Genomisk selektion och uppbyggnaden av avelsprogram hos mjölkkor
During the last decade a new technique in animal breeding has developed called genomic selection. It is based on estimations of the effect from genetic markers on traits that are calculated in a reference population. By genotyping individuals, genomic breeding values can then be estimated without phenotypic observations. The aim of this essay is to investigate the response of genomic selection on breeding schemes for dairy cattle. The accuracy of the genomic breeding values is affected by the proportion of observations included in the validation set and how often the equation for estimating breeding values is reevaluated. Overall, genomic selection leads to a lower rate of inbreeding per generation and can be combined with varying levels of progeny testing. Breeding schemes based on unproven bulls selected on genomic breeding values only could, compared to breeding schemes that combined genomic selection whit progeny testing, result in higher rate of inbreeding and a lower accuracy but also a higher genetic gain. This is because unproven bulls can compensate for a lower accuracy whit a shorter generation interval. Genomic breeding values that incorporate more than one population are beneficial both when incorporated as a combined reference population or as GMACE. Many studies that are based on simulated data have presented results that studies based on field data cannot correspond to. Knowing this it is important that genomic breeding values are incorporated with caution even though it is tempting whit a high genetic gain.