http://permaculturenews.org/2014/08/22/can-cow-produce-100-pounds-pig-feed-day-poland/
That article discusses the basics of integrating herbivores and omnivores in a way to yield significant feed for the omnivore. The herbivore doesn't have to be cows, we have done similar things with rabbits, goats, and even chickens.
With small livestock, you also have significant slaughter waste, which can be cooked and fed to the pigs, or better yet, lacto-fermented and fed.
If you don't have pigs, you can put chickens in that slot, they will eat just about anything a pig eats. This is the basis behind our Food Web project:
http://velacreations.com/foodweb By integrating species and maximizing connections between multiple species, you can significantly increase your output while maintaining or even reducing your inputs.