Nutritional Modulation of Epigenetic Responses to Heat Stress in Farm Animals: Evidence, Limitations and Perspectives.

Rising global temperatures pose a serious threat to the productivity of farmed animals. Prolonged heat exposure impairs growth, reproduction and immunity; suppresses feed intake; and disrupts intestinal barriers, leading to substantial economic losses. Conventional cooling strategies offer limited relief, spurring research into the underlying molecular dysregulation. Epigenetic mechanisms link heat stress (HS) to gene expression. Specific nutrients that modulate these mechanisms could help mitigate HS. This review critically summarizes how methyl donors, short-chain fatty acids (SCFAs), vitamins, and phytochemicals reshape the epigenome of poultry, ruminants, and swine under HS conditions, focusing on heat shock protein (HSP) modulation, intestinal barrier reinforcement, and enhancement of antioxidant capacity. Across these interventions, several consistent observations emerge: methyl donors appear to modulate HSP70 expression, butyrate reinforces intestinal barrier integrity, and folate reverses stress-induced hypermethylation in swine-although direct epigenetic evidence remains limited in most cases. However, knowledge gaps remain, especially regarding aquatic animals and interactions among dietary components. By integrating mechanistic and empirical evidence, this review provides a basis for precision nutrition that goes beyond single-nutrient strategies. Targeted dietary intervention may influence thermal tolerance through epigenetic mechanisms. Looking ahead, direct measurements of epigenetic endpoints and systematic cross-species comparisons will be essential to validate and extend the current findings.