Suppose that your doggy friend, Eddie, has been especially well-behaved recently, and you want to reward him with a treat. Does ethics have anything to say about how one should reward their well-mannered doggo?
As it happens the answer is affirmative. It must be said first, though, that ethical theories are guides to action; they tell us, at least in theory, else morality requires of us in a given situation. And one of the most prominent ethical theory is utilitarianism. This is the view, as stated by John Stuart Mill (one of the founders of the view), that,
The creed which accepts as the foundation of morals […] that actions are right in proportion as they tend to promote happiness, wrong as they tend to produce the reverse of happiness. By happiness is intended pleasure, and the absence of pain; by unhappiness, pain, and the privation of pleasure.
One should choose those actions which will produce the most happiness in ourselves and others, and will avoid the most suffering in oneself and others, too. And this moral theory has an undeniable ring of truth: we want to increase happiness in our lives. We call that good. We also want to avoid an increase in our suffering. We can that bad. And there's no good reason to expect that others capable of happiness and suffering would think about the matter that much differently.
How does this apply to Eddie? Imagine you want to reward your dog with a few peanut butter biscuits (his favorite treat, btw). How should you distribute the dog treats? Start by thinking about people. You want to give your mother a bunch of gifts for her birthday, and maximize her enjoyment of them in the process. You can either give them to her all at once, or you could give them to her over a few days (clustered around her special day).
What do you do? Given that most of us have a finite capacity for happiness, it would make sense to choose the latter option: maximize your mother's enjoyment of her birthday gifts by giving them to her over the course of a few days.
And likewise for your noble doggo: you could give him the peanut butter biscuits all at once, but doing so would likely overwhelm his capacity for enjoyment. Better to spread them out. You might ask: can ethics apply to animals, like dogs and cats? They can be happy, and they can suffer. That's all that's needed for utilitarianism to apply.
It's interesting to see a piece on animals and utilitarianism and no mention of Peter Singer.
My current views on our duties to animals falls somewhere between Kant's and Singer's views. As much as I'm informed, there seems to be levels to sentence. Humans definitely have duties to other humans and higher order animals, those with greater levels of sentience, but not so much to those at the other end of the spectrum.