EFFECTS OF HULLS OF FABA BEANS (VIOLA-FABA L) WITH A LOW OR HIGH CONTENT OF CONDENSED TANNINS ON THE APPARENT ILEAL AND FECAL DIGESTIBILITYOF NUTRIENTS AND THE EXCRETION OF ENDOGENOUS PROTEIN IN ILEAL-DIGESTAAND FECES OF PIGS

In three experiments (Exp. 1, 2, and 3) with young pigs (BW 10 to 26 k g), the effects of dietary inclusion of hulls of faba beans ( Vicia fa ba L.) (200 g/kg) with a low (<.1% catechin equivalents; LT) or high t annin content (3.3% catechin equivalents; HT) on the apparent ileal (E xp. 1 and 2) and fecal (Exp. 3) digestibility of nutrients were determ ined. In addition, the true digestibility of protein of the diets and the excretion of endogenous protein (N x 6.25) in ileal digesta and fe ces of pigs were measured, using the N-15 isotope dilution technique ( Exp. 3). Diets contained either casein and faba bean cotyledons as hig hly soluble (HS) protein sources (Exp. 1 to 3) or potato protein, soy concentrate, sunflower meal, meat meal, and fish meal as protein sourc es with a low solubility (LS) (Exp. 1). Control diets contained cellul ose as a fiber source (64 to 73 g/kg). Inclusion of either type of hul ls decreased the apparent ileal digestibility for DM, organic matter ( OM), and nonprotein organic matter (NPOM) (P < .05). Inclusion of LT h ulls instead of cellulose only reduced the apparent ileal digestibilit y of crude protein (N x 6.25; CP) in Exp. 3 (P < .05). Inclusion of HT instead of LT hulls reduced the apparent ileal digestibility of CP (b y 7 to 10 units) and amino acids (by 4 to 29 units) (P < .05). The LT hulls decreased apparent and true ileal digestibility of CP from 88 to 83 and from 97 to 94, respectively (P < .05). Inclusion of HT instead of LT hulls decreased apparent and true ileal CP digestibility from 8 3 to 74 and 94 to 90 (P < .05) and increased the excretion of endogeno us CP from 22 to 32 and from 13 to 23 g/kg of DM intake at the ileal a nd fecal level, respectively (P < .05). It is concluded that condensed tannins in faba beans interact with both dietary and endogenous prote ins in the digestive tract of pigs. This reduces the true digestibilit y of dietary protein and increases the excretion of endogenously secre ted proteins. Tannins from faba beans show some preference to interact with proteins with a high content of proline and histidine.