The effects of diet form and particle size on the performance, apparent metabolisable energy (AME), coefficient of apparent ileal digestibility (CAID) of nitrogen, starch and fat, jejunum morphology and digestive tract development in young broiler chicks were investigated in this experiment. Two diet forms (mash and crumble-pellet) and three particle sizes (fine, medium and coarse) were examined in a 2 × 3 factorial arrangement of treatments. Birds fed on crumble-pelleted diets had higher weight gain and feed intake, and greater villus length and crypt depth than those fed on mash diets. In mash diets, fine grinding resulted in lower feed per unit gain compared to medium and coarse grinding. Feeding crumble-pelleted diets reduced the relative length of all small intestinal segments and the relative weight of proventriculus and gizzard. Medium and coarse grinding increased gizzard weight compared to fine grinding. Pelleting reduced the CAID of nitrogen and increased the ileal fat digestibility. In crumble-pelleted diets, pellets made from medium and coarsely ground maize led to higher starch digestibility. Increasing maize particle size from fine and medium to coarse resulted in higher AME in mash and crumble-pelleted diets. Overall, the current results showed that diet form had a greater influence on the recorded parameters than did maize particle size. Coarse grinding of maize, through increased digestive development and functionality, was beneficial to nutrient and energy utilisation and performance in young broilers fed on crumble-pelleted diets.
