Age of dam and maternal effects for dystocia in Holsteins.

Genetic correlations between dystocia in first with later parities and between direct with maternal effects for dystocia were estimated. Dystocia in first and later parities represent similar traits because of a large genetic correlation of .84. This similarity should allow calving reports on older dams and heifers to be combined in predicting a bull's calving performance. Correlations for direct with maternal effects were -.38 for the heifer population and -.25 for the cow (second and greater parities) population. This correlation would reduce progress from selecting for reduced dystocia if only direct effects were considered. Breeding programs to reduce dystocia should consider both direct and maternal performance.