Let Talk About Poop

Poop. Everybody does it, and dog and cat owners are almost universally fixated on the quality and frequency of their animal’s defecation habits. Is it too soft, too hard, too smelly, too frequent, in the wrong place? I think just about every consult I had in my referral practice was either about poop, or poop would get worked into the discussion somehow. For some of my patients it was diarrhea that brought them to my exam room, but even in those with “healthy” gastrointestinal tracts, occasional soft stool or diarrhea, especially after a diet change or overindulgence (usually the unintended stealing-food-off-the-counter kind), would occur.

everyone poops

A must read for everyone with human kids.

Pet owners are aware of their dog or cat’s defecation habits more so than their own, and definitely more so than their other human family members (unless you are the caregiver of a kids still in diapers). My kids are well passed potty-training and as a parent of pre-teen kids I’d be hard pressed to tell what their poop is like day-to-day unless my son forgets to flush the toilet (he is a boy after all). My cats, though, are a different story.  I know that the youngest one, Loki (1), gets diarrhea if he eats too much canned cat food or with certain brands of dry cat food, but he can eat small amounts of people foods without ill effect; the oldest one, Oliver (17), gets colitis if he eats the wrong variety of canned food but seems to do well with just about any dry foods; and my middle cat, Cosette (3), has an iron stomach and has had perfect poops since we brought her home as a kitten no matter the diet. And yes, I can identify each of their poops in the litter boxes and know that Cosette and Loki like to poop in one box and pee in another, but that anything goes with the third box. I also know that the old man of the bunch has pretty bad arthritis and long hair so he occasionally gets hangers-on because he stands instead of squats now. TMI with the litter box habits, but if other pet owners can share with me I should be able to share with you, too.

So what causes diarrhea and how can you as a caregiver decrease the risk that you will be cleaning it up off laundry room floor? The first thing to understand is roughly how the gastrointestinal tract works. The basic idea is that the process of digestion begins in the stomach with acid and enzymes breaking down proteins. Food exits the stomach into the upper small intestine in a controlled fashion to help prevent overwhelming small intestine’s absorptive capacity (the small intestine can handle only so much food at a time). In the upper small intestine (the duodenum), the pancreas releases bicarbonate to neutralize the acid and additional enzymes to continue the protein breakdown as well as start digestion of fats and carbohydrates. The gall bladder also releases bile into the duodenum at the same time to allow fat to be absorbed. These smaller particles are then absorbed along the length of the rest of the small intestinal (primarily the jejunum, but also the ileum to some extent). A dysfunction of any one of these organs will prevent normal absorption and can cause diarrhea (with a different appearance and more severe health consequence compared to diet-induced colitis), but so can feeding a larger volume of food or a larger amount of protein, fat, or carbohydrates than what the body is equipped to handle at that time. Diarrhea caused by making an abrupt diet change will often get better over 3-4 days, about how long it takes for the pancreas, liver (where bile is made), and  small intestine to catch up, but sometimes needs medical from your Veterinarian help to clear up faster.

Once the nutrients have been absorbed in the small intestine, whatever is left makes its way to the large intestine (colon) were it is formed into what we recognize in the litter box and yard as normal poop. The colon acts as a “holding tank” until the appropriate time and place to move the poop out; water and nutrients that are dissolved in water can be absorbed from the colon; and the colon is home to a large number of bacteria, many of which support animal health and normal colon function. These beneficial bacteria can release essential vitamins from the remaining foodstuff (like vitamin K), can produce compounds that support colon cell health (such as butyrate, the preferred energy of the colon cells), and can outcompete pathogenic bacteria such as Salmonella and Campylobacter preventing them from getting a foothold and causing disease. The beneficial colonic bacteria prefer to use dietary plant fibers (fermentable fibers specifically) as a food source, but will use protein, fat and starches if necessary. Some of the most noxious gasses produced in the colon (such as cadaverine, the smell of rotting flesh that some gassy dogs can make) are created by the bacterial fermentation of undigested animal proteins. Non-fermentable, insoluble fibers (like bran or cellulose) are necessary as well, adding bunk and form to the poop and acting as “nature’s broom” sweeping out sloughed intestinal cell and extra bacteria.  Changes in diet, especially changes in protein, fat and fiber levels, can cause a bacterial dysbiosis (meaning the amount and types of bacteria in the colon get out of whack) and are a common cause of diarrhea in dogs and cats.

