Johnson, Jay S., Green-Miller, Angela R., McConn, Betty, Robbins, Lindsey, Gaskill, Brianna N., Lay, Donald C., and Schinckel, Allan P.
Several management practices and technologies have been developed to mitigate thermal stress in swine. However, recommended temperature thresholds for implementing thermal stress mitigation are variable and may not accurately reflect the thermal requirements of non-pregnant and gestating sows with modern genetics. Therefore, a tool to support environmental management decisions for non-pregnant and gestating sows was created. The decision support tool is based on several published works by our group that characterized responses of non-pregnant, mid-gestation, and late-gestation sows across a wide temperature range. Cool, comfortable, and warm ranges were identified based upon behavioral thermal preferendum, and physiological responses were used to determine mild, moderate, and severe heat stress thresholds. The inflection points of respiration rate and body temperature as a function of dry bulb temperature were used to establish heat stress thresholds by gestation stage. Non-pregnant, mid-gestation, and late-gestation sow mild heat stress thresholds differed (P < 0.05) and occurred at 25.5, 25.1, and 24.0 °C, respectively. Body temperature inflection points indicative of moderate heat stress differed by gestation stage (P < 0.05) and occurred at 28.1, 27.8, and 25.5 °C, respectively. Severe heat stress inflection points were lower (P < 0.05) for late-gestation sows (30.8 °C) but were similar for non-pregnant and mid-gestation sows (32.9 °C). Dewpoint influenced heat stress response for mid- and late-gestation sows (P < 0.05) but did not have an effect on non-pregnant sows (P > 0.05). Heat stress threshold data were integrated with behavioral thermal preferendum data. For non-pregnant and midgestation sows, similar (P > 0.05) cool (< 13.2°C) and comfortable (13.2 to 16.4°C) temperature ranges were observed. However, late-gestation sows had lower (P < 0.05) cool (< 12.6°C) and comfortable (12.6 to 15.6°C) temperature ranges relative to non-pregnant and midgestation sows. The dry bulb temperature (TDB) that non-pregnant, mid-gestation, and late-gestation sows found to be warm was estimated as TDB preference range < TDB < mild heat stress. The decision support tool was integrated into a smartphone application called HotHog. This smartphone application provides hourly and daily predictions of thermal comfort and stress in non-pregnant, mid-gestation, and lategestation sows. Users can set geographical locations, either manually or by current location, for thermal index predictions. Additionally, hourly and daily precipitation, and temperature predictions are displayed for the selected location. Management observations and mitigation options, as well as expected physiological and behavioral changes, are provided for each thermal index category to help users identify stressed pigs and assist with management decisions. HotHog will support swine producers in making more informed decisions related to in-barn environmental management to reduce the negative effects of thermal stress on sows and their gestating offspring. Furthermore, the tool may be helpful for teaching thermal management to livestock technicians and students. [ABSTRACT FROM AUTHOR]