Optimizing management of kinship and inbreeding coefficients in dairy cattle selection

Abstract

This paper describes the methodological approach followed for managing genetic variability in selected dairy cattle populations, when procreating young bulls (upward step), using service bulls (downward step) and selecting recently progeny-tested bulls (approval step).The objective was to minimize the average pairwise kinship coefficient in the existing population augmented by the individuals to be bornfrom the planned matings, while setting their average genetic level to a pre-defined value. A posteriori full scale tests are carried out onthe Holstein, Montbéliard, Norman breeds. In comparison with the most recent actual matings, the optimization method reduced the averagekinship coefficients by about 20 to 30 % (upward and downward steps), while maintaining the average genetic level to its observedvalue. Optimized approval rejects an important proportion of the bulls already approved and accepts some new bulls, previously dismissed.The potential of using an overall EBV penalized for coancestry was investigated.