A behavior and physiology-based decision support tool to predict thermal comfort and stress in non-pregnant, mid-gestation, and late-gestation sows

Authors: MCCONN, BETTY - Orise Fellow; SCHINCKEL, ALLAN - Purdue University; ROBBINS, LINDSEY - Purdue University; GASKILL, BRIANNA - Purdue University; GREEN-MILLER, A.R. - University Of Illinois; LAY, DONALD - US Department Of Agriculture (USDA); Johnson, Jay

Submitted to: Journal of Animal Science and Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/3/2022
Publication Date: 12/10/2022
Citation: McConn, B., Schinckel, A.P., Robbins, L., Gaskill, B.N., Green-Miller, A.R., Lay, D.C., Johnson, J.S. 2022. A behavior and physiology-based decision support tool to predict thermal comfort and stress in non-pregnant, mid-gestation, and late-gestation sows. Journal of Animal Science and Biotechnology. 13. Article 135. https://doi.org/10.1186/s40104-022-00789-x.
DOI: https://doi.org/10.1186/s40104-022-00789-x

Interpretive Summary: Heat stress is a threat to swine productivity, health, and that will become increasingly common as global temperatures continue to rise and extreme climatic events increase in frequency. Gestating sows and their offspring are particularly susceptible to the effects of heat stress and both short and long-term negative consequences to health, productivity, and welfare have been observed. As such, a variety of cooling methods have been developed for use in swine production facilities to alleviate the negative effects of heat stress. However, despite the availability and continued development of cooling and management strategies to mitigate heat stress, recommended or perceived temperature thresholds for implementation may not accurately reflect the thermal requirements of swine. Therefore, the study objective was to develop a swine specific decision support tool using both behavioral and thermoregulatory metrics derived from animal experimentation that would provide thermal recommendations for sows at three reproductive stages. Based on results from the present study, heat stress thresholds were influenced by reproductive stage and differed from previously established thresholds. In addition, the decision support tool developed through this research may be used to predict environmental conditions sows consider to be cool, comfortable, warm, mild heat stress, moderate heat stress, and severe heat stress. To our knowledge, this is the first thermal index developed specifically for gestating sows that incorporates both physiological and behavioral metrics of thermal preference and stress.

Technical Abstract: Background Although several thermal indices have been proposed for use in swine, few have been directly developed using behavioral and physiological data collected specifically in pigs and none differentiate by reproductive stage or predict thermal comfort. Therefore, the study objective was to develop a behavior and physiology-based decision support tool to predict thermal comfort and stress in multiparous (3.28 ± 0.81) non-pregnant (n = 11), mid-gestation (n = 13), and late-gestation (n = 12) sows. Results All sows were exposed to gradually increasing dry bulb temperature (TDB) ranging from 19.84 ± 2.15°C to 35.54 ± 0.43°C and a relative humidity of 40.49 ± 18.57% over a 400 min period. Respiration rate (RR), skin temperatures (TS), and body temperatures (TB) were measured every 20 min. Regression analyses were performed using PROC MIXED in SAS 9.4 to determine the optimal environmental indicator (TDB and dew point) of heat stress (HS) in non-pregnant, mid-gestation, and late-gestation sows with RR and TB successively used as the dependent variable in a cubic function. A linear relationship was observed for TS indicating that TDB rather than the sow response to HS was impacting TS and so TS was excluded from further analyses. Reproductive stage was significant for all analyses (P < 0.05). Heat stress thresholds for each reproductive stage were calculated using the inflections points of RR for mild HS and TV for moderate and severe HS. Mild HS inflection points differed for non-pregnant, mid-gestation, and late gestation sows and occurred at 25.5, 25.1, and 24.0°C, respectively. Moderate HS inflection points differed for non-pregnant, mid-gestation, and late gestation sows and occurred at 28.1, 27.8, and 25.5°C, respectively. Severe HS inflection points were similar for non-pregnant and mid-gestation sows (32.9°C) but were differed for late-gestation sows (30.8°C). These data were integrated with behavioral thermal preference data from previous research by our group to establish the behavior and physiology-based decision support tool. Conclusions Results from the study provide valuable information regarding thermal comfort and thermal stress thresholds in sows at three reproductive stages. The development of a behavior and physiology-based decision support tool to predict thermal comfort and stress in non-pregnant, mid-gestation, and late-gestation sows is expected to provide swine producers with a more accurate means of assessing thermal comfort and stress in gestating sows.