Effects of fiber source and heat processing of the cereal on the development and pH of the gastrointestinal tract of broilers fed diets based on corn or rice.

We studied the influence of the cereal (corn and rice), heat processing (HP) of the cereal (raw and steam cooking), and fiber inclusion (none; 3% oat hulls, OH; and 3% soy hulls, SH) in low-fiber diets on the development and pH of the digestive tract in broilers. There were 12 treatments arranged factorially and 3 replicates (a cage with 12 chicks) per treatment. Digestive traits were measured at 1, 5, 9, 15, and 22 d of age, and digesta pH was determined at 22 d of age. The relative weight (% BW) of proventriculus and gizzard was greater in chicks fed corn than in chicks fed rice (P < or = 0.01). Heat processing had little effect on relative weight (RW) of the digestive organs. An interaction between cereal and HP of the cereal was detected for the gizzard and the liver; HP of corn reduced RW of the gizzard and increased that of the liver, but no effect was observed with HP of rice. The RW of the proventriculus was increased by SH inclusion (P < or = 0.05), whereas the RW of the gizzard was increased by OH inclusion (P < or = 0.001). Also, SH inclusion increased gizzard digesta (P < or = 0.01) and moisture (P < or = 0.001) content. Dietary treatment did not affect relative length (cm/kg of empty BW) of the intestines. Feeding rice tended to increase gizzard digesta pH (P = 0.081) but reduced that of the intestines (P < or = 0.001). Neither HP of the cereal nor hull inclusion affected pH of the digestive tract. We conclude that the RW of the proventriculus and gizzard is reduced by feeding rice and increased by hull inclusion. Dietary treatment had little effect on the weight and relative length of the intestines. Chicks might require a minimal amount of fiber in the diet to stimulate the development of the upper gastrointestinal tract.