I know "ray of stupidity" went away in the PF conversion, but are there any attacks which reduce intelligence in the same manner?
Because if there are, they would seem to be an easy way to put an animal companion out of a fight.
There are no such spells that I know of. I once made a caster who was focused on reducing stats in 3.5. It was pretty ridiculous. I have not seen a method to duplicate it in pathfinder.
There are some, like touch of idiocy, but most of the ones I find have a "Minimum of 1" limitation. Animals are actually the least offended by the spell. Int poisons would be the thing to watch out for.
Touch of idiocy also has that limitation which limit it to a 1.