One of the immediate results when feeding my raw cat food is less cat poop, and cat poop that smells less. While some cat owners welcome this change, some are concerned that their cats might be constipated.

Feeding raw can closely resemble NUTRITIONALLY what cats would eat naturally if living wild in their native habitat, but it is, despite best efforts, not a truly natural diet. The natural diet can only be replicated by feeding small whole prey. One of the biggest differences between feeding raw and the natural prey diet is: FUR. Fur, ingested with prey, has no nutritional function, but serve two key mechanical functions which we lack when feeding a home-made raw diet: A.) by action of cats biting down on small prey, the fur of the prey is brushing up against the teeth of cats, helping to wipe away plaque and preventing accumulation of tartar. B.) it has an important role as a non-irritating stool bulker.


Above: my cat Charlie hunts and eats wild Eastern Cottontail rabbits. The juvenile rabbits he is mostly catching weigh up to 500 gram (~ 1 pound) and he will consume most of it! Stomach, intestines, and cecum are always left behind, and so are the feet. The head is often eaten. Otherwise, Charlie eats the whole rabbit – skin, fur and bone. Note how his teeth sink into the fur – wiping away plaque on the teeth. The resulting scat from Charlie is deposited as little dry pellets which are very light. They are almost like dense felt! Their content is crumbly digested bone, lots of hair, some grass and even teeth from the rabbit. (Click to enlarge image)

Unfortunately, fur is next to impossible to substitute in the raw meat diet, because we can not add hair or fur to a recipe. Instead, people resort to a number of ingredients from plant origin to fulfill this need. The cereals, potatoes, peas, and beet pulp in commercial pet foods are not only intended as a source of inexpensive calories and for texture, but they also serve to bulk stool. The same goes for vegetables and fiber supplements in home-made recipes. But fur is protein, while stool bulkers from plant source are cellulose and starch based. Cellulose and starch is fermented in the lower digestive tract by different bacteria than fur would be, and this can cause problems. Problems may arise right from the start when cats are reluctant to eat a food filled up with vegetables or fiber supplements, or regurgitate the food because of it.

Perhaps, what some cat owners observe as constipation isn’t really a problem? Perhaps it is a trademark of an animal that is native to a mostly semi-arid climate?

Having evolved in the dry climate of Africa and the Near East, cats are superbly equipped to conserve water. They do not sweat and rarely pant; they concentrate their urine to a high degree and extract all possible fluids from feces before they leave their body. They are so efficient in conserving water that they can exist on the fluids provided by eating prey alone. Their feces will naturally be very firm, pellet-like, dry, and off-white or with a yellow tint. Their content will be crumbly, held together largely by hair – cat hair and that of prey. Below is an image of scat from a wild African Wildcat (Felis silvestris lybica), courtesy of the Hoedspruit Endangered Species Centre in Africa.

African Wildcat scat

The following image is scat from a wild Scottish Wildcat (Felis silvestris grampia) courtesy of Highland Tiger (Royal Zoological Society of Scotland).

wild cat scat_Highland Tiger_the Scottish wildcat

If your cats’ feces look similar to the above or below image, all could be well, but is possibly not what YOU thought the feces of cats should look like. The feces pictured in these images are certainly something that I see in my own raw fed cats. My attempts to change the appearance of the feces by addition or omission of ingredients have been unsuccessful. As a result, my cats produce small, dry feces and often only twice per week. Over the past 20 years that has simply not led to any problems in my cats. Based on the description of what constipation is, my cats should be constipated.

Constipation includes infrequent bowel movements (typically three times or fewer per week), incomplete bowel evacuation, and difficulty during defecation due to hard, dry stool, causing straining during more than 25% of bowel movements, the cause of which is a slow transit time (the time which elapses from when food is ingested to its excretion in the form of stool).

Scats from eating mice vs. scats from eating a raw diet

Above: scat study from 1998 with my own cats. Left column of images is scat from cats eating frozen mice. Right column is scat from the same cats eating my raw food which also contained Psyllium husk. Do you see a difference?

Scats from eating a raw diet without fibre

Above: scat study from 2008 with my own cats to determine if cats require fibre. All scat samples pictured are from eating a diet without added Psyllium husk, which had been a main staple in the diet for years. The scat samples do not differ from scat samples in the previous images.

Some cats have a real problem with constipation, however. Restlessness, lack of appetite, vomiting, and frequent trips to the litterbox to defecate WITHOUT results requires Veterinary attention. A Veterinarian will help to diagnose its cause and find an appropriate solution, because constipation is not always diet related. To relieve the acute condition, A Veterinarian will administer an enema and prescribe medication and laxatives.

To help prevent constipation, various methods have been tried. Some are successful; others only in the short term; some are of no benefit at all. Interestingly, some of the successful methods are often effective for only some time, until cats have dry, infrequent bowel movements once again despite of it.

