Field evaluation of a water-cooled cover for cooling sows in hot and humid climates

The hot and humid summer climates in certain parts of China can adversely impact on the production and welfare of gestating sows. Hence, effective cooling means to alleviate heat stress are essential to pig production. A field experiment was conducted to evaluate the efficacy of a water-cooled cover (WCC) attached to the sow’s stall with regards to thermal microenvironment in the sow occupied zone (SOZ), and the physiological and behavioural responses of the sows. The results showed that black-globe temperature (BGT) in SOZ under WCC with or without the presence of the sow averaged 4.8 or 5.4 °C below that of the control (without WCC) when the indoor air temperature was 34.3 °C. The temperature reduction in SOZ was proportional to the temperature difference between the inlet and outlet water of WCC. Increasing water flow rate through WCC enhanced cooling efficiency up to 4 l min−1 beyond which little additional benefit could be gained from further increase in water flow rate. Respiratory rate and surface temperature of the sows with access to WCC were significantly lower than those for control group (P < 0.001). The WCC sows spent 74% of their time lying under WCC, while the control sows spent 94% of the time lying in the pen. The sow’s thermoregulatory responses and behaviours were observed to lag 1–3 h behind the peak air temperature. Results of the present work suggest that WCC can alleviate heat stress of gestating sows in hot and humid climates.