Well the inconvenient thing is that objectively we aren't more important than other species. What you're actually doing is just overriding that objective fact with a subjective one.
Edit: or do you see cross-species minimization of pain as an objective objective (ha)? Or maximization of pleasure?
There is no "objective" answer to ethics.
But yes, if we want to base it on empathy, it would mean XY... so many philosophical arguments have been made about this. But it stands there is no "objective" ethics, at least to my knowledge.
Without even involving animals, there's not even a definite way how to answer the trolley problem without violating my subjective ethical values.
Human life as an ulterior value seems to be the best bet for explaining rational ethics.