The intestinal tract in strict carnivores is much shorter than in other animals. And unlike dogs, cats eat the intestinal tract of their prey last, or not at all, thus avoiding the plant fiber of the intestinal contents. These facts have led scientists and veterinarians to assume that cats need little fiber in their diet. The assumption being that a diet devoid of plant fiber is a non-fiber diet. But plants are not the only source of fiber.
Animal Fiber
The undigested fur, bone, cartilage, tendon and ligaments of prey also constitute intestinal fiber. The undigested hair from the fastidious grooming of cats also provides intestinal dietary fiber. Animal fiber may be extremely important in the nutrition of strict carnivores. A recent study in cheetahs has highlighted these insights.
The Study
Scientists alternately fed 14 captive cheetahs diets consisting of raw, supplemented butchered beef without bones and whole raw rabbits with fur. Each diet was exclusive for an entire month. The scientist monitored various fecal fatty acids and chemicals. What they found was that when cheetahs were fed whole rabbits the fatty acid profile in the feces was more favorable and resulted in a significantly decreased production of toxic metabolic chemicals. The scientist made no mention of fecal volume or consistency differences between the two diets. This study pioneers the concept of animal fiber and the digestive health of captive and domesticated cats. It also raises the question of whether substituting plant fiber in our cats’ diets adequately substitutes for animal fiber for intestinal health.
Plant Fiber in Commercial Cat Food
Oddly, cats share nearly the same spot on the mammal food chain as rabbits. Lacking the stamina to outrun their predators, wild cats have relatively short life spans and high infant mortality. That is why they are induced ovulators (if they have sex they get pregnant) like rabbits and easily become pregnant even while nursing.
As prey, cats have developed biological and behavioral traits to minimize the attention of predators. The feces or “scat” of wild cats is very small and not highly odiferous (smelly). Like their urine, they bury it to further hide any scent. Contrast that with the stool of cats on commercial dry food. Stool in cats fed those diets have huge stool “logs” that can be smelled two rooms away. Granted, this is not important for inside cats but such stool in outdoor or indoor/outdoor cats could draw the attention of dogs and coyotes. Without study, we have no way of knowing whether the substitution of plant fiber for animal fiber has the same beneficial effect in the colon that the cheetah study found. Are we creating larger amounts of stool without knowing its benefit or lack of benefit?
The grooming behavior of cats results in the ingestion of large amount of fur or animal fiber. Current owner preoccupation with preventing or blaming all digestive upsets and coughing on "hairballs" may actually be contrary to the digestive health needs of the cat.
In 29 years of veterinary practice, some feline exclusive, I have yet to remove a hairball from the intestine or esophagus of a cat. Sure it happens, but not to the extent to warrant the present level of concern. Why? Cats fed dry diets generally vomit much more than cats fed canned or meat diets. In addition to food, vomiting also brings up stomach fur. These cat parents assume the hairball is causing the vomiting. Hence all of the vomited Vaseline treated cat kibble to ward off hairballs. In light of the cheetah study the observation should be turned around. The dry food is causing the vomiting and preventing the hair to reach the intestines as intended. Owners who decrease or eliminate dry food from their cat’s diet almost always experience less vomiting and fewer hairballs in their pets, despite the same degree of grooming and hair consumption. Going back to the study, maybe plant fiber is not a good substitute for animal fiber and has unintended consequences in strict carnivores.
More Study
Obviously much more study is needed in this area. It would certainly help us understand the nutritional needs of these interesting carnivores that share our lives. I hope you found this study as interesting and stimulating as I did.
Dr. Ken Tudor
Image: meirion matthias / via Shutterstock