This experiment was conducted at Guangdong Wen’s
Foodstuffs Group Co. Ltd. and was approved according
to the animal care and handling procedures at the
Institute of Animal Sciences, Chinese Academy of Agricultural
Sciences, Beijing. A 3 × 2 factorial, completely
randomized design was used for the experiment. One
hundred and twenty 15-wk-old Chinese yellow roosters
were selected by weight (2.3 to 2.5 kg) and randomly
divided into 3 groups with 40 birds per group. All of the
birds were placed into individual cages (0.50 m length
× 0.42 m width × 0.55 m height) in a temperaturecontrolled
room (25°C) under 12 h of light per day. The
birds from 1 group were fitted with cannulas in the
duodenum, the remaining 2 groups were cannulated in
the jejunum or ileum according to procedures described
by Zhao et al. (2007). The duodenal cannula was fitted
on the U-shaped corner of the duodenum, whereas the
jejunal cannula was fitted 1.5 to 2.0 cm from Meckel’s
diverticulum of the jejunum, and the ileal cannula was
placed parallel to the end of a pair of ceca. After the intestinal
cannulation, feed was withdrawn and the birds
were tube-fed 20 mL of a dextrose solution (20 g/100
g of water) 3 times daily for 3 d. Then, birds were fed
a pre-experimental diet (Table 1) from d 4 to 15 of the
experiment. On d 16, 30 of the 40 cannulated chickens
in each group were randomly selected and divided into
2 subgroups. There were 5 replicates with 3 cannulated
chickens each.