Oliver in his younger poopy bottom days.

Oliver in his younger poopy bottom days.

In my experience, inadequate fiber intake in otherwise healthy dogs is a relatively common cause of colitis-like signs especially if they are a large breed or when they are fed certain commercial diets. Boxers, German Shepherd Dogs, and Labrador Retrievers are just a few of the breeds that tend to do better with extra fiber in their diet (both fermentable and non-fermentable types). They are the ones I think of as being at a higher risk for colitis when fed some of the so-called “premium” diets. Unless the food is being made by a company knowledgeable about animal health and nutrition it will often have low fiber, high fat and high protein levels; the perfect storm to create a bacterial imbalance.

My fiber and pet food soapbox: Most of the “premium” priced foods are actually distributed by marketing companies with little to no understanding of animal nutrition. Their motivation is to sell food at a “premium” price. (As an aside, the term “premium” within the pet food industry actually indicates the price point, not the quality of food; owners just assume it is a nutritional value statement as well and none of these companies are going to correct them.) These “premium” priced foods companies have been telling pet owners  that fiber is a “filler” and that higher fiber ingredients like corn and wheat are “bad” ingredients used by “cheap” dog foods. This pet food myth has also been perpetuated by pet food “advice” sources who are parroting the marketers and giving these benign foods almost supernatural powers to cause all sorts of ills. Yes, the US grows a lot of corn and wheat so the cost of these ingredients is relatively low compared to other grains like barley or amaranth and, yes, lower cost pet foods tend to have higher proportions of corn and wheat (and rice but that is a low fiber food so I’m ignoring it for now) since these grains are also less expensive than animal protein.  That doesn’t make corn and wheat “bad” foods to include in pet foods, just common and less expensive ones, and these “premium” priced food would loath to be considered common.

Porkchop and corn

Taffy and one of her favorite foods, freshly killed corn!


Fiber is also not considered an essential nutrient for survival for dogs, cat, or people (meaning you won’t die if fiber is left out of your diet, but you’ll sure feel like it) and there is no legal requirement for it to be added to pet food. Very high levels of dietary fiber can interfere with nutrient absorption and an over reliance on cereal grains is not an optimally balance diet either. Too much fiber can increase the volume of stool, making your Yorkie poop like a Labrador. It can also interfere with absorption of essential fatty acids and essential minerals required for optimal skin and coat health, so dogs and cats on high fiber diets that are not balanced correctly can start to look pretty shabby.

Big, well-formed poops, and a dry hair coat won’t cause you to make a midnight trip to the Emergency Vet, but chronic low fiber intake may. Dogs not getting enough dietary fiber are the ones that seem to get diarrhea out of the blue and are acting normal otherwise. Metronidazole (Flagyl) usually clears things up within a day, but then anywhere from 1 to 3 months later these dogs get diarrhea again. Usually at 2 AM on a Sunday morning. Cats being carnivores are adapted to a lower fiber diet so inadequate fiber intake is not much of a problem in otherwise healthy cats. But even cats can develop diarrhea from too quick of a diet change or from increases in fermentable fibers intake that upset the bacteria balance (things like guar gum, pectin, inulin, and carrageenan are all fermentable fibers that can be used in canned cat foods). Colitis in cats makes a mess in the little box and is not fun for anyone, especially if you have a long-haired cat like mine, who would leave little poo-poo butt prints wherever he went.


