Animal Digest is a common ingredient used in pet foods. As defined by the AAFCO, it is material which results from chemical and/or enzymatic hydrolysis of clean and undecomposed animal tissue. The animal tissues used shall be exclusive of hair, horns, teeth, hooves and feathers, except in such trace amounts as might occur unavoidably in good factory practice and shall be suitable for animal feed.
A cooked-down broth made from specified or unspecified parts of animals (depending on the type of digest used). If the source is unspecified (e.g. "Animal" or "Poultry", the animals used can be obtained from any source, so there is no control over quality or contamination. Any kind of animal can be included: "4-D animals" (dead, diseased, disabled, or dying prior to slaughter), goats, pigs, horses, restaurant and supermarket refuse and so on. Rats, miscellaneous road kills, animals euthanized at animal control facilities are not permitted and are to be properly disposed at secure landfills per USDA and AAFCO and State of WI DNR. A number of bald eagles were killed and others sickened by improperly disposed euthanized pets in central Wisconsin. The matter became Federal in 2011 under protected species laws and regulations. Any poisoned animal matter is prohibited but not diseased, i.e., the bacteria or viruses become a digested part of the digest and no longer pose any threat. see following FDA link..
FDA: Digests, which are materials treated with heat, enzymes and/or acids to form concentrated natural flavors. Only a small amount of a "chicken digest" is needed to produce a "Chicken Flavored Cat Food," even though no actual chicken is added to the food. - (FDA)