Effect of Meteorological Condition and Temperature Humidity Index (THI) on Milk Quality of Holstein Cow

Abstract

Increasing in ambient temperature by global warming is likely to reduce milk yields and negatively affect milk quality in dairy cows. The projected increase in temperature would impact on dairy industry since production costs would increase with reductions in milk production. In Korea, dairy farmers are paid according to the composition of the raw milk components (milk fat concentrations, somatic cell counts and bacteria cell counts). In this study, to assess changes of milk quality caused by ambient temperature and relative humidity in the southern part of Korea (Gyeongbuk province), the temperature-humidity index (THI) was calculated on the base of the equation suggested by Schoen's model. Correlation and regression analysis were performed to determine the effects of the temperature, relative humidity and THI on milk quality. Increased Corresponding author: Jin Wook Kim Tel : +82-55-772-1885 Fax : +82-55-772-1889 E-mail : jinkim@gnu.ac.kr 156 ... Journal of Agriculture & Life Science 47(6) temperature and THI significantly reduced milk fat concentrations from 4.0-4.1% during the winter to 3.6-3.7% during the summer. Occurrence ratio of the 1st grade somatic cell counts (1 SCC) was lower during April to September compared to that of annual average. The THI was negatively correlated to milk fat concentrations (r=-0.8914) and 1 SCC (r=-0.6067) in the overall Gyeongbuk region. There were significant effects of the temperature and THI on milk fat concentrations and 1 SCC. Whereas occurrence ratio of 1A bacteria cell counts (1 BC) had no correlation with the temperature, relative humidity and THI. To make predictions for milk fat concentrations and 1 SCC, the regression model was developed to fit data. Overall, these results suggest that the THI is a useful and easy way to assess the risks of heat stress and is a candidate parameter to predict milk quality.