This study was conducted to investigate
the effects of exogenous enzymes on growth performance,
ileal digestible energy (IDE) and apparent ileal
digestibility of CP and amino acids (AA) in broiler
chickens fed corn-soy diets formulated using 3 different
sources of corn (corn 1, corn 2, and corn 3). One-dayold
male broiler chicks (n = 3,600) were allocated to
15 dietary treatments as 5 treatments for each corn as
follows: positive control (PC) with no exogenous enzymes
and adequate in all nutrients; negative control
(NC) without exogenous enzymes and a 3% reduction
in calculated ME relative to the PC diet; NC plus a
commercial xylanase; NC plus a commercial mixture of
xylanase, amylase, and protease; and NC plus a commercial
mixture of xylanase and β-glucanase. Enzyme
products had no effects on performance variables, and
in some instances, they had negative impacts. In most
cases, there were no effects of enzyme products on IDE
and digestibility of CP and AA in the starter and finisher
phases. Effects of exogenous enzymes on ileal digestibility
were mainly found in the grower phase, and
these responses were mostly observed in birds fed corn
2 diets compared with birds receiving corn 1 or corn 3
diets. Although analyzed nutrient contents of 3 corn
samples were similar, supplementing corn 2 diets with
enzyme products was associated with greater responses
on digestibility parameters. Factors related to diets
(e.g., availability of substrates) and birds (e.g., enzymatic
activities in the digestive tract) may have limited
nutrient digestibility, and these limitations may have
provided favorable conditions for exogenous enzymes to
specifically work on their substrates in corn 2 diets in
the grower phase. Effects of enzyme products on IDE
and digestibility of CP and AA were not consistent and
varied depending on