There are many sites of interest in the web related to zoo animal nutrition and pathology. However, it is important to select only that information that has a scientific base:
National Research Council - Nutrient Requirements.
U.S. Department of Agricultural Research Service. Food and Nutrition Information Center.
U.S. Department of Agricultural Research Service. Food Safety and Inspection Service.
U.S. Department of Agricultural Research Service. National Agricultural Library.
Legislation, nutrition, and captive wildlife husbandry manuals.
Pathology
European Association of Zoo and Wildlife Veterinarians
European Association of Avian Veterinarians
Association of Reptilian and Amphibian Veterinarians
