Importance of feed structure (particle size) and feed form (mash vs. pellets) in pig nutrition - A review

According to available data, optimal particle size of diets for pigs is in the range between 500 and 1600 μm, while particles smaller than 400 μm are considered as undesirable with high ulcerogenic capacity. Optimal particle size could be designed in the grinding process, and it was shown that the most convenient grinding method is to combine roller mill and hammer mill. Concerning that nowadays pigs are mainly fed pelleted feed, and that pelleting causes strong additional grinding of feed particles, particle size distribution (PSD) obtained within the grinding process would be dramatically changed during pelleting. The possibilities to decrease the intensity of grinding of particles during pelleting, by variation of parameters of pelleting process, are very limited. Modified extrusion process (i.e. processing using expander) followed by shaping element, is suggested in the literature as an alternative for pelleting in order to obtain agglomerated pig feed with preserved PSD, but this process is not extensively studied so far.