PEDIGREE INDEXING OF HOLSTEIN BULLS USED IN ARTIFICIAL INSEMINATION

Bulls entering artificial insemination in Canada from 1957 to 1980 were indexed, using various combinations of ancestors, for milk, fat percentage, and 10 conformation traits. Correlations between the indexes and actual progeny test proofs were used to compare indexes with different combinations of ancestors. When sire, dam, and both maternal grandparents were used in the index, the correlations were 0.52 for milk yield, 0.64 for fat percentage, and 0.41 for final class. When only the sire was included, the corresponding correlations were 0.57, 0.48, and 0.39. The regression coefficients for predicting a bull’s proof from only the sire’s proof and dam’s estimated transmitting ability were 0.457 and 0.308, respectively, for milk yields, and 0.526 and 0.478 for fat percentage. For the type classification traits, the dam’s and maternal granddam’s actual classifications, coded 1 to 6 for poor through excellent, were used rather than an estimated transmitting ability. The regression coefficients for predicting a bull’s type proof from only the sire’s proof and dam’s classification were 0.064 and 0.507, respectively, for feet and legs, 0.147 and 1.310 for final class, 0.213 and 0.969 for rump, and 0.131 and 0.957 for mammary system. Trends in indexes of young bull entries have increased over time for production and type.