Selection of sub-populations to preserve with high priorities for the conservation of genetic diversity in the Japanese Black cattle population

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Since liberalization of beef import restriction in 1991, domestic production of high-quality beef has received more emphasis in Japan, and meat quality (especially, ‘beef marbling') of Japanese Black cattle has been remarkably improved by the genetic evaluation system of breeding animals. However, due to the intensive use of a few sires with high genetic merit of beef marbling, drastic decline of genetic diversity is an increasing problem of this breed. In the present study, the sub-populations (i.e., local strains) to preserve with high priorities were assessed to conserve the genetic diversity in the Japanese Black population. Two different methods, i.e., the Weitzman's method and the core set method, were applied to the pedigree and body measurement data obtained from 25 major local populations. The results from the two methods strongly suggest that the five traditional populations in Chugoku district (Hyogo, Tottori, Okayama, Hiroshima and Shimane) and the three regional populations in Kyusyu district (Oita, Miyazaki and Kagoshima) should be preserved with high priorities. It has been proposed that rotational mating system with several sire lines could be efficient for the conservation of genetic diversity in the Japanese Black population. The result obtained from this study is expected to give basic information for the application of the rotational mating.