Influence of feed form on the apparent metabolisable energy of feed ingredients for broiler chickens.

• Feed form influences metabolisable energy of ingredients for broiler chickens. • Pelleting increased apparent metabolisable energy of cereal grains. • Pelleting effect on metabolisable energy of protein sources depends on the ingredient. • Pelleted diets should be used in energy evaluation assays. The influence of feed form (FF) on the apparent metabolisable energy (AME) of seven feed ingredients for broiler chickens was examined in two experiments. The first experiment was conducted to investigate the interaction between four cereal grains (maize, sorghum, wheat and barley) and two FF (mash vs. pellet) on the nitrogen-corrected AME (AMEn) contents using the direct method. The test diets contained 962 g/kg of each grain. Each diet was randomly allocated to six replicate cages (six birds per cage) and fed for 7 d from 21 to 28 d post-hatch. The feed intake and total excreta output for each replicate cage were measured over the last 4 d of the assay. No interaction (P > 0.05) between grain type and FF was found for the AMEn. Maize and sorghum showed the highest AMEn, barley the lowest and wheat being intermediate. Regardless of the grain type, pelleting increased (P < 0.05) the AMEn of the grains by 0.22 MJ/kg, compared with mash diets. The second experiment was conducted to examine the effect of FF on the AMEn of three protein sources (meat and bone meal [MBM], soybean meal [SBM], and canola meal [CM]) using the difference method. A maize-soybean meal basal diet was formulated, and the test diets were developed by replacing (w/w) 30 % of the basal diet with MBM, SBM or CM. Each diet was randomly allocated to six replicate cages (six birds per cage) and fed for 7 d (d 21–28) and, feed intake and total excreta output were measured over the last 4 d. There was a significant (P < 0.05) interaction between the protein source and FF. Pelleting reduced the AMEn of MBM, had no effect on that of SBM, but increased the AMEn of CM. Overall, pelleting process increased the AMEn of all cereal grains and influenced those of protein sources with the effect varied depending on the ingredient. The current findings suggest that the application of AMEn values determined based on assays using mash diets might result in over- or under-estimation of available energy content of ingredients in commercial pelleted broiler diets and highlights the need for the use of pelleted diets in energy evaluation assays. [ABSTRACT FROM AUTHOR]