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Fibre for dogs: what it does and when to add it
Fibre affects the stool and feeds gut bacteria. Complete food already contains it, so most dogs need no supplement. Always discuss it with your vet.
In the analysis on the bag of kibble there is a line almost nobody reads: “crude fibre” and a percentage next to it. Yet this inconspicuous component determines what your dog’s poop looks like and what the bacteria in the large intestine live on. It also determines whether that piece of pumpkin in the bowl is actually doing anything useful.
- Fibre for dogs is the part of plant food that a dog’s digestive enzymes cannot break down, so it passes into the large intestine.
- Soluble fibre binds water and affects the consistency of stool, fermentable fibre feeds gut bacteria and insoluble fibre adds bulk.
- Complete food already contains fibre, so most healthy dogs need no supplement.
- More fibre is not automatically better: it can increase stool volume and wind, and reduce how well nutrients are used.
- Pumpkin is a safe vegetable, but there is still no evidence that it fixes a dog’s diarrhoea or constipation.
What is fibre and why can a dog not digest it?
Fibre is a component of plant food (mainly polysaccharides) that a dog’s digestive enzymes cannot break down, so it carries on into the large intestine. There the bacteria take it over. A dog is not a herbivore and does not need fibre as a source of energy, but the large intestine can work with it, because bacteria make useful substances from it.
The main ones are short-chain fatty acids, among them butyric acid (butyrate). According to the review by Pilla and Suchodolski (2020), butyrate is the preferred energy source for the cells of the large intestine. This principle has been studied in detail mainly in humans, and in dogs it is described by review papers and smaller studies. You can read more about who lives in the gut in the article Dog gut microbiome: what it is and why it matters.
What is the difference between soluble, insoluble and fermentable fibre?
Soluble fibre dissolves or swells in water, while insoluble fibre does not dissolve and adds bulk to the stool. Fermentability is a different property: it tells you how readily bacteria break the fibre down. So one fibre can have several properties.
| Type | Example sources | What it does |
|---|---|---|
| Soluble, viscous (forms a gel) | psyllium (plantain husks) | Binds water, changes stool consistency, bacteria partly break it down. |
| Rapidly fermentable (prebiotics) | inulin, FOS (fructooligosaccharides) | Bacteria break it down quickly, and it serves as their food. |
| Moderately fermentable | beet pulp | Bacteria break it down more slowly, and it prolongs the production of fatty acids in the large intestine. |
| Insoluble, almost non-fermentable | cellulose | Adds bulk to the stool, and bacteria hardly use it. |
| Mixed | pumpkin | Contains soluble fibre (for example pectin) and insoluble fibre. It has a lot of water and less fibre per portion. |
What do studies in dogs say?
Studies in dogs suggest that soluble fibre may help some dogs with gut problems, and that prebiotics mainly change the chemistry of the stool and less so the composition of the bacteria. The evidence is weaker than you might expect, though.
- 22 dogsIn a Portuguese study of police working dogs with chronic large bowel diarrhoea, stool improved in 90% of the dogs after a month of psyllium (one group, no comparison group). The number of bowel movements fell from 3.5 to 2.9 a day.Alves et al., 2021
- 37 dogsA retrospective review of records: most dogs with chronic large bowel diarrhoea responded very well to a highly digestible food with added soluble fibre. It was not a controlled trial.Leib, 2000
Prebiotics are fibres that feed beneficial gut bacteria. Swanson et al. (2002) studied four adult female dogs with an ileal cannula (a permanent opening from the end of the small intestine through which samples are taken) and gave them FOS, MOS (mannanoligosaccharides) or both. When FOS was given (alone or with MOS), the dogs had less indole and phenols in the stool, which are substances formed by the breakdown of proteins. MOS alone did not have this effect.
Four dogs are not enough for big conclusions, though.
So, to be honest: for psyllium and soluble fibre in dogs with chronic large bowel diarrhoea we have mainly observational data so far. For prebiotics we have small feeding studies. You can read more about how prebiotics differ from probiotics in the article Probiotics for dogs: what they are and how to choose. When to deal with digestive problems together with your vet is summarised in the article Digestive problems in dogs: signs, causes, what to do.
