Dog foods come in four types: canned (also called wet or moist), dry, semimoist, and raw (frozen). Choosing the right one or a balanced combination is up to you, so you need to understand the pros and cons of each type. The food you select should be nutritionally geared to your dog's age, condition, and health history. Your budget is a consideration as well, but keep in mind that bargain-basement dog foods may lead to higher vet bills down the road.

Canned Food

Canned dog food consists of 60 to 85 percent water. Brands vary widely in quality as well as in protein sources, cereals, and other ingredients, so you need to do your homework before you buy. Premium brands offer good protein sources as well as sufficient vegetable fiber content, and some are further enhanced by vegetables and fruits. Small dogs that eat a canned food diet must also have hard chewy food, treats, or toys as well to aid in teething, to satisfy their need to chew, and to keep their teeth and gums healthy. If the canned food you choose has a high meat content, feed it mixed with a little dry kibble.

Dry Food

These foods vary in texture and size of the particles, from gravel-like kibble to extruded forms that look like breakfast cereal, uniform in shape. Their moisture content is usually 10 to 12 percent. Dry foods have most of the moisture removed and are therefore more economical than canned. They may be eaten dry or mixed with water, canned food, or raw food, but remember that when your dog chews its dry food, it is also cleaning its teeth and gums. Since many small breeds are prone to problems with their teeth, plain dry is better for their dental health. Its hard and crunchy texture helps satisfy the pup's need to chew as well.

Semi-Moist Food

High in sugar and preservatives, semi-moist foods usually contain 40 percent water and high sugar levels. Their chewy consistency is sometimes provided by propylene glycol, a chemical compound used as an emulsifier, which has been linked to severe health problems in cats. Artificial food coloring makes these foods look like real meat or cheese, a marketing strategy aimed at owners, not pets. Most dogs love this doggie fast food, but all that the sugar can contribute to obesity and dental problems.

Raw Food

The latest thing in feeding, raw dog foods have emerged during the last decade as one of the strongest trends in the dog food arena. Their popularity reflects a growing belief that our dogs need a raw, natural diet like their ancestors ate to achieve maximum health and vitality. Accompanying this theory is the opinion that commercial dog foods do not supply the nutrients our dogs need. A new generation of consumers is now questioning the belief that all dog food comes prepackaged and that as dog owners, our only role is to open that can or bag and serve it up.

One of the earliest proponents of the raw diet was Dr. Ian Billinghurst, an Australian veterinarian who instituted what he termed the Biologically Appropriate Raw Food, or BARF, diet. This is Billinghurst's recipe for returning our dogs to their evolutionary roots. It relies on raw meaty bones and ground up vegetables and organ meats. The diet is further enhanced by a myriad of supplements such as vitamins, essential fatty acids, probiotics, kelp, alfalfa, and herbs.

The raw-food revolution's appeal is based on the belief that many of today's dog diseases and allergies are directly linked to commercial dog foods, most of which contain substandard meats and lack essential live enzymes, vitamins, and other nutrients. It is further fueled by the desire of many dog owners to take back the responsibility for dietary decision making from mass manufacturers. (Of course, numerous companies producing these raw foods have sprung up all over.)

Raw diets are said to simulate the menu that nature intended for canine carnivores. Dogs have a shorter digestive tract, designed to quickly process the food that they eat before harmful bacteria can multiply and cause problems (the reason a dog can eat a rotting carcass without getting sick). Their jaws and teeth are designed to rip and tear, not to move side to side in a grinding motion like ours do as we chew. Human saliva contains enzymes that start breaking down our food before we even swallow it, but dogs have no such enzyme in their saliva. All of their digestion takes place in their stomach. Among the benefits claimed by raw-diet enthusiasts are a decrease in common canine illnesses, longer lives, and less dental disease.

The raw-food revolution is not without its detractors. Some warn that feeding uncooked meats calls for vigilant preparation and storage to prevent the spread of deadly bacteria like salmonella and E. coli. Spoiled raw food can make a dog very ill.

Feeding raw food is also a lot more work. For the dog owner, a large part of the popularity of prepared commercial dog foods is their convenience. Homemade and commercial raw diets need to be tweaked with all sorts of supplements to make them nutritionally balanced. For your dog's sake, such a switch should not be undertaken lightly. It's another area that calls for lots of homework.