Dietary non‐extractable condensed tannins as indigestible compounds: Effects on faecal weight, and protein and fat excretion

The possible degradation of non‐extractable condensed tannins (NECT) within the intestinal tract and their effect on faecal weight and composition was studied. Two groups of male Wistar rats were fed either a NECT‐free control diet, or a diet containing 100 g carob pod concentrate kg −1 (53 g NECT kg −1 dry matter) for 5 weeks. A slight effect of NECT on growth rate was observed in the fifth week. The NECT diet did not affect food intake. Significant increases of total faecal output as well as water, nitrogen and fat excretion were observed. NECT were not degraded in the intestinal tract, since they were quantitatively recovered in faeces (98 ± 1%). Since the usual spectrophotometric methods gave contradictory results on NECT levels in the diet and faeces, an alternative method based on Klason lignin residues was used.