By Dr. Becker
In a recent study on kitty diets, it was discovered that domestic cats have the ability to select and combine different types of commercial cat foods to consistently meet their nutritional requirements for protein, fat and carbohydrates.
Scientists at the Waltham Centre for Pet Nutrition in England conducted the research in collaboration with scientists from the University of Sydney and the Institute of Natural Sciences at Massey University in New Zealand. The study was published in the December 2012 Journal of Comparative Physiology B1.
How the Study Was Conducted
The study was conducted in four experiments, each involving three phases. Phase 1 lasted seven days, during which all the cats were exposed to all the different foods (three dry commercial formulas and three wet commercial formulas) simultaneously. The goal of phase 1 was to assess how the kitties self-selected their nutrition from foods that were unfamiliar to them.
In phase 2, the cats were cycled through eight three-day periods during which they were fed a different pair of wet and dry foods on each of the three days. In this phase, researchers measured the nutrients the cats selected from their food-pair options. Also during this phase, the kitties got more accustomed to the foods.
Phase 3 was a repeat of phase 1, except that now the cats were "experienced" with the foods.
Experiment 1 involved 18 cats who were fed one wet food and three dry foods in separate bowls during phases 1 and 3. For phase 2, the kitties were fed the wet food paired with one of the dry foods for each three-day cycle.
In experiment 2, 17 cats were fed one dry food and three wet foods in phases 1 and 3, and the dry food paired with each of the wet foods during the eight three-day cycles.
Experiment 3 involved 10 of the 18 cats from experiment 1. The kitties were fed three wet and three dry foods in six separate bowls during phases 1 and 3, and three different wet food/dry food pairs in phase 2.
In experiment 4, the cats were offered a food combination of one wet food and one dry food, similar to what they might be offered at home. The foods contained about the same levels of macronutrients (protein, fat, carbohydrate), and the goal was to determine if different formats of food affected the ability of the cats to appropriately self-select a combination of the two foods that met their nutritional requirements.
What the Study Showed
The researchers' conclusion:
"Using nutritional geometry we demonstrate convergence upon the same dietary macronutrient composition in the naïve and experienced self-selection phases of each experiment as well as over the course of the 3-day cycles in the pair-wise choice phase of each experiment. Furthermore, even though the dietary options were very different in each of these experiments the macronutrient composition of the diets achieved across all experiments were remarkably similar. These results indicate that a mammalian obligate carnivore, the domestic cat, is able to regulate food selection and intake to balance macronutrient intake despite differences in moisture content and textural properties of the foods provided."
Remarkably, the amounts of protein, fat and carbohydrate the cats in the study self-selected were right in line with the results of a study published in 20112 -- a study that represents the most extensive analysis of macronutrient regulation ever conducted on any carnivore.
The 2011 study showed that cats have a daily dietary macronutrient intake target of 52 percent protein, 36 percent fat, and 12 percent carbs. These percentages are similar to those reported for free-ranging feral cats, who self-select in proportions of 52 percent protein, 46 percent fat and 2 percent carbohydrates.
The study authors suggest the difference in the carbohydrate intake between pet cats and feral cats could be because domestic kitties have evolved to tolerate a higher level of carbs in the diet from their long association with humans. Put another way, since most commercial cat foods in the last 50 years – especially dry formulas – have contained large amounts of carbohydrates, cats' bodies have acquired a level of resilience to the presence of biologically inappropriate ingredients in their diets.
Most importantly, the study indicates that pet cats have somehow retained the ability – given the opportunity – to regulate their nutritional intake to closely match the natural diet of felines in the wild. And this phenomenon holds true even when kitties are presented with complex combinations of different wet and dry foods.
What This Means for You and Your Cat
One of the study authors and a scientist at Waltham, Dr. Adrian Hewson-Huges states:
"This research has important implications for owners as it shows that cats are able to select and combine wet and dry foods to achieve their target intake of protein, fat and carbohydrate. In terms of products currently on the market, wet foods typically have higher proportions of protein and fat, while dry foods have a higher carbohydrate content."
"Providing cats with a combination of both wet and dry foods enables them to not only mix a diet in line with their preferred macronutrient target, but also express their desire to sample different foods."
Waltham is the parent company of Mars Petcare, manufacturer of several large pet food brands including Pedigree, Whiskas and Royal Canin. As such, in addition to conducting pet nutrition studies, the company also has a clear interest in selling their products.
Since an increasing number of veterinarians and pet owners are recognizing the tremendous importance of moisture in cats' diets, one could logically conclude that manufacturers of dry cat food – which is much less costly to produce than a reasonably high quality canned food – are concerned for the future of their kibble products.
While I agree with Dr. Hewson-Hughes that kitties should be offered a variety of different foods (as should dogs), I don't believe dry cat food should be on the menu. One thing the recent study doesn't address is the critical need for moisture in feline diets. A cat's natural prey is 70 to 80 percent moisture. Most dry foods are around 12 percent. Feline bodies are designed to get most of the moisture they need from the food they eat and not from gulping large quantities of water like dogs do. Your cat doesn't have a strong thirst drive compared to other species.
If you want to feed your cat a healthy variety of foods, you can offer a combination of homemade raw (or cooked), commercially available raw, dehydrated raw, and/or human grade canned. It's crucially important that any diet you feed your pet be nutritionally balanced, species-appropriate, and made from high quality protein sources.
One more thing …
While domestic cats have the ability to select the right percentage of protein, fat and carbs when given the option, this doesn't mean they can select the appropriate amount of calories they require for their typically sedentary lifestyles.
Animals living in the wild have no opportunity to overeat – their problem is often the opposite. But pet cats (and dogs) living indoors with their human families are another matter.
Keep in mind that your cat is a natural hunter, and much of the food seeking he does around your house is not driven by hunger, but by his drive to hunt prey.
If you leave "prey" in his bowl, he'll eat it. If you leave too much in his bowl or keep refilling it, he'll eat that, too. He'll keep "hunting" and eating as long as there is food available to him.
All that to say … you must feed portion-controlled meals to your cat – preferably one in the morning and one in the evening. Don't leave it up to her to decide when she's full. And don't indulge Fluffy with an all-day, all-she-can-eat buffet. Of course, this is especially true if you're feeding a diet that spoils quickly at room temperature. But even if you're still feeding some kibble, I recommend you offer two portion-controlled meals daily.
If your cat is overweight or you have no idea how many calories he should consume in a day, you can figure it out using the formula and information in my article Valuable Tips for Helping Your Heavy Cat.