ABSTRACT A study was conducted to evaluate the
effects of dietary protein level and protein digestibility
on the growth performance and carcass characteristics
of broilers from 1 to 35 d of age. Broiler chickens (n =
320) were fed 4 different ideal protein-balanced, isocaloric
diets in a 2 × 2 factorial design with 2 levels of
protein [high protein (HiPro; 20 and 18% or 200 and
180 g/kg) and low protein (LoPro; 18 and 16% or 180
and 160 g/kg) on d 1 to 14 and d 15 to 35, respectively]
and 2 levels of protein digestibility [high digestibility
(HiDig) and low digestibility (LoDig); approximately
85% and 80% CP digestibility, respectively]. The Hi-
Dig diets were formulated using soybean meal and
fishmeal, whereas the LoDig diets used wheat distillers
dried grains with solubles and meat and bone meal
as the primary protein sources. The standardized ileal
digestibility (SID) values of the wheat distillers dried
grains with solubles and meat and bone meal (56.5 and
72.0% SID for lysine, respectively) were measured