Methods were developed for the national genetic evaluation of herd life for Canadian Holstein sires. The genetic evaluations incorporate information from survival (direct herd life) and information from conformation traits that are related to herd life (indirect herd life) after adjustment for production in first lactation to remove the effect of culling for production. Direct genetic evaluations for herd life were based on survival in each of the first three lactations, which was analyzed using a multiple-trait animal model. Sire evaluations thus obtained for survival in each of the first three lactations were combined based on their economic weights into an overall sire evaluation for direct herd life. Sire evaluations for indirect herd life were based on an index of sire evaluations for mammary system, feet and legs, rump, and capacity. A multiple-trait sire model based on multiple-trait across country evaluation methodology was used to combine direct and indirect genetic evaluations for herd life into an overall genetic evaluation for herd life. Sire evaluations for herd life were expressed in estimated transmitting ability as the number of lactations and represent expected differences among daughters in functional herd life (number of lactations); the average functional herd life was set equal to three lactations. Estimated transmitting abilities were normally distributed and ranged from 2.31 to 3.43 lactations.

Several approaches for analysis of survival in the first three lactations were compared using data from approximately 700,000 Canadian Holsteins. Two approaches (linear model and threshold model) were used to analyze a binary measure of survival. Other approaches were survival analyses to evaluate two measures of the number of days that cows were in milk during their first three lactations. One measure restricted days per lactation to < or = 305; the other was based on the actual number of days in milk without an upper limit on days per lactation. Variance components and breeding values (EBV) were estimated. Sire models were used almost exclusively, but one set of EBV was obtained using a linear animal model. Effects in the models were herd-year of calving, age at first calving, interaction of several factors related to herd, and production. Thus, all EBV were for functional herd life. Heritabilities were approximately 0.04, 0.07, and 0.10 from linear, threshold, and survival analyses, respectively. Correlations among sire EBV from all analyses using sire models were high, particularly for linear and threshold models (0.98). In contrast, correlations of EBV from sire models with EBV from the linear animal model were less than 0.90, regardless of the approach taken. In Canada, the current linear animal model remains in use for sire evaluation of herd life, but research with survival analyses will continue.

Effects of the interaction between type and production on two measures of functional herd life were examined for Canadian Holsteins. Data were records of survival through first lactation for 1,153,706 cows and number of lactations initiated (maximum of five lactations) for 705,930 cows. Survival data were regressed on ETA for type traits of the sire of each cow after the cows were assigned to groups with low, medium, or high production. Survival through first lactation was analyzed with a threshold model. Factors in the model included herd-year-season; age at calving; month of calving; interaction of registry status, change in herd size, and season; fat and protein production; and linear regressions of sire ETA for type within each production class. Numbers of lactations were analyzed with a linear model that also included month of last calving. Overall conformation and udder traits had the largest effects on survival through first lactation. Effects on number of lactations for feet and leg traits were about the same as for udder traits. Interactions were significant. Type traits were relatively unimportant for herd life of low producing cows. Few differences were observed in the relationships between herd life and type for medium versus high producing cows, indicating no need to increase the emphasis on type in response to current trends for greater production.

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 > or = .93. Genetic and phenotypic correlations, respectively, of early partial (two parities total) with total life-time 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.

Genetic and phenotypic correlations were estimated between 6 lifetime production and 28 linearized type traits using REML. The data set contained 34,322 cows, each with a record for all 34 traits. The analyses accounted for the fixed effects of herd, year-month, classifier, age at first calving, and stage of lactation. Heritabilities were low for lifetime traits and moderate for most type traits except stature, size, capacity, thurl width, and pin setting, which had high heritabilities. Most phenotypic correlations between lifetime production and type were in the range of .15 to .20 except for capacity, rump, and feet and legs, which were around .07. Genetic correlations were strong between lifetime production and angularity (.44 to .55) and dairy character (.53 to .56). Genetic correlations were low to moderate between life-time production and stature (.14 to .25), size (.07 to .18), texture (.19 to .26), style (.11 to .27), head (.15 to .23), pin setting (.10 to .16), rear udder (.19 to .25), and rear attachment (.10 to .22). The only notable negative genetic correlations were lifetime production with rear heel (-.16 to -.27), thurl width (-.18 to -.24), and fore udder (-.05 to -.11).