Effects of type of cereal, heat processing of the cereal, and fiber inclusion in the diet on gizzard pH and nutrient utilization in broilers at different ages

An experiment was conducted to study the effects of type of cereal (60% corn or 60% rice), heat processing of the cereal (raw or steam-cooked), and fiber source (control without hulls, 3% oat hulls, and 3% soy hulls) on gizzard pH and total tract apparent retention (TTAR) of nutrients in broilers at different ages. There were 12 treatments arranged factorially (2 x 2 x 3) and 6 replicates (8 chicks) per treatment. The 2 basal diets were based on soy protein concentrate and fish meal and had a neutral detergent fiber content of 3.5% for the rice and 7.3% for the corn diet. Gizzard pH was lower at 13 d than at 8 or 20 d of age (P <= 0.05) and was lower for the corn than for the rice diets (P <= 0.001). The inclusion of additional fiber reduced gizzard pH in broilers fed rice but not in broilers fed corn (P <= 0.001). Except for acid soluble ash, TTAR of nutrients increased from 4 d to 8 or 13 d of age (P <= 0.001) and then remained constant until 20 d. Nutrient retention was higher for the rice than for the corn diets (P <= 0.001) at all ages. The inclusion of oat hulls or soy hulls improved TTAR of nutrients and the effects were more pronounced for the rice than for the corn diet (P <= 0.001). Also, the beneficial effects of fiber inclusion on TTAR of ether extract and AME(n) of the diet were higher at younger ages (P <= 0.05). It is concluded that rice is a cereal of choice in prestarter diets for broilers. The reduction in gizzard pH and the improvement of TTAR of nutrients observed with additional fiber suggests that young broilers might need a minimal amount of fiber in the diet for optimal performance.