ブタの閉鎖育種群におけるモンテカルロシミュレーションを用いた非線形利益関数に対処するための選抜指数の比較 A Comparison of Alternative Selection Indices for Non-Linear Profit Function in Closed Breeding Herds of Swine Using Monte Carlo Simulation

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非線形の利益関数に対応する選抜指数を,ブタの系統造成を想定したコンピュータシミュレーションによって比較した.比較した選抜指数は,(1) 基礎世代の集団平均値に対応した線形選抜指数,(2) 段階的に補正した線形選抜指数,(3) 次世代の利益を最大にする線形選抜指数,(4) 多世代選抜後の利益を最大にする選抜指数,(5) 選抜期間の累積利益を最大にする選抜指数,(6) 2次の選抜指数および(7)希望改良量に基づく選抜指数である.発育速度(線形)と背脂肪の厚さ(2次)を選抜形質とする2次の総合育種価を想定し,遺伝的および経済的選抜反応を計算した.その結果,選抜指数を一定に保った線形選抜指数((1))と二次の選抜指数は((5))は,利益関数の非線形性の程度が大きい場合,利益損失が大きくなった.いっぽう,改良目標に基づく選抜指数は,背脂肪の厚さを最適値に導くことができたが,実際の利益関数や,利益関数の非線形性の程度がそれより小さい条件では,大きな利益損失を招いた.比較した選抜指数の相対的効率は,利益関数の非線形性の程度や利益の評価世代数に従属した.以上の結果は,経済的な視点からの育種計画の重要性を示唆している.

Seven different selection indices for non-linear profit function were compared using stochastic simulation in closed breeding herds of swine. The indices compared were a linear index constant over generations, (2): a linear index adjusted stepwise, (3): an optimum linear index for maximization of profit in the next generation, (4): an optimum linear index for maximization of profit at the last generation, (5): an optimum linear index for maximization of accumulated profit over the planning generations, (6): a quadratic index and (7): a desired gain index. For all the indices, the simulated population consisted of 10 boars and 50 sows, each sow having 1 male and 2 female progeny as candidates of breeding animals to reproduce the next generation. Genetic and economic responses over multiple generations were simulated considering non-linear profit function with growth rate and back fat thickness combined. The alternative economic values for the linear and quadratic terms in the profit function were assumed and these changed to reflect 3 different situations; the function A based on practical situation, the function B with a one-tenth economic values for the linear and quadratic terms of back fat thickness and the function C with ten hold economic values for them. When the degree of non -linearity of profit function was high, the linear index constant over generation ((1)) and the quadratic index ((6)) yielded considerably lower economic response. Relative efficiencies of the linear index adjusted stepwise ((2)) and the optimum linear index for maximization of profit in the next generation ((3)) depended on the degree of non-linearity of the profit function and choice of generation number. The desired gain index ((7)) allowed stabilization of back fat thickness at optimum level, but led to a large economic loss in the practical function A, and it led to a larger economic loss in the function B whose degree of non-linearity of profit function was lower than that of the practical function A. The optimum index for maximization of accumulated profit over an assigned generation number of selection ((6)) provides favorable results for all the situations. However, the expected genetic responses were not always realized for the optimum indices((3), (4) and (5)), indicating that stochastic simulation implicitly caused the reduction of additive genetic (co) variance through selection processes. These results indicate the importance of breeding programmes from the economic point of view.

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(3), 281-292, 1998-03-25 

    Japanese Society of Animal Science

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各種コード

  • NII論文ID(NAID)
    10021726670
  • 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  CJP引用  J-STAGE 
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