Stool volume and frequency of bowel movements increases as the portion of indigestible matter in food is raised. Large, frequent bowel movements indicate that the food eaten is largely indigestible, and little of it is being utilized. If it is desirable to increase fecal output, the order of the day must be to increase the content of indigestible matter (filler) in the food. Commercial dry foods, for example, produce bowel movements of unnaturally large size, loose texture, intolerable odour, and high frequency due to the high content of ingredients of poor nutritional value.

WATER. Adding more water to the diet in hope of making feces softer does not work. Cats physiology is such that they naturally extract as much moisture from feces as possible before voiding them. Adding water to food will increase urine output, but reduce food intake, because the same volume of food now contains more moisture. Reduced food intake will result in fewer feces and makes constipation worse.

INCREASED FOOD INTAKE. I have observed that kittens are rarely constipated. Every day they void nice feces on the raw food. Compared to adult cats, kittens consume proportionally much more food to support their daily energy requirements and support growth. Active cats that eat more food to support the energy requirement of their lifestyle also have larger and more frequent bowel movements. Simply put, food volume translates into fecal volume. Increased food intake signals more frequent emptying of the bowel before feces become excessively desiccated in the colon which perpetuates the constipation problem. Inactive cats that just nibble on their food instead of eating it with gusto are very prone to constipation. It is important to increase palatability of the food to assure that cats eat a healthy portion at each feeding.

CAT HAIR. If the fur of prey is an ideal stool bulker, then cat hair is a second best. Cats will naturally ingest a lot of their own hair during grooming, and this should not be discouraged. Excessive brushing and bathing may leave your cat short on laxatives! Cat hair should pass through the entire alimentary tract without causing any concern. Healthy cats eating my raw food regurgitate almost no hair balls. If cats regurgitate hairballs, crave eating grass, and also bring food back up then something is wrong!

BONE. The feeding of raw bones or bone meal has been linked to constipation. There are two sides to feeding bones, however. Whole bone recipes deliver an excess of dietary Calcium, because Calcium needs to be in balance to Phosphorus, which bones add in abundance to the diet as well. (Calcium in bone is present as Calcium Phosphate). An excess of Calcium in the diet can contribute to constipation. But bones are not entirely made of Calcium Phosphate or minerals. Bones are mostly a dense protein matrix in which mineral stores are laid down to give bone rigidity, but also serve the body as a reserve of minerals. This protein matrix of bone isn’t unlike fur. It is largely indigestible and as a result bulks stool! Undigested bone in feces looks like crumbly lime.

MAGNESIUM. Calcium can contribute to constipation, while Magnesium may be used to relieve it. Magnesium has many functions in the body, including buffering stomach acid and moving stool through the intestines. As an essential mineral it must be present in the diet in sufficient amounts, but due to its connection to urinary struvite crystals, many diets for cats are low in Magnesium. Some cases of constipation could, therefore, be a Magnesium deficiency. A larger dose of Magnesium can be used therapeutically as a laxative. The laxative property of Magnesium has two mechanisms. Magnesium is essential for proper muscle function in that it aids in muscle relaxation in general, but is also responsible for a smooth rhythm of the intestines. Magnesium also attracts water, increasing the amount of water in the colon to help soften the stool.

DRY CAT FOOD. Often, for those not opposed to feeding a combination diet of raw foods and commercial foods, feeding some dry foods adds all the bulk needed to the diet. As long as the diet is mostly comprised of raw or wet foods, feeding some dry food to keep cats regular should not expose them to the same risks as feeding exclusively dry food (cats exclusively fed dry food often have a inadequate intake of water which predisposes them to bladder and kidney disorders). However, the problem with including some dry food is that some cats become more and more reluctant to eat their raw food and only want dry food. Including any amount of commercial foods also means that cats are still exposed to a risk of eating potentially “tainted cat food”.

RAW LIVER AND FAT. Raw liver can act like a mild laxative. Increasing the fat content of the meat used to make the diet can encourages a faster transit time of matter through the digestive tract and can encourage more frequent emptying of the bowel. Mild flavored vegetable oil like canola or sunflower oil can be added to the food as well or instead of using fattier meats. Some cats really enjoy olive oil and will lap it up pure. Vegetable fats are not as easily digested by the cat and may help hasten things along in a similar manner as oral petroleum jelly remedies would.

PUMPKIN. By far one of the most popular remedies for constipation in cats by Veterinarians and owners alike is inclusion of pure canned pumpkin to the diet. Results are mixed. According to data by the USDA, canned pumpkin is 90% moisture and 2.8% fibre. That means that with each tablespoon of canned pumpkin mixed into a portion of cat food, mostly water and little fibre is added. This means that canned pumpkin is not a stool bulker, but must have other laxative effects. I have heard that canned pumpkin has short-lived effects, however. Cats appear to get accustomed to it, and feces return to being small, dry, and infrequent. Although canned pumpkin is accepted by many cats, some cats will not eat food in which it was included.

