Comparative Behavioural Responses of Vechur and Frieswal Heifers Under Simulated Tropical conditions

Heat stress is a major constraint in dairy production, particularly in tropical regions like Kerala, where high temperature and humidity prevail for most of the year. Behavioural responses are among the earliest indicators of thermal discomfort and provide valuable insights into breed-specific adaptation strategies. This study evaluated the behavioural responses of indigenous Vechur and the Frieswal (Holstein Friesian x Sahiwal) heifers under thermoneutral and cyclic heat stress conditions in a climate-controlled chamber. Three heifers per breed were first acclimatised under thermoneutral conditions, followed by exposure to a cyclic temperature regimen (28–42°C) with 70–75% relative humidity. Feed intake, water intake and standing time were recorded as key behavioural parameters. Vechur heifers maintained relatively stable feed and water intake, with only a marginal increase in standing time during heat stress. In contrast, Frieswal heifers exhibited a marked reduction in feed intake, and a significant increase in water intake and standing time (p < 0.001), indicating greater thermal stress. Vechur cattle exhibited prolonged recumbency, fewer posture changes and intermittent feeding patterns, suggesting efficient behavioural coping. Mutual licking (allogrooming) increased in both breeds during heat stress, but was more frequent in Vechur heifers, reflecting stronger social cohesion and calmer behavioural responses. Overall, the findings demonstrate that Vechur heifers exhibit superior behavioural adaptation to heat stress compared to Frieswal heifers. These results highlight the importance of indigenous breeds in climate-resilient dairy systems and support their role in sustainable livestock production under tropical conditions.