Corn extrusion and enzyme addition improves digestibility of corn/soy based diets by pigs: In vitro and in vivo studies

Three experiments were conducted to assess enzymes with potential to improve the digestibility of dietary components by pigs fed diets based on extruded (EXd) or non-extruded (nEXd) corn. In Exp. 1, effects of enzyme blends (amylase, protease and xylanase) at different dose rates [high (H) vs. medium (M) vs. low (L)] on the coefficient of apparent digestibility (CAD) were investigated in vitro using a two-stage enzyme incubation method. The CAD of starch and NDF were both higher (P<0.05) in H- and M-enzyme diets than in L-enzyme and control diets. Though the CAD of DM, GE, starch and NDF did not differ between H- and M-enzyme diets, the CP CAD was higher (P<0.05) in H-enzyme than in M-enzyme diets. Exp. 2 was designed to further examine the effects of corn extrusion, the addition of phytase and its combination with H- and M-enzyme on the CAD of dietary components. In this experiment M-levels of xylanase and amylase were included in both the H- and M-enzyme blends, with protease dosage being held the same in each blend as in Exp. 1. The CAD of all dietary components evaluated was higher (P<0.05) in EXd than in nEXd corn diets. For nEXd corn diets, the combination of phytase with M- and H-enzymes resulted in a higher (P<0.05) CAD of GE, CP, NDF and starch than did phytase addition alone. In Exp. 3, both in vitro and in vivo trials were conducted to evaluate responses of corn-based diets to the extrusion process and the addition of phytase, H- and M-enzyme blends. Five cannulated pigs were fed five diets according to a 5×5 Latin square design. Similar to the results observed in the in vitro trial of Exp. 3, the EXd corn diet had higher (P<0.05) CAD of DM, CP, starch, NDF and GE than nEXd corn diets. M- and H-enzyme addition both resulted in increased (P<0.05) DM and CP CAD of nEXd corn diets. The CAD of amino acids of nEXd corn diets with H-enzyme addition was comparable with that of the EXd corn diet, and was higher (P<0.05) than that of the nEXd corn control diet except for Met, Thr, Trp and Cys. These results suggest that extrusion and multiple enzyme addition are effective ways to improve the nutritional value of corn-based diets for pigs.