The digestibility in piglets of faba bean (Vicia faba L.) as affected by breeding towards the absence of condensed tannins

Abstract

Seed samples from two near-isogenic faba bean (Vicia faba L.) lines were examined for the levels of so-called anti-nutritional factors (ANF). From the ANF known to be present in faba beans, trypsin inhibitor activity, functional lectins, condensed tannins and pyrimidine glycosides were analysed. It was concluded that the lines differed only in the content of condensed tannins being < 0.5 g/kg and 5.2 (sd 0.2) g/kg for the low (LT)- and high (HT)-tannin lines respectively. In addition, the level of pyrimidine glycosides in the LT line was slightly higher than that in the HT line. The LT line showed a reduced proportion of the seed coat (105 v. 119 g/kg) and a lower seed weight (0.85 v. 1.01 g). The apparent ileal and faecal digestibility values of dry matter and nitrogen from the HT and LT line were determined for piglets which were fed on diets containing chromium oxide as a marker. The mean apparent ileal and faecal digestibility values for dry matter for the LT line were 0.694 and 0.889 and for N 0.828 and 0.879 respectively. For the HT line, these values were approximately 0.05 and 0.10 lower (P > 0.05). A multi-enzyme technique was used to predict the in vitro protein digestibility (IVPD) of the two lines. The IVPD of the LT line was 0.965 and about 0.05 higher than the HT line, confirming the difference in digestibility as measured in vivo. The present study shows the positive effects on digestibility of removal of condensed tannins in faba beans which was achieved by plant breeding.