Abstract
The purpose of this study was to investigate the genetic relationships between calf market weight with carcass traits and image analysis traits of Japanese Black steers using calf and carcass markets in Hokkaido. Eight hundred five Japanese Black steers with calf market records, grading records and digital images of the carcass cross section were used. We analyzed calf market weight, carcass weight, ribeye area, rib thickness, subcutaneous fat thickness, yield estimate and BMS number as grading records, and fat area ratio, overall coarseness of marbling particles, and coarseness of maximum marbling particles in ribeye as image analysis traits. The daily gain was classified into 6 subclasses (0.8, 0.9, 1.0, 1.1, 1.2 and 1.3 kg/day) by dividing the calf market weight by calf market age in order to examine the influence of overweight. Direct and maternal heritability estimates of calf market weight were 0.15 ± 0.07 and 0.12 ± 0.07, respectively. The direct genetic correlations of calf market weight with ribeye area, subcutaneous fat thickness, yield estimate, and BMS number were negative (−0.76 to −0.08). The direct genetic correlations of calf market weight with all the image analysis traits were also negative (−0.70 to −0.34). Around 1.0 kg/day of the daily gain may be desirable for marbling at calf market. The genetic relationship between calf market weight and the variant traits should be considered when improving calf market weight.
