わが国ホルスタイン種の遺伝学的分析

Abstract

The trends in the values of coefficients of average inbreeding and inter-se relationship in the Holstein cattle in Japan as well as in the degree of subdivision of the population indicated by the relative values of the both coefficients were analyzed in the previous paper. In that analysis, the average relationship coefficients among male parents and among female parents and between male and female parents of the sample heifers, besides the average inbreeding coefficient and inter-se relationship coefficient of the sample heifers themselves, were estimated so that these estimates were used to examine the nature and the influence of different factors affecting the above trends. The first purpose of the present paper is to give a note on the theoretical background for the technique of analysis used there. It was shown in here that any change in value from generation to generation of the coefficients of inter-se relationsoip and average inbreeding of the sample heifers (_??_R and _??_F) and also _??_(F-R/2) could be expressed, in an approximate manner, in terms of separate contributions of the change in each of average male-male, female female, and male-female relationship coefficients brought about by selection and migration in the parent and grand-parent generations and also the contributions from the non-randomness of mating in the both generations, using the values of the above three kinds of average relationship coefficients among the parents of the sample heifers. Then, in the second place, as an example of application of this technique, the contributions of the different factors to some actual values of _??_R, _??_F, and _??_(F-R/2) which appeared in the previous paper were calculated and brief comments were given on some important points suggested by the tabulated results.