초록
Studies on the genetic and environmental effects on M.longissimus thoracis area (MLTA), fat thickness (SFT), rib thickness (RT) and marbling score (MS) were conducted on 21,086 steers and 7,151 heifers of Japanese Brown breed. All carcass traits were affected significantly (p<0.01) by sire, sex and initial year effects. Both of the MLTA and MS of steers were greater than heifers. Their differences were $1.4cm^2$ for MLTA and 0.05 for MS, respectively. Cattle started for fattening in winter tend to have higher of MLTA and MS and thicker of SFT and RT than those in other seasons. MLTA increase from 1987 to 1989 (about $1.9cm^2$) and decrease until 1994 (about $2.4cm^2$) and then increase again up to 1995 (about $1.5cm^2$). MS were nearly equal from 1987 to 1991 (about "1") and then decrease up to 1995 (about "1"). Heritability estimates of MLTA, RT, SFT and MS were ranged from 0.22 to 0.36. Genetic and phenotypic correlations of MLTA, RT, SFT and MS were positive and ranged from 0.05 to 0.62 and from 0.03 to 0.32 except SFT with MLTA was negative (-0.14 and -0.03).