By far, the majority of dog food sold in the United States is dry, accounting for 80 to 90 percent of sales. Canned foods are slightly more popular among owners of toy breeds, such as the Yorkshire terrier, than in the general dog population. Semimoist packaged products have nearly disappeared from shelves, while frozen foods have not yet gained much of the market share.

Dry Food

Dry food is easy to store and available in a wide variety of package sizes. Packaging adds little to the cost. With its low moisture content, dry food is energy dense. A smaller quantity meets the dog's daily energy requirements. Dry food may be left down for the dog to eat free choice, or can be fed in meals. Something called “mouth feel” factors into how attractive a food is to a dog, and some dogs prefer the crunch of dry. Additionally, dry food may help remove tartar from teeth.

Stool quantity depends to a large extent on the food's digestibility. If the piles in your yard would lead people to think you have a Great Dane rather than a Yorkshire terrier, you may want to consider switching brands. Though the price of your current brand may seem like a bargain, you're paying for a lot of ingredients your dog can't use.

Dry food is generally extruded — the dough is pushed through a die to form shapes. A coating of fat is sprayed on, and the shapes are dried to nugget hardness. A few dry foods are still made as kibbles, baked in sheets and then broken into pieces, rather than pressure-cooked like extruded foods.

Canned Food

Most advertising of canned foods is aimed at toy dogs because it's an uneconomical way to feed. You're buying a lot of water content, and a large-breed dog would likely need several cans per meal. Canned food can't be fed free choice because it spoils if left out. Additionally, because they contain little or no carbohydrates, canned foods can create softer stools. Dogs switched abruptly from dry to canned may suffer diarrhea.

Canned food is generally higher in fat than dry food. Also, the increased palatability may encourage dogs to overeat. Canned food also tends to stick to teeth and gums, and it can hasten dental problems if not cleaned away. It can also lead to more pungent doggy breath.

Owners using canned foods have a tendency to overfeed because the dog shows more enthusiasm for freshly opened food. Owners tend to ladle out all the contents of the can, regardless of whether it's an appropriate serving amount. Canned foods are helpful, however, for anorectic dogs or those with tooth or mouth problems. The high moisture content releases both flavor and odor, encouraging dogs to eat, even through oral pain.

Food in Other Forms

Semimoist foods, most often sold in hamburger-like patties or ribbon chunks with a white strip of “fat” running across each chunk, have decreased in popularity. These products require sugars to prevent spoilage, as well as preservatives. They are the canine equivalent of fast foods.

Frozen foods have gradually increased in popularity, though they still lag far behind dry and canned. These foods do not have to be processed at high temperatures, sparing nutrients from destruction by heat. They do have to be refrigerated, and should be heated to room temperature before serving. Their fat content may be too high for a Yorkshire terrier.