Characterization of the nutritive value of tropical legume grains as alternative ingredients for small‐scale pork producers using in vitro enzymatic hydrolysis and fermentation*

Abstract

In the tropic, the small-scale pork production is negatively influenced by the low availability of high protein ingredients. The study aimed to compare the protein and starch hydrolysis as well as fibre fermentation of five tropical legume grains (Canavalia brasiliensis, CB; Lablab purpureus, LP; Vigna unguiculata, white WVU; pink PVU and red RVU) and a control (extruded full-fat soybean (SB)), using an in vitro model that simulated digestion in the gastrointestinal tract of pigs. A sequential in vitro hydrolysis was carried out with pepsin (120 min) and pancreatin (240 min) to determine the degree of hydrolysis (DH) of protein and starch. The indigestible residue was fermented in vitro with pig faecal inoculum to compare the modelled kinetics of gas production over 72 h and the production of short-chain fatty acids (SCFA). After 360 min of pepsin-pancreatin hydrolysis, SB and WVU had the highest protein hydrolysis (76% and 66%) and PVU and WVU the highest starch hydrolysis (70% and 64%) (p < 0.01). The in vitro fermentation of the indigestible residue of WVU resulted in the highest (482 ml/g DM; p < 0.001) and CB the lowest (335 ml/g DM) gas production. These data were consistent with the SCFA production. Butyrate, propionate and total SCFA were higher (or tended) for RVU and WVU when compared with CB and SB (p = 0.015-0.085). In conclusion, the high DH of protein and starch as well as the high gas and SCFA production obtained with raw WVU makes it an interesting alternative to SB as a feedstuff for swine nutrition in the tropic. Other legume grains (LP and CB) cannot be used by pigs in their raw form.