Over millenia humans have shaped the genetic composition of today’s livestock. Traditional breeding schemes and more recently marker assisted selection strategies have been successfully used for incremental genetic improvement of livestock. In principle transgenic technology which creates the potential to enhance existing characteristics at unprecedented magnitude and speed can be seen as the logical progression from these more traditional efforts to modify livestock genomes. Unlike traditional breeding and selection the technology is not restricted by the species barrier and can utilise the gene pool of other species to introduce entirely novel and unique characteristics. The recent development of cell-mediated transgenesis for livestock based on somatic cell nuclear transfer allows for the introduction of a wide repertoire of genetic modification. This includes not only additive strategies to introduce a new gene function (gain of function) but also the deletion of gene functions (knockout loss of function) replacing a gene function with a different one (knockin exchange of function) or the transfer of genes in a spatial-temporal manner (conditional knockout). The use of the mammary gland’s high protein production capacity in dairy animals for the production of biopharmaceutical proteins in the milk has so far been the main driver for this technology platform due to strong economic incentive ethical justification greatest public acceptance and relative simplicity. The first biomedical product arising from a transgenic goat has recently been approved bringing transgenic technology into commercial reality. The genetic engineering of livestock provides also exciting opportunities to incorporate additional health benefits into important foods such as milk thereby creating entirely novel foods with unique properties not achievable by conventional means. Such food applications are however much more complex than biopharming and while presently in the research and development stage their eventual introduction into the food chain remains some distance in the future.