When we fed raw we were using recipes from the "K9 Kitchen, Your Dogs' Diet: The Truth Behind The Hype" that utilized various "cuts" of meats and various vegetables in very specific proportions (measured with a scale). Each ingredient was selected to add certain nutrients to the diet; ingredients like muscle, heart, liver, and bone (typically ribs or necks) plus certain vegetables. The diet explained why each item and amount was added in terms of the desired balanced nutrition (protein, fat, vitamins, minerals, etc).
We were feeding raw to help one of our dogs with what has since been identified as Border Collie Collapse (similar to
Exercise Induced Collapse in labs); the thought at the time was increasing the amount of L-carnitine would help with this and that the
bioavailability of L-carnitine in tablets is much lower than dietary sources (especially in mutton heart).