The animal protocol for this experiment was approved
by China Agricultural University Animal Care and Use
Committee. The experiment was divided into two phases,
which included starter (d 0-21) and grower (d 22-42) phases.
A total of 288 Arbor Acre male broilers (1 d of age, initial
BW = 27.03±0.10 g) were randomly allocated to four
dietary treatments. The birds were housed in 90×60 cm pens
containing 12 birds, and each treatment contained 6
replicate pens of birds. All birds were raised in an
environmentally controlled room with continuous light (10
to 20 lux). Temperature was maintained at 33°C from 0 to 5
d and then gradually reduced, according to normal
management practices, until a temperature of 22°C was
achieved. Feed and water were supplied ad libitum.