Embryonic thermal manipulation enhances splenic immunity and regulates inflammatory responses toin broiler chickens.

Abstract

INTRODUCTION: Escherichia coli () infections continue to pose a significant health and economic burden to the poultry industry, with increasing restrictions on antibiotic use underscoring the need for alternative strategies to improve host resilience. Thermal manipulation (TM) during embryogenesis has been proposed as an economical strategy to enhance thermotolerance, stress resilience, and immune functionality in broilers. This study aimed to investigate the effect of TM during embryonic development on the immune response of broiler chickens following anchallenge. METHODS: A total of 740 Ross broiler eggs were assigned to either a control incubation (37.8 °C, 56% RH) or TM (39 °C and 65% RH for 18 h daily, on embryonic days 10-18). After hatching, chicks were subdivided into saline- or-injected groups. Splenic expression of pro-inflammatory mediators (iNOS and TNF-α), signaling receptors (NF-κB, p65, TLR-2, and TLR-4), and immunoregulatory cytokine (TGF-β) was quantified by RT-qPCR. At the same time, serum levels of acute-phase proteins (α1-acid glycoprotein (AGP) and C3) and total circulating immunoglobulins (IgA, IgM, and IgY) were assessed by ELISA. RESULTS: TM significantly modulated post-challenge immune responses, including downregulation of iNOS, TNF-α, NF-κB, TLR-2, and TLR-4, and upregulation of TGF-β. Notably, TM was associated with a stronger and more sustained circulating IgA response after infection. Additionally, TM lowered serum AGP levels under thechallenge, which indicates reduced systemic inflammation. DISCUSSION: These findings show that embryonic TM boosts both splenic and systemic immune regulation while reducing excessive inflammatory responses to bacterial challenges in broilers.