It is perfectly possible to formulate a healthy diet for a dog - but it’s not as easy as most people think! For example, if you just feed raw meat and bones, your dog will get some potentially serious nutrient deficiencies, because dogs are adapted to eat a mixture of whole animals, roots and berries - unlike cats they aren’t true carnivores, but facultative omnivores like us.
Usually - but not entirely. For starters, there are many foods that, although perfectly safe for us, are potentially lethal to dogs. Most people know about chocolate, but there are a range of foodstuffs - including coffee, onions, garlic, leeks, chives, raisins, grapes, peanuts, and macadamia nuts - that are toxic to dogs.
The next problem is that, although their digestions are very similar to ours, their metabolic and nutritional requirements are very different - especially in terms of their protein and fibre requirements.
Like all animals (including us), a dog’s diet needs to contain enough energy, and the correct balance of protein, fat, carbohydrate, fibre and micronutrients (vitamins and minerals).
Dogs can get energy from protein, fat and carbohydrate in the diet - which one/s they utilise depends on the total energy in the food. If you give them too much energy, they’ll put on fat and become overweight or obese; however, if you don’t give them enough, they’ll starve. The amount of energy needed varies with activity, age, life-stage (e.g. growth or pregnancy), and of course between individuals.
A healthy diet for the average adult dog needs to have at least 18% protein; and 22% for growing puppies, or pregnant bitches. However, this is assuming the protein quality is good - in other words, that there is the right ratio of the different amino acids (lysine, serine, methionine etc). It is a common mistake to assume that all protein sources (beans, peas, meat, milk, for example) are the same - the protein quality of plant-based foods is much lower than animal-based ones (which is the main reason it’s very hard to formulate a healthy vegan diet for a dog).
In addition, dogs have a very high requirement for the amino acid taurine in their diet (at least 1mg/g in dry food, and 2mg/g in wet foods) - without it, they’ll suffer from heart problems (cardiomyopathy). Nowadays, taurine-deficiency cardiomyopathy is only seen in dogs fed a home-cooked diet - all commercial foods have sufficient to prevent the disease.
Fats and oils:
Fats provide not only calories, but also essential vitamins (A, D, E and K) that are needed for a healthy skin and coat, hormone production, immune function, and general health. In addition, if you don’t put enough fat in the food, the dog won’t eat it - palatability depends more on fat content than any other factor! In general, it’s usually better to provide energy as fat rather than carbohydrates.
Carbohydrate (starch and sugar):
These only provide energy - they have no other function in the diet - and strictly speaking most dogs don’t require any at all. The exception is in pregnancy and lactation, when at least 23% carbohydrate in the diet is needed to feed the puppies or make milk sugars!
Unlike us, dogs do not require fibre in their diet. However, up to 5% is probably beneficial, and should be a mixture of fast- and slow-fermenting fibres.
Micronutrients (Vitamins and Minerals):
A dog’s requirement of these is pretty similar to humans, although there are differences - dogs can, for example, make Vitamin C, unlike us.
It’s also important to remember that in some disease conditions (e.g. diabetes, urinary crystals, liver or kidney disease, heart disease, and many others) their dietary needs may be very different from a normal healthy adult dog.
For most people, the best way is to feed a properly balanced commercial food.
If, however, you want to do it yourself, you’ll need to consult with a properly qualified nutritionist. Don’t try to make it up as you go along, or follow some fad doggy diet plan on the internet! If you give us a call, we can try to put you in touch with one.