Bali cattle are native to Indonesia and are highly adaptable to tropical environments. However, fluctuations in temperature and humidity can affect their physiological responses. This study aims to identify the main physiological traits that contribute to the adaptation of Bali cattle to hot tropical conditions in East Kalimantan. A total of sixty-three Bali cattle, including males, non-pregnant females, and pregnant females, were intensively raised and used in this study. Data were analysed using a descriptive approach, correlation test, one way Analyses of Variance (ANOVA), Least Significant Difference (LSD) test, and Principal Component Analyses (PCA). The parameters observed included body surface temperature at various anatomical sites, respiratory rate (RR), heart rate (HR), and rectal temperature. Descriptive analyses showed that respiratory rate had the highest coefficient of variation (CV = 26.15%), indicating high sensitivity to changes in temperature and humidity, while rectal temperature was the most stable (CV = 1.58%). The LSD test showed that bulls had the highest RR and HR values (p < 0.05; p < 0.001), while pregnant cows showed greater inter-individual physiological variation. Correlations between parameters showed a strong relationship between surface temperature and respiratory rate, but a weak relationship between body temperature and respiratory rate (r < 0.2). PCA analyses could identify two principal components explaining 55.2% of the total variation. PC1 represents the external body temperature component, while PC2 represents the internal physiological response (RR, HR). These results indicate that a combination of physiological factors and reproductive status influences Bali cattle adaptation to heat stress. These results provide a basis for developing precision selection strategies and environmental management in local cattle farming systems.
Tamar et al. (Tue,) studied this question.