The idea that animal suffering is less important than human suffering is a religious one. It assumes a special creation, and that we--you and I--are different in kind than other animals. We are morally separate from rats or horses or chimps, not based on any particular physical difference between us, but just because we claim that we're sacred by our nature and have dominion over them. It's a story we tell that lets us do what we do. Consider the question without that filter, and it looks very different.