In animal husbandry, the performance of animals is influenced both by improving management and selection of animals with certain (superior) characteristics. In the dairy industry, this is common practice for different characteristics, such as milk yield, fertility, udder health and survival. In this PhD thesis, possible interactions between management changes and the result of selection have been investigated. It was shown that milk yield of animals having a high genetic potential for milk yield, changed relatively most as a result of changes in herd environment. However, animals having the highest genetic ability for milk yield had, despite the increased sensitivity, the highest yield under different circumstances. Also, fertility of animals having a high genetic ability for fertility was least sensitive to changes in herd environment. This finding indicates that selection for fertility leads to robust animals with respect to fertility.