A strong duty to relieve suffering that does not discriminate between species would require radical changes in the ways that we relate to other animals. It would, for example, require an end to the practice of factory farming, in which billions of animals are annually subjected to extreme suffering in order to supply humans with meat and other products at the lowest possible cost. It would also raise difficult questions about the practice of experimenting on animals to obtain medical benefits for humans. These cases, much discussed in the literature on animal ethics, involve suffering that is inflicted by human beings. But a species-blind duty to relieve suffering would also make it a prima facie requirement to save animals from suffering brought upon them by natural conditions and other animals. That seems right to me.
Jamie Mayerfeld, Suffering and Moral Responsibility, Oxford, 2002, p. 117