Characteristics in the Pedigree Structure of Cow Populations in the Okayama Strain of Japanese Black Cattle

Abstract

The pedigree structure of cattle, as represented by the genetic contributions of several ancestors, may be useful, in the breeding of ability and carcass characteristics as already reported by the author. Therefore, the pedigree structure of two breeding cow populations in the Okayama strain of Japanese Black cattle was investigated. The first population was composed of 1, 313 cows that had been active in 1972-1974, and the second population was composed of 972 cows that had been active in 1980. All the ancestors of each cow were checked with the aid of a herdbook and written into a computer file. Male and female ancestors that contributed genetically to any population by at leas 3.5%, and male ancestors that contributed to any regionally divided second population by at least 4%, were picked out. Male ancestors that contributed to any population by at least 0.5%, but which did not belong to the Okayama strain, were also picked out. It was clarified that an ancestor HANA-YAMA, 13. who was born in 1920, had contributed genetically as high as 18% to both populations, and to whom every bull and cow belonging to the Okayama strain may be traced. Because of this, the strain seems to be a linebred population related to HANA-YAMA, 13. Genetic contributions of some ancestors who were closer-related ascendants to MATSU-DA, 11. and NAKA-YAMA, 2. were higher in the second population than in the first population, because of the very frequent insemination of these two bulls' semen in those days. Almost every ancestor contributed evenly to regionally divided populations, though a few ancestors contributed highly to only one or two regional populations. During the investigation, it was found out that some old ancestors belonging to the Hyogo strain had contributed highly to both populations. However, the present cattle which belong to the Okayama strain might merely be related to others of their native strain, due to common ancestry, since a generation gap from the ancestors would dilute relations between them. The effects of other ancestors that did not belong to the Okayama strain were few and limited only to part of the total population because their "effect" was passed on only through descendant bulls in relatively new generations. Therefore, the Okayama strain seems to be almost an independent population from the other strains. There were some female ancestors which contributed genetically much to the populations. However their effects would be negligible, because they affected only through their sons or grandsons which contributed highly to the same population.