dog aggression at feeding .

I keep my cur dogs penned together, males in one pen and gyps in another. I have a gyp that inhales her food as fast as possible, then goes and pushes the smaller gyps off their food bowls. if I stand out by the pen she wont do it and everything is OK, but as soon as I turn my back and walk towards the house she would start on the smaller dogs. I got tired of this, and now I just put her on a chain where she can reach her food bowl and water...I wait 30 minutes or so then go back out and release her...