DEVELOPMENT OF A DECISION SUPPORT TOOL FOR IMPROVING SOW WELFARE DURING A HEAT STRESS EVENT

• Sponsoring Institution: National Institute of Food and Agriculture
• Project Status: COMPLETE
• Funding Source: AFRI COMPETITIVE GRANT
• Reporting Frequency: Annual
• Accession No.: 1015472
• Grant No.: 2018-67015-28130
• Cumulative Award Amt.: $499,700.00
• Proposal No.: 2017-05226
• Project Start Date: May 15, 2018
• Project End Date: May 14, 2022
• Grant Year: 2018
• Program Code: [A1251]- Animal Health and Production and Animal Products: Animal Well-Being

Recipient Organization
AGRICULTURAL RESEARCH SERVICE
1815 N University
Peoria,IL 61604

Performing Department
(N/A)

Non Technical Summary
Heat stress negatively impacts swine well-being resulting in greatermortality, and reduced welfare continues to occur despite advances in livestock cooling system technologies and management strategies. With an increase in the magnitude and frequency of extreme hot weather events occurring globally, the need to refine and re-develop heat stress mitigation and management strategies is of utmost importance. The first step in developing mitigation strategies is to identify when sows are experiencing heat stress. Despite the need for this basic information, current heat stress guidelines for swine are based on data that is over 30 years old. Therefore, it is likely that these guidelines are inaccurate considering that improvements in sow productivity have increased metabolic rate by 16% in modern sows. Furthermore, the availability of a user-friendly decision support tool for swine producers to predict when sows are experiencing heat stress is non-existent. The overall objective of this proposal is to re-evaluate temperature thresholds that result in heat stress in modern sows and develop a decision support tool to assist swine producers with management decisions during times of heat stress. Specific objectives are to: 1) re-evaluate thermal preferences based on sow perception, 2) determine physiological response to increasing ambient temperatures, and 3) develop a decision support tool to improve sow welfare during heat stress. Successful completion of this proposal will update or validate the current recommendations for heat stress in modern sows and provide swine producers with a decision support tool to determine when to intervene during times of heat stress.

Animal Health Component

33%

Research Effort Categories

Basic

33%

Applied

33%

Developmental

34%

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
306	3510	1020	100%

Knowledge Area
306 - Environmental Stress in Animals;

Subject Of Investigation
3510 - Swine, live animal;

Field Of Science
1020 - Physiology;

Keywords

behavior

heat stress

physiology

smart phone application

sows

thermal index

welfare

Goals / Objectives
The most up to date recommendations for thermal stress in swine published by the Federation for Animal Science Societies (FASS) are based on data from over 30 years ago and do not include guidelines for gestating sows or differentiated by sow parity and increasing weight. As such, there is a critical need to re-evaluate and establish new temperature thresholds that can result in heat stress in modern production pigs, especially considering that total metabolic heat production in modern commercial pigs has been measured as 16% greater than the metabolic rate of swine when FASS standards were established >30 years ago. This increase in total metabolic heat production is important to consider when determining heat stress thresholds since environmental controls (i.e., ventilation rate, heating and cooling requirements, equipment selection) within swine production facilities are often determined based on total heat production values. In addition to the increased metabolic heat production, climate change continues to increase the frequency and severity of heat waves both in the United States and globally, further threatening the sustainability of animal production and welfare of livestock species. Therefore, in order to combat the negative effects of heat stress in modern production sows, this research project seeks to develop a metric similar to the thermal index developed for cattle that will aid in predicting levels of thermal strain during heat stress events based on both sow behavior and physiology to improve management practices and animal welfare. This research project will use a three-fold approach using multiparous sows at three reproductive stages (Open, Mid-gestation, Late-gestation) to determine thermal preferences based on sow perception and use this information to evaluate the physiological response to increasing ambient temperature. Data generated by these studies will be used to develop a decision support tool in the form of a smartphone application that can be immediately used by producers to determine when to provide management interventions during times of heat stress. Furthermore, information provided by this research project will provide academic researchers with up to date and scientific information as to what is considered heat stress in modern sows when performing heat stress experiments, and will be a valuable tool for Institutional Animal Care and Use Committees to decide what temperatures will cause distress in modern production sows. Therefore, this project will have three primary objectives: 1.) to determine temperatures that are preferred and those that are aversive, for sows at three reproductive stages (Open, Mid-gestation, Late-gestation), 2.) to evaluate the temporal pattern of the physiological response of sows to heat stress using thermoregulatory, production, and blood biomarker data when sows at three reproductive stages are exposed to increasing ambient temperatures ranging from the low end of a sow's thermoneutral zone to just above the upper critical temperature as currently defined by the AgGuide, and 3.) to create a decision support tool based on updated and scientifically sound behavioral, thermoregulatory, and physiological data from objective 1 and 2 to predict heat stress in modern commercial sows at three reproductive stages.

