Molecular Basis of Breed-Specific Variation in Thermal Resilience among Cattle in Tropical Environments

Heat stress is a primary barrier to sustainable cattle production in tropical regions, where breeds exhibit markedly different levels of thermal resilience. To elucidate the molecular basis of these variations, we conducted a comparative whole-blood transcriptome analysis using RNA-seq. The study contrasts three distinct populations under high-heat conditions (Temperature-Humidity Index: 44.68): the heat-tolerant indigenous Kedah-Kelantan (KK), the intermediate Brangus (BR), and the heat-vulnerable exotic Holstein Friesian (HF). By analyzing the global gene expression profiles of these divergent breeds, we identified key transcriptomic signatures associated with adaptation. Differential expression analysis revealed significant breed-specific regulation of pathways critical to homeostasis, including thyroid hormone metabolism, mitochondrial bioenergetics, lipid metabolism, and cellular stress responses. Notably, the indigenous KK cattle displayed a unique molecular response compared to the HF cattle, while the crossbred Brangus exhibited intermediate transcriptomic profiles. This dataset provides a comprehensive resource for understanding the regulatory networks governing bovine heat tolerance. These findings offer potential biomarkers for thermal resilience and support the development of genomic selection strategies aimed at improving climate adaptation in both dairy and beef cattle production systems.