Comparative Assessment of Thermotolerance in Indigenous and Commercial Chickens Using Expression of HSP70 and HSP90 Gene

Abstract

The experiment was conducted during November 2023 at Madras Veterinary College, Chennai. In poultry production, environmental stressors such as high ambient temperature decreased productivity of birds to counter these adverse effects, HSP70 and HSP90 are rapidly synthesized under heat stress to protect cells by stabilizing denatured proteins, preventing aggregation, and promoting proper refolding, thereby mitigating cellular damage in Poultry. This study evaluated the expression of HSP70 and HSP90 genes in four chicken genotypes namely, indigenous Siruvidai, TANUVAS Aseel, White Leghorn, and commercial broiler subjected to acute heat stress (38 ± 1 °C for 1 h). Heat shock proteins (HSPs) were essential molecular chaperones that protected cells by stabilizing misfolded proteins and preventing aggregation under stress. Liver tissues were collected from six heat-treated and three control birds per group. Total RNA was extracted, reverse transcribed to cDNA, and analyzed by quantitative real-time PCR using β-actin as a reference gene. Relative expression was calculated using the ΔΔCt method. Results showed that HSP70 expression was upregulated in indigenous Siruvidai (1.42 ± 0.12fold), TANUVAS Aseel (1.19 ± 0.09 fold), and White Leghorn (7.57 ± 0.31fold), but downregulated in broilers (0.40 ± 0.05fold) compared to their respective controls. In contrast, HSP90 was strongly upregulated in indigenous Siruvidai (4.76 ± 0.20 fold), but downregulated in TANUVAS Aseel (0.63 ± 0.07fold), White Leghorn (0.17 ±0.03fold), and broilers (0.18 ± 0.04 fold). These findings suggested that indigenous breeds exhibited a balanced and adaptive thermotolerance strategy with moderate HSP induction, whereas White Leghorns mount an exaggerated HSP70 response and broilers showed a blunted chaperone response, reflecting their thermal susceptibility. Overall, the results highlighted the genetic potential of native breeds for heat resilience and supported the use of HSP70 and HSP90 expression profiles as molecular markers in breeding programs to enhance thermotolerance in commercial poultry. In future, HSP70 and HSP90 expression profiling could aid in selecting and breeding poultry strains with improved heat tolerance and adaptability to climate change.