A Cross-regional Comparison of Growth in Japanese Black Calves

Abstract

This study, conducted over a four-year period (January 2013 to December 2016) in Northern and Southern Japan, aimed to compare environmental factors affecting the growth of calves born at the same time of the year in these two geographical regions. Data were collected from calf markets to calculate the daily gain (DG) of each calf based on body weight and age (in days). There were no significant differences in DG between the two regions. In both regions, DG of calves born in winter and spring tended to be lower than that of calves born in summer and fall. In Northern Japan, the mean DG showed a significantly negative correlation with the temperature–humidity index (THI) during the three months after birth. However, there was no significant correlation with THI during the month of birth. By contrast, in Southern Japan, the mean DG showed a significantly positive correlation with THI during the month of birth. However, there was no significant correlation with THI during the three months after birth. These observations suggest potential drawbacks of the current barn structures adapted to the environment of each region and indicate the importance of appropriate rearing management, considering the seasonal changes of each region.