Influence of grain type and feed form on performance, apparent metabolisable energy and ileal digestibility of nitrogen, starch, fat, calcium and phosphorus in broiler starters

Abstract

The influence of grain type and feed form on performance, apparent metabolisable energy (AME) and coefficient of ileal apparent digestibility (CIAD) of nitrogen (N), starch, fat, calcium (Ca) and phosphorus (P) in broiler starters was examined in this study. Two grain types (maize and wheat) and three feed forms (mash, pellet and re-ground pellet) were evaluated in a 2×3 factorial arrangement of treatments. In both maize- and wheat-based diets, pellet-fed birds had higher (P<0.05) weight gain and feed intake than those fed mash and re-ground pellets. In both grain types, feed per unit gain of birds fed mash and pelleted diets was similar (P>0.05), but lower (P<0.05) than those fed re-ground pellets. However, dramatic decrease in the weight gain and feed intake, and a marked rise in the feed per unit gain of birds fed re-ground wheat-based pellets resulted in a significant (P<0.001) grain type and feed form interaction. In maize-based diets, pelleting had no influence (P>0.05) on the CIAD of N, but re-grinding the pellets resulted in higher (P<0.05) N digestibility than that of the mash diet. Feed form had no effect (P>0.05) on the CIAD of starch in maize-based diets. Ileal apparent digestibility coefficient of fat was improved (P<0.05) by the pelleting of maize-based diet compared to the mash diet with the improvement in fat digestibility maintained in re-ground pellets. In maize-based diets, pelleting increased (P<0.05) the CIAD of Ca and P, and the digestibility coefficients were further improved by re-grinding the pellets. In wheat-based diets, pelleting reduced (P<0.05) the CIAD of N and re-grinding the pellets resulted in the highest (P<0.05) N digestibility. Pelleting reduced (P<0.05) starch digestibility in wheat-based diets. While pelleting reduced (P<0.05) CIAD of fat, Ca and P in wheat-based diets, re-grinding the pellets improved fat, Ca and P digestibility to an extent higher than the mash diet. Feed form had no effect (P>0.05) on the AME of maize-based diets, but pelleting reduced (P<0.05) the AME of wheat-based diets. Overall, the current results suggest that effects of feed form on CIAD of nutrients depend on the cereal used and the nutrient considered. In maize-based diets, there was no negative impact of pellet feeding on CIAD of nutrients. In contrast, in wheat-based diets, feeding pelleted diets had negative effects on the digestibility of all nutrients. These negative effects on nutrient utilisation, however, are compensated by increased feed intake and the resultant higher nutrient intake in pellet-fed broilers.