Now that you've been introduced to the business of commercial dog food, the next step is to learn to understand what your pup (or dog) needs from food to remain healthy for many years. You're looking for some nutritional essentials here: proteins, carbohydrates, vitamins, minerals, and fats. They are all contained conveniently in commercially prepared foods.

The ingredients are listed in descending order by weight — that is, how much of the ingredient is actually in the product. Therefore, if a pure meat source like chicken, beef, or lamb is right up there at the top, you can be sure you're buying a protein-rich food.

Proteins are present in all kinds of meat and meat by-products, such as chicken, lamb, beef, or chicken meal. These are the best sources of protein for your dog. Many foods use vegetable proteins such as soy. These are harder for your dog to digest, so although you will invariably find them in his food, make sure they aren't major ingredients. A dog's need for protein varies — most notably for age, size, and activity level. Puppy foods have high levels of protein, whereas senior foods contain lower levels.

Carbohydrates, which are necessary for energy, also make up some of the primary ingredients in dog food. Their sources are typically rice, corn, or some other grain, though more and more frequently vegetables such as sweet potatoes are being used as well. Wheat and soy can sometimes trigger an allergic reaction in dogs, which is why more and more formulas use rice as their starch. Some dogs aren't affected at all, however, so it's always wise to monitor your dog's overall health.

Dogs need vitamins and minerals to keep their bodies functioning. A lack of iron means not enough hemoglobin to pick up red blood cells in the lungs, which means a less energetic dog. A lack of vitamin E can result in brittle skin. Vitamin C has been called a wonder vitamin for its curative powers. Several commercially available foods on the market add special vitamins and minerals to the food to compensate for certain conditions. One of the most popular is the addition of glucosamine and chondroitin in foods for senior dogs to promote joint health. If you note a substantial amount of an unfamiliar ingredient in your dog's food, do some research and, most important, observe your dog for the potential side effects (hopefully good ones).

Fat is a necessary part of any dog's diet. Fat is what keeps the skin supple and the coat shiny. Too little fat, and your dog will end up with a dry, brittle coat and dry skin; too much fat, and you'll end up with an obese, “well-greased” dog. Fat is extremely palatable to dogs, as well, so manufacturers use it for nutritive and taste values. This can lead to problems with storage, as fats tend to oxidize and go rancid when exposed to air or heat. They must be properly preserved in order to hold.

Canine nutrition is a hot topic, and this chapter only skims the surface. The bottom line is: How does your dog do with the food you feed him? If you select a premium brand and feed according to the guidelines in this chapter, your dog should show all the signs of being healthy: clear, shiny eyes; soft, supple coat; pink gums; normal stool and urine; and appropriate energy level. If he doesn't seem healthy to you, speak with your veterinarian and research a dietary change.

All-Important Water

No discussion of what to feed a dog is complete without mentioning water. This is a nutrient as important to dogs as it is to other living things. Dogs can go longer without food than they can without water. To stay hydrated, and to cool off, dogs need a constant supply of fresh, clean, cool water.

It's absolutely necessary to leave out a clean bowl of water at all times for your puppy or adult dog. Never regulate the water supply. Dogs can't tell you when they're thirsty, so it's vital that you leave water for them at all times. When they're thirsty, they'll drink. Change the water in your dog's bowl a few times a day, and clean the bowl thoroughly once a day. Attention to the water bowl may also alert you to any changes in how much — or little — your dog is drinking, which can be an indication of a serious medical condition.