Assessment of housing environment and its impact on dairy behavior and milk production in Northeastern China

Abstract. Northeastern China is a dominating area of dairy milk production and characterized by a warm summer and an extremely cold winter. The aim of this study was to assess the thermal environment of the dairy barn in summer and winter, using the indices of THI (Temperature Humidity Index), BGHI (Black Globe-Humidity Index) and CCI (Comprehensive Climate Index) based on the continuous measurement of thermal environmental factors, as well as core body temperature (CBT), behavior and milk yield information of dairy cows. Results showed that cows went through mild to moderate heat stress in summer (40.9% and 17.9% of the total hours during the measurement, respectively) and no to mild cold stress in winter (87.5% and 12.3% of the total hours during the measurement, respectively). Under heat stress, CBT of the cows increased from 38.8oC to 39.3oC (P<0.05). From no to moderate heat stress, lying time of the cows statistically was reduced from 51.3% to 42.3%, and the production fell by 9.2% when THI reached above 75 (P<0.05). Relative humidity (RH), CO2 and NH3 concentrations inside the barn exceeded the thresholds of recommendations in winter due to insufficient ventilation. Overall average CO2 and NH3 concentrations were 4,472.7 mg m-3 and 13.3 mg m-3, respectively. Actual ventilation rate was about 79.1% of the recommended minimum ventilation (RMV) based on the moisture balance of the barn. Solutions of increasing ventilation or using evaporative cooling, etc., were recommended during moderate heat stress to alleviate its impacts in summer. A ventilation rate at 0.15-0.16 m3 h-1per kg body weight for the surveyed barn was suggested to control the indoor temperature over 0oC and RH at approximately 80% in winter.