First, we value human life above animal life, so we always prioritize humans and their pleasures above animals (with the limits being either another human's property, or when the human is showing signs of excessive brutality, such as intentionally torturing animals instead of simply killing them).
Then, when a human is not directly involved, what matters is the potential impact of any intervention. Nature is extraordinarily brutal by itself, and we can't hope to change that overall, regardless of what we might prefer. Even at a basic emotional & moral level, we can't protect every baby animal that gets killed by a predator or a parasite, regardless of the suffering we see in it, or we would be causing the death of the predator's babies to starvation. And then, at a more rational higher scale, we know that this type of intervention would typically end up destroying the entire ecosystem if we actually tried to do it consistently.