Project Methods
Objective 1: Thermal Preference Testing This study is designed to determine, from the sow's perspective, what temperatures are preferred, and those that are avoided. Therefore, 24 multiparous sows (maternal line Yorkshire x Landrace; evenly distributed between parity 2 - 8) will be individually placed into a test pen which will allow them to freely walk between and choose 1 of 6 temperature environments: 10°C, 15°C, 20°C, 25°C, 30°C, and 35°C. These temperatures were selected to represent a range from the low end of a sow's thermoneutral zone to just above the upper critical temperature. Temperatures were selected to ensure that the differences between all temperature levels was equal in order to improve our statistical interpretation of the data. The effect of reproductive stage on temperature preference will be determined by categorizing sows as Open (not pregnant, n = 8), Mid-gestation (50-60 days pregnant, n = 8), or Late-gestation (80- 90 days pregnant, n = 8).The Test Apparatus. The test pen will offer individual sows free access to 6 identical thermal chambers radiating from a central area. Each thermal chamber will be fully enclosed with overhead lighting. Temperature will be maintained by ducts that enter the chamber at the top and deliver the air through a diffuser for even distribution and are controlled by a thermostat. The central area will have boards on the floor to discourage the sow from lying in this area. The chambers will be connected to the central compartment through a custom designed swinging door will be elevated from the floor to prevent sows from lying in between a thermal chamber and the central area. Each chamber will have a nipple water attached to a flow meter, which will be used in combination with video recorded drinking duration behaviors.Test protocol. A sow will be introduced to each experimental temperature in a random order for 2 h per temperature (12 h total) to allow the sow to experience each of the options prior to free-choice. Following this 12 h period, the sow will have free-choice for an additional 12 h in the entire apparatus to explore all chambers before testing. All sows will be limit-fed based on reproductive stage, and 1/6 of the sow's daily feed allowance will be placed into each chamber to encourage sows to explore each chamber. The test will commence thereafter for 48 h with each chamber set at one of the six experimental temperatures.Measurements.Behavior. Behavioral data will be collected continuously using digital video and will includethe duration in each chamber, number of entries, panting, as well as the time spent sitting, lying (sternal or lateral), and standing will be quantified.Body temperature and environmental conditions. Vaginal temperature will be recorded in 10 min intervals. Ambient temperature and relative humidity will be recorded in 5 min intervals.Objective 2: Physiological Assessment of Heat Stress This study is designed to determine the sow's thermoregulatory and physiologic response to thermal conditions. In 4 repetitions, 36 multiparous sows (maternal line Yorkshire x Landrace) will be individually housed in gestation stalls. The effect of reproductive stage on the physiological response to heat stress will be determined by categorizing sows as Open (not pregnant, n = 12 total sows), Mid-gestation (50-60 days pregnant, n = 12 total sows), or Late-gestation (80-90 days pregnant, n = 12 total sows). Prior to treatment a jugular catheter will be inserted into each sow and then sows will be moved to a gestation stall into an environmentally controlled room. Nine sows (n = 3 Open; n = 3 Mid-gestation; n = 3 Late-gestation) will be tested in each repetition. To initiate the experiment, each sow will be exposed to 10°C. In 2 h increments, the ambient temperature will be increased by 5ºC for a total of 12 h until it reaches 35ºC.Physiological measures. Blood samples (5 mL) will be collected in 20 min intervals, starting at 0600 h and continuing for 12 h. Blood volume will be replaced with 5 mL of sterile saline at each collection. A total of 36 blood samples will be collected from each sow through the trial. Respiration rate will be measured in 15 min intervals immediately prior to blood sample collection. Heart rate will be continuously monitored in 15 min intervals using telemetric heart rate monitors. Whole body skin temperature and vaginal temperature will be monitored with infrared thermography in 15 min intervals. Water intake will be recorded using flow meters and video-recorded drinking duration. The general postures of the sows (standing, sitting, or lying) will be video-recorded for the duration of the test. After the study, all sows will be weighed, catheters will be removed, and sows will be returned to the herd. Weight loss due to treatment will be recorded. Sows will be followed through breeding/gestation to record subsequent production data from their litter. Data for sows that were Open will also include number of inseminations. Blood samples will be analyzed for NO2- and NO3- using HPLC; CO2, O2, pH, and HCO3 by electrochemical sensing technology with a VetScan i-STAT cartridge; and differential leukocyte counts and red blood cell counts using a fully automated hematological analyzer.Objective 3: Decision support tool developmentAheat index tool will be developed using the thermal preference data collected in Objective #1 along with the thermoregulatory and physiological data collected in Objective #2 to predict the severity of a heat challenge for sows at three reproductive stages. In order to develop this decision support tool, the physiological measures of heat stress and thermal preference data for each stage of gestation will be fitted to a series of mixed model nonlinear functions. The functions will include a random effect of animal and the environmental conditions (i.e., temperature and humidity). The functions evaluated will include polynomial, nonlinear and nonlinear -plateau models of temperature and humidity. Some variables including rectal temperatures may be best fitted by a biphasic nonlinear equations. It is expected that respiration rates will fit a polynomial -plateau model in which a maximal response can be estimated. The results of the mixed model regression will be used to determine 4 transition points from thermo-neutral to mild, mild to moderate, moderate to severe and severe to extreme levels of heat stress. It is expected that these levels will be different for each gestational stage. The transition from TN to mild will be determined at the point in which the animals are initially responding to the heat stress behaviorally and have increased skin temperatures at 15% of the maximal response with little change in internal temperatures. The transition from mild to moderate heat stress will be estimated at 30% of the maximal respiration response and a small increase in rectal temperatures. The transition from moderate to severe heat stress will be estimated at the point in which 50% of the maximal respiration response in achieved rectal temperatures have increased approximately 40% of the maximal increase measured. The transition from severe to extreme will be estimated at the point in which the animals achieve 70% of their maximal response in respiration rate, the difference in skin and rectal is minimal and the physiological measurements indicate that 10% of the animals are responding with their maximal response to heat stress. Percentages were determined based on previous research on the effects of gradual increases in ambient temperature on the respiration rate, rectal temperature, and skin temperature of sows. Once the thermal categories have been established, a mobile smartphone application will be developed under contract by the Center for Environmental and Regulatory Information Systems at Purdue University.

