Expression of genes related to ileal barrier function in heritage and modern broiler chickens

Authors: Kpodo, Kouassi; Miska, Kate; Schreier, Lori; Proszkowiec-Weglarz, Monika

Submitted to: British Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/16/2024
Publication Date: 5/8/2024
Citation: Kpodo, K.R., Miska, K.B., Schreier, L.L., Proszkowiec-Wegla, M.K. 2024. Expression of genes related to ileal barrier function in heritage and modern broiler chickens. British Poultry Science. https://doi.org/10.1080/00071668.2024.2337187.
DOI: https://doi.org/10.1080/00071668.2024.2337187

Interpretive Summary: Modern fast-growing chickens have been selected for production traits, including rapid growth and improved feed efficiency, which allow them to grow faster than heritage birds and reach the market as little as six weeks. However, the production system of fast-growing chickens has been associated with reduced welfare, and this has stimulated an increase in consumer’s preference for slow and medium-growing chickens. The improvement of production traits relies on intestinal efficiency and there is a need to better understand intestinal digestive, absorptive, and barrier function differences among slow, medium, and fast-growing chickens. The selection for production traits has been shown to improve intestinal development and digestive function. However, little is known about the effects of selection on intestinal barrier function as related to intestinal permeability to luminal pathogens and macromolecules. In this study, three fast, two medium, and one slow-growing chicken lines were used. Intestinal samples were collected at embryonic day 19, hatch, and days 7, 14, 21, 28, and 35 post-hatch. The effects of selection on intestinal barrier function were investigated through mRNA expression of genes related to the components of the junctional complexes (tight junction and adhesion molecules) connecting intestinal epithelial cells as well as the first line of immune defense (mucus layer and immunoglobulins) in the intestine. Most of the genes show no clear expression differences among the fast, medium, and slow-growing chicken lines; however, some of the genes were increased with age. The gene expression patterns suggest that selection for production traits may have not induced changes in junctional complexes and immune defense genes. However, the results confirm that the expression of these genes are age dependent.

Technical Abstract: The experiment was conducted to determine differences in the expression of genes encoding intestinal barrier proteins between fast, medium, and slow-growing chickens. Chicken lines Athens Canadian Random Bred (ACRB), Ross708, Hubbard H1 (HH1), Cobb500, Longenecker’s Heritage (LHR), and RedBro, were raised for 35 days. Ileal samples were collected at embryonic day 19 (-2 days post-hatch), hatch, and days 7, 14, 21, 28, and 35 post-hatch to assess the expression of genes encoding tight junction proteins (claudins, CLDN; occludin, OCLN; zonula occludens, ZO), junctional adhesion molecules (JAM), mucin (Muc2), immunoglobulin A (IgA), polymeric immunoglobulin receptor (pIgR), and fatty acid binding protein (FABP2). Expression of CLDN-1 was increased (P < 0.0001) in LHR compared to Cobb500 while CLDN-5 was increased (P < 0.0001) in ACRB, HH1, RedBro, and Ross708 compared to LHR as well as in ACRB compared to Cob500. Occludin was upregulated (P = 0.01) in ACRB and LHR compared to Ross708 at day 14 post-hatch. Expression of ZO-1 was upregulated (P = 0.001) in LHR compared to Ross708, HH1, and Cobb500. Tight junction genes, except CLDN-4, JAM-2, and JAM-3 were downregulated (P < 0.0001) at hatch and day 7 post-hatch. Expression of Muc2 was increased (P < 0.0001) in LHR compared to RedBro and from -2 days to day 7 post-hatch. Immunoglobulin A was increased (P = 0.001) in LHR compared to Ross708 and HH1 at -2 days post-hatch and in LHR compared to ACRB, Cobb500, and Ross708 at hatch. In addition, IgA was increased in all lines at day 14 post-hatch while pIgR was upregulated (P = 0.02) in Cobb500 and Ross708 compared to ACRB, HH1, LHR, and RedBro at hatch. The gene expression patterns suggest that selection for growth may have not induced changes in junctional complexes and immune defense genes. However, the results confirm that the expression of these genes are age dependent.