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With pet-food manufacturers marketing hundreds of food varieties from mostly plant-based feed to "premium" brands with human-edible cuts of beef and poultry, a pet owner faces a difficult decision.
"Pet owners have to decide what kind of diet to feed their animals," said University of Illinois animal scientist George C. Fahey, who has studied pet nutrition for 20 years. "The premium-type diets are oriented toward the pet owner who can let the pet out in the morning and in the evening. Such diets lead to small stool production, which is an ideal situation for a person who goes off to work for 10 hours and leaves the animal inside."
In a paper published in the September 1997 issue of the Journal of Animal Science, Fahey's team reported that pet food with either raw meat or animal by-products (beef and poultry) were nearly identical in digestibility, that both were slightly better digested than a plant-based control diet of defatted soy flour, and that some poultry by-products were only slightly less digestible in the small intestine than was food with raw poultry. Overall, by-products in feed are good sources of digestible nutrients, the authors concluded.
The poultry by-product effect, Fahey said, probably resulted from extraneous material, such as feathers and egg shells being included in the feed. By-products are rendered edible by cooking them at high temperature and high pressure, and their use is both legal and acceptable in pet food.
According to the American Association of Feed Control Officials, only amounts of hair, feathers, hooves, horn and other such materials that are naturally occurring in raw animal materials may be used in processed animal by-products. The problem for concerned consumers is that food labels only show that by-products are used, Fahey said.
When it comes to choosing pet food, an owner should remember that dogs are not true carnivores, Fahey said. Dogs can get sufficient nutrition from plant-based feed, but some plants such as soybeans can result in greater stool production and flatulence, neither of which is a desirable trait in indoor dogs. Premium meat-based foods produce fewer stools and less gas. They also may cost more, but they are often fed in lesser quantities because they contain higher levels of protein.
Authors of the report were:
Fahey;
animal-science graduate student Sean M. Murray;
postdoctoral researcher Avinash R. Patil;
and Neal R. Merchen, a professor of animal science and of
nutrition,
all of the University of Illinois;
and Denzil M. Hughes, a pet nutritionist of Farmland Industries
Inc. of Kansas City, Mo.,
which provided partial funding for the research.