Genetic history of the pedigree Poll Hereford breed in Australia: effect of the importation ban

Registrations of animals in 1975 were used in a study of the importance of Imported and Horned animals and of individual herds and animals, the degree of inbreeding and the generation length. Results were compared with an earlier analysis (1960) of the breed, and considered in relation to the prohibition on the importation of ruminant animals into Australia from 1959 to 1969. The rate of increase in inbreeding (0.44% per generation) and the average generation length (5.3 years) have remained relatively stable throughout the breed history in Australia. While there has been some decrease in the emphasis on Imported animals, the breed maintains a high relationship to animals imported since 1930, and six of the 15 important animals (relationship to breed greater than 2.0%) were imported. It is concluded that the importation prohibition has had little effect on the genetic history of the breed, because of line breeding to bulls imported prior to 1959.