Abstract

An experiment was designed to determine the immune profile of broiler chickens between hatch and 9 days of age when fed diets with different fibre and betaine concentrations. A total of 240 day-old Cobb 500 male chickens were allocated to 16 cages with 15 chickens each. Treatments were arranged in a 2 x 4 factorial design, with 2 replicate cages per treatment. Treatments consisted of two feed formulations (low and high fibre diets) and four levels of betaine (0, 1, 3 or 5 kg/tonne). Before the start of trial (hatch), 10 broilers were weighed and blood samples were collected by cardiac puncture, then euthanised by cervical dislocation and jejunal samples collected for the determination of gene expression of claudin 1, claudin 5, occludin and interleukin 2 by PCR. Mononuclear cells populations in the blood samples were determined by flow cytometry. On days 4 and 9, five birds/cage (10 birds/treatment) were selected, euthanised and samples taken as per the start of hatch. Gene expression of claudin 1, claudin 5 and occludin was reduced between 4 and 9 days, independent of the group tested, while interleukin tended to increase between hatch and 4 days and decreased thereafter. Betaine inclusion reduced claudin 5 and occludin gene expression and increased CD8- CD28+ and CD8+ CD28+, suggesting it may aid in accelerating maturation of both the gastrointestinal tract and immune system for broilers in the early days post-hatch.