Is it OK to purchase cat food? Forgive a (possibly) silly question - but I have a cat as a pet, and of course I purchase cat food for him and feed it to him. Being a pretty recent participant of Buddhist thought and practice, I also understand that eating meat (something I admittedly still do myself) is frowned upon, but the thought occurred to me the other day - is it also frowned upon to buy my pet meat-based products? By doing so I participate in the killing of animals. On the other hand, cats are pretty much carnivores by nature, and trying to get a cat to go vegetarian would likely harm him.
I also understand that eating meat (something I admittedly still do
  myself) is frowned upon


It depends on the tradition and personal beliefs. If you follow Theravada Buddhism, you wouldn't have any issue with feeding yourself or your cat with meat products. In Theravada Buddhism, the word of the Buddha is valued higher than personal opinions. So you or your cat is less likely to get frowned upon, just for eating meat. :) Vegetarianism is usually treated as a personal food preference.