There are dog foods made especially for young dogs, old dogs, pregnant and nursing dogs, and overweight dogs, and, happily, there are now dog foods formulated specifically for small dogs.
The Association of American Feed Control Officials (AAFCO), composed of a panel of veterinarians and nutritionists, has set nutritional guidelines for dog food when the dog is growing and when he’s an adult. AAFCO has established minimums and maximums for some nutrients, and then assumed the optimum is somewhere in between. To choose a complete and balanced food for your dog, look for a statement on the package that says the food meets AAFCO requirements.
However, levels of specific nutrients are far from the whole story. Pet foods are formulated according to the energy density of the product, because the idea is that an animal will eat enough to meet his energy needs. In a complete and balanced diet, however, when the animal has eaten enough to meet his energy needs, he should also have met all his other nutritional needs. Nutrients also interact in a delicate balance, so these interactions, plus digestibility, availability, and palatability of the food must be considered, as well. Making a good dog food is even more difficult than choosing one!
One issue that has caused some controversy is the preservatives used in dry food. All the preservatives used in pet foods are clinically tested for safety, so the evidence against them is strictly anecdotal. Some breeders, for instance, will swear that synthetic preservatives cause their bitches to have all sorts of reproductive problems. The Food and Drug Administration has looked at these claims and can find nothing scientific to back them up. And manufacturers have been using synthetic preservatives for more than thirty years. Still, for those who prefer only natural ingredients, there are foods preserved with added vitamins C and E. These foods will say so on the label. Make sure to look at the freshness date on the package, because a food with only natural preservatives has a shorter shelf life.
There has been much talk in human nutrition about chelated minerals. A chelated mineral is one that’s attached to an organic compound. Some-but certainly not all-nutritionists believe that in this form the mineral will be better absorbed into the bloodstream. We do know that the way minerals are absorbed is affected by the form in which they are consumed. And there is some evidence that the biological availability of certain minerals might be improved by giving them as an organic complex, as opposed to an inorganic molecule. This means dogs could eat less of a chelated mineral and still absorb all they need. What’s not clear is how valuable that outcome really is. If you know the bioavailability of an inorganic mineral, you can still calculate how much of the mineral you must add to the dog’s food to ensure he gets enough. This is simpler and less expensive than using chelated minerals, which are more complicated to manufacture.
Minerals that are more efficiently absorbed are not always a good thing, either. With iron, for instance, the body will regulate absorption as needed. In this way the body avoids both iron deficiency and iron excess-each dangerous in its own way. But if you start attaching iron to organic compounds that are being absorbed via different mechanisms, it cheats the natural regulatory system. The body might then end up with too much iron.