Adult Nutrition: Accounting For Your Dog's Size

As your dog enters adulthood he will transition from puppy food to adult food. But at exactly what age he goes from being a puppy to an adult depends in large part on his adult size. Toy dogs reach their adult size at a much earlier age---sometimes by only 7 months of age---than do giant breeds, of dogs, which may take up to 2 years to reach full height. Even after reaching full height, most dogs of any size continue to bulk out a bit for some time; in giant breeds, this bulking may take another year or even two. So when do you stop feeding puppy food and start feeding adult food? 

Generally, once your puppy has reached full height you can switch from puppy to adult food. If your adult is not maintaining enough weight after being switched, then go back to puppy food or better, find a premium adult food that is high in calories.
The kind of adult food you feed will also depend somewhat on your dog's size. Start with the obvious: kibble size. If you're feeding a dry food, you want a kibble that your dog can crunch and enjoy. Not only do toy dogs tend have smaller and weaker jaws, but their teeth are smaller. If you feed your tiny dog a giant kibble, he may not be able to chew it and may have to swallow each piece whole. if you feed your giant breed kibble designed for toy dog, he won't derive much pleasure from crunching the tiny pellets. But remember, just because a dog has a large body doesn't mean he has a strong jaw. Large dogs with skinny jaws, such as Greyhounds, may prefer a kibble that is slightly smaller than you may have guessed from their body size alone. 

It's not just kibble size; dogs of different sizes have different caloric needs. Little dogs must eat proportionately more than big dogs. According to one study, whereas a 100 pound adult dog needs 23 calories per pound of body weight to maintain that weight, a 6 pound adult dog must eat about 47 calories per pound of body weight in order to maintain. That's twice as many calories per pound! But even though a small dog requires twice as many calories per pound, its stomach is not proportionately twice as large as a big dog's. That means that a little dog may require more calorie-dense food or several small meals a day. Of course, we've all seen little dogs that look more like engorged ticks, so don't get carried away!
When it comes to treats, size definitely matters. Whereas you can give your big dog a your leftover junk food without it affecting his nutrition too much, these same amounts of junk can amount to a big part of a little dog's diet, and even fill him up enough to discourage eating nutritious food. If you feed your little dog snacks, make sure they're little-dog-sized ones. 

Any dog's diet must be adjusted based on the dog's individual metabolism, activity level, and even the temperature in which it spends time. Temperature especially affects small dogs because they lose more body heat in cold weather compared to large dogs. Body heat is generated from the body's mass and lost from the body's surface area. Small bodies have a smaller body mass compared to surface area big bodies. Large round bodies keep their body heat much better than do small, lean and leggy bodies, which is one reason an Italian Greyhound loses heat more than a Pug. Even small dogs with long coats can lose body heat rapidly, especially because many, if not most, longhaired toy breeds have virtually no undercoats. In cold weather, a toy breed will burn many more calories maintaining body heat than a large breed does, so must eat even more calorie-dense foods. During cold weather, you may need to feed a food with a higher fat content to provide these extra calories. 

In general, your dog's weight is the best indicator of whether you need to feed him more or less. For dogs of most breeds, the body should have an hour-shape outline whether viewed from above or the side. The area around the loin and abdomen should be narrower than it is around the chest and hips. There should be no roll of fat over the withers nor a pad of fat over the rump. The tail should not emerge from beneath a roll of fat. You should be able to feel the ribs and some backbones, but they shouldn't protrude in most breeds. If your dog is too fat, consult your veterinarian to make sure it's a simple case of being overweight rather than a medical problem that causes the appearance of being fat. If your dog is too skinny, again, your veterinarian may find there is an underlying problem. But many dogs--especially large ones---tend to be on the thin side when young adults, only gradually putting on weight throughout adulthood. 

Keep your dog in good weight and provide him with good nutrition throughout adulthood, and you'll have the best chance of him entering his senior years in good health.