Pet-nutrition experts say that the best dog food is made from top-grade ingredients like meat, whole grains and vegetables. What you don't want is a lot of filler as the primary ingredients; these are items that have less nutritional benefit.
According to reviews, better-quality dog food results in a healthier coat, fewer digestive problems and firmer stools. Because your dog will absorb more nutrients from better-quality dog food, less will be passed as waste.
Dogs love meat, and they need protein. Unlike cats, which need high amounts of protein and no carbohydrates at all, dogs need a diet that contains as much as 50 percent carbohydrates. Still, experts say meat should be the first ingredient, followed by healthy carbohydrate sources such as potatoes or more absorbable grains like rice.
If you've read any dog food labels, you might have noticed the term "byproduct." Meat byproducts consist mainly of animal parts that are not used for human consumption, such as bones, organs, blood, fatty tissue and intestines. If a label says "chicken byproduct," all the parts must come from chicken; the same goes for lamb, beef, etc.
There are two schools of thought when it comes to byproducts in dog food. Some say that because a dog in the wild would eat the entire animal when killing prey, including skin, organs and bones, some amount of byproduct in dog food is just fine. The other school of thought is that byproducts should be avoided entirely, and that a dog's diet should contain meat, vegetables and absorbable grains. These critics say that it's simply too hard to know what exactly is included in byproducts.
Even reviews that say byproducts are fine say that dog owners should look for specific origin, such as chicken byproduct or lamb byproduct. Note that in poultry-based dog foods, the term "byproduct" is used to identify byproduct meals. However, in other types of dog food, byproduct meal can be labeled as "meat and bone meal" (MBM) or even "beef and bone meal." This type of labeling is legal, but clearly misleading.
In dry foods the listing of meat at the top of an ingredient list can be misleading, because meat has a high water content that is removed when processed into dry pet food. However, so-called "meat meal" is meat with the water removed, and finding it high up in the ingredient list is a good indication of a high-protein dry food.
The quality of the carbohydrate sources also matters. High-quality grains, such as rice, provide good nutritional value, but other grains deliver less of what dogs need in their diet. Corn, in particular, gets some scorn among pet-food advocates. Mike Sagman at DogFoodAdvisor.com looks at the pros and cons -- mostly cons -- of corn in dog food. Glutens are another group of ingredients that experts say don't provide much nutritional value to dogs and are a particular concern since 2007's massive recall of pet foods tainted by contaminated wheat and rice gluten from China.
Dog food companies are making moves to get away from using artificial preservatives in dog food. Chemicals used as preservatives, like BHA, BHT and ethoxyquin, have been under scrutiny, and many companies are switching to natural preservatives like vitamin C (ascorbate) and vitamin E (tocopherols). Naturox, which is made from natural ingredients, is also gaining in popularity. Reviews say natural preservatives are much safer. Ethoxyquin has been of particular concern to some because it is also used to preserve certain ingredients -- mainly fish meals -- before they reach the pet-food maker and hence is not included on ingredient lists.