The breed structure and genetic analysis of the pedigree cattle breeds in Australia

Abstract

Barker (1957) discussed the influence of imported animals in the development of the pedigree Jersey breed in Australia. Random four-line pedigrees were drawn back either to a foundation animal (one present in Australia in 1900) or to an animal imported since 1900. The proportion of lines tracing back to each of these (equivalent to the genetic contribution) was determined for each of five samples of pedigrees. However, in this calculation, all four lines were used. This was incorrect as the pedigrees were drawn out by the method of Robertson and Mason (1954), in which one line was drawn back at random on each side of the pedigree and at each generation in the line both sire and dam were written down, though the line was only carried back through one of them. Therefore only those two lines which have actually been followed through should be used in an analysis of influence of importations. The analysis has been repeated on the same pedigrees as previously, and the correct results are shown in Figure 1. Imported animals have been more important in this breed's development than the original analysis showed. The influence of foundation stock declined rapidly until the 1928 sample, and has been declining at a slower rate since then. In the 1950 sample, the genetic contribution of foundation stock was only 14.76 per cent., while the following were the genetic contributions of animals imported since the date stated : From importations since 1940 2.50 per cent. From importations since 1930 29.25 per cent. From importations since 1920 44.76 per cent. From importations since 1910 68.50 per cent. From importations since 1900 85.25 per cent. Animals imported between 1900 and 1919 still have a large influence on the breed (a 40 per cent. genetic contribution to the 1950 sample), but their influence is declining. Animals imported since 1920 are still showing an increasing genetic contribution.