It has been argued that some animals are moral subjects, that is, beings who are capable of behaving on the basis of moral motivations. In this paper, we do not challenge this claim. Instead, we presuppose its plausibility in order to explore what ethical consequences follow from it. Using the capabilities approach, we argue that beings who are moral subjects are entitled to enjoy positive opportunities for the flourishing of their moral capabilities, and that the thwarting of these capabilities entails a harm that cannot be fully explained in terms of hedonistic welfare. We explore the implications of this idea for the assessment of current practices involving animals.