Ileal and faecal digestibility in piglets of field beans (Vicia faba L.) varying in tannin content

The ileal and faecal digestibility of nutrients of four varieties of field beans was determined in piglets (15-30 kg) fitted with a post-valvular T caecum cannula. The varieties differed in their content of condensed tannins. Beans of a white flowering variety (cultivar 'Blandine') had a low content of condensed tannins (< 0.1%). The other beans originated from coloured flowering varieties and had a medium (0.4%) (cultivar 'Herz Freya') or high tannin content (1.0%) (cultivars 'Mythos' and 'Alfred'). The low-tannin beans were evaluated as such and after autoclave treatment (30 min, 105°C). Beans were included in the diets at a level of 300 g kg-1. Diets were tested in 18 piglets in two experimental periods (n = 6). The ileal N digestibility (%) was higher (P < 0.05) for the low-tannin beans (85.7) than for the medium- and high-tannin varieties (73.7, 72.4, 71.5 for 'Herz Freya', 'Mythos' and 'Alfred', respectively). Faecal N digestibility values were 89.3, 85.7, 82.4 and 79.4 for 'Blandine', 'Herz Freya', 'Mythos' and 'Alfred' beans, respectively. The values for 'Blandine' and 'Alfred' beans differed significantly (P < 0.05). For individual amino acids differences in digestibility between 'Blandine' beans and the average value for beans of the three tannin-containing varieties ranged from 8 units for aspartic acid to 18 units for cystine. Autoclaving the low-tannin field beans 'Blandine' did not improve their N digestibility at the ileal (85.7 (raw) versus 82.3 (autoclaved)) and the faecal level (89.3 versus 88.9). Apparent ileal digestibility of starch was similar for all raw and the autoclaved beans. The absence of condensed tannins in field beans seems to have a positive effect on ileal and faecal digestibility of particularly crude protein and amino acids of faba beans in pigs. Autoclaving low-tannin faba beans did not improve the nutritional value for pigs. © 1993.