To answer this question let’s go back to a time when dogs and cats were first domesticated and there was no billion-dollar a year pet food industry. Those early canines and felines must have been useful to the societies that adopted them. Dogs ate garbage and provided an alarm system against invaders. Humans found them to be loyal companions, protective of both their territory and their people and useful for tasks such as pulling travois or sleds. Cats, no doubt, proved valuable for the control of rodents and other pests.
People, pigs and other species of omnivores are capable of digesting and utilizing a wide variety of food products. Omnivores have longer digestive tracts, teeth capable of thorough mastication (something my wife is constantly reminding me about) and the ability to digest much of what they consume. Dogs and cats are carnivores with teeth designed for grasping and tearing rather than efficient mastication. Their digestive tracts are shorter and their nutritional requirements are different. Wild carnivores consume more than muscle and organ tissue, they also ingest partially digested vegetable material from the intestines, often consumed first.
Both dogs and cats require ten essential amino acids that they get from animal origin protein and essential fatty acids from animal or vegetable fat. Cats need more protein than dogs. Both dogs and cats require the proper balance of vitamins and minerals. The FDA requires any pet food that advertises with the words “complete” or “balanced” on the package to have everything your pet needs. The only problem with feeding your pet “people food” is that it takes knowledge and planning to provide all the nutritional requirements.
So far, I have avoided the question of feeding table scraps. Here we go. Do not feed your pet from the table while you are eating. The result will be an annoying pet that begs whenever you sit down to eat. The food may or may not be healthy but the behavior generated from table feeding is irritating and the result is usually a bad mannered, spoiled animal. Given that, I have been responsible for many family pets over the years and routinely mix small quantities of leftover food from our plates in with their regular commercial pet food. I avoid giving highly spiced foods but have routinely added meat gravy and fat, small bits of uneaten steak, even potatoes and cooked vegetables. All our dogs have thrived and appreciated these treats, most of our cats have turned up their nose, what does that tell you? Never provide cooked bones, they can splinter and cause all manner of problems. I have removed steak bones and chicken vertebrae from more than one obstructed GI tract.
If you look on the internet, you can find many recipes for homemade pet foods that seem to contain all the necessary ingredients for a healthy diet. I would be a little apprehensive about feeding a diet with raw red meat, poultry or seafood, too easy for bacterial contamination. If it is cooked fresh, introduced gradually, and your pet doesn’t react adversely to it, you should be OK. If you opt for a vegan diet, you have to be extremely careful to supply all the necessary essential amino acids, vitamins and minerals, not easy to do. It seems to me that feeding your pet organic foods or foods you prepare is more about lifestyle, cultural and moral beliefs than nutritional needs or food safety, but if it makes you feel better, why not?
Some animals do have special dietary needs because of illness, age or some other condition. If your veterinarian prescribes a special diet, you must use the commercial diet recommended or have a lengthy discussion about what you can prepare yourself to meet all the patient’s requirements.