Initial Evaluation of Floor Cooling on Lactating Sows Under Acute Heat Stress

The objective was to evaluate the effects of floor cooling on lactating sows under severe summer heat stress. 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 (LOW, n = 3), 0.55 (MEDIUM, n = 2) or 0.85 (HIGH, n = 2) l/min for 90 min. The cooling was initiated 1 h after the room reached 35ºC. Respiration rates (RR), rectal temperature (RT) and skin temperature (ST, 15 cm posterior to the ear) were recorded before the trial, prior to cooling, and after 90 min of cooling. Water flow rates, inlet and outlet water temperatures were recorded 6 times (every 15 min) to calculate the heat removal (watts) after cooling initiation. In all 3 replications, treatments were switched randomly between sows. Data were analyzed using the MIXED procedure in SAS. Respiration rate, RT, ST and heat removal, were analyzed using repeated measures with compound symmetry covariance structure with sow as a repeated random effect. For RR, RT and ST measurements the model included treatment, phase (before trial, prior to cooling and at the end of the trial) and their interactions as fixed effects and replication as a random block. For the cooling phase, heat removal model included treatment, cooling time and their interactions as fixed effects and replication as a random block. The mean room temperature and relative humidity during the trial were 35.3 ± 0.7ºC and 57.8 ± 3.1%, respectively. The treatments impacted RR, RT and ST after 90 min of cooling. At the end, mean RR’s were 132, 89, 71 and 31 breaths/min for the CONTROL, LOW, MEDIUM and HIGH treatments, respectively (P < 0.001). The mean RT and ST were 39.9 and 39.8ºC for the CONTROL; 39.5 and 39.1ºC for the LOW; 39.2 and 38.8ºC for the MEDIUM; and 39.1 and 39.2ºC for the HIGH treatment (P < 0.001 and P = 0.079, respectively). Overall heat removal during the trial was 196.2, 278.3 and 320.7 watts for the LOW, MEDIUM and HIGH treatments, respectively (P < 0.001). Cooling pads with MEDIUM and HIGH water flow rates reduced RR and RT in lactating sows.