Behavioral and thermoregulatory responses of dairy heifers under different roofing materials in a humid tropical climate

Understanding how dairy heifers respond to different roofing materials in humid tropical climates is critical for improving their welfare and productivity. This study analyzed dairy heifer’s behavioral and thermoregulatory responses under different roofing materials in a humid tropical climate. The study involved five growing heifers, each under two years old and averaging 210 kg in body weight. Two roofing materials were tested: a conventional roof (CR) made from asbestos and a modified roof (MR) constructed with layers of UPVC, aluminum foil, and rock wool. The heifers underwent a two-week adaptation in CR, followed by one week of data collection. They then transitioned to MR for another two weeks of adaptation and subsequent data collection. The data collected included behavior observations (lying, standing, and lying bout frequency) and thermoregulatory responses (rectal temperature, respiration, and heart rate). The results showed that the average lying and standing time behaviors were differed significantly between two roof materials (p<0.05). The ambient temperatures tended to be lower in MR, especially during noon and the afternoon. Roof surface temperatures were significantly reduced by 27–32% (p<0.05) compared to CR. The study indicated mild to moderate heat stress, with overall means showing significant differences in rectal temperature, heart rate, and respiration rate (p<0.05), consistently lower in MR than CR. Modifying roof materials demonstrates a better microenvironment, improves the comfort and productivity of heifers under humid tropical climate and is important for sustainable dairy production in tropical regions.