286. Effects of Cooled Drinking Water on Performance of Heat-stressed Lactating Sows.

Abstract Lactating sows experience varying degrees of heat stress in many parts of the world including the Upper Midwest region of the U.S. during summer. Heat stress negatively impacts sow performance and comfort. Management practices that mitigate heat stress could improve sow welfare and enhance profitability and sustainability of pig production systems. We hypothesized that providing cooled drinking water to heat-stressed sows during farrowing and lactation would improve sow performance and comfort. To test this hypothesis, we housed mixed-parity, crossbred sows (n = 87; parity = 1 to 7) in individual farrowing stalls in two mirror-image rooms over three cohort sow groups. Target temperatures in each room were: 27 °C from 0700 to 1900 h and 24 °C from 1900 to 0700 h). Water was provided through nipple drinkers for each sow at ambient room temperature in one room (Con) or cooled to a target temperature of 13 °C in the second room (Cool). Heat stress and water temperature treatments were imposed when sows entered the farrowing rooms at about day 109 of gestation and continued to weaning (lactation length = 18.3 + 1.4 d). Sow weight was recorded on day 109 of gestation, within 24 h postfarrowing, and at weaning. Sow backfat depth and loin eye area were recorded using realtime ultrasonography on day 109 of gestation and at weaning. Litter size and weight were recorded at birth and weaning. Voluntary feed intake of sows was recorded weekly throughout lactation. Focal sows (n = 8/room/cohort group) were selected to measure resting respiration rate and rectal body temperature on d 10 postfarrowing. Sows were monitored for expression of estrus through d 7 postweaning. Data were analyzed using Proc Glimmix (SAS version 9.4) with a statistical model that included the fixed effect of water temperature and random effects of cohort group and parity. Parity was removed from the model to analyze water temperature data. Average daytime (27.6 vs. 27.2 °C) and night-time (24.5 vs. 24.1 °C) room temperatures were not different (P > 0.156) between Con and Cool rooms, respectively. Temperature of drinking water was different (P < 0.001) between Con and Cool (28.5 vs. 17.7 °C) as expected. Resting respiration rates and rectal temperatures of sows were not affected by consumption of Cooled drinking water (Table 1). Cooled drinking water had no effect on voluntary feed intake of sows, changes in sow body condition or interval to postweaning estrus. Neither litter size nor weight at weaning were affected by provision of cooled drinking water to sows. In conclusion, cooling drinking water to about 18 °C had no effect on performance of heat-stressed lactating sows or their litters. For image description, please refer to the figure legend and surrounding text.