Effects of particle size reduction, pelleting, and extrusion on the nutritional value of ingredients and diets fed to pigs: A review

Particle size reduction, pelleting, and extrusion are feed processing technologies used to improve nutrient digestibility and achieve maximum pig growth performance. Particle size reduction may improve the digestibility of energy and nutrients. Digestibility of gross energy may be improved when the particle size is reduced in lupins, corn, soybean meal (SBM), field peas, barley, wheat, and sorghum. Reducing particle size in corn, sorghum, and wheat may also improve growth performance due to increased digestibility of nutrients. Particle size reduction may also reduce the production of short-chain fatty acids and improve dressing percentage. It has, however, been demonstrated that particle size reduction may result in development of ulcers and gastric keratinization. Pelleting is a hydrothermal technique that may improve palatability, reduce feed wastage, and modify structures of starch. Pelleting may improve the digestibility of gross energy in diets containing corn, distillers dried grains with solubles (DDGS), sorghum, barley, wheat, and SBM. Digestibility of amino acids and pig growth performance may also be increased in diets containing corn, SBM, and DDGS. Extrusion may improve the digestibility of nutrients from diets containing peas, SBM, barley, corn, DDGS, sorghum, wheat, wheat bran, and potato starch. Growth performance was improved in weanling and growing-finishing pigs upon extrusion of diets containing chickpeas, wheat, or barley. However, extrusion of ingredients resulted in inconsistent effects on growth performance. Thus, more research is needed to address the impact of feed processing technologies on different diets. Optimum temperature and pressure for pelleting and extrusion of feed ingredients must also be addressed to maximize the beneficial effect of thermal treatments.