It's a little dated, but still has good info:
http://www.armchairpatriot.com/Home-Vet/Plumb's Veterinary Drug Handbook [Desk Ed.] 6th ed. - D. Plumb (Blackwell, 2008) WW.pdf
Both of these veterinary text books
and other info:
Nutrient Requirements of Poultry
Contains chapters on chickens, turkeys, ducks, geese, and misc. game birds
Field Manual of Wildlife Diseases
Contains plenty of poultry and waterfowl diseases
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