Preference among cooling systems by gilts under heat stress.

A preference experiment was conducted to compare and evaluate the use of three cooling systems by mature gilts. Systems evaluated were snout coolers (S), drip coolers (D), and conductive cool pads (P). Preference for cooling system and pen position were continuously monitored and evaluated during daily heat stress conditions (34.2 +/- 2.8 degrees C), nightly warm conditions (26.6 +/- 2.3 degrees C), and for total time. The physiological variables of respiration rate (RR) and rectal temperature (Tr) were measured at three separate times daily. Gilts naive to the cooling systems were individually housed in pens with three free stalls, each stall containing a different cooling system. After 1 d of warm temperature (27.6 +/- 2.5 degrees C) acclimation, gilts were exposed to 10 h of the heat stress conditions and 14 h of the warm night conditions each day for six consecutive days. Cooling system use was higher during the hot period (80.2%) than during the warm period (66.2%). The conductive cool pad was preferred over the drip cooler (P < .02) and the snout cooler (P < .0002). The preference for the conductive cool pad persisted in the warm period. Cooling system use had a significant effect on Tr and RR (P < .001). The Tr (P < .005) and RR were lower (P < .005) with the use of the conductive cool pad, whereas the drip cooler and snout cooler showed no effect on these variables.