A systematic review on the modulation of heat shock protein 70 in broilers at different stages of growth under thermal stress

This systematic review synthesises evidence from published articles investigating nutritional strategies to modulate heat shock protein 70 (HSP70). A total of 1 616 records were identified from four databases and snowballing. After screening and eligibility assessment, 25 studies comprising 29 reports published between 2004 and 2025 were included. The analysis shows that targeted interventions particularly antioxidants (vitamins C, E, and selenium), amino acids and their derivatives (methionine, betaine), and phytogenic compounds effectively downregulate HSP70 expression in a dose or tissue-dependent manner. This modulation is associated with improved growth performance, enhanced redox balance, and normalised stress hormone profiles. Key findings indicate that synergistic combinations outperform single additives in suppressing HSP70 and improving carcass yield under chronic heat stress (32-38 °C); the early-life nutrient delivery modulates HSP70 expression and influences post-hatch thermotolerance; and organic mineral or methionine hydroxy analogue are more effective than inorganic forms. However, efficacy varies by life stage, with most studies focused on Ross and Cobb genotypes, and is influenced by gut microbiota interactions. Major research gaps remain, including defining stage-specific optimal HSP70 thresholds, clarifying links between HSP70 modulation, immunity or gut health, understanding long-term effects of early-life nutritional programming, and determining the influence of administration routes on nutrient efficacy.