Fibre

Fibre (US: fiber) is the group of carbohydrates that resist digestion by the animal's own enzymes and instead reach the large intestine largely intact, where they shape transit, stool quality and the gut flora. Fibre is conventionally split into two functional types with quite different effects. Insoluble fibre, such as cellulose, mainly adds bulk and speeds transit, helping firm the stool and prevent constipation. Soluble and fermentable fibre, such as that in [beet pulp](/glossary/beet-pulp) or [inulin](/glossary/inulin), is broken down by colonic bacteria into short-chain fatty acids that nourish the cells lining the gut and support a healthy microbiome, making these fibres function as [prebiotics](/glossary/prebiotics). Most premium diets use a blend, because each type does something the other cannot. Fibre also plays a practical role in weight management: it adds volume and promotes satiety while diluting [energy density](/glossary/energy-density), so an animal can eat a satisfying portion for fewer calories. On a pack, fibre appears as crude fibre (US: crude fiber) in the analytical constituents, though this figure captures mainly the insoluble fraction and understates total dietary fibre. Dogs and cats both benefit, though cats, as obligate carnivores, need only modest amounts. Too much fibre can reduce overall [digestibility](/glossary/digestibility), so balance is key. See the [Petipedia glossary](/glossary).

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