Effects of dietary inclusion of hulls of faba beans (Vicia faba L.) with a low and high content of condensed tannins on digestion and some physiological parameters in piglets

In an experiment with young piglets (8-17 kg), the effects of condensed tannins in the hulls of faba beans (Vicia faba L.) on faecal nutrient digestibility, N utilisation, organ weights and some other physiological parameters were studied. Hulls of a white-flowering variety (cv. 'Blandine') with a low content of condensed tannins (less than 0.10% catechin equivalents) and of a coloured-flowering variety (cv. 'Alfred') with a high content of condensed tannins (3.3% catechin equivalents) were included at a level of 200 g kg-1 in experimental Diets 2 and 3, respectively. In a control ration (Diet 1) tannin-free, autoclaved (120°C, 20 min) hulls of peas were incorporated at a level of 152 g kg-1. Diets were balanced as to calculated contents of net energy, crude protein (N × 6.25; CP), lysine, methionine plus cystine, threonine, tryptophan, vitamins and minerals. Diet 1 showed the highest faecal digestibility coefficients for dry matter (DM), organic matter (OM), crude fibre (CF) and nitrogen-free extract (NfE) (P < 0.05). Diet 3 had a lower apparent faecal digestibility for DM, CP, OM, CE, NfE and individual amino acids than both Diets 1 and 2 (P < 0.05). Apparent faecal digestibility was most severely reduced for histidine, glycine and proline. N excretion in the urine was lowest for piglets fed Diet 3 (P < 0.05). N retention tended to be lower for the animals receiving Diet 3 (10.0 g N day-1 vs. 10.9 g N day-1 and 11.0 g N day-1 for Diets 1 and 2, respectively). The wet empty weight of the caecum was lower for the group fed the high-tannin diet (P < 0.05). Activity of trypsin and chymotrypsin in digesta from the small intestine was lower in animals fed the high-tannin diet (P < 0.05). Faecal mucin excretion, as measured via faecal glucosamine and galactosamine content, did not differ between treatments. It was concluded that condensed tannins from faba beans in diets for piglets exert anti-nutritional effects by reducing the apparent digestibility of nutrients, in particular of protein and amino acids. This can lower N retention and growth in pigs. Faba bean condensed tannins do not seem to cause systemic effects, when the dietary content does not exceed 0.6% catechin equivalents. © 1993.