1970 Volume 41 Issue 5 Pages 242-249
The coefficients of inbreeding and relationship in dairy cattle populations of the important breeders (Machimura farm, Koiwai farm, and Utsunomiya farm as private breeders, and national livestock breeding stations and Shizuoka prefectural livestock station as public breeders) and change of them between 1950 and 1960 have been investigated. Analysis was made by 2-line pedigree method proposed by Wright and McPhee, tracing ancestors back until imported animals through herdbooks.
Results obtained are as follows:
1. Both private and public breeders have high average coefficients of relationship within herds. Whereas actual coefficients of inbreeding in private breeders are rather low owing to strong inbreeding avoidance, the populations in the livestock breeding stations of national government have actual inbreeding coefficients showing almost random mating as to pedigree.
2. Coefficients of relationship between breeders seem to diminish from 1950 to 1960. This indicates that the breeders tend to have performed dairy cattle breeding independently from each other. This tendency is particularly evident in the Utsunomiya farm and Shizuoka prefectural livestock station.
3. It has already been pointed out that the function of the important breeders is multiplying imported animals rather than improving genetically their own animals. The present study has also shown that the majority of important animals having much genetic contribution to the dairy cattle population of the important breeders are the animals imported from U. S. A. or Canada, or the offspring of imported sires, which have functioned as cores in dairy cattle breeding in Japan.
