A genetic analysis of the pedigree Landrace pig breed in Australia

Abstract

The population dynamics, breed structure and degree of inbreeding of the pedigree Landrace pig population in Australia was investigated. The Landrace registrations increased rapidly after its introduction into Australia in 1959. This period of expansion was followed by a decline in registrations from 1963 to 1967 and then a more gradual increase in both registrations and average herd size from 1968. The Landrace is now the second most important pig breed in Australia. The initial rapid expansion from a small number of foundation stock resulted in a high level of inbreeding (0.69 per cent per generation). The level of migration of breeding stock between states and the tendency for herds within states to exchange breeding stock frequently would have limited the degree of genetic differentiation to a low amount. The Landrace breed has developed a hierarchial structure which is arranged roughly into two strata with the ten major herds contributing 69.6 per cent of the genes to the breed in 1973. Those particular herds and individual animals that have made a large contribution to the breed were identified.