The use of clones and dairy cattle breeding

<p>The aim of this thesis was to determine a breeding scheme that optimally uses large scale production of genetically identical individuals (clones) in dairy cattle. Such a breeding scheme should optimize the continuous genetic improvement of the breeding population (genetic response), and the selection of genetically superior cows to produce cloned embryos (clonal response), so as to disseminate high merit breeding material to milk producers. The effect on the genetic and clonal response of testing several clones per genotype in a nucleus breeding scheme was studied using simulation models, assuming a fixed number of cows tested each year. The breeding scheme was optimized by comparing genetic and clonal response for various breeding designs. Unlike for semen, the use of cloned embryos can exploit both additive and dominance genetic effects. To fully exploit dominance effects, theory on prediction of individual dominance effects in populations with inbreeding was studied extensively. Subsequently, relevant factors were determined that influence market share of commercially available cloned embryos compared to semen. In addition, ethical aspects of the use of clones in dairy cattle production were discussed