Correlation between blood, physiological and behavioral parameters in beef calves under heat stress

Objective: The performance, health, and behaviour of cattle can be strongly affected by climate. The objective of this study was to determine the effect of heat stress on blood para meters, blood proteins (haptoglobin [Hp]; heat shock protein 70 [HSP70]), rectal temperature (RT), heart rate (HR) and rumination time in Korean native beef calves. Methods: Thirtytwo Korean native beef calves were randomly assigned to 8 groups with 4 animals per group. They were kept in environmental condition with temperaturehumidity index (THI) ranging from 70.01 to 87.72 in temperaturehumidity controlled chamber for 7 days. Results: Their HR, RT, and serum cortisol and HSP70 levels were increased (p<0.05) in high THI compared to those at low THI. But, serum Hp level was decreased (p<0.05) in high THI compared to these at low THI. In addition, HR, RT, serum cortisol and HSP70 were positively correlated with THI (R 2 = 0.8368, p<0.01; R 2 = 0.6162, p<0.01; R 2 = 0.581, p<0.01; R 2 = 0.2241, p = 0.0062, respectively). There was also positive association between HR and cortisol (R 2 = 0.4697, p<0.01). Similarly, RT and cortisol were positively associated (R 2 = 0.4581, p<0.01). But, THI and HR were negatively correlated with Hp (R 2 = 0.2157, p = 0.02; R 2 = 0.3362, p = 0.003). Hematology and metabolites results were different among treatment groups. Standing position was higher (p<0.05) in the high THI group compared to that in the low THI group.