Effect of floor cooling on late lactation sows under acute heat stress

The objective was to evaluate the effects of floor cooling on late lactation sows under severe summer heat stress. Ten 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 = 4), 0.25 (LOW, n = 2), 0.55 (MEDIUM, n = 2) or 0.85 (HIGH, n = 2) L/min for 100 min. The cooling was initiated 1 h after the room reached 35 °C. Respiration rates (RR), vaginal temperature (VT) and skin temperature (ST, 15 cm posterior to the ear) were recorded before the trial, prior to cooling, and 5 times (20 min intervals) after the cooling phase began. Rectal temperature (RT) was recorded before the trial, prior to cooling and in the last 20 min of cooling. Water flow rates, inlet and outlet temperatures were recorded 5 times (20 min intervals) to calculate heat removal after the cooling started. The procedure was repeated 8 times (2 times/d for 4 d), and treatments were randomly switched in each repetition. The mean room temperature and relative humidity during the trial were 35.1 ± 0.4 °C and 68.4 ± 3.2%, respectively. Cooling treatments impacted RR, VT, ST and RT after 80 min of cooling, where the mean RR's were 122, 76, 67 and 45 breaths/min for the CONTROL, LOW, MEDIUM and HIGH flow rate treatments, respectively (P < 0.001). After 80 min of cooling, the mean VT, RT and ST were 40.1, 40.0 and 39.4 °C, respectively for the CONTROL; 39.5, 39.5 and 39.0 °C, respectively for the LOW; 39.4, 39.2 and 38.9 °C, respectively for the MEDIUM; and 39.2, 39.0 and 38.6 °C, respectively for the HIGH flow rate treatment (P < 0.001). Overall heat removal during the trial was 193, 321 and 365 W (SD=137) for the LOW, MEDIUM and HIGH flow rate treatments, respectively (P < 0.001). Cooling pads with LOW, MEDIUM and HIGH water flow rates reduced RR, RT and VT in lactating sows.