Google helped me find this article by George Washington Carver concerning sweet potatoes: How the Farmer Can Save His Sweet Potatoes | Aggie Horticulture
It has some good info and is well-written and interesting. But the part that made me post is about 2/3 of the way down under "As Food for Stock". Protein is referred to as "muscle builder" and carbohydrate as "fat-former". Pretty awesome.