Differential proteomic responses to short-term heat stress in Vechur and crossbred cattle of Kerala.

The objective of this study was to compare the proteomic responses of indigenous Vechur and crossbred cattle to cyclical heat stress under high humidity. Kerala experiences a humid tropical climate throughout the year, and recent increases in ambient temperature have intensified heat stress in dairy cattle, adversely affecting productivity, health, and welfare. These effects are more severe in high-yielding crossbred cattle than in thermotolerant indigenous breeds such as Vechur. Understanding breed-specific molecular responses to heat stress is essential for developing climate-resilient livestock systems. Six heifers (n = 3 per breed) were exposed to cyclical heat stress and high relative humidity for three days in a controlled climate chamber simulating tropical summer conditions. Crossbred cattle showed significantly higher behavioural and physiological indicators of heat stress (p < 0.001). Serum proteomic profiling using liquid chromatography tandem mass spectrometry (LC-MS/MS) identified distinct, differentially expressed proteins between the breeds (p < 0.05). Vechur cattle seem to exhibit an early and energy-efficient stress response characterized by activation of co-chaperones (DNAJB1, HSPBP1), strong antioxidant defenses (TXNRD1, CAT, GST, SOD2), enhanced protein quality control (PSMD2, SQSTM1), and improved DNA repair mechanisms (APEX1, PCNA). These coordinated responses limit the oxidative and cellular damage during heat stress. In contrast, crossbred cattle showed increased expression of proteins associated with stress recovery and mitochondrial repair, including DNAJC7, HTRA4, PSMD8, SOD1, SQOR, OSR1, PON1, and PARP1, indicating a delayed response following oxidative injury rather than sustained protection. The findings demonstrate superior cellular resilience of Vechur cattle under tropical heat stress and highlight the potential of indigenous breeds for climate-resilient breeding and improved heat stress management in dairy production systems.