Luckily I'm in Cattle Country, too–I've got a bunch of leads to follow up. Two of my nieghbours have offered to let me graze a steer with their herd, but we don't have a big enough freezer! Most of the stock is non-registered organic, and I'm told many ranchers who raise for the farmer's market will sell heart, tongue & green tripe for a very good price--provided they're not keeping it for their own dogs!
@Debra, the Vet was mostly referring to fat and probiotics, and largely in the quality/freshness sense. But Non-medical diets (in Canada, anyway) may list their primary protein source as Duck, but are allowed a certain percentage of "off label" protein--I think it's 20, maybe 30%--and fat can be from ANY source. Duck has been my go-to protein source for years, even more so than fish...but who can afford prescription hypoallergic duck for multiple dogs?
As for probiotics, my previous vet wanted me to try a probiotic blend from Nestle, but the additives to make it taste good were pretty much abbatoir rendering sludge. With two sickly puppymill "babies" and an old "Nannydog" I'm at the stage where I'm afraid to feed them Human Grade meat for fear of making them worse...what a world we live in!