Evaluation of Floor Cooling on Lactating Sows Under Mild and Moderate Heat Stress

The effectiveness of sow cooling pads during lactation was evaluated under mild and moderate heat stress conditions to reduce indicators of heat stress. The moderate heat stress rooms (n =2) were targeted to achieve 32ºC from 0800-1600 h and 27ºC for the rest of the 24-hour day. The mild heat stress rooms (n=2) were targeted to achieve 27ºC and 22ºC for the same periods, respectively. Yorkshire-Landrace sows were blocked by parity and BW, and assigned to two farrowing rooms which differed only in environmental temperature. Each sow was provided a cooling pad made with aluminum plate on top, a high-density polyethylene base, and eight copper water pipes. Sows received either a constant cool water flow of 0.00 (CONTROL, n = 9), 0.25 (LOW, n = 12), or 0.50 (HIGH, n = 10) L/min. Water inlet and outlet temperatures and flow rates were recorded to estimate heat removal. Respiration rates (RR) were measured for 2 -30 second intervals. Rectal temperatures (RT), skin temperatures 15 cm behind the ear (ST) and RR’s were recorded every day (0700 and 1500 h) from the second day in the farrowing room to weaning. The sow RR, ST, RT and estimated heat removal were affected (P < 0.036) by pad treatment (PT), time of day, room temperature (RTEMP), day of lactation, and all two variable interactions. The RR increased (P < 0.001) as heat stress increased. The difference in heat removal between the HIGH and LOW flow rates was 16 watts (132.1 versus 116.1) in the mild heat stress rooms, but increased to 43.4 watts in the moderate heat stress rooms (181.4 versus 138.0, (P = 0.048 for RTEMP × PT). Sow cooling pads reduced measures of heat stress. The results indicate that the LOW flow rate is adequate from 22 to 27ºC (with 40 to 45 % relative humidity) but the HIGH flow rate is needed at temperatures above 27ºC.

Variable	Pad Treatment	Mild – 700 h	Moderate – 700 h	Mild – 1500 h	Moderate – 1500 h
RR	CON	23	56	41	89
	LOW	21	24	29	41
	HIGH	18	20	24	27
ST	CON	35.4	37.3	37.2	37.3
	LOW	34.4	36.5	36.6	36.5
	HIGH	33.7	36.2	36.5	36.2
RT	CON	38.8	39.0	39.2	39.6
	LOW	38.8	38.8	39.1	39.0
	HIGH	38.8	38.8	39.1	39.0