Derivation of economic weights for carcass traits in Japanese Black cattle from field records
1998
Hirooka, Hiroyuki | Sasaki, Yoshiyuki
SUMMARY: Economic weights for carcass traits of 5333 Japanese Black steers each month were derived from April 1988 to December 1990 by multiple regression analysis. The carcass traits considered were marbling score (BMS No.), rib-eye area, rib thickness and subcutaneous fat thickness. Two economic variables were adopted as aggregate genotype (i.e. breeding objectives): carcass unit price (yen/kg carcass) and carcass sale price (yen/head). The economic weight for marbling score increased from 1988 to 1990, indicating that the relative economic importance of marbling score increased during the 3 years in Japan. Correlations among two indices calculated from different economic weights (i.e. a maximum value versus a minimum value of each trait) were very high, whichever economic variable was adopted. The results indicated that the effect of variation in the economic weights on efficiency of selection might be quite small under field conditions. Furthermore, differences between the standard selection index with economic weights and a desired gains selection index were calculated using genetic parameters from the literature and the economic weights derived in this study. It is concluded that the use of the standard selection index with economic weights may be more practical for the improvement of carcass traits of the Japanese Black, because the economic weights can be derived from field data, breeding objectives of farmers may differ from those of breeders and there is little effect of variation of economic weights on selection efficiency in Japan.
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