That non-human animals can make moral claims on us does not in itself indicate how such claims are to be assessed and conflicting claims adjudicated. Being morally considerable is like showing up on a moral radar screen—how strong the signal is or where it is located on the screen are separate questions. Of course, how one argues for the moral considerability of non-human animals will inform how we are to understand the force of an animal's claims.
According to the view that an animal's moral claim is equivalent to a moral right, any action that fails to treat the animal as a being with inherent worth would violate that animal's right and is thus morally objectionable. According to the animal rights position, to treat an animal as a means to some human end, as many humans do when they eat animals or experiment on them, is to violate that animal's right. As Tom Regan has written,
…animals are treated routinely, systematically as if their value were reducible to their usefulness to others, they are routinely, systematically treated with a lack of respect, and thus are their rights routinely, systematically violated. (Regan, 1985)
The animal rights position is an absolutist position. Any being that is a subject of a life has inherent worth and the rights that protect such worth, and all subjects of a life have these rights equally. Thus any practice that fails to respect the rights of those animals who have them, e.g. eating animals, hunting animals, experimenting on animals, using animals for entertainment, is wrong, irrespective of human need, context, or culture.
The utilitarian position on animals, most commonly associated with Peter Singer and popularly, though erroneously, referred to as an animal rights position, is actually quite distinct. Here the moral significance of the claims of animals depends on what other morally significant competing claims might be in play in any given situation. While the equal interests of all morally considerable beings are considered equally, the practices in question may end up violating or frustrating some interests but would not be considered morally wrong if, when all equal interests are considered, more of these interests are satisfied than frustrated. For utilitarians like Singer, what matters are the strength and nature of interests, not whose interests these are . So, if the only options available in order to save the life of one morally considerable being is to cause harm, but not death, to another morally considerable being, then according to a utilitarian position, causing this harm may be morally justifiable. Similarly, if there are two courses of action, one which causes extreme amounts of suffering and ultimate death, and one which causes much less suffering and painless death, then the latter would be morally preferable to the former.
Consider factory farming, the most common method used to convert animal bodies into relatively inexpensive food in industrialized societies today. An estimated 8 billion animals in the United States are born, confined, biologically manipulated, transported and ultimately slaughtered each year so that humans can consume them. The conditions in which these animals are raised and the method of slaughter causes vast amounts of suffering. (See, for example, Mason and Singer 1990.) Given that animals suffer under such conditions and assuming that suffering is not in their interests, then the practice of factory farming would only be morally justifiable if its abolition were to cause greater suffering or a greater amount of interest frustration. Certainly humans who take pleasure in eating animals will find it harder to satisfy these interests in the absence of factory farms; it may cost more and require more effort to obtain animal products. The factory farmers, and the industries that support factory farming, will also have certain interests frustrated if factory farming were to be abolished. How much interest frustration and interest satisfaction would be associated with the end to factory farming is largely an empirical question. But utilitarians are not making unreasonable predictions when they argue that on balance the suffering and interest frustration that animals experience in modern day meat production is greater than the suffering that humans would endure if they had to alter their current practices.
Importantly, the utilitarian argument for the moral significance of animal suffering in meat production is not an argument for vegetarianism. If an animal lived a happy life and was painlessly killed and then eaten by people who would otherwise suffer hunger or malnutrition by not eating the animal, then painlessly killing and eating the animal would be the morally justified thing to do. In many parts of the world where economic, cultural, or climate conditions make it virtually impossible for people to sustain themselves on plant based diets, killing and eating animals that previously led relatively unconstrained lives and are painlessly killed, would not be morally objectionable. The utilitarian position can thus avoid certain charges of cultural chauvinism and moralism, charges that the animal rights position apparently cannot avoid.
It might be objected that to suggest that it is morally acceptable to hunt and eat animals for those people living in arctic regions, or for nomadic cultures, or for poor rural peoples, for example, is to potentially condone painlessly killing other morally considerable beings, like humans, for food consumption in similar situations. If violating the rights of an animal can be morally tolerated, especially a right to life, then similar rights violations can be morally tolerated. In failing to recognize the inviolability of the moral claims of all morally considerable beings, utilitarianism cannot accommodate one of our most basic prima facie principles, namely that killing a morally considerable being is wrong.