Microscopy and protein solubilization of digesta from pigs fed wheat, corn, or soybean meal-based diets, with or without protease and a Bacillus spp. direct-fed microbial

•There were key differences in the microstructure of wheat, corn and SBM at the level of diet and digesta.•Pig ileal digesta from all three ingredients contained undigested fiber-protein or starch-protein complexes.•Protease and DFM increased protein solubilization from soybean meal.