On d 21 and d 42, two birds from each pen were randomly
picked out and the jejunum (from the entrance of bile ducts to
Meckel's diverticulum) and ileum (from Meckel's diverticulum to
the ileo-cecal junction) were immediately removed and dissected
after the birds were killed by cervical dislocation. A 3 cm long
ileum section before the ileo-cecal junction was separated and
kept at 4 °C for cell isolation. The remaining ileum and the whole