Relationships Among Herd Life, Milk Production, and Calving Interval

Abstract

Whether to select for longer life in the herd or shorter calving interval depends on the genetic and phenotypic relationships among herd life, amount of milk in first lactation, and calving interval. Herd life and average calving interval are essentially phenotypically uncorrelated. The phenotypic and genetic correlations of herd life and milk in first lactation ranged from .19 to .25 and from .54 to .77, respectively. The phenotypic correlation of average calving interval and milk in first lactation ranged from .19 to .21. Estimates of the heritability of herd life ranged from .05 to .14. This heritability was reduced by 30% when the influence of milk in first lactation was eliminated. Selection of females for longer herd life or shorter calving interval would not be advantageous, but some consideration of the herd life of half-sisters and close ancestors could be of value in choosing young sires for testing.