Cats & Fiber: feeding plant matter?

In the article about the supplements that I use in Néline and Praline’s diet, I mentioned that I add psyllium as a source of fiber. In today’s article, I’m going to go into more detail about the complex subject of fibers: I’ll explain what they are and how to properly supplement your cat’s diet.

What are fibers?

Fibers are the non-digestible part of plant matter. More precisely, they are polysaccharides: a special type of carbohydrates. In fact, the bonds in these polysaccharides can’t be broken down by the enzymes found in the intestinal tract and so they can’t be directly digested. However, unlike enzymes, some of the bacteria in the large intestine are able to break down some of the fibers.

Fibers can be separated into two categories: soluble and insoluble fibers.

Soluble fibers

As their name indicates, soluble fibers can dissolve in water: they will form a gel in contact with water. Soluble fibers are, generally, moderately to highly fermentable in the intestine, which means that they will be broken down and fermented by the bacteria in the large intestine. When fermenting the fiber, the bacteria will release short-chain fatty acids as well as other compounds. [2]
The short-chain fatty acids which are released by the bacteria fermenting the fibers have several benefits:

• They are a source of energy for the cells lining the intestine and, so, promote the good health of the intestine;

• They promote a better absorption capacity of the colon, which leads to overall better health;

• Prevention of diarrhea;

• Promoting the growth of beneficial gut bacteria while inhibiting the growth of harmful microbes and bacteria, to resume it maintains a healthy microbiota.

While short-chain fatty acids are beneficial, feeding too much fermentable fiber or too highly fermentable fiber may cause diarrhea, loose stools, gas and interfere with nutrient absorption.
Additionally, because of the physical property of soluble fiber to store water, they can moisturize and soften the stool which can be helpful in case of constipation, as well as retaining water in case of diarrhea. [6]

Insoluble fibers

While insoluble fibers can retain some water, they don’t form a viscous solution with water, contrary to soluble fibers. They are generally much less fermentable, meaning that they are not broken down by gut bacteria. They bulk the stools, may contribute to the feeling of satiety, and decrease the intestinal transit time. [1][9]
As they bulk the stools, insoluble fibers can be helpful in case of constipation if it’s caused by the stools being too small.
However, too much insoluble fiber (more than 10% of the dry matter) will decrease the digestibility of the diet and the absorption of nutrients.

Which ingredients contain fiber?

Fibers are part of the carbohydrates family and, therefore, they come from plant matter: they are present in fruits, vegetables, legumes, cereals, and grains (especially in bran).
We have seen that there are two main types of fiber but one ingredient can contain both insoluble and soluble fibers and in different proportions. It’s the case of oat bran which is a mix of insoluble and soluble fibers.
In the table at the end of the article, you will find a list of ingredients and their fiber content.
Dry ingredients such as wheat bran or psyllium have a much higher fiber content than vegetables (which are mainly composed of water).
So, vegetables need to be fed in bigger quantities to provide enough fiber when compared to dry ingredients. However, vegetables also provide moisture and antioxidants. I will write more details on vegetables in a specific article.

How much fiber should you feed your cat?

There isn’t a precise answer to this question and if you look at the nutrient requirements calculator you will see that fibers aren’t present at all. In fact, fibers aren’t essential, meaning that your cat won’t die or get a nutrient deficiency if fibers aren’t provided in its diet.
However, this doesn’t mean that adding fibers doesn’t have benefits, as we have seen before.
The ideal proportion seems to be a mix of both insoluble fiber and soluble fibers with a ratio of 3:1 of insoluble fiber to soluble fiber. [10]
Too much fiber isn’t always better and it’s recommended to feed less than 5% of fiber on a dry matter basis. [11]
In the table at the end of the article, you will find how much of a given ingredient you need to feed your cat to provide 0.5g of fiber, which is roughly equivalent to 1% of fiber on a dry matter basis if your cat eats 150g a day.
I would recommend that you experiment with different fiber quantities and fiber types to see what fits your cat best.