Tips to keep your pet regular:

  1. Don’t change diets abruptly, unless this is already your routine. If your cat or dog is used to eating a new type of food with varied levels of protein, fat and fiber each day (like your own diet) then you are probably ok to continue rotating foods. But if you are like the vast majority of pet owners who buy the same bag of kibble each time, any change in food (even if it is more expensive) will cause a few days of diarrhea. This is not your pet “purging” the “bad” food out (one of my favorite marketing gimmicks to rationalize a food causing diarrhea), this is just normal physiology. Usually it will clear up in a few days, but occasionally requires a course of metronidazole to get the bacteria back in balance. To avoid this, gradually transition between different foods over 5-7 days.


  1. Know how much fiber in your dog or cat’s current food. The pet food label will indicate Crude Fiber (which is mostly the non-fermentable, bulking-type fiber), but a quick check of the ingredient list will tell you if there are fiber containing ingredients or supplements added. Whole grains of any kind will have a higher fermentable and insoluble dietary fiber content. Potatoes and sweet potatoes are high in fermentable fibers, but low insoluble fiber (so bacteria growth without the bulk to push them out). Higher protein diets (dry or canned) will typically have low fiber levels as well.


  1. Add fiber if needed. If your dog or cat is eating a low fiber food and everything is working well, then don’t change a thing, other than following Tip #1. But, if you have a standing order of metronidazole at your local pharmacy or veterinary clinic, then you may want to consider either changing to a diet with more fiber or adding fiber to the current diet. I have a busy family schedule so personally like to simplify meal times and would just change the diet, but not everyone can do this. If your dog or cat is on special diets for medical reasons (like food allergies or kidney disease) then you should check with your Veterinarian to find out if there is a higher fiber option available. Some therapeutic diets will have a lower Calorie version, which is the same base diet with fiber added. For other dogs and cats you may be able to add a fiber supplement or higher fiber food (that is compatible with the feeding plan) to the existing diet.


Examples of Fiber Supplements and Dietary Fiber Amounts:

Canned pumpkin: Relatively low fiber, but dogs (and some cats) like the flavor so I will often use this to hide other fiber supplements.  One 1/4 cup of canned pumpkin provides 20 Calories and 2 grams of total dietary fiber (1 fermentable, 1 non-fermentable/insoluble).

Ground Psyllium: More concentrated fiber supplement. Ground psyllium becomes gelatinous when wet and can increase frequency of defecation in some dogs, which will mimic signs of colitis, so be careful with the amount. Depending on the brand used, 1 level teaspoon can provide 10 Calories and 3 grams of total dietary fiber (2 fermentable, 1 non-fermentable/insoluble).

Oat Bran: Used as a fiber supplement, but with different fiber distribution than psyllium. Depending on the brand used, 1 rounded teaspoon provides 5 Calories and 3 grams of total dietary fiber (1 fermentable, 2 non-fermentable/insoluble).

Inulin: Used as a fiber supplement, but with different fiber distribution than psyllium or oat bran. Depending on the brand used, 1 rounded tablespoon provides 5 Calories and 3 grams of total dietary fiber (3 fermentable, no non-fermentable/insoluble).


Just like most nutrients there is not a one-size-fits-all fiber intake for every dog or cat, but hopefully I have given you some insight into how you can keep your dog or cat looking and feeling good for years to come.

Happy Feeding!

Lisa P. Weeth, DVM, DACVN

16 thoughts on “Let Talk About Poop

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  4. Hi, I’m wondering about switching my dog’s food. He’s currently eating Purina One True Instinct Salmon and Tuna, which he loves, and I love that his poops are small, well-formed, and easy to clean out of the yard. His coat looks really good, too. Unfortunately, I don’t like that this food contains garlic oil. I’m looking to change him to either Purina One Grain-Free Chicken and Sweet Potato, or Purina Beyond Simply 9 Chicken & Barley. Or maybe Purina Pro Plan Natural Chicken & Rice. The cost (for the medium-sized bags, which is all that he will eat before it starts to go bad) is almost the same, and none of them contains garlic oil. I am leaning towards the Beyond food because it is the easiest to find in the store…but it does contain more fiber than the Purina One Grain-Free (whose main source is cassava root flour). Will the extra fiber negate the easy poop cleaning? Or will it maybe be better for his colon so that would be a good thing? Purina One contains 3.41% fiber and Beyond contains 4.55% fiber as calculated after the moisture is removed. (Of course, plain-out Purina One is a LOT cheaper, but I’m stuck on not wanting to feed him garlic oil.)


