Vol. 9, Issue 4, Part E (2024)

Author(s): Praveen Kumar I, Harikumar S, Sabin George, Kannan A, V Beena, Balusami C, Parvathy VS and Sajana OK

Abstract: The production, reproduction and well-being of livestock are all hampered by heat stress (HS). In tropical humid regions like Kerala, where high temperatures and humidity lead to decreased productivity, the goal of this observational study is to identify the temperature humidity index (THI) threshold on heifer behaviour, which is directly influenced by heat stress and affects the animal welfare. Study conducted in a controlled climate setting with varying temperature and humidity combinations, which examined under THI ranges from 73.14 to 93.88. Results showed a significant difference in the duration of lying and standing postures between the control group (T₁) and all other treatments. Specifically, heifers spent more time standing (188.9 ± 0.20 and 197.3 ± 0.29 minutes) under extreme heat stress conditions, with reduced rumination time (17.65 ± 0.16 minutes). Additionally, increased salivation (18.20 ± 0.13) and higher water consumption were observed under HS conditions. Based on findings of behaviour the threshold level of THI was found to be around 82.92. These findings indicate that behavioural responses are closely linked to HS, providing valuable insights into the responses of heifers in controlled climate environments.