Dogs prefer foods high in fat while cats are carb lovers, according to study results published in the Journal of Experimental Biology. The study, conducted by Carlson College of Veterinary Medicine at Oregon State University, monitored 17 healthy adult dogs and 27 cats over a 28-day period using four types of foods designed to encourage subjects to make food choices based on what their bodies were telling them they needed—not based on flavor. If palatability isn’t balanced between foods, cats prefer to eat high levels of protein and dogs want to eat high levels of fat, according to OSU’s Jean Hall, DVM, Ph.D., DACVIM, the study’s corresponding author. With the flavor factor removed, the results were “much different than what traditional thinking would have expected,” said Dr. Hall. “Some experts have thought cats need diets that are 40 or 50 percent protein,” she said. “Our findings are quite different than the numbers used in marketing and are going to really challenge the pet food industry.” The dogs and cats in the study had four food choices: high-fat, high-carbohydrate, high-protein, and balanced foods. Dogs had one hour each day to eat all they wanted up to a predetermined caloric threshold; cats had 24-hour access up to the same cutoff. Food container placement for both was changed daily to prevent bowl-position bias. On average, the cats chose to get 43 percent of their calories from carbs and 30 percent from protein; dogs chose foods containing 41 percent fat and 36 percent carbs. No animal chose to get the highest percentage of its calories from protein. Younger cats with less lean body mass tended more strongly toward protein consumption than younger cats with leaner body mass. Younger cats in general wanted protein more than older cats. Among dogs, high-protein foods were the least popular with younger animals with less fat body mass; dogs with greater fat body mass had the strongest preference for protein. “Because the choice of macronutrients was influenced in both dogs and cats by age and either lean body mass or fat body mass, that suggests a physiological basis for what they chose to eat,” Hall said. The study also aimed to determine how the diets affected selected metabolites of each macronutrient class—what they break down into in the body. Hall found that the blood of older cats contained much lower levels of DHA. “None of the foods had ingredient sources of DHA or EPA, but cats are able to synthesize DHA by elongating and desaturating fatty acids,” Hall said. “The older cats, though, are a lot less efficient at that.” Also, older cats’ concentrations of sulfated microbial catabolic products were significantly higher. “Just like with older people, older cats may have a different gut microbiome than younger cats, which would mean different microbial metabolic activities,” Hall said. The Pet Nutrition Center of Hill’s Pet Nutrition Inc. supported the research.
