Whether you feed your dog a premium commercial food or prepare homemade meals, it is important to understand the fundamentals of canine nutrition. Here is a review of the basics to help you get started in making the right and informed choices for your dog.

There are six major classes of nutrients: protein, fat, carbohydrates, vitamins, minerals and water.

It all begins with energy, the basic requirement of life. The energy content(measured in calories) of a food is determined by how much of the first three elements the food contains. Vitamins and minerals are also essential for many functions of the body and, because about 70 percent of a dog’s body is made up of water, that too is critical.

PROTEINS
Proteins are complex molecules made up of amino acids, the building blocks of cell growth, maintenance and repair. In companion animals, one of the biggest demands for protein comes from the maintenance of fur and hair, which can use up to 30 percent of the daily protein intake, according to Barbara Fougère, BVSc.

Proteins are made up of 20 amino acids. While dogs, cats and even humans produce about half of these amino acids internally, the other half, termed “essential amino acids,” need to be provided by the diet. The 10 essential amino acids are arginine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine. If even one of these “essentials” is deficient, as Lowell Ackerman, DVM, explains, the body cannot make specific proteins effectively. Amino acids work in a step-by-step fashion to manufacture protein.

If one of the steps is missing, the process stops. The biological value of proteins indicates how efficiently an animal utilizes them. Animal nutrition expert Donald Strombeck, DVM, notes that this value is high for proteins from meat, most meat by-products, eggs and dairy products. “Dogs digest these proteins efficiently and they provide amino acids in proportions suitable for tissue protein synthesis. In contrast, the biological value of most plant proteins is low, due to insufficiencies of specific amino acids and lower digestibility.”

FATS
Fats provide the most concentrated source of energy in the diet. They also supply the fatty acids that are important building blocks for important substances and essential to maintaining normal, healthy cells. Along with protein, fats contribute to a diet’s palatability, plus aid absorption of the fatsoluble vitamins A, E, D and K.

Like protein’s essential amino acids, fat has its own essential fatty acids (EFAs): linoleic acid, linolenic acid and arachidonic acid. Because they make up an important part of every cell, they are also required by animals. Linoleic acid is the source of omega-6 fatty acids, and linolenic acid is the source of omega-3 fatty acids. According to Strombeck, animals need more omega-6 (linoleic acid) than omega-3 fatty acids for health.

CARBOHYDRATES
Although dogs do not need carbohydrates because their bodies can get energy from protein and fats alone, carbohydrates that can be broken down by the digestive system and converted to glucose can also be a source of energy. (Carbs can be the main caloric source in some dog foods.)

Carbohydrates in the form of whole grains can furnish iron, minerals and fiber as well as other beneficial nutrients. Since cooking determines starch digestibility, and therefore its availability, starches need to be well cooked; otherwise, they tend to ferment in the large intestine. Carbohydrates can be found in vegetables and fruit, which also supply minerals, fiber, antioxidants, phytochemicals and some protein.

VITAMINS
Fresh, wholesome food provides your dog (as well as you) with the best source of vitamins, organic substances required for normal functioning of the body. They are also important in the conversion of calories to energy. Ackerman points out that they are needed in only small amounts: “All of the vitamins needed by your dog on a daily basis could be provided by a fraction of a teaspoon.” (See chart on for ingredient sources for vitamins and minerals.)

MINERALS
Minerals are inorganic nutrients that make up less than 1 percent of a dog’s body weight but are essential to many important functions, such as growth and strong bones and teeth. They are classified as either macrominerals or microminerals. It is important to note that two of the macrominerals, calcium (the most abundant mineral in the body) and phosphorus, must be in balance and given in correct proportions (the ideal calcium:phosphorus ratio is between 1:1 and 2:1). Microminerals (also known as trace minerals) serve very important functions as well. Balance is critical with all minerals because they interact; too much of one can interfere with the absorption of another.

BOTTOM LINE
If you elect to feed your dog commercial food (and most of us do), here’s what to look for and what to avoid when you’re standing in front of a shelf of carefully designed bags, cans, pouches or boxes.

High-quality named animal proteins should be the first ingredient, and, ideally appear more than once as top items on the ingredient list. Note that whole meat is made up of a lot of water (up to 75 percent), so if a whole meat is listed as the first item, the food might not contain an equal amount of meat by weight unless there is another whole meat, or a specifically named meat meal (chicken meal, for instance, which is about 10 percent water). Avoid foods that use generic “meat” meal; the actual type of meat needs to be named: lamb meal or chicken meal, for example. Fat should also come from named source, avoid generic “animal” fat.

Whole fruit, vegetables and whole grains which contain the entire grain kernel. For example, rice rather than rice flour or bran. Refined grain products, gluten and mill runs should be avoided.

Natural preservatives like tocopherols (Vitamin E) and Vitamin C, or antioxidants like rosemary extract.

Avoid: All by-products (from meat, grain or any other source); added sweeteners (which are usually listed as grain fragments); artificial preservatives such as BHA, BHT, ethoxyquin, propylene glycol; and artificial flavors or colors.

Dry-Matter Basics
When you compare different types of foods — canned, kibble, etc. or simply different brands — you need to keep in mind the moisture content so you can compare like to like. Use the dry-matter basis.

First, establish the amount of dry matter by subtracting the percentage given for moisture from 100 percent. If the moisture is given as 10 percent, the food’s dry-matter content is 90 percent.

Next, convert the protein found in the Guaranteed Analysis statement to a drymatter basis by dividing its percentage by the amount of dry matter (calculated in the previous step). For example, if the protein is given as 26 percent, it converts to 28 percent on a dry-matter basis (26 divided by 90). If the moisture level had been, say, 30 percent, the dry matter content would have been 70 percent and protein would have been 37 percent (26 divided by 70).

You can do similar calculations for fat and fiber after converting their percentages to a dry-matter basis.

TREATS
Although treats are usually given in small portions (or ought to be!), make sure that you pay the same high level of attention to what’s in them as you do for all of your dog’s food. Look for organic, wholefood ingredients, including named meats, whole grains, lots of good fruit and/or vegetables and natural, food-based sweeteners (if they are used at all) — applesauce, honey or molasses, for example. Avoid by-products, artificial coloring, artificial flavoring and artificial preservatives. Look for individual portions that are easy to break into smaller bits.

Treats are often high in calories, so factor them in when thinking about your dog’s overall food intake. It is recommended that “treat substitutes” make up no more than 5 to 10 percent of a dog’s diet. If the calorie count isn’t listed on the label, find out what it is before giving them to your dog. Contact the manufacturer for calorie information if need be.

To keep bagged treats fresh — and make it a little more difficult for the diligent treat-hound to score — keep the bags sealed. If the seal doesn’t work (often they don’t), use heavy-duty zip lock–type bags or store them in glass or ceramic containers with tightfitting lids.

Dogs love variety, and with the wide array of treats on the market, it’s easy to find a selection that will satisfy most co-pilots.