Animal fibers: an ongoing research

We have seen that fibers are plant matters that can be beneficial for cats. However, you may ask yourself: “but in nature cats don’t consume plant matter?” and indeed the consumption of carbohydrates in nature is almost negligible. This is a question that researchers have asked themselves and that’s why there is ongoing research on animal fibers.
In fact, fibers are sometimes defined as all dietary constituents that are not digested by the enzymes in the small intestine. In this definition, fibers aren’t limited to plant matters.
Scientists have hypothesized that some animal matter such as tendon, cartilage, feathers, hair, skin, fur, … could play the same role as plant fibers for obligate carnivores such as cats.
While there are no studies on domestic cats, studies on cheetah have shown that some animal matter (such as collagen and cartilage) was fermentable in the large intestine and so could play the same role as soluble fiber. Other matters such as hair, skin, and bone were bulking the stools and regulating the intestinal transit time like insoluble fiber.
In this context, feeding whole prey which includes animal fiber can be an alternative to traditional plant fibers. [4][5][6][7][8]

My personal experience

When I wrote the article about supplements in April 2020, I was regularly feeding psyllium as a source of fiber. Since then I have experimented with different fibers and quantities to find what works best for Néline and Praline. The different fibers I experimented with are psyllium, wheat bran, and oat bran. As fiber isn’t an essential nutrient with a precise recommendation in terms of quantities, I also experimented with the quantities without measuring it exactly. I tried with quantities from a sprinkle to a teaspoon. For each experiment, I kept feeding the same quantity and type of fiber for a few days so I could then observe the stools of my cat.
I reached the conclusion that the wheat bran is what suits my cat best for the moment. Because oat bran tends to have bigger pieces while wheat bran is more of a powder, wheat bran is more easily accepted by Néline and Praline.
Néline does better with a very small quantity of fiber, just a sprinkle or her stools tend to be too bulky. On the other hand, Praline needs a bit more fiber, otherwise, her stools are too small and she can be constipated.

In addition, I also feed my cats nutritional yeast daily: I do it mainly for the B-vitamins, but it also provides fiber. 
On the days where I feed chicks, which are whole prey with feathers, I noticed that the stools of the cats are bulkier: I, therefore, reduce the quantity of fiber I’m adding to their diet.

To conclude, as they are non-essential from a nutritional point of view, fibers and their benefits are too often forgotten in raw diets. I recommend that you experiment with different plant-based fiber types if you can’t feed animal fiber and find what fits your cat best.
The research on the effect of fibers on cats is still ongoing, especially in the field of the prevention of hairballs.
In a future article, I will talk about prebiotics and probiotics, which are linked to fibers.

Fiber in common ingredients

This table show the fiber content of common fiber supplements and vegetables per 100g, as well as the amount (in g) of the ingredient you need to feed your cat to provide 0.5g of fiber.

Ingredient	Fiber (g)	Insoluble (g)	Soluble (g)	Amount to get 0.5g of fiber
Coconut flour	60.0	56.0	4.0	1
Flaxseed	22.3	10.2	12.2	2
Nutritional Yeast	31.4	1.1	30.3	2
Oat bran	15.6	6.4	9.2	3
Psyllium husk	86.2	14.6	71.1	1
Rice bran	51.4	46.7	4.7	1
Wheat bran	54.2	49.6	4.6	1
Wheat germ	14.0	12.9	1.1	4
Wheat grass powder	27.2	23.1	4.1	2
Vegetables
Broccoli, raw	3.3	3.0	0.3	15
Carrot, raw	2.5	2.3	0.2	20
Celery, raw	1.5	1.0	0.5	33
Cucumbers, peeled	0.6	0.5	0.1	83
Green beans	1.9	1.4	0.5	26
Pumpkin, canned	2.9	2.4	0.5	17
Spinach, raw	2.6	2.1	0.5	19
Sweet potato, baked	1.8	1.3	0.5	28
Zucchini, steamed	1.4	1.0	0.4	36

Additional reads

A great article on fiber by Better Cells Nutrition

Sources

National Research Council. 2006. Nutrient Requirements of Dogs and Cats. Washington, DC: The National Academies Press.

[1] Butowski CF, Thomas DG, Young W, Cave NJ, McKenzie CM, Rosendale DI, et al. (2019) Addition of plant dietary fibre to a raw red meat high protein, high fat diet, alters the faecal bacteriome and organic acid profiles of the domestic cat (Felis catus). PLoS ONE

[2] Rochus K, Janssens GP, Hesta M. Dietary fibre and the importance of the gut microbiota in feline nutrition: a review. Nutr Res Rev. 2014 Dec;27(2):295-307.

