GMO is Genetically Modified, like round up ready soybeans. There have not been enough studies done to see how these genetically altered foods affect people and animals, so I avoid them when at all possible. If I'm not going to eat something, then I'm not one to let my animals eat it either.
Luvs2ryde, I've really never researched Purina. So many people use Purina and they have been in the business so long that you'd think they'd be a very trusted feed company. When I first got Major I was using a very cheap feed from a local company and he ended up colicing several times. He did stop colicing but I not only changed the brand of the feed but the type, plus several other things, so there is really no way of knowing what made the difference. I guess it's time for me to do some research.