Estimates of repeatability of reproductive measures in Canadian Holsteins

Repeatabilities and heritabilities of days to first service, days open, and number of services per conception were estimated from 235,589 records on 80,333 Holstein cows, daughters of 306 sires obtained from the Quebec Dairy Herd Analysis Service, by REML. The model for statistical analyses included herd-year-season as a fixed effect and sire, cow (sire's daughter) within sire, and error as random effects. Variance components corresponding to sire, cow within sire, and error were then estimated by REML. Heritability estimates, obtained from the sire variance component, were .03, .05, and .03 for days to first service, days open, and number of services per conception, respectively. Repeatability estimates, obtained from the sire and cow within sire variance components were .08, .10, and .07 for days to first service, days open, and number of services per conception, respectively.