Regrind the coarse fraction of hammer-milled grains can be used to improve the efficiency of feed use in pigs for both barley-based and sorghum-based diets. Pelleting diets also reduced (improved) FCR compared to feeding mash, but to a lower extent than regrinding the coarse fraction. Optimal processing depends on interactions between grain type, particle size and thermal processing, which affect nutrient digestibility. Regrinding the coarse fraction could be an alternative method to pellet processing for maximising energy delivery to growing pigs because it resulted in statistically similar FCR values and does not increase the fraction of small, dust-like particles. Optimal particle size distribution occurs when all particles are smaller than the particle size which is too large for macronutrients (particularly starch) to be completely digested by the end of the small intestinal of pigs. This optimal size will vary with grain type and processing, and depends largely on diffusion rate of α-amylase into grain particles and rate of passage of digesta through the stomach and small intestine. Further research is required to determine, for each grain type, the target particle size to be separated for re-grinding and the optimum method to efficiently achieve particle size separation, in order to improve the efficiency of grain utilisation in growing pigs