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Comparison of Mixed Model Methods of Sire Evaluation

Animal Physiology and Genetics Institute, Animal Improvement Programs Laboratory ARS, USDA, Beltsville, Maryland 20705

ABSTRACT

Data were from the United States Department of Agriculture, Dairy Herd Improvement Association Sire Summary files for the active Artificial Insemination bulls summarized in September, 1972. The data consisted of all first lactation records of artificial insemination sired progeny of those bulls. Six different variations of the mixed model currently in use for sire evaluation in the Northeast United States were compared. Three different methods of nesting sires into groups were employed on Holstein data based on the year in which sires entered service, stud year, and region-year. All dairy breeds were evaluated in a grouping method involving years, and estimates for year trends for all breeds and region-year trends for Holsteins are given.

Holstein sires (48) with greater than 1,000 daughters with comparisons were compared for all six methods of evaluation. Solutions for the different grouping methods showed that yield and the mean of sire transmitting ability has been increasing in all breeds during the years for which data were included (1960 to 1970). Guernseys, Jerseys, and Holsteins have been increasing since 1964 at average yearly rates of 68, 47, and 45 kg while trends in the Ayrshire and Brown Swiss breeds have been less uniform. Group estimates for Holsteins for region-years point out that artificial insemination bulls in the northeastern portion of the country have the highest evaluation of any region. The method of grouping had a marked influence on evaluation of the bull but was not as important an influence as genetic merit of herdmates.