Dietary 25-hydroxycholecalciferol supplementation modulates intestinal inflammation and barrier integrity in young broiler chickens

Vitamin D signaling is important for intestinal homeostasis. Increase of vitamin D receptor in immune cells can modulate cell phenotype and cytokine secretion. Cytokines regulate both pro- (interleukin 17; IL-17) and anti-inflammatory (IL-10) responses triggered by external stimuli. Inflammation in the gut can disrupt structure and remodeling of epithelial tight junction complexes, thus compromising the protective barrier. The objective of the study was to determine the impact of dietary supplementation with 25-hydroxycholecalciferol (25OHD3), hydroxylated metabolite of vitamin D, on the local immune response and epithelial barrier integrity over time in broilers. A randomized complete block design experiment was conducted to evaluate the effect of dietary 25OHD3 inclusion on relative protein expression of the cytokines, IL-17 and IL-10, and tight junction proteins, zona occludens 1 (ZO-1) and claudin 1 (CLD-1), in broiler chicken duodenum and ileum from 3 to 21 d post-hatch. On d 0, male chicks (n = 480) were randomly assigned to raised floor pens. The experimental corn-soybean meal-based treatments were (1) common starter diet containing 5,000 IU of D3 per kg of feed (D3) and (2) common starter diet containing 2,240 IU of D3 + 2,760 IU of 25OHD3 per kg of feed (25OHD3) fed from d 0 to 21. On d 3, 6, 9, 12, 15, 18, and 21, 12 birds per treatment were euthanized to collect tissue samples for quantitative, multiplex, fluorescent western blot analysis. Target proteins were quantified using Image Quant TL 8.1 and expressed relative to total protein. Feeding 25OHD3 post-hatch decreased ileal IL-10 (anti-inflammatory) protein expression in 21 d-old broilers compared with D3 only (P = 0.0190). Broilers fed only D3 post-hatch had greater IL-17 (pro-inflammatory) protein expression in the ileum at 18 and 21 d of age (P = 0.0412) than those fed 25OHD3. However, CLD-1 expression was lowest in the ileum of D3 fed birds at 21 d of age (P = 0.0427). Dietary inclusion of 25OHD3 altered the abundance of key inflammatory cytokines and tight junction proteins in the ileum of young broilers.

Key Words: 25-hydroxycholecalciferol, cytokine, inflammatory response, interleukin.

Presented at the 9th Symposium on Gut Health in Production of Food Animals, St. Louis, USA, 2021. For information on the next edition, click here.