| Summary: | The objective of this study was to estimate the relationship between survival at various stages of productive life (17, 30, 43, 55 and 96 months of productive life) and type traits in Quebec Holstein and Ayrshire cows. The original data set from the Programme d'Analyse des Troupeaux Laitiers du Quebec contained 559,203 lifetime records calculated from 2,237,081 lactation records including calvings from 1979 to 1995. Lifetime records containing type classification information provided by the respective breed associations were used to study true survival variables (opportunity to survive to 17, 302 43, 55 and 96 months) and functional survival variables opportunity to survive to the same ages, independently of the level of production). K. Meyer's EQREML program was used to analyse these data by fitting a sire model. Heritabilities varied between 0.03 and 0.11 for both breeds. Final score and rear udder were two of the traits most highly correlated with survival. Specifically, in Holsteins, mammary system and fore udder showed the highest genetic correlation with functional survival, and dairy character showed the highest genetic correlation with true survival. In Ayrshires, final score, breed character, dairy quality, style and fore udder had the highest genetic correlations with both true and functional survival across all survival stages. In a second study, lifetime records not having type information and type records without lifetime information were analysed with D. L. Johnson and R. Thompson's AIREML program which enabled linking of sires in common between type and lifetime data sets. Only survival to 96 months was studied here, but the effect of supervised and non-supervised records was considered. In Holstein supervised records, body traits were more highly correlated with survival, whereas udder traits were more highly correlated in the non-supervised records. Ayrshire results were not conclusive.
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