ブタの枝肉横切断面脂肪面積割合と枝肉格付け成績との関連 Relationship between Carcass Grade and Proportion of Fat in the Carcass Cross-sectional Area in Fattening Pigs

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豚枝肉の格付け規格が枝肉の脂肪蓄積とどの程度関連しているかを明らかにするため,枝肉格付け規格成績,格付け背脂肪厚,枝肉横切断面の全面積に対する皮下脂肪,筋間脂肪および全脂肪面積割合との遺伝相関(rG)と表型相関(rP)について分析を行った.材料は宮城県米山町農協管内のミヤギノポーク(LWD)生産農家18戸から出荷された326頭の肥育豚である.屠殺翌日の格付け終了後に第4,5胸椎間で枝肉半丸を横切断し,切断面を写真撮影した.画像解析装置を使い写真の切断面面積,皮下脂肪と筋肉間脂肪面積を測定した.さらに,筋肉間脂肪スコア(Seam fat score: 1~5)により筋肉間の脂肪蓄積状況を評点した.出荷時期(I: 8~11月,II; 12~1月,III: 2~3月)の効果は日齢,皮下脂肪面積割合で有意であり,II期の出荷日齢が早く(181.7日),III期が遅かった(213日).また,III期の皮下脂肪面積(26.2%)がI(28.0%),II期(27.8%)より少なかった.性の効果は枝肉重量を除く全ての形質で有意であり,去勢は雌より出荷日齢が早く,上物率も高く,脂肪の蓄積が多い.格付け等級別にこれらの形質を比較すると,格付け「上」の出荷日齢が最も早く,格付け脂肪厚,皮下脂肪面積,全面脂肪面積およびSeam fat scoreも「上」,「中」ほど「並」より脂肪蓄積が多かった.しかし,筋肉間脂肪面積は等級間で差が認められなかった.格付け背脂肪厚は皮下脂肪面積割合(rG: 0.69, rp:0.61),全脂肪面積割合(rG: 0.94, rP: 0.55),Seam fat score (rG: 0.80, rP: 0.38)とそれぞれ比較的高い遺伝相関と表型相関を示し,枝肉の脂肪蓄積状態を反映しているが,筋肉間脂肪面積割合との相関は低く(rG: 0.37, rP: 0.17),筋肉間脂肪の評価には枝肉切断面の情報を直接取り込むことが必要と思われた.

The relation between carcass grade and fat accumulation was examined by estimating genetic and phenotypic correlations among carcass grade, backfat thickness and carcass cross sectional areas of subcutaneous fat, intermuscular fat and total fat. Carcasses of 326 fattening pig were graded and the cross-section cut between the fourth and fifth thoracic vertebra was photographed for each animal for analyses of fat accumulation. Areas of cross-section, subcutaneous fat and intermuscular fat were analyzed by computer image analysis and fat accumulation around the loin was graded for seam fat score (1-5). Slaughtering season (I; Aug.-Nov., II; Dec.-Jan. and III; Feb.-March) significantly affected age at slaughtering and subcutaneous fat area and all the traits examines in this study were affected by sex except for carcass weight. Comparisons of these traits also show that carcasses graded as "upper class" were of pigs which were slaughtered at younger age than those of carcasses of lower classes. Carcasses graded as "upper class" and "middle class" had thicker backfat, larger subcutaneous and total fat areas and a higher seam fat score than those graded as "ordinary class" although there were no significant difference in intermuscular fat area among the classes. Backfat thickness was highly correlated to subcutaneous fat area (rG: 0.69, rP: 0.61, genetic and phenotypic, respectively), total fat area (rG : 0.74, rP: 0.55) and seam fat score (rG: 0.80, rP: 0.38), however, its correlation to intermuscular fat area was found to be poor (rG: 0.37, rP: 0.17). These results suggest that it may be necessary to incorporate fat accumulation in the carcass cross section into the carcass grading system so that carcass intermuscular fat accumulation is evaluated.

収録刊行物

  • 日本畜産學會報 = The Japanese journal of zootechnical science  

    日本畜産學會報 = The Japanese journal of zootechnical science 69(1), 40-45, 1998-01-25 

    Japanese Society of Animal Science

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各種コード

  • NII論文ID(NAID)
    10021727037
  • NII書誌ID(NCID)
    AN00195188
  • 本文言語コード
    JPN
  • 資料種別
    ART
  • ISSN
    1346907X
  • データ提供元
    CJP書誌  J-STAGE 
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