Integrative Multi-Criteria Decision Analysis Reveals Thyroid-Mediated Metabolic Regulation as a Key Driver of Heat Stress Resilience in Cattle

Climate change-induced heat stress threatens tropical livestock production. While indigenous breeds are known to be thermo-tolerant, the underlying physiological mechanisms remain poorly characterized. This study comprehensively evaluated the haematological, biochemical, and hormonal responses of three cattle genotypes (n = 40/group) Holstein Friesian (HF), Brangus (BR), and Kedah-Kelantan (KK) maintained under severe natural heat stress (Temperature-Humidity Index: 79–88). During the peak thermal challenge, HF cattle exhibited significantly elevated leukocyte counts (15.87 ± 0.94 vs. 8.33 ± 0.68 × 10⁹/L in KK; p < 0.001), indicating heightened inflammation, as well as elevated hepatic enzymes and disrupted electrolyte homeostasis (p < 0.05). In contrast, KK cattle maintained stable erythrocyte parameters and displayed the highest FT4 concentrations (13.69 ± 0.88 vs. 10.17 ± 0.40 pmol/L in HF; p = 0.005) and FT4/FT3 ratios (3.69 ± 0.27 vs. 2.60 ± 0.14 in HF; p = 0.002), suggesting adaptive metabolic down regulation. Multi-Criteria Decision Analysis (MCDA) integrating all the parameters consistently ranked thermo-tolerance as KK > BR > HF (p < 0.001). Linear Discriminant Analysis confirmed robust breed-specific differentiation (88.9% classification accuracy; Wilks' λ = 0.18, p < 0.001). These findings establish thyroid hormone regulation and immune modulation as pivotal determinants of thermal resilience and demonstrate that the applied MCDA framework is a suitable approach for identifying climate-resilient cattle breeds.