Effect of enzyme supplementation and extruding process on the digestibility of nutrients and phenolic acids of defatted rice bran based diets in ileal-cannulated growing pigs

To improve the efficiency of nutrient utilization in defatted rice bran (DRB) used as animal feed ingredient, the effects of enzyme supplementation and extruding process on the coefficient of apparent ileal digestibility (CAID) and apparent total tract digestibility (CATTD) of nutrients and nutraceutical phenolic acids were evaluated using growing pigs (initial body weight = 18 +/- 1.2 Kg) permanently fitted with ileal T-cannula. The extruded DRB ingredient (EDRB) was prepared by extruding the DRB ingredient at 130-135 degrees C using a single-screw extruder. The enzyme preparation contained cellulase, xylanase, phytase, and ferulic acid esterase. Eight cannulated pigs were allocated according to a 4 x 4 double Latin square arrangement. In each period, 1 of 4 tested diets, i.e., DRB basal diet, EDRB basal diet, and their enzyme added counterparts were randomly distributed to 2 pigs (1 pig form each square). The feces were sampled on the 6th and 7th day, and the ileal digesta were collected on the 8th, 9th and 10th day in each period. The results shown that pigs fed EDRB containing diets exhibited higher CAID values of dry matter (DM), organic matter (OM), gross energy (GE), and ether extract (EE) (P < 0.001), and CATTD values of DM, OM, GE, crude protein (CP) and EE (P < 0.002) comparing with that of DRB containing items. The CATTD values of most NSP fractions and their constituent residues in EDRB diets were positively affected by the extruding process; however, only the CAID values of insoluble arabinose and xylose were increased (P < 0.05). Enzyme inclusion improved the CAID of DM, OM, GE, ash, Ca, total phosphorus (TP) and phytate phosphorus (PP, P < 0.05), and the CATTD of ash, Ca, TP, PP, and Mg (P < 0.05). The added enzyme increased the digestion of NSP fractions in the foregut of pigs whereas the effect was not obvious in the large intestine of pigs except for insoluble arabinose. The enzyme addition did not show any effect on the CAID and CATTD of CP, and the CAID of amino acids in the rice bran containing diets. On the contrary, the CAID of amino acids were decreased and the CATTD of CP was increased by the extruding process. To sum up, the extruding temperature adopted in this study (130-135 degrees C) was too high for DRB processing with the aim of improving the efficiency of amino acids utilization, while it was helpful to improve the digestion of most of gross nutrients and NSP fractions over the whole digestive tract of pigs.