[3] K. R. Kerr, C. L. Morris, S. L. Burke, K. S. Swanson, Influence of dietary fiber type and amount on energy and nutrient digestibility, fecal characteristics, and fecal fermentative end-product concentrations in captive exotic felids fed a raw beef-based diet, Journal of Animal Science, Volume 91, Issue 5, May 2013, Pages 2199–2210, 

[4] Kerr KR, Morris CL, Burke SL, Swanson KS. Apparent total tract energy and macronutrient digestibility of one- to three-day-old, adult ground, extruded, and canned chicken-based diets in domestic cats (Felis silvestris catus). J Anim Sci. 2014 Aug;92(8):3441-8.

[5] Kerr KR, Morris CL, Burke SL, Swanson KS. Apparent total tract macronutrient and energy digestibility of 1- to- 3-day-old whole chicks, adult ground chicken, and extruded and canned chicken-based diets in African wildcats (Felis silvestris lybica). Zoo Biol. 2013 Sep-Oct;32(5):510-7.

[6] Beloshapka AN, Duclos LM, Vester Boler BM, Swanson KS. Effects of inulin or yeast cell-wall extract on nutrient digestibility, fecal fermentative end-product concentrations, and blood metabolite concentrations in adult dogs fed raw meat-based diets. Am J Vet Res. 2012 Jul;73(7):1016-23.

[7] Depauw S, Bosch G, Hesta M, Whitehouse-Tedd K, Hendriks WH, Kaandorp J, et al. Fermentation of animal components in strict carnivores: a comparative study with cheetah fecal inoculum. J Anim Sci. (2012)

[8] Depauw S, Hesta M, Whitehouse-Tedd K, Vanhaecke L, Verbrugghe A, Janssens GP. Animal fibre: the forgotten nutrient in strict carnivores? First insights in the cheetah. J Anim Physiol Anim Nutr (Berl). 2013 Feb;97(1):146-54.

[9] Loureiro BA, Sakomura NK, Vasconcellos RS, Sembenelli G, Gomes MOS, Monti M, Malheiros EB, Kawauchi IM, Carciofi AC. Insoluble fibres, satiety and food intake in cats fed kibble diets. J Anim Physiol Anim Nutr (Berl). 2017 Oct;101(5):824-834. doi: 10.1111/jpn.12468.

[10] Case, L., Carey, D.P., Hirakawa, D.A., & Daristotle, L. (2000). Canine and feline nutrition : a resource for companion animal professionals.

[11] HandMichael, S., Morris, M., & Novotny, B.J. (2000). Small animal clinical nutrition.

Sources for the table

Dhingra, Devinder et al. “Dietary fibre in foods: a review.” Journal of food science and technology vol. 49,3 (2012)

Claye SS, Idouraine A, Weber CW. 1996. Extraction and fractionation of insoluble fiber from five fiber sources. Food Chem.

Yadav DN, Rajan A, Sharma GK, Bawa AS. Effect of fiber incorporation on rheological and chapati making quality of wheat flour. J Food Sci Technol. 2010 

Pasha, I., Huma, N., Farhan Jahangir Chughtai, M., Jan, S., Ahmad, S., Sajid Manzoor, M., & Ahmed, F. (2018). Biochemical, Nutritional and End Use Perspectives of Wheat Grass as Potential Dietary Supplement. International Journal of Biochemistry Research & Review.

P.T. Trinidad, A.C. Mallillin, D.H. Valdez, A.S. Loyola, F.C. Askali-Mercado, J.C. Castillo, R.R. Encabo, D.B. Masa, A.S. Maglaya, M.T. Chua. Dietary fibre from coconut flour: a functional food. Innovat. Food Sci. Emerg. Technol., 7 (4) (2006).

Marlett JA, Cheung TF. Database and quick methods of assessing typical dietary fiber intakes using data for 228 commonly consumed foods. J Am Diet Assoc. 1997 

Kalala G, Kambashi B, Everaert N, Beckers Y, Richel A, Pachikian B, Neyrinck AM, Delzenne NM, Bindelle J. Characterization of fructans and dietary fibre profiles in raw and steamed vegetables. Int J Food Sci Nutr. 2018 

Lee SC, Rodriguez F, Storey M, Farmakalidis E, Prosky L. Determination of soluble and insoluble dietary fiber in psyllium-containing cereal products. J AOAC Int. 1995 

Yamada EA, Sgarbieri VC. Yeast (Saccharomyces cerevisiae) protein concentrate: preparation, chemical composition, and nutritional and functional properties. J Agric Food Chem. 2005