Technical Note: Initial evaluation of floor cooling on lactating sows under acute heat stress1

Our study objectives were to evaluate an acute heat stress protocol for lactating sows and evaluate preliminary estimates of water flow rates required to cool sows. Twelve multiparous sows were provided with a cooling pad built with an aluminum plate surface, high-density polyethylene base, and copper pipes. Treatments were randomly allotted to sows to receive a constant cool water flow of 0.00 (control, n = 5), 0.25 (LO, n = 3), 0.55 (MED, n = 2), or 0.85 (HI, n = 2) L/min for 90 min. The cooling was initiated 1 h after the room reached 35°C. Respiration rates (RR), rectal temperature (RT), and skin temperature (15 cm posterior to the ear) were recorded before the trial, before cooling, and after 90 min of cooling. Water flow rates and inlet and outlet water temperatures were recorded 6 times (every 15 min) to calculate heat removal after cooling initiation. In all 3 replications, treatments were switched randomly among sows. The mean ambient temperature and relative humidity during the trial were 35.3 ± 0.7°C and 57.8 ± 3.1%, respectively. Treatments affected RR and RT after 90 min of cooling. At the end, the mean RR and RT were 132 breaths/min and 39.9°C for the control; 89 breaths/min and 39.5°C for the LO; 71 breaths/min and 39.2°C for the MED; and 31 breaths/min and 39.1°C for the HI treatment (P < 0.001 and P < 0.001, respectively). Cooling pads with MED and HI water flow rates reduced RR and RT in lactating sows.