Effects of processing of wheat or oats starch on physical pellet quality and nutritional value for broilers

Two experiments were conducted to investigate the influence of cereal starch exposed to various processing techniques on physical pellet quality and nutritional value of the diets fed to broiler chickens. In experiment 1, diets with equal amounts of oat hulls, rapeseeds and fish meal were cold-pelleted or steam-conditioned and pelleted with or without inclusion of 200 g pure wheat starch/kg. Durability of the pellets was reduced (p<0.05) for the starch-containing diets compared to non-starch diets under both processing conditions. Despite a significant improvement (p<0.05) in pellet quality within starch containing-diets as a consequence of gelatinised starch addition, pellet durability was lower (p<0.05) for gelatinised starch-containing diets compared to non-starch diets. In experiment 2, wheat and de-hulled oat-based diets were cold-pelleted, steam-pelleted or extruded before being fed to broiler chickens. The extent of starch gelatinisation was higher for oat diets than for wheat diets under all processing conditions. Feed/gain was lower (p<0.05) and AMEn higher (p<0.05) for oat versus wheat diets. The increase in AMEn was also reflected in starch digestibility which was significantly higher for oats compared to wheat diets in all segments of the gastrointestinal tract. As a consequence of increased gelatinisation a significant improvement (p<0.05) in starch digestibility was observed for extruded wheat diets compared with either cold- or steam-pelleted wheat diets. An improved (p<0.05) starch digestibility due to extrusion processing was only observed at a duodenal level for oat diets.