Fibre is the indigestible part of plant foods. It is classed as a complex carbohydrate that is resistant to digestion in the small intestine. Fibre is important to keep the digestive system healthy. As it is not digested in the small intestine, fibre passes through unchanged until it reaches the large intestine. In the large intestine, bacteria act on the fibre to ferment it. The primary function and benefit of fibre is to increase bulk and water in intestinal contents, maintain optimum levels of good bacteria and promote gut health. Some examples of fibre include cellulose, lignin, fructans and mannans.
Classification of Fibre
Fibre can be classified based on its fermentability (ability to be broken down in the large intestine by bacteria) and solubility (ability to be dissolved in water).
Rapidly or highly fermentable fibres produce more short chain fatty acid by-products and gas than slowly fermentable fibres. The short chain fatty acids by-products of fermentable fibres are important for the health of the cells in the lining of the large intestine. Excessive fermentation can lead to excessive flatulence and bloating.
Slowly fermentable fibres are the most effective stool bulking agents as they retain their structure for longer and are most resistant to break down. Slowly fermentable fibres can increase faecal bulk which is known to be beneficial in the treatment of digestive diseases such as inflammatory bowel disease and constipation.
Solubility is the ability of the fibre to disperse in water. All fibres can hold water to a degree however more soluble fibres have a greater water holding capacity. Some fibres are a combination of soluble and insoluble fibres.
Fibre as Food
Fibre can also be classified as a prebiotic. Prebiotics serve as nourishment to stimulate the activity and growth of good bacteria in the gut. An example of such a fibre in the Royal Canin diets is fructo-oligosaccharides (FOS). This fibre is included in the diet to selectively stimulate specific bacteria in the colon and improve digestive health. It is essentially food for the good bacteria.
The amount and type of fibre in a pet food has an overall effect on the digestibility; the amount of nutrients digested and absorbed from food. In pet foods, the fibre is measured using different laboratory methods and listed as either crude fibre or total dietary fibre.
Crude fibre is the measure of the quantity of indigestible (non-fermentable) fibre in the diet. These fibres have little nutritional value but provide bulk to the diet.
Total dietary fibre refers to the quantity of overall fibre in the diet. This includes fermentable and non-fermentable fibres. This is a reflection of the fibres that have little nutritional value but also fibres that play a prebiotic or digestive health role. The total dietary fibre is a good indication of how digestible the diet will be and is an important parameter to consider when comparing two diets.
The role of Fibre in our pets
Fibre has been successfully used in pet foods to help with weight management, diabetes mellitus, diarrhoea and constipation. A pet food that is high in slowly fermentable fibre increases the bulk of the stomach contents, helping pets feel full and satisfied. This ensures they eat fewer calories and is helpful in long term weight management. Slow and rapidly fermentable fibres have beneficial effects on blood glucose in diabetic animals. Fibre can absorb water content in cases of diarrhoea and adds moisture in cases of constipation.
No fibre = diarrhoea
Excessive fibre = soft and large stools
Fibre in pet food is about a balance of fermentable and non-fermentable fibres to achieve optimum gut health and digestibility of food.