Why is more fibre not always better?
Too much fibre can bother a dog, because it increases the volume of stool and bacterial fermentation produces more gas. A large amount of fibre can also reduce how well some nutrients are used. For example, in the study by Weber et al. (2007), a food high in fibre had lower protein digestibility.
- Wind. Bacteria ferment fibre, and rapid fermentation produces gas.
- Bigger poops. More undigested material means larger and more frequent stool.
- Fewer nutrients used. In lean, active dogs or in puppies this can be a problem.
New fibre is introduced into the diet gradually, just like any other change. How to switch to new food is explained in the article Switching dog food.
Does my dog need extra fibre if I feed complete food?
Complete dog food already contains fibre, usually from beet pulp, cellulose, cereals or pulses, and most healthy dogs need nothing added. You will find the figure in the analysis on the packaging as “crude fibre”.
Adding fibre can make sense for a dog with repeated stool problems, but let your vet decide. They will choose the type of fibre, the amount and the length of time, because the same problems can have different causes. If you notice changes in your dog’s stool, start by watching: you can find a description in the article Soft stool in dogs.
How do you read the fibre figure on a food packet?
The packaging of a food states “crude fibre”, a laboratory figure that says how much material is left after chemical breakdown of a sample. It does not tell the whole story, though: it misses a large part of the fibre that dissolves or that bacteria ferment.
Brazilian and German scientists compared several ways of measuring fibre in six dry dog foods. Crude fibre came out lowest of the methods and was the only one that did not correlate with any of the other methods. Total fibre came out higher. The authors suggest combining the two figures, because the difference between them shows how much of the fibre is partly fermentable (de-Oliveira et al., 2012).
Does fibre help with weight loss and feeling full?
Fibre may help dogs feel fuller, though the effect is strongest in combination with a higher protein content. Studies mainly looked at this combination, not fibre alone. A dog’s weight loss always belongs in the hands of a vet.
In an experiment with six adult female dogs (Weber et al., 2007), after a restricted meal, the dogs ate 51% less over the next three hours of a food high in both protein and fibre than of a food high in protein only. In this test, however, fibre alone, without a higher share of protein, led to a similar intake to a food high in protein only. In another of the experiments, the dogs ate less of both high-fibre foods than of the food rich only in protein. The high-fibre food was also less palatable and had lower protein digestibility. Most of the study’s authors worked at a pet food manufacturer’s research centre.
In another study (German et al., 2010), obese dogs on such a diet lost 31.8% of body weight (median, 15 dogs) compared with 20.0% for dogs on a diet high in protein with moderate fibre (27 dogs). The groups were different sizes and the study was carried out in cooperation with a pet food manufacturer.
Fibre and constipation in dogs: when should you pay attention?
Constipation in a dog is when the dog strains or the poop does not come for a long time, and fibre may not reliably fix it. We have not found a good-quality study on fibre for constipation in dogs, and there are several causes: for example too little water, pain or something the dog has eaten.
So do not try adding fibre, pumpkin or powders on your own. A wrongly chosen intervention can make the problems worse.
Also book your dog in with the vet if no poop comes for a long time or the stool stays hard and small. You will find when to call straight away in the red box below.
Pumpkin for dogs: what is true and what is a myth?
Pumpkin is generally a safe vegetable for dogs, with fibre and water, but good evidence that it reliably fixes diarrhoea or constipation is lacking. We did not find a controlled study of pumpkin in dogs with diarrhoea in the PubMed database. The advice to “give pumpkin” is therefore based mainly on experience and on what we know about fibre in general.
| Claim | The reality |
|---|---|
| Pumpkin is poisonous to dogs. | Myth. Plain cooked pumpkin is safe. |
| Pumpkin reliably stops diarrhoea. | Not proven. We have no study in dogs, and the cause of diarrhoea must be determined by a vet. |
| Pumpkin is “natural”, so it cannot do harm. | Myth. A large amount can cause wind and softer stool. |
| Shop-bought pumpkin pie filling is the same as plain pumpkin. | No. It contains sugar and spices that do not belong in a dog’s bowl. |
Always consult your vet about fibre supplements first, and do not give them during acute problems.
