Sample Collections
At 21 and 42 d, 2 birds from each replicate pen were
selected according to the average BW within the pen
after a 12-h fasting, and weighted individually. Then
chicks were killed by cervical dislocation in a germfree
isolation chamber sterilized by UV radiation. The
foregut (about 12 cm from the end of the duodenum
to the middle section of the jejunum; Miyazaki et al.,
2007) of broilers was removed and flushed with a cold
phosphate buffer containing 154 mM NaCl, 3 mM KCl,
12 mM Na2HPO4, and 2 mM KH2PO4 (pH 7.4, 0°C) as
described by Sato et al. (2009). The foregut (about 1 g)
was frozen in liquid nitrogen and stored at −80°C until
analysis. The remainder of the foregut was used for
intestinal intraepithelial lymphocyte (IEL) subpopulation
measurements.