I'm looking for the best book to learn about feeding poultry/poultry nutrition. I have the usual books for backyarders such as Storey's guide to chickens, ducks, etc.. and Harvey Ussery's Small-Scale Poultry Flock. I read Lisa Steel and The Chicken Chick. I'm looking for the types of books that one would purchase to obtain a degree in agriculture. I'm looking for textbooks, not someone's personal opinions. I would really like to expand my knowledge. I did a quick search and found books over $250 and they seemed to be old. Many thanks!