The capacity of the duodenum (by calculating the length and diameter of the duodenum) to hold the digesta of birds fed the fine ground CM diet was 2 % and 8 % less than the capacity of the duodenum of birds fed the fine + crumbled CM diet and crumbled CM diet respectively. However, the birds fed the fine ground CM diet had 9 and 18 % more digesta in their duodenum than those birds fed the fine + crumbled and crumbled CM diet respectively. It is possible that more quantity of digesta in the duodenum of birds fed the fine ground CM diet, in this current study, may slow down gastric motility and thus affect feed passage rate. According to Duke (1986), duodenal distention inhibits gastric motility. This mechanism may explain the lower feed intake of birds fed the fine ground CM diet.