This chapter explores Foucault’s concept of biopower and its focus on the regulation and fostering of life. It examines the analytical potential of Foucault’s anthropocentric conceptualisation in examples involving nonhuman animals. Specifically, it explores the empirical case study of livestock breeding in the UK, focusing on the increasing use of ‘genetic’ knowledge-practices in this context. It is argued that genetic techniques represent new ways of regulating life, and are associated with the emergence of a particular mode of biopower in livestock breeding which can be seen as part of a wider social process of ‘geneticisation’ .The chapter concentrates on the idea of ‘population’, a central element of Foucault’s discussions of biopower, but develops a more heterogeneous sense of the term via an engagement with the notion of ‘biosocial collectivity’ . As such, the chapter attends to the conceptualisation of nonhuman actors within the set of analytical tools provided by Foucault’s biopower. First, after outlining the notion of biopower, it is argued that, from the basis of its focus on life, nonhuman animals can be understood in terms of relations of biopower, drawing on conceptions of population and biosocial collectivity. Second, the chapter examines empirically how new genetic knowledge-practices might be reconstituting the populations and biosocial collectivities associated with livestock breeding. Third, it is suggested that the emergence of genetic knowledge-practices might signal a new inflection of biopower, tied to new senses of population and biosocial collectivity.