Carbohydrates digestibility and faecal nitrogen excretion in rats fed raw or germinated faba bean ( Vicia faba )- and chickpea ( Cicer arietinum )-based diets

Abstract

Raw or germinated faba bean ( Vicia faba minor var. Alameda) and chickpea (Cicer arietinum kabuli var. Athenas) seed meals were incorporated in essential amino acid-supplemented and energy-equalized diets for growing (65 (SD 1) g) male Wistar rats as the only sources of dietary protein. A lactalbumin-based diet was used as the control. Faecal dry weight and N excretion of animals fed legume-containing diets were greater ( P <0·01) and DM digestibility lower ( P <0·01) than controls. Apparent faecal digestibilities of amino acids were found to be not different or lower ( P <0·01) than controls in rats fed diets containing legume seeds, either germinated or not. Total diaminopimelic acid (DAPA) and purine bases excretion were significantly ( P <0·01) higher than controls in rats fed both legume seed meals. Faecal bacterial N calculated according to DAPA or purine bases values was similar and significantly higher ( P <0·01) than controls in rats fed legume seed meals. Bacterial N accounted for 50 to 80 % of total faecal N in rats fed legume diets. Apparent faecal N digestibility values (53–65 %) of rats fed legume-based diets were lower ( P <0·01) than controls, but became substantially higher (85–92 %) when calculated taking into account bacterial N values. Faecal NSP digestibility values for legume diets were 40–57 g/100 g ingested. Germination decreased starch faecal excretion ( P <0·05) and increased ( P <0·05) faecal starch and NSP digestibilities of faba bean seeds.