Embryonic thermal manipulation reshapes hepatic transcriptome profiles of heat-stressed broiler chickens

Heat stress (HS) is one of the major environmental challenges affecting poultry health, productivity, and welfare, particularly in broilers, which have limited thermoregulatory capacity. High temperatures disrupt metabolic balance, induce oxidative stress, and trigger cellular damage in vital organs such as the liver. Embryonic thermal manipulation (TM) has emerged as a promising approach to enhance thermotolerance through developmental reprogramming. Nonetheless, the molecular mechanisms facilitating TM-induced hepatic adaptation to HS remain predominantly unexamined. Herein, we leveraged bulk RNA-seq in a two-factorial design comparing standard incubation (Con_N: 37.8 °C, 56% RH) and thermally manipulated incubation (TM_N: 38.5 °C, 65% RH, 18 h per day), each exposed or not exposed to acute HS at day 22 post-hatch (Con_AHS and TM_AHS: 35 °C for 12 h). Liver samples were collected on embryonic day 19, post-hatch day 7, and day 22 to capture developmental and stress-induced transcriptomic dynamics. Hierarchical clustering of GO identified six functional clusters distinguishing TM and acute HS responses. TM caused subtle but long-lasting changes in the transcriptome of structural and regulatory pathways, such as the organization of the cytoskeleton, phosphorylation signaling, ion transport, and gap junctions. Acute HS activated protein refolding and chaperone-mediated pathways, reflecting proteostasis signatures. In contrast, TM chickens exposed to acute HS exhibited an attenuated stress response, characterized by reduced expression of heat shock proteins and enrichment of pathways related to tissue remodeling and homeostasis. Overall, TM reprogrammed gene networks to stabilize proteostasis and maintain metabolic homeostasis in response to thermal challenge. Our findings provide insights into the transcriptomic landscape of avian thermoregulation, supporting embryonic TM integration into sustainable, stress-resilient poultry under a changing climate.