Well then that sounds fine. You had me thinking they were in the paddock 24/7. If you are concerned, still talk to the vet. To answer your question earlier, little pieces of hamburger every now and then isn't going to hurt them, but giving them whole hamburgers every day isn't all that good either. And it would be a lot more expensive to feed them on hamburgers.

-Edit... Cracked corn is not very nutritious, however it is very high energy feed. That is probably why she feeds it if she is barrel racing.