[TeMPOraL]

This argument is valid forwards, but not universally backwards. Otherwise you could repeat it with pigs and ants, and then with ants and bacteria.

There is a spectrum of life, on one end you have self-propagating chemical reactions, on the other you have beings with moral significance. Whether or not experiments on animals are morally justified depend on where those animals lie on this spectrum, and the form and goal of the experiment.

I'm not trying to say here where pigs lie on the spectrum, just that this discussion needs to happen on a much deeper level of details than "humans are more important than pigs" vs. "but aliens could say the same thing about us" for it to be useful.

(Personally, as long as the brains remain comatose all the way through, I don't feel there's a problem here. If they were active... that would be animal cruelty to me. But that's just my individual moral intuition.)