The field studies reported here compare the performance of three cooling systems for relieving farrowing/lactating sows of heat stress under the warm and humid production climate in southern China. The comparative systems included (1) tunnel ventilation (TV) with vertical head-zone ventilation (HZV) vs. TV with HZV and drip cooling (DC), (2) TV only vs. TV with DC, and (3) horizontal air mixing (HAM) only vs. HAM and DC. For the HZV, a perforated overhead air duct was used to create an air velocity of 0.6 to 0.8 m/s (118 to 157 ft/min) in the head zone of the sow. The paired tests were conducted successively in an experimental commercial farrowing barn housing 42 sows. Body temperature (Tb) and respiration rate (RR) of the sows were used to evaluate the efficacy of the systems. The results indicate that sows under TV + DC or TV + HZV + DC had significantly lower Tb than those under TV only or TV + HZV (P \u3c 0.01 and P \u3c 0.001, respectively). DC under HAM was less effective for Tb reduction (P \u3e 0.05). DC reduced RR in all cases, 42% under TV (P \u3c 0.01), 41% under TV + HZV (P \u3c 0.01), and 22% under HAM (P \u3e 0.05). It was concluded that TV with DC provides the most cost-effective cooling scheme