    • Thanks for reading and taking the time to post a comment and question. Garlic oil is one of those ingredients that I would consider to be a “label filler”. It doesn’t provide any real tangible health or nutritional benefit, but makes that food more appealing to some pet owners (both the aroma of the food and the fact that it’s included in the diet). I’m not a fan of it in pet foods either, but garlic oil does contain a much lower concentration of the toxic organosulfate compound than fresh or dried garlic and in the amounts used in the food drop that exposure even lower. I’ve also questioned the folks at Nestle Purina about their use of garlic oil and they assured me that the levels found in their diets are safe and have been extensively safety tested.

      Hope that helps assuage your concerns!

      Liked by 1 person

      • Just saw that I missed this question from a few months back. The fiber levels reported on pet food and treat packages are “Crude Fiber”, which is the insoluble, bulky-type of dietary fiber, but doesn’t capture any of the insoluble fiber (the type that tends to dissolve in water). Total Dietary Fiber, which is what people food labels report, is a combination of the two. The optimal type and amount of dietary fiber depends on the dog. Large breed tend to do better with more soluble and insoluble fiber in their diets and animals with constipation do better with less insoluble and more soluble fiber. The only way to know for sure is trial and error for some dogs.



  5. Thanks, Lisa. I didn’t know that about the fiber types being reported differently on pet food labels vs. people food labels. I’ve got him on Eukanuba now and his poop is slightly on the soft side but he is otherwise doing well. I made a lot of spreadsheets of nutritional data, but I don’t always know how to interpret my findings, so I appreciate your replies!


  6. HI Lisa,
    Thanks for the fiber info. My seven-month-old cat gets diarrhea when I give him a half can of wet cat food. (5.5 ounce Wellness). He’s is fine with a quarter can and with dry food. Would it help to add a quarter teaspoon of oat bran to a half-can serving of wet food? I want to feed him a half can of wet food in morning and half can of wet food in evening and not so much dry food.


    • Hi Eve,

      Thanks for reading and taking the time to post a question. Have you tried different brands/varieties of canned kitten food and does the same thing happen each time?

      While I can’t comment on the specifics of what’s going on in your kitty there are a couple of things that could be occurring in a situation like this. 1) One is that young animals (both kittens and puppies) having less mature intestinal tracts and may not be able to digest and absorb the higher protein and fats contents in canned food as efficiently as they eventually will once they get a bit older. This isn’t a problem with the kitten/puppy or the food necessarily, just the amount they get and these type of kitten or puppy diarrhea will often get better and eventually go away with age. 2) The other possible problem is that there is something in the food that is not being tolerated in larger amounts. Not a food allergy (so no immune component), but something that in larger amounts causes bacterial overgrowth and irritation of the colon leading to diarrhea. Canned foods in general support larger intestinal bacteria amounts in cats, but there are certain ingredients that can cause more proliferation than others. Increasing total dietary fiber may help firm up the stool, but avoidance of the offending agent is ideal. One of my own cats was sensitive to canned food as a kitten/young adult and would get wet mucousy to bloody diarrhea if he ate more than a teaspoons worth of canned foods. After much trial and error with different canned foods (brands and varieties at all different price points) I found that if I avoided canned foods that used carrageenan as a binding agent (carrageenan is a non-toxic soluble fiber, but a a soluble fiber nonetheless) he would not get diarrhea. Guar gum was ok, as was aspic, just no carrageenan.

      So if you have seen your regular vet for it and your kitten is otherwise healthy, active and growing normally, I would read the ingredients in the canned variety you are using now and try something new. Hope it all works out well your kitten!



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