Simulation on the consequences of genomic selection in a cattle breeding programme

Phenotypic variances and heritabilities were chosen according to the traits milk yield and somatic cell score and were sigma(2)(P) = 1,000,000, h(2) = 0.30, sigma(2)(P) = 1.50 and h(2) = 0.15, respectively. The fertility of the dams was 0.80 and we assumed a selection intensity of 0.05 for bulls and 0.02 for bull clams. Furthermore we assumed that in the genomic breeding program offspring information was available immediately and therefore no progeny testing was necessary. The main goal of all breeding programs in this study was the selection of 10 proven bulls and 60 bull dams. The number of offspring ranged from 10 to 100. The genetic gain per generation in the conventional breeding program was 505 kg and -0.40 points for milk yield and somatic cell score, respectively. If genomic breeding values were used for the selection genetic gain was 643.60 kg and -0.52 points for milk yield and somatic cell score, respectively. Finally we calculated the genetic gain per year for the different breeding programs. The genetic gain per year for the conventional breeding program was 145.44 kg milk and -0.11 somatic cell score points. The breeding programs based on genomic breeding values gave higher genetic gains per year for all traits. The genetic gain was 381.78 kg milk and -0.31 somatic cell score points.