Thus, moral standing is not determined by an appeal to moral rights. Rather, moral standing is determined by whether a creature can be an experiential subject, capable of having a series of experiences that can make the creature's life go well or not depending on the quality of those experiences. It has a welfare that can be improved or negatively affected by what we do to it. Normal adult humans fall in this category, but so do demented patients, frogs and lion cubs. This is so whether or not we agree they all have moral rights or are all moral agents.
Moral standing varies with the quality of life.
The quality of a life is a function of its capacity for richness. A normal adult human with the capacity to appreciate music, literature, science has a richness and hence quality of life not approached by a puppy. Nonhuman animal life, in general, probably would not have the same value as human life because the quality of life is not as high. Nevertheless, even if an animal lacks some of the richness of the normal adult human, it still has some value, and animals are not to be simply sacrificed the way one might discard broken lab apparatus. Quality of life includes more than considerations of pain and suffering, although those considerations are morally relevant.