Dietary fibre type influences protein and fat digestibility in dogs

Fibre can interfere with digestibility of fat by accelerating intestinal passage or by increasing chyme viscosity. Lecithin is an important emulsifier which can improve fat digestion. The study aims to determine if fibre solubility may interfere with apparent or true total tract digestibility (ATTD; TTTD) of macronutrients and energy and if adding lecithin could improve fat digestibility. Stool quality was evaluated regarding fibre and lecithin inclusion. Eighteen adult dogs fed 130 kcal metabolisable energy × BW kg0.75/day were assigned in a 3 × 2 factorial Design, two blocks of 10 days to complete six replications per treatment. Two factors were tested, the source of fibre replacing starch and the inclusion of lecithin. Six diets were formulated with 10% corn starch or cellulose powder, or beet pulp and then all of the diets were dressed with 10% poultry fat or 1% soy lecithin + 9% poultry fat. The fibre inclusion reduced ATTD of dry matter, organic matter, carbohydrates, and energy. The ATTD of fat, crude protein, acid detergent fibre (ADF), and energy, and the TTTD of fat were decreased by adding soluble fibre in the diet, while the ATTD of ADF was greater for the cellulose diet. Soluble fibre impairs absorption of fat and other nutrients, then energy, while insoluble fibre is more related to effects on energy dilution. Lecithin is not able to restore fat digestibility, but lecithin improves energy absorption when insoluble fibre is included. Both sources can be used to produce low energy diets and modulate faecal score: soluble fibre holds water in the faecal content while insoluble fibre tends to produce dried faeces.Highlights Soluble fibre inclusion reduces digestibility of protein, fat, and energy. The content of water in the faeces was increased by adding soluble fibre, and faecal score was damaged but remained under acceptable conditions. Insoluble fibre increases the faecal bulk but reduces faecal water content. Lecithin did not compensate the effects of soluble fibre on reducing fat digestibility, but improved fat digestibility with insoluble fibre inclusion.