Partitioning of international genetic trends by origin in Brown Swiss bulls

Breeders improve their population by domestic selection and/or import of animals from foreign populations. Assessing the impact of these two sources is important to understand the sources of genetic changes (good or bad) in population. Partitioning breeding values by the origin of Mendelian sampling terms is a possible way to address this issue. We describe this method and apply it to international Multiple Across Country Evaluation in Brown Swiss breed. Partitioning of global genetic trends for the population of bulls and their ancestor revealed a large impact of USA on increased production as well as on decreased somatic cell score and fertility. The trend for somatic cell score has been reversed by the same country. Other countries have achieved smaller genetic gains in production and maintained no change in somatic cell score and fertility.