Optimization of progeny testing schemes when functional traits play an important role in the total merit index

Abstract

The inclusion of functional traits in a total merit index is expected to have some consequences on the design of progeny testing schemes in dairy cattle. Due to the usually low heritabilities of functional traits more daughter records per sire seem to be necessary to improve the accuracy of the breeding values of these traits. A complex deterministic approach was used to optimize the design of progeny testing schemes for Austrian Simmental and Brown Swiss cattle. The total merit index for Simmental included dairy traits (fat and protein yield), beef traits (daily gain, dressing percentage, EUROP grading score) and functional traits (functional longevity, persistency, fertility, calving ease, stillbirth and somatic cell count); the Brown Swiss total merit index consisted of dairy and functional traits only. The proportion of recorded cows mated with test bulls (test capacity) and the number of test bulls were varied. Annual monetary genetic gain and discounted profit were used to evaluate the different progeny testing schemes. The inclusion of functional traits in a total merit index has a positive effect on the annual monetary genetic gain. The annual genetic gains of functional traits are either positive or at least the negative trend can be reduced. Extending the number of daughter records per test bull from 60 (current situation) up to around 100 leads to a small increase of annual monetary genetic gain for Simmental, whereas no positive effect can be found for Brown Swiss. Discounted profit can be considerably improved, especially for Brown Swiss.