My own version of adding pumpkin to the diet is to create a VEGETABLE MIX with butter. For that 450g (2 cups) canned pumpkin are heated and 220g (1 cup) butter is melted and blended into the warm pumpkin. This is then added to a recipe of raw cat food using 900g raw meat and 100g raw liver. Before serving, it is best to warm this type of food. The butter increases fat content of the diet, which can encourages a faster transit time of matter through the digestive tract, but also increases palatability. Alternatively, and perhaps preferably, steam-cooked and pureed yam or butternut squash can be used instead of canned pumpkin.

VEGETABLES. I can not truly recommend the addition of any vegetables to the diet of cats. If vegetables are to be included as an aid in helping to prevent constipation, I would have a preference to using cooked or canned pumpkin, squash, or yam as described above. Some cats do appear to have a liking to canned peas and chick peas, and, perhaps, including them in the diet, pureed, is helpful for some cats. I hear that some owners like feeding pureed vegetable baby food from jars.

GROUND SUNFLOWER SEEDS. Sunflower seeds, for cats, represent an interesting solution to help bulk stool. They are very mild in flavor and practically indigestible for cats, which means that they pass through the alimentary tract of cats fairly unchanged. They can be ground into a powder with the help of an electric coffee bean grinder. 20 years ago, when I began formulation my raw diet for cats, I included them successfully as part of a seed and nut mix which attempted to mimic the stomach content of a mouse.

GROUND FLAX SEEDS. Flax seeds are a popular fibre supplement for people. Their mild and nutty flavor may make them suitable for use in cats to bulk stool. BUT USE WITH CAUTION! Flax seeds must be added to the food just before cats eat it, or they must be boiled first. All flax seeds contain cyanocenic glycosides which release toxic hydrogen cyanide in the presence of water. The longer raw fax seeds sit in water (or in raw food!), the greater the concentration of toxins. Boiling the flax seeds neutralizes the toxin. Flax seeds are best used finely ground, or use a defatted flax fiber supplement. Remember to boil all flax products before including them in cat food. Flax boiled in water creates a gelatinous texture that creates an overall pleasing food texture and may aid in increasing moisture of feces.

PSYLLIUM HUSK. Psyllium husk, also sold as the popular brand “Metamucil”, is a well known remedy for preventing constipation in humans. It is also used by Veterinarians and cat owners for cats with constipation. Its effectiveness may be short lived, however. It appears that with long term inclusion of Psyllium husk in the diet of cats the remedy loses its effectiveness. It is, therefore, best used as a short term therapeutic remedy. CELLULOSE GUMS have a similar function and in a similar way as Psyllium husks lose their effectiveness if used long term.

BRAN. Bran is a well known source of fibre from wheat, oats, or rice. Wheat and rice bran is not very palatable. Oat bran is high in starch. Personally, I would not subject my cats to any form of bran for fear of causing undue discomfort like regurgitation, vomiting, gas, or diarrhea.

Do cats need a source of fibre in their diet? Fibre is not considered essential for simple stomach carnivorous mammals like cats. As part of their natural prey diet, cats do not ingest dietary plant fibre and their digestion requires no substrate or medium for food fermenting bacteria to live on. Fibre plays an important role in the diet of omnivores, and is essential in the diet of herbivores which exist largely on byproducts created by bacterial fermentation of cellulose (fibre), but cats as strict carnivores have no natural need for fibre.

Introducing plant fibre or starches into the digestive tract of cats means creating a habitat for bacteria which might otherwise not multiply there or be part of the natural gut flora of cats. When these bacteria proliferate and begin to ferment the fibre and starches they create gases which can not only be very uncomfortable to cats, but they can also be toxic and cause inflammation. Inflammation of the intestines will then result in loose stool or diarrhea. Inclusion of plant based fibres and starches in the diets of cats needs to be approached with caution and cats need to be observed for regurgitation, excessive gas, or irritation to the lower digestive tract resulting in loose stool or diarrhea. High levels of fibre in the diet of cats from excessive inclusion of foods or supplements from plant source can depress digestibility of nutrients and outright displace nutrients. Sometimes the cause of constipation is not related to the diet or lack of bulk in the diet, in which case adding fibre will not promote stool bulking and more frequent bowel movements.

Cats with a tendency to regurgitate their food should not be given fibre, although they may be constipated, because fibre supplements or addition of vegetables may increase the frequency of regurgitation. Cats that regurgitate food should be fed several small meals of highly digestible food throughout the day. They should not have essential nutrients and calories replaced by bulk in their diet. Constipation in these cats may simply be the result of a lack of food volume passing through the digestive tract. Consistent, small meals throughout the day of highly digestible food should soon remedy this while, with the help of a Veterinarian, the underlying cause of the repeated regurgitation of food is being investigated.