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 thermotolerant, 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. Integrating these multidimensional parameters through Multi-Criteria Decision Analysis (MCDA) revealed a consistent thermotolerance hierarchy where indigenous KK ranked most resilient, followed by composite BR, while exotic HF were most susceptible (KK > BR > HF; p < 0.001 for both TOPSIS and VIKOR methods). Linear Discriminant Analysis confirmed this 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.