Information here is provided for education purposes and does not replace proper and necessary veterinary care for pets.
Is Fiber Essential?
The short answer is no, but it is highly beneficial to include in the diet.
Fiber is not an essential nutrient, the way certain amino acids, minerals and vitamins are, but they play an important part in regulating digestion and maintaining gut health.
There’s a lot of attention on gut bacteria right now and for good reason! A healthy gut is the home to bacteria that can produce beneficial compounds like Vitamin K and short chain fatty acids, which the body relies on. These bacteria also prevents the growth of harmful bacteria, plays a part in modifying toxins to safer forms, and may even help prevent IBS and food related allergies.
And in order to maintain a healthy gut, fiber is critical. Fermentable fibers are the primary energy source for all those helpful microbes in the gut. This is what prebiotics do – prebiotics are made up of carefully selected fiber sources that nourish certain beneficial bacterial strains. Without fiber, gut bacteria cannot flourish.
In addition to the role they play in the gut, fiber can also bind sugars to slow absorption, decrease and increase the speed of digestion, and regulate stool quality. Basically – it plays an important role in a healthy gut and healthy digestion.
The two categories of fibers we will look at here are soluble and insoluble fibers and how we can use them in homemade pet foods to regulate stool quality.
Soluble Fiber
Soluble fibers dissolves in water and turns into a gel (like psyllium husk + water = gel). This slows down the digestion process, which can help the body feel full longer. Soluble fibers are also a fermentable energy source for gut microbes and a necessary part of a healthy gut. However, excessive soluble fiber in the diet can lead to over fermentation, which can causes flatulence. Because soluble fibers are used as energy by gut bacteria, you should introduce it slowly.
Insoluble Fiber
Insoluble fibers do not dissolve in water, but helps speed up digestion and contributes bulk to stools, which helps prevent constipation. Because insoluble fibers are not digested, they can also help in weight-loss diets to increase the bulk/weight of the food fed without increasing the caloric intake. High amounts of insoluble fiber in diets (10% DMB) can interfere with nutrient absorption.
How Much to Add?
For total fiber, which includes soluble and insoluble fibers, 1.5-5% dry matter basis is generally the ideal range for homemade diets. Commercial dry foods tend to be higher than that, and anything over 10% fiber DMB would be consider a very high fiber diet, and used in clinical foods and formulations.
There is not a fixed ratio of insoluble to soluble fibers for pet diets for optimal gut health. (For humans, the general ratio is 3:1, so that soluble fibers make up 25% of your total fiber.) The best way to determine would be to look at your dog’s current/previous diet, but it may be difficult to determine how the breakdown of the total fiber of the food.
For healthy dogs, I would recommend starting with the same total fiber content the dog is currently eating. Assess stool quality and GI health, and then make adjustments from the current food by either adding additional fiber for lower fiber diets, or swapping out a fiber source for a different fiber source. Adjustments would be made for too firm/constipated stools as well as loose stools and excessive flatulence.
For example, if your dog’s stool quality is a 2, and the diet is very low fiber, I would recommend adding in a source of both insoluble and soluble fiber and reassessing. If your dog’s stool quality is a 5, and the diet has enough fiber already, you would swap out a soluble-fiber source for a insoluble fiber source, such as replacing oatmeal with quinoa. (All these changes, of course, should be made such that the diet is still complete and balanced)
Type 1 and 2:
Hard, lumpy stools indicate that the pet is constipated. Ratio diets without plant matter often produce stools like this, but this can lead to unnecessary strain and anal gland issues.
Recommended: if the diet is low fiber, add more total fiber. If the diet already has ample fiber, increase insoluble fiber in the diet and reducing soluble fiber.
Type 3 and 4:
Sausage like stools are ideal! They are easy to pass and firm.
Type 5 and 6:
Stools that are mushy without clear form but still hold shape, indicate that digestion may be happening too quickly. This can also happen naturally with stools that are excreted faster during/right after exercise, or with low digestibility foods.
Recommendation: If the diet has ample fiber, try adjusting total fiber content down. If there is no fiber in the diet, you can try increasing soluble fiber.
Type 7:
Diarrhea, or liquid stood, indicates inflammation and digestive upset. Short-term diarrhea can be caused by many things, but dietary causes include sudden high fat consumption or food intolerance.
If diarrhea is occurring regularly, this indicates a more significant health issue and you need to consult with your veterinary team.
White, chalky stools (usually type 1-2):
White, powdery stools that disintegrate quickly indicate there is a lot of mineral ash in the stool. This is usually a result of adding too much bone in the food.
Recommended: reduce ash content of food (usually from bone)
Common raw food advice recommends adding more bone to “firm” up loose stool, but this is not a healthy way to regulate stool quality – instead, this ensures that minerals are not getting properly absorbed during the digestion process. If stool is too loose, see notes under type 5-6 for recommendations.
