Sample collection. On day 28, 6 blood samples per treatment were
harvested from the jugular vein by using tubes without anticoagulant
(Becton Dickinson). Blood samples were allowed to clot at room
temperature for 20 min and centrifuged at 1610 3 g for 10 min at 4C.
Serum was then removed and stored at 220C until assay. Intestinal
segments (duodenum, jejunum, ileum, and colon); mucosa in the
duodenum, jejunum, ileum, and colon; as well as chyme from the ileum
and colon were obtained and stored at 280C until further assay