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The importance of fibre in dog food

Over the last decade, fibre has been gaining more prominence in dog food due to the relationship it has with the gut microbiota.

Dietary fibre is a key nutrient whose importance in dog nutrition has been neglected. It is not considered an essential nutrient, as its deficiency does not imply a collapse in body function; in fact, the AAFCO and FEDIAF have not stipulated minimum requirements for fibre. However, in the last decade, fibre has been gaining more consideration, partly thanks to several scientific advances about the gut microbiota, where a large part of a dog’s immune system resides.

Distinguishing between the types of fibre

Dietary fibre can be broadly defined as carbohydrates that cannot be digested by the body. Although there are different classifications, the main distinction is between soluble and insoluble fibre:

Soluble fibre can attract water and forms a gel during digestion, and it is usually available for fermentation by the gut microbiota. This encompasses a wide range of molecules and forms, while the biodiversity of sources enhances health and well-being.
Insoluble fibre, on the other hand, usually comes in the form of more inert fibre that is not available for bacterial fermentation (in dogs). It basically consists of cellulose, hemicellulose, lignin and a few other compounds.

Fibre’s benefits for dog health

Perhaps one of the most recognised effects of fibre is its benefits for intestinal transit and faecal quality, although it can act on several levels, as explained below.

Intestinal transit

The addition of fibre, especially insoluble fibre, increases faecal bulk and aids in laxation, shortening gastric emptying and accelerating transit.
On the other hand, it also helps give the faeces structure and retain free water, improving compaction.
In cases of diarrhoea, a mixture of soluble and insoluble fibre may help normalise stool consistency earlier. This is most noticeable in certain types of diarrhoea, such as some types of colitis, which have a very positive response to the inclusion of fibre. It has also been seen to benefit in the management of certain chronic diarrhoeal processes.
Finally, fibre can help resolve most cases of constipation. Soluble fibre can form gels, which facilitate transit, and has a prokinetic effect due to the short-chain fatty acids (SCFA) derived from its fermentation. Insoluble fibre, on the other hand, brings more bulk, which can help also intestinal transit.

fibre in dog foods

Prebiosis

Fibre is the main nutrient responsible for prebiosis, and the most studied to date. A prebiotic can be understood as a substrate used by the gut microbiota, and which confers a benefit for the host.

Soluble fibre is the main contributor to this prebiotic effect. Among the plethora of compounds considered soluble fibre, the most studied in dogs are fructans, which mainly consist of fructo-oligosaccharides (FOS) and inulin, both of which are known to be very good fermentable sources.When fermented by certain bacteria, they produce SCFAs, which provide multiple benefits to intestinal health. For example:

An increase in butyrate promotes the proliferation, homeostasis and correct function of colonocytes, as well as some beneficial immunomodulatory activity.
The increased production of SCFAs also decreases gut pH, preventing the growth of potentially pathogenic bacteria.

These prebiotic compounds, as they are only used by certain microorganisms, selectively promote the growth of beneficial species and microbial diversity, both considered positive factors for the microbiota. In addition, by regulating the microbiota and other mechanisms yet to be fully understood, they may help with disorders such as inflammatory bowel disease (IBD), osteoarthritis and chronic kidney disease (CKD) or by stimulating the immune system.

Obesity

Fibre has a very low calorie content, especially insoluble fibre, so its inclusion in diets reduces the food’s energy density. It also has positive effects on digestibility and satiety.

High fibre levels generally tend to affect the digestibility of macronutrients and consequently the energy that can be absorbed from them. On the other hand, by filling space, trapping water and providing bulk, fibre also activates certain satiety mechanisms based on distension. Hence, diets with a high fibre content promote weight lose in obese patients while naturally protecting their well-being throughout the process. Gut microbiota with a balanced diversity has been shown to keep a dog’s weight under control, otherwise an imbalance leads to weight gain.

Glucose regulation

Fibre can help control blood sugar and insulin levels. This is mainly down to the soluble type of fibre, as the viscous gel it produces hinders glucose absorption, slowing the process down and controlling its peaks in the blood. This is particularly relevant in dogs with diabetes; therefore, most therapeutic diets for diabetic animals have a high fibre content.

Other benefits

Some further advantages of fibre, although still under study, are its possible benefits in terms of control over the lipid profile, cardiovascular health, geriatric nutrition and reproductive health.

Conclusions

Fibre provides a number of benefits for dogs, but there a lot of research still needs to be completed for present and future applications. There are various types of fibre, and they can have very different effects, so each patient may benefit from a distinct type. Fibre’s role in the diversity of the gut microbiota is key to the dog’s active defence system and well-being.

Questions

Does fibre have any contraindications?

Fibre may be harmful in cases of intestinal dysmotility, megacolon, severe constipation or bacterial overgrowth. Diets with a high fibre content are not recommended in convalescing animals and those who require a high level of energy intake. Finally, too much soluble fibre can degrade faecal quality and consistency, so a correct balance is important.

Are some fibres better than others?

One type of fibre is not necessarily better than another. Some fibre sources have different ratios of soluble/insoluble fibre and, therefore, different medical applications, as we have seen above. Citrus fibres, guar gum and pulps tend to have a lot of soluble fibre, whereas hulls, bran and cellulose contain more insoluble fibre.

Furthermore, we have acquired more scientific evidence about the role of certain types of fibre, such as FOS or chicory root, while others are yet to be studied in detail.

Finally, some fibres, such as fibrous components in fruits, come from ingredients that contain other beneficial components such as polyphenols. As such, a wide variety of options is available and some will be more suitable than others depending on the nutritional objective.

References

Devries J. W. (2004). Dietary fiber: the influence of definition on analysis and regulation. Journal of AOAC International, 87(3), 682–706.

Moreno, A. A., Parker, V. J., Winston, J. A., & Rudinsky, A. J. (2022). Dietary fiber aids in the management of canine and feline gastrointestinal disease. Journal of the American Veterinary Medical Association, 260(S3), S33-S45.

Perini, M. P., Pedrinelli, V., Marchi, P. H., Henríquez, L. B. F., Zafalon, R. V. A., Vendramini, T. H. A., Balieiro, J. C. de C., et al. (2023). Potential Effects of Prebiotics on Gastrointestinal and Immunological Modulation in the Feeding of Healthy Dogs: A Review. Fermentation, 9(7), 693.