A shorter small intestine in birds may be explained that the diameter of the intestine increased and that the surface area was similar or greater with the WR diet treatments. Wu et al. (2004), however, found that 200 g/kg whole wheat inclusion pre-pelleting had no effect on digestive tract measurements. Santos et al. (2006) also reported that intestinal length was not affected by dietary inclusion of wood shavings in turkeys. This can be explained that effects on the modification of digestive tract depend on grain type as reported by Amerah et al. (2008), who found that birds fed maize-based diets had arelatively heavier gizzard than those fed wheat-based diets. Jorgensen et al. (1996), comparing three fibre sources (pea fibre,wheat bran or oat bran), also reported that the effects of fibre on digestibility and digestive tract development in poultry depended on the source.