How much corn oil should I put in his grain?

I asked our vet who specializes in nutrition about corn oil and the Omega 6 problem. She agreed that it's best to avoid it until all the research is in. Soooo, better to feed rice bran oil, or cocosoya or one of the other oils available, and it's also best, safest, to start with 1/4 cup (in each feeding, so 1/2 cup, if you want) and to monitor your horse's weight. You can usually add up to 2 c per day without causing digestive problems. Also, 14% protein is a little high for a 7 year old horse who isn't in heavy work (endurance, racing, polo etc.).