ABSTRACT 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 × 2 × 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 AMEn 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.