Abstract
Data on 82,835 Holstein cows, daughters of 703 sires and with first calving from September 1979 to December 1984 from 2384 herds enrolled in the Quebec Dairy Herd Analysis Service, were used to estimate genetic and phenotypic parameters of partial and total lifetime performance traits with REML. The model included herd-year-season of first calving, age at first calving, and proven sires as fixed effects and young sires and residuals as random effects. Individual lactation records were precorrected for year-month of calving before lifetime totals were calculated. Only cows with at least 5 yr of opportunity for production were analyzed. The ranges of heritability estimates were .11 to .13 for lifetime production and profit, .07 to .09 for measures of longevity, and .28 to .32 for yield per day of productive life. Correlations among total lifetime yield and profit traits and among measures of longevity were ≥.93. Genetic and phenotypic correlations, respectively, of early partial (two parities total) with total lifetime yield and profit and longevity traits ranged from .81 to .94 and .66 to .78. Selection on early performance seems to be desirable and, given the high positive genetic correlations, should increase both lifetime yield and longevity.
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