Abstract
Data on 5,314 Japanese Black cattle fattened in Yamagata prefecture were collected to estimate genetic parameters for melting point of fat (MP) and fatty acid composition, which have a relation to the taste and flavor of beef. Fat and meat (M. trapezius) samples were taken from the carcasses of these fattened cattle for determination of MP and fatty acid composition of total lipid of intra-muscular adipose tissue. Genetic parameters were estimated using uni- and bivariate animal models containing fixed effects of sex, slaughter year, slaughter month, farm and regressions for slaughter age. In addition, the pedigree information for 17,332 animals was used. Breeding values were estimated by same animal model to investigate the effect of the sire groups against beef marbling score (BMS), and against MP and major monounsaturated fatty acids (sum of 16 : 1 and 18 : 1) per major saturated fatty acids (sum of 16 : 0 and 18 : 0) (RMUS). Cluster analysis was used for classification of the sires. The genetic distance for cluster analysis was defined as one minus relationship coefficient. The sires were classified into 9 groups when the dendrogram was truncated at 0.25 of the average relationship coefficient. The means of breeding values of these traits within the sire groups were compared using multiple comparison test. Heritabilities for MP, each fatty acid and RMUS were middle to high (0.31-0.73). Genetic correlations between BMS and MP or each fatty acid or RMUS were weak (−0.09 to 0.15) except 18 : 2 (−0.40). Also, genetic correlations between carcass traits (carcass weight, rib eye area, rib thickness, subcutaneous fat thickness) and MP or RMUS were weak (−0.11 to 0.14). Genetic correlations between MP and each saturated fatty acid were positive, while those between MP and RMUS or each unsaturated fatty acid were negative. Differences among the sire groups in BMS, MP and RMUS were all significant (P < 0.05) as the result of the multiple comparison test. The order of the sire groups in MP and RMUS had similar trend. These suggest that MP and RMUS have the characteristic by the sire line. The relations between BMS and MP or RMUS were independent not only in genetic correlations but also in breeding values within sire groups. These results suggest that it is possible to improve simultaneously both the quantity and quality of beef fat.
