal Science, Life and Industry Convergence Research Institute, Pusan National University, Miryang 50463, Korea, Republic of. Phone: +82-55-350-5513. E-mail: jseo81@pusan.ac.kr.

© Copyright 2022 Korean Society of Animal Science and Technology. This is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

<strong>Objective:</strong> The aim of this study was to investigate the effects of heat stress on milk traits in South Korea using comprehensive data (dairy production and climate). <strong>Methods:</strong> The dataset for this study comprised 1,498,232 test-day records for milk yield, fat- and protein-corrected milk (FPCM), fat yield, protein yield, milk urea nitrogen (MUN), and somatic cell score (SCS) from 215,276 Holstein cows (primiparous: n=122,087; multiparous: n=93,189) in 2,419 South Korean dairy herds. Data were collected from July 2017 to April 2020 through the Dairy Cattle Improvement Program, and merged with meteorological data from 600 automatic weather stations through the Korea Meteorological Administration. The segmented regression model was used to estimate the effects of the temperature-humidity index (THI) on milk traits and elucidate the break point (BP) of the THI. To acquire the least-square mean of milk traits, the generalized linear model was applied using fixed effects (region, calving year, calving month, parity, days in milk, and THI). <strong>Results:</strong> For all parameters, the BP of THI was observed; in particular, milk production parameters dramatically decreased after a specific BP of THI (<italic>p</italic> &lt; 0.05). In contrast, MUN and SCS drastically increased when THI exceeded BP in all cows (<italic>p</italic> &lt; 0.05) and primiparous cows (<italic>p</italic> &lt; 0.05), respectively. <strong>Conclusion:</strong> Dairy cows in South Korea exhibited negative effects on milk traits (decrease in milk performance, increase in MUN, and SCS) when the THI exceeded 70; therefore, detailed feeding management is required to prevent heat stress in dairy cows.

Keywords: Big data; Heat stress; Milk performance; Temperature-humidity index