This paper explores the co-constitutive practices associated with robotic milking technologies. Introduced commercially in 1992, robotic milkers are sold with the promise of improved dairy cow welfare and productivity, reduced labour costs and the liberation of farmers from the routines of conventional milking: the machines milk cows individually, at any time of a cow's choosing, without direct human involvement or presence. Drawing on semi-structured interviews with UK dairy farmers and observational research on farms using robotic milking, in this paper we examine the effects of introducing robots on human-cow relationships. Frictions may develop when cows behave in unanticipated ways, robots find some cows more appropriate for their tech...