Comparative Heat tolerance of Sahiwal and Hariana Zebu Cattle

In tropical and semi-arid environments, heat stress significantly impacts livestock productivity; hence, it is necessary to assess the comparative heat tolerance of the breeds. Under typical summer heat stress circumstances, the current study evaluated the relative heat tolerance of Sahiwal and Hariana cattle. The experiment was conducted during the hot-dry season (15 May–15 June 2025), when the temperature–humidity index (THI) ranged from 75 to 86. A total of 106 heifers (53 per breed) were monitored for rectal temperature (RT), respiration rate (RR), pulse rate (PR), and body surface temperature (BST) during morning (06:00–07:00 h) and afternoon (14:00–15:00 h) hours. Changes in RT, RR, and PR were calculated, and heat tolerance indices (Iberia Heat Tolerance Index, Benezra Coefficient of Adaptability, and Dairy Search Index; DSI) were derived. The afternoon increase in RT and PR was comparable between breeds (p > 0.05), whereas the rise in RR was significantly higher in Hariana cattle than in Sahiwal cattle (p < 0.05). Infrared thermography revealed significantly greater diurnal increases in ear, muzzle, neck, and croup surface temperatures in Sahiwal cattle (p < 0.05), while eye temperature did not differ between breeds (p > 0.05). Heat tolerance indices showed similar Iberia coefficients (p > 0.05); however, Hariana cattle exhibited significantly higher Benezra coefficient and DSI (p < 0.05). The correlation analysis revealed that the Iberia Heat Tolerance Coefficient was substantially correlated with the eye and croup regions (p < 0.05). These results suggest that, in semi-arid climates, Sahiwal cattle have more resilient to heat stress than Hariana cattle.