Some of the ingredient listed in the table here are also great sources of starches and carbohydrates to contribute energy to a diet, such as oatmeal, sweet potato, quinoa, buckwheat and brown rice. These are labeled as “Energy Dense” sources. Use these types of foods in larger amounts as a base ingredient in your recipe.
Others, like fruits and vegetables, would be good “Toppers” to add, which can contribute some vitamins (like folate) and other phytonutrients, but do not contribute heavily to mineral or caloric content of a recipe. Use these foods in smaller amounts to add on top of a generally complete and balanced recipe.
Ingredients like psyllium husk and flax seed are listed as “Supplements”, and should be added in very, very small quantities like supplements due to their very high fiber content. (Too much fiber can also cause digestive upset and issues with nutrient absorption!). Use these foods as a boost of fiber to a complete and balance recipe. For flaxseeds, be careful about the fat content (you generally should not use so much flaxseed that it contributes a significant amount of fats to the diet).
Sources listed in the Insoluble column have much higher ratio of insoluble to soluble fiber. Sources listed in the Both column have a slightly more insoluble fiber than soluble fiber. Sources listed in the Soluble column have higher soluble fiber than insoluble fiber.
| Total Fiber (g) | Insoluble (g) | Soluble (g) | |
|---|---|---|---|
| Apple, with skin | 2.4 | 1.8 | 0.6 |
| Apple, without skin | 1.3 | 0.9 | 0.4 |
| Asparagus, cooked | 2.0 | 0.8 | 1.2 |
| Beet greens, cooked | 2.9 | 1.6 | 1.3 |
| Beets, cooked | 2.0 | 0.8 | 1.2 |
| Blackberries | 5.3 | 4.3 | 1.0 |
| Blueberries | 2.4 | 2.2 | 0.2 |
| Broccoli, cooked | 3.3 | 1.7 | 1.7 |
| Brown rice, cooked | 1.6 | 1.5 | 0.1 |
| Brussels sprouts, cooked | 2.6 | 1.0 | 1.6 |
| Buckwheat groats, cooked | 2.7 | 2.3 | 0.4 |
| Cabbage, green, cooked | 1.9 | 1.1 | 0.8 |
| Cabbage, red, cooked | 2.6 | 1.5 | 1.1 |
| Cantaloupe | 0.9 | 0.7 | 0.2 |
| Carrots, cooked | 3.0 | 1.7 | 1.3 |
| Cauliflower, cooked | 2.3 | 1.7 | 0.6 |
| Celery, cooked | 1.6 | 1.1 | 0.5 |
| Bok-choy, cooked | 1.0 | 0.6 | 0.4 |
| Collards, cooked | 4.0 | 1.6 | 2.4 |
| Corn, cooked | 2.4 | 2.0 | 0.4 |
| Cranberries | 3.6 | 2.7 | 0.9 |
| Cucumber, raw | 0.6 | 0.5 | 0.2 |
| Eggplant, cooked | 2.5 | 1.8 | 0.7 |
| Flax seeds | 28 | 19.6 | 8.4 |
| Green (string) beans, cooked | 3.2 | 1.9 | 1.3 |
| Honeydew melon | 0.8 | 0.6 | 0.2 |
| Kale, cooked | 4.0 | 1.8 | 2.2 |
| Mango | 1.6 | 1.0 | 0.6 |
| Oatmeal, cooked | 1.7 | 0.9 | 0.8 |
| Parsley leaves | 3.3 | 0 | 3.3 |
| Parsnip, cooked | 3.6 | 1.5 | 2.1 |
| Peas, cooked | 5.5 | 3.9 | 1.6 |
| Green bell pepper, cooked | 1.8 | 0.6 | 1.2 |
| Red bell pepper, cooked | 1.8 | 0.7 | 1.1 |
| Yellow bell pepper, cooked | 1.2 | 0.8 | 0.4 |
| Psyllium husks | 70 | 10 | 60 |
| Pumpkin, canned | 2.9 | 2.5 | 0.4 |
| Quinoa, cooked | 2.8 | 2.4 | 0.4 |
| Radish, raw | 1.6 | 1.2 | 0.4 |
| Raspberries | 6.5 | 5.8 | 0.7 |
| Spinach, cooked | 2.4 | 1.9 | 0.5 |
| Strawberries | 2.0 | 1.5 | 0.5 |
| Sweet potato, boiled | 2.5 | 1.6 | 0.9 |
| Sweet potated, baked | 3.3 | 2.1 | 1.2 |
| Tomato paste | 4.1 | 3.3 | 0.8 |
| Wild Rice, cooked | 1.8 | 1.6 | 0.2 |
| Zucchini, cooked | 1.0 | 0.6 | 0.4 |
References:
- www.prebiotin.com
- Functional Properties of Flax Seed Mucilage
- USDA Food Database
- Small Animal Clinical Nutrition, Ed 5
- Featuring Fiber: Understanding Types of Fiber & Clinical Uses