Looking into this further, the Avocado cat (& dog) food site has
this info refuting the ASPCA's claims, while every single pet food safety page on the ASPCA site claims Avocados are toxic to all pets. Looking into it even further, I found
this warning info on a government of Canada site which notes a few studies that have found the leaves to be toxic to several animals, and
this article which sites many more recent studies. Wikipedia talks about the specific toxin
Persin and sites some studies that seem to point to it's toxic nature for mammals. None of the actual research I read refers any studies on cats, but with all the varieties of mammals (dogs, hosss, goats, hares, rats) and birds that avocados have been found to be toxic to, I suppose that's where the ASPCA's blanket opposition to the feed of avocados to all pets comes from. I've found several assertions all over the web that Avocado is toxic to cats, but not a single reference to an actual instance where this has been the case or any study that included cats. It's interesting that so many sites offer assertions without any back up. At least I was able to find several studies that show avocados as being toxic to mammals. I wont be intentionally giving them avocados any more since they don't need them in any way. All the more for me!