Lipid source and peroxidation status alter immune cell recruitment in broiler chicken ileum

Authors: FRIES-CRAFT, KRYSTEN - Iowa State University; MEYER, MEAGHAN - Iowa State University; LINDBLOM, STEPHANIE - Iowa State University; Kerr, Brian; BOBECK, ELIZABETH - Iowa State University

Submitted to: Journal of Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/14/2020
Publication Date: 12/9/2020
Citation: Fries-Craft, K.A., Meyer, M.M., Lindblom, S.C., Kerr, B.J., Bobeck, E.A. 2020. Lipid source and peroxidation status alter immune cell recruitment in broiler chicken ileum. Journal of Nutrition. 151(1):223-234. https://doi.org/10.1093/jn/nxaa356.
DOI: https://doi.org/10.1093/jn/nxaa356

Interpretive Summary: Fats and oils are used in poultry diets to increase the concentration of dietary energy and often reduce diet costs. Thermally processed fats and oils contain various lipid peroxidation products which have been shown to reduce broiler performance, but the mechanisms causing this reduction remains to be elucidated. The current study was conducted to evaluate ileal morphology, liver cytokine gene expression, and ileal immune cell populations in broilers fed control or thermally processed lipids with varying fatty acid profiles. Data from this experiment indicate that lipid source and concentration of lipid peroxidation products did not affect effect intestinal histomorphology or liver cytokine profiles analyzed by quantitative polymerase chain reaction as a marker for systemic immunity. The data also suggest that broiler immune responses to varying lipid sources and lipid peroxidation products are primarily localized to intestinal tissues without grossly impacting intestinal structure. This information is important for nutritionists at universities, feed companies, and poultry production facilities on understanding mechanisms of how lipid peroxidation impacts intestinal function, thereby providing a basis from which to assess damage to fats or oils used in feed production.

Technical Abstract: Background: Restaurant oil in poultry diets increases energy content, reduces production costs, and promotes sustainability within the food supply chain. However, variable oil composition and heating temperatures among restaurant oil sources may impact broiler chicken health due to heat-induced lipid modifications. Objective: A 21d experiment was conducted to evaluate ileal morphology, liver cytokine gene expression, and ileal immune cell populations in broilers fed control or peroxidized lipids with varying chain and saturation characteristics. Methods: Day-old broilers were housed in battery cages (5 birds/cage) and fed diets containing 5% control or peroxidized oils. Eight diets were randomly assigned in a 4×2 factorial arrangement consisting of oil source (palm, soybean, flaxseed, or fish) and peroxidation status (control or peroxidized). At d21, samples were collected for ileal histomorphology (villus height (VH), crypt depth (CrD), and the VH:CrD ratio), and liver cytokine expression (qPCR). Ileum cytokine expression and T-cell markers were analyzed by RNAscope in situ hybridization (ISH). Data were analyzed as a mixed model (SAS 9.4) with fixed effects of lipid source, peroxidation, and lipid×peroxidation interaction. Results: CD3+ T-cells in the ileum decreased 16.2% due to peroxidation (P = 0.001) with 30.3% reductions observed in birds fed peroxidized flaxseed oil (P = 0.01). Peroxidation increased IL6+ and IL1B+ cells by 62.0 and 40.3%, respectively (P = 0.01). Soybean oil increased IFNG+ cells by 55.1% compared to palm oil, regardless of peroxidation status (P = 0.007). Lipid source and peroxidation did not alter ileal histomorphology or liver cytokine expression. Conclusions: Lipid peroxidation increased ileal IL1B and IL6 in broiler chickens, while soybean oil diets increased IFNG. Generally, peroxidation decreased overall CD3+ T-cell populations, suggesting impaired T-cell presence or recruitment. These results identify potential immunomodulatory lipid profiles in restaurant oil while supporting RNAscope-ISH as a method to describe avian tissue-level immune responses.