I was feeding my dog the Muenster Natural (small pieces) and it took her a while to finish it. The ants didn't take long to turn up and the dog did not want food with ants in it. My solution was to find a flat-bottomed (for stability) ceramic dish and set it in a shallow galvenized pan I found over at Home Depot. I put a little water in it and -- no ants. But if she dropped food in it, it tended to float and go to waste, so I had to clean this every couple of days.
The solution I found was in changing the dog food. I went down to Marshall Grain to get a bag of the same food but in the big bites, and now the dog eats it so fast there is no need for an ant barrier. In about 60 seconds she has polished off her 3 cups of food. The new pup who is her companion eats in the house right now, as we get them accustomed to sharing the space. She inhales her 2 cups in half of the time.