How would I make food for my pot belly? I need a recipe.?

I can only find commercial hog feed in my area, and the cost of shipping the pot belly food to me is prohibitive. Does anyone have a recipe? Can I mix horse feed (grains, etc) with hog feed? I am willing to mix it myself, but I need to know what to put in it. My pig is outside, we live on 4.5 acres, half grass half wooded, and she roots around freely. Any tips would be appreciated, thank you.