Frequently asked questions
Does a dog need fibre?
Fibre is not the main source of energy for a dog, but it benefits the large intestine. Bacteria make short-chain fatty acids from it, and fibre affects the volume and consistency of the stool. Complete food usually contains enough of it, so most healthy dogs need no supplement.
Can I give my dog psyllium?
Psyllium is the husk of plantain seeds, a soluble fibre that studies in dogs have looked at for chronic large bowel diarrhoea. Whether it is suitable depends on the dog and the cause of the problems, and some of the studies had no comparison group. So do not try psyllium on your own; talk to your vet instead.
What are prebiotics for dogs?
Prebiotics are fibres, such as inulin and FOS, that serve as food for beneficial gut bacteria. Smaller studies in dogs mainly showed changes in stool chemistry, and changes in the composition of bacteria were weaker. Probiotics are something different: they contain live bacteria. You can find out which is which in the article on probiotics.
What does crude fibre on a food packet mean?
Crude fibre is a laboratory figure that mainly captures the part of the fibre resistant to breakdown. It misses soluble fibre and a large part of the fibre that bacteria ferment. A study of dog foods therefore suggests comparing it with total fibre. So you cannot tell a food’s effect on stool from one figure.
Can a dog eat pumpkin every day?
Plain cooked pumpkin is safe for dogs, but regular feeding for no reason has no proven benefit. A large amount can cause wind or softer stool. If you want to include pumpkin regularly, ask your vet to recommend the amount and suitability based on how old your dog is, what they eat and what problems they have.
Why does my dog have bigger poops after I add fibre?
Fibre, especially insoluble fibre, increases the volume of stool, because the dog cannot digest it and bacteria break it down only partly. Bigger or more frequent poops after adding fibre are therefore not necessarily a problem. But if they are soft, last longer than a few days or get worse, call your vet. With puppies and older dogs, do it sooner.
Sources
- Pilla R, Suchodolski JS (2020). The Role of the Canine Gut Microbiome and Metabolome in Health and Gastrointestinal Disease. Frontiers in Veterinary Science. doi.org/10.3389/fvets.2019.00498
- Alves JC, Santos A, Jorge P, Pitães A (2021). The use of soluble fibre for the management of chronic idiopathic large-bowel diarrhoea in police working dogs. BMC Veterinary Research. doi.org/10.1186/s12917-021-02809-w
- Leib MS (2000). Treatment of chronic idiopathic large-bowel diarrhea in dogs with a highly digestible diet and soluble fiber: a retrospective review of 37 cases. Journal of Veterinary Internal Medicine. doi.org/10.1111/j.1939-1676.2000.tb01495.x
- Swanson KS et al. (2002). Supplemental fructooligosaccharides and mannanoligosaccharides influence immune function, ileal and total tract nutrient digestibilities, microbial populations and concentrations of protein catabolites in the large bowel of dogs. Journal of Nutrition. doi.org/10.1093/jn/132.5.980
- Barry KA et al. (2009). Low-level fructan supplementation of dogs enhances nutrient digestion and modifies stool metabolite concentrations, but does not alter fecal microbiota populations. Journal of Animal Science. doi.org/10.2527/jas.2008-1659
- Weber M et al. (2007). A high-protein, high-fiber diet designed for weight loss improves satiety in dogs. Journal of Veterinary Internal Medicine. doi.org/10.1892/07-016.1
- German AJ et al. (2010). A high protein high fibre diet improves weight loss in obese dogs. The Veterinary Journal. doi.org/10.1016/j.tvjl.2008.12.004
- de-Oliveira LD et al. (2012). Fibre analysis and fibre digestibility in pet foods: a comparison of total dietary fibre, neutral and acid detergent fibre and crude fibre. Journal of Animal Physiology and Animal Nutrition. doi.org/10.1111/j.1439-0396.2011.01203.x
This article is educational and does not replace a veterinary examination. If you are not sure, ask your vet.
This article was proofread with the help of AI. This is a translation from Czech, so it may contain inaccuracies.