Relationship of Meteorological Data with Heat Stress Effect on Dairy Cows of Smallholder Farmers

Global warming has been increasing heat stress threat in animals, which can be monitored via the Temperature Humidity Index (THI). The present study describes the THI pattern and the relationship between THI and the production performances of dairy cows in a selected area of Bangladesh. The THI value was calculated using weather station data gathered over 35 years. Based on the THI pattern, January and June were identified as the coolest and hottest months, respectively. Consequently, the production performances of 10 crossbred cows with homogenous characteristics were monitored every January and June for a 5-year period. The average THIMEAN was found to be 17% higher in June when compared to January; with this increment of THIMEAN, average milk production was decreased by 24.4% (p < 0.05). The milk fat and protein content were also reduced (p < 0.05) by 14.5 and 15.2%, respectively, suggesting a negative correlation. However, ash content increased by 15.3%, which indicates a positive correlation. In addition, multiple regression analysis revealed that, with each point increase in THIMEAN and rectal temperature, there was a decrease in milk yield of 0.04 and 1.17 kg ECM, respectively. In contrary, each point increase in THIMEAN resulted in 0.059 °C increase of rectal temperature. Taken together, THIMEAN calculated using meteorological station data has a distinct relationship with the production performances of lactating crossbred dairy cows.