Correlation between ambient temperature and body weight of Hanwoo calves (Korean native cattle).

Objective: Changes in ambient temperature negatively impact livestock productivity, with thermal stress causing physiological changes that affect beef quality and quantity. The calf stage is critical, as thermal stress during this period can have lasting effects on productivity. This study examined the impact of weather conditions on calf growth, carcass traits, and their interrelationships in Korean native Hanwoo steers.

Methods: Data from 8,727 male Hanwoo calves were selected from 41,107 data points. Meteorological data were collected from 60 cities in Korea between 2016 and 2019. The input data included calf growth, carcass traits, and weather conditions at birth for each calf.

Results: Temperature, relative humidity (RH), and temperature-humidity index (THI) increased from winter to summer and decreased from summer to winter. Summer-born calves had significantly lower birth body weight (BBW) than those born in winter. The average daily gain (ADG) of the calves was highest in winter and lowest in spring and fall. A high carcass weight (CW) was observed in steers born in summer and winter. BBW and ADG were negatively correlated with ambient temperature, RH, and THI. Positive relationships were observed between BBW, ADG, and CW. Only CW was positively correlated with the meat quality grade of steers. Thus, temperature negatively affects the BBW of male Hanwoo calves, in turn affecting the daily gain, CW, and meat quality grade.

Conclusion: This study demonstrates that temperature, RH, and THI adversely affect the BBW of male Hanwoo calves, leading to reduced ADG and influencing CW and meat quality grade. Negative correlations were observed between BBW, ADG, and environmental factors, while CW showed positive correlations with BBW, ADG, and meat quality grade. These findings highlight the critical impact of climatic conditions on the growth performance and productivity of Hanwoo cattle.