Immune Cell Populations in the Broiler Ileum Exhibit Differential Cytokine Profiles in Response to Lipid Source and Peroxidation

Used restaurant oil offers a sustainable and affordable energy source in broiler diets but variable lipid composition and the presence of harmful peroxidation products may alter intestinal immunity. The objective of this study was to evaluate the effects of feeding different lipid sources with variable peroxidation statuses on immune cell populations producing interleukin-6 (IL6) and interferon-γ (IFNG) in the broiler ileum. Two hundred broilers were fed diets with 5% inclusion of control or peroxidized palm, soybean, flaxseed or fish oil in a 4 × 2 factorial treatment design. At 21d, 2 birds/ treatment were euthanized for ileum collection and immune cell populations were analyzed by RNAscope- in situ hybridization (ISH). Ileal production of IL6 increased 85.8% by feeding peroxidized flaxseed oil while IFNG-producing cells were increased 55.1-59.9% by feeding either control or peroxidized soybean oil (P ≤ 0.05). Feeding peroxidized lipid generally reduced CD3+ T cells not producing either IL6 or IFNG by 14.9-39.0% (P ≤ 0.05). Overall, these results suggest that IL6 and IFNG have differential responses to lipid source and peroxidation while lipid peroxidation negatively impacts T cell presence in the broiler chicken ileum. Inflammatory outcomes observed in broilers fed peroxidized flaxseed oil suggest that yellow grease containing this type of oil may detrimentally impact broilers, while soybean oil generally contributes to intestinal inflammation regardless of heat exposure