Dear Dr. Jody: We have just adopted a new dog from the humane society. “Bella” is a 6 year old shepherd cross. We want to provide her with the best nutrition possible, but so many pet foods, even supposedly premium pet foods, list corn and meat by-products high in their ingredient list. Why would pet food manufacturers include these ingredients?
The public seems to have developed a definite fear of feeding corn to their dogs. Despite the fact that corn is held in high regard as a nutritious summer indulgence that graces our tables at barbecues and family picnics, corn has received an unfair reputation as being low quality filler in pet foods. Controlled clinical trials have demonstrated quite the opposite. Corn is a low fat source of protein and carbohydrates. It contains no fewer than 18 essential amino acids, and is a very high source of vitamins and minerals including thiamine, niacin, folic acid, vitamin C, iron, magnesium, and potassium. Corn offers an easily digestible source of energy and yet has a lower glycemic index than brown rice or pasta. Because dogs are omnivores and not obligate carnivores, the same qualities that render corn a high quality source of nutrition for humans make it an appropriate addition to dog foods. Numerous clinical trials have demonstrated that dogs are actually significantly higher risk for developing allergies to beef and dairy ingredients than they are to corn.
In answer to the second half of your question, by-products are not necessarily evil ingredients in pet foods. One of my colleagues works at a wolf sanctuary. When the wolves are fed whole fresh highway-killed deer, the veterinarian reports the wolves rarely spend much time gnawing on meat. First they eat the intestines, stomach, and other digestive organs that are filled with corn, grass, and other greenery from farmers’ fields. The birds and other scavengers eat the meat for about three days before the wolves finally start consuming this part of the carcass. They then consume the bones. Given the choice, wolves seem to prefer the by-product parts of the carcass. By-products can actually be a very high source of nutrition that is sought out by wild canids.
Many premium pet food companies chastise veterinary lines of pet food for including by-products in their ingredients when they themselves are including by-products under different names. For example, one popular line of premium pet store dog food states that the second and fourth ingredients are chicken and turkey meal. Poultry meal by definition is the meat, skin, and bones of a bird’s carcass. Bones and skin are by-products. Chicken liver and chicken fat, also on the ingredient list, are by-products as well. And one of the most high quality dog treats available is freeze-dried liver bites. And guess what…liver is a by-product! By-products are not necessarily something to be avoided.
Many premium pet foods make their product more appealing to the human consumer by including ingredients such as apples, cranberries, and blueberries. An independent study revealed that the approximate volume of blueberries included in one of these brands is one-half of one blueberry per pound of kibble! Including ingredients that appeal to human consumers, even if the ingredient is not included at significant levels, can be a very clever marketing tool used by many pet food manufacturers.
The take home message is that corn and by-products are not necessarily four-letter words. Not every food is appropriate for every pet. If you have specific questions about the quality and ingredients of your pet’s food, please contact your veterinarian. Many veterinarians have advanced university-level training in nutrition, and we are more than happy to discuss your pet’s nutritional needs.
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