RELATIONSHIP BETWEEN UNITED-STATES AND CANADIAN GENETIC EVALUATIONS OF LONGEVITY AND SOMATIC-CELL SCORE

Canadian and US evaluations of Holstein bulls were compared for longev ity measures (433 bulls) and somatic cell score (354 bulls). Bulls wer e required to have a birth year of greater than or equal to 1975, daug hter information from greater than or equal to 20 herds, and a reliabi lity of greater than or equal to 50% in both Canada and the US. The nu mber of bulls with longevity evaluations was greater for early years b ecause longevity information was available from lactation data and dau ghters were required to be greater than or equal to 3 yr of age for US evaluations; evaluations for somatic cell score required additional c ollection of data and did not have corresponding numbers of bulls unti l the 1980s. Correlation between longevity measures in the US (product ive life) and Canada (herd life) was 0.60. This low correlation was ex pected because US productive life includes yield information, but yiel d is excluded from Canadian herd life. For evaluations for somatic cel l score, the correlation between the two countries was 0.82. Genetic c orrelations with productive life were estimated to be 0.69 for herd li fe and 0.81 for herd life combined with protein yield. Conversion equa tions were developed to predict a US evaluation for somatic cell score from a Canadian evaluation for somatic cell score and to predict a US evaluation for productive life from Canadian evaluations for herd lif e and yield.