I actually do not consider Livestock as towards food production. A lot of the waste from the Industrial Process is fed to livestock, as it still has a significant nutritional value. Not to mention is usually easier for the Stock to digest...A majority is used for food production.
According to 2005 numbers:
58% is fed to livestock for food production. Despite giving them ulcers and helping foster diseases that don't exist in grass fed livestock.
25% Exported
17% Food, seed or industrial (ethanol or HFCS).
If you don't consider livestock to be producing food, then you are correct. I personally consider it food, as corn is the most prevalent thing in the average American's diet.