Population Structure of Multipliers' Prefectures and Amount of Relationship between Breeders' Prefectures and Multipliers' Prefectures in Japanese Black Cattle

Abstract

The prefectural populations of Japanese Black Cattle are classified into two types, i.e., Breeders' Prefecture and Multipliers' Prefecture. Multipliers' Prefectures are introducing breeding stocks from Breeders' Prefectures and multiplying their genes. In this paper, the population structures of Multipliers' Prefectures were analyzed and average coefficients of relationship between Breeders' Prefectures and Multipliers' Prefectures were estimated. Twenty Multipliers' Prefectures, in each of which more than 500 heifers were registered in 1980, were used. The pedigree data were obtained from randomly selected 200 heifers registered in each prefecture in 1980. The results are summarized as follows: 1. The diversity of sires in Multipliers' Prefectures tended to be larger than that in the Breeders' Prefectures. 2. In most of the Multipliers' Prefectures, 90-100% of heifers were born from sires produced in other prefectures. Bulls produced in Ohita, Miyazaki and Kagoshima were used as sires in other Multipliers' Prefectures. These results indicate that a functional stratification, in which these three prefectures are located at the upper stratum, exists in Multipliers' Prefectures. 3. In most of the Multipliers' Prefectures, FIT and FST tended to be higher than those in the Breeders' Prefectures. 4. In the Multipliers' Prefectures which are at the lower stratum in the functional stratification, FIS and the index of subdivision indicated that subdivided structure existed within prefectural populations. On the other hand, in the three Multipliers' Prefectures located at the upper stratum, FIS and the index of subdivision indicated that random mating and/or line cross were practiced. 5. One sire produced in Hyogo, one of the Breeders' Prefectures, had a large contribution to the average coefficients of relationship between the Breeders' Prefectures and the Multipliers' Prefectures at the lower stratum in the functional stratification. On the other hand, such tendency was not observed in the three Multipliers' Prefectures; Ohita, Miyazaki and Kagoshima. These three prefectures and Fukushima were considerably highly related with Tottori. These results suggest that the prefectural populations can be classified into a few genetic groups on the basis of the average coefficients of relationship.