Breeding for Improvement of Feed Efficiency in Egg Layers:I. Estimation of Genetic Parameters
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概要
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The present study was undertaken to study the efficiency of selection for improvement of feed conversion in egg-type layers. The first experiment was concerned with the estimation of genetic and phenotypic parameters of the trait and other economically important traits in two strains of WL purebreds, which have been maintained in the station for many years with the average flock size of approximately 500 pullets every generation, while the second experiment involved the result obtained in the progeny originated from one generation of selection, based on dam's performance in feed efficiency.Heritabilities and genetic correlations of various traits were estimated by analyses of variance and covariance and are presented in Tables 3, 4, 5 and 6. The estimated heritability of feed conversion seemed to be different between two strains but they are still of seizable magnitude so that individual selection or combination selection of individual and family merits should be effective to improve the trait. The realized heritability of feed conversion obtained by one generation of selection was .34, compared with the estimated value of .27.Multiple regression analyses of feed conversion with four independent variables, i.e., egg number (X2), egg weight (X4), body weight (X5), and body weight gain (X6) were also made. Among these four variables the relative contribution of egg number was approximately 87-98%, followed by body weight with additional 2-12%. The accuracy of the multiple regression (R) was roughly 90%. The equation best fitted to the data wasY=6.35-.014X2-.038X4+.007X5+.003X6.The relative efficiency of different selection criteria to improve feed conversion was compared by use of selection indices which were consisted of (I1) egg number+body weight, (I2) egg number+egg weight, and (I3) egg number+body weight+egg weight, relative to the direct selection for feed conversion. The efficiencies of I1 and I2 were about 80% while that of I3 was reduced to 72%.
- 日本家禽学会の論文
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