Effects of Thermal Manipulation on mRNA Regulation of Response Genes Regarding Improvement of Thermotolerance Adaptation in Chickens during Embryogenesis

Simple Summary Heat stress is a threat to poultry, affecting both animal welfare and productivity. Temperature manipulation during embryogenesis is considered one of the mitigation strategies with which to reduce the negative impact of high ambient temperature. However, the mRNA regulation underlying genes that are responsible for thermotolerance acquisition during embryogenesis remain unclear. The pattern of gene expression, focusing mainly on heat shock proteins, antioxidants, and immunological genes, of chickens that have undergone thermal manipulation during their embryonic stages was emphasized in this review. Considering the importance of animal welfare, temperature manipulation during embryogenesis indicated the enhanced adaptability of chickens towards encountering heat stress at later stages in life. The phenomenon of increasing heat stress (HS) among animals is of particular significance when it is seen in economically significant industries, such as poultry. Due to the identification of the physiological, molecular, and genetic roots of HS responses in chickens, a substantial number of studies have focused on reducing the effects of HS in poultry through environmental management, dietary manipulation, and genetic alterations. Temperature manipulation (TM) during embryogenesis has been claimed to increase the thermal tolerance and well-being of chickens without affecting their capacity for future growth. There has been little investigation into the vulnerability of the epigenome involving TM during embryogenesis, although the cellular pathways activated by HS have been explored in chickens. Epigenetic changes caused by prenatal TM enhance postnatal temperature adaption and produce physiological memory. This work offers a thorough analysis that explains the cumulative impact of HS response genes, such as genes related to heat shock proteins, antioxidants, and immunological genes, which may aid in the enhanced adaptability of chickens that have undergone thermal manipulation during their embryonic stages.