Carbohydrate
Carbohydrate is generally not listed on the label, but if you add up the percentages of everything listed, fat, protein, "ash," water, etc. and subtract from 100, you will get the percentage of carbohydrate. Carbohydrate comes from grains and other starches such as potatoes and sweet potatoes that are used in some foods.

We have not found authoritative information on the effect of feeding dogs a lot of carbohydrates. Veterinary gastroenterologist Donald R. Strombeck, DVM, PhD, the most trustworthy source we have been able to find, advises that diets including a lot of grain are not healthy for dogs, but the diets he recommends do contain modest amounts of carbohydrate.

Water
Canned foods contain a lot more water than kibble. To compare the nutrient contents of a canned brand with a dry brand, you must calculate the dry percentages in the canned brand-what it would contain if it was dried out. To do this, first subtract the percentage of water from 100 to get the "dry weight" in 100 grams of food. For each ingredient of interest, divide the percent on the label by this "dry weight" number, and multiply by 100 to get the "dry" percentage of that ingredient for comparison to dry food.

Sugar and Salt
Salt is often added in much greater quantities than required for health, to improve palatability, just as in human foods. Sugar is added for the same reason. We are told that dogs are subject to some of the same problems as people who consume excessive sugar and salt. We recommend that you keep a careful eye on the salt and sugar content of the foods you feed.

When preparing boiled chicken and rice, or otherwise using meats packaged for human consumption, be aware of the recent trend to inject ("enhance") meat and poultry with salt or "brine," "broth," or "seasoning" solution. Terms such as "natural" on the label are no assurance the meat or poultry has not been so treated. If in doubt, look at the nutrient label. Naturally occurring sodium is in the double digits, not the triple digits. If you are nursing a sick dog with chicken and rice, get untreated chicken and avoid that extra salt.

Vitamins and Minerals
These are frequently assumed to be adequate in commercial pet diets.

Preservatives
Preservatives get some bad press, but of course they are necessary to keep dry food from spoiling. Vitamin E is a popular antioxidant, but note that it is used up in the process, so its use as a preservative does not mean your pet is getting plenty of Vitamin E. Ethoxyquin is a common antioxidant preservative that has been extensively studied in pet foods (and in pets). It has anti-cancer properties and, as far as we know, no known injurious effects on health.

Additives
Additives such as DHA, glucosamine, probiotics, and so forth have been demonstrated beneficial in various studies. A caveat, though, is whether the quantity included in the various pet foods is enough to be effective, or whether it's simply a marketing ploy. We add fish oil (source of DHA) and probiotics to our own dogs' food.