Effect of feed structure on nutrient digestibility, growth performance, and gastrointestinal tract of pigs – A Review

The objective of this manuscript has been to analyse published data on the effect of feed structure (coarse/fine, meal/pelleted) on some parameters of the nutritional value of feed, performance of pigs and their gastrointestinal tract. The papers reporting mean geometric particle size or distribution of particles on sieves for the feeds used, were mainly considered. The literature data have indicated that finely ground feeds have a higher ileal digestibility of crude protein and amino acids and higher faecal digestibility of nutrients. They also contain more digestible and metabolisable energy than coarser ground feeds. Reduction of feed particle size has a stronger impact on the gain/feed ratio increase than on the daily gain of pigs. However, coarser feed structure and roller milling are efficient in maintaining the health of stomach. Lactic bacteria, stomach pH, short chain fatty acids in the gastrointestinal tract (GIT), as well as the volume and character of mucins positively responded to coarser and to non-pelleted feeds. Less intensively ground feeds, especially before pelleting, are also better at protecting the GIT of pigs against microbial infection by Salmonella enterica. Based on the references, some recommendations of grinding intensity have also been included.