Progress 05/15/21 to 05/14/22

Outputs
Target Audience:During this reporting period, target audiences included academic and goverment researchers, swine industry researchers and facility managers and institutional animal care and use committee members. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?The PhD student, the postdoctoral research associate, and the undergraduates employed to work on this project have been given several training opportunities including learning new laboratory techniques, data analysis skills, data interpretation skills, and the ability to present data at scientific conferences. In addition, the PhD student and postdoctoral research associate have been given the opportunity to mentor undergraduate researchers. How have the results been disseminated to communities of interest?Results from this project have been disseminated to academic and government scientists as well as industry representatives at scientific conferences, producer meetings, and through the publication of scientific and popular press articles. In addition, researchers involved in this project have given several presentations to swine industry groups. What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? An increase in the frequency and intensity of heat stress events negatively impacts swine health, productivity, and welfare. Management practices to alleviate heat stress in swine populations depend on an updated and accurate understanding of what constitutes heat stress in swine based upon life stage. Unfortunately, current recommendations are based upon outdated data and may not be relevant for modern swine. Furthermore, there is limited information on how gestation stage influences temperature preferences or heat stress thresholds. As such, the overall project objective is to re-evaluate the thermal preferences and heat stress thresholds of non-pregnant and gestating sows in order to develop a decision support tool that will allow swine producers to more precisely manage the environments their pigs are raised under. During the current reporting period, we have completed objective 3 by developing the decision support tool and apeer-reviewed publication describing it's development and use has been published in the Journal of Animal Science and Biotechnology. This tool has been integrated into a smartphone application named "HotHog" that is currently undergoing beta-testing and then will be made freely available to producers, researchers, and the general public through both the Apple App Store and Google Play. It is expected that this tool will provide swine producers with more accurate knowledge of thermal comfort and thermal stress for their non-pregnant, mid-gestation, and late-gestation sows. In addition to the work described in the project objectives, we have also completed similar work in boars, nursery and growing-finishing pigs, and pre-nursery pigs with the goal of developing similar decision support tools for those populations for integration within the smartphone application. Knowledge of temperatures that pigs find comfortable and stressful can assist producers in more effectively managing the environments pigs are raised in. Furthermore, from an economic standpoint, greater knowledge of the temperature ranges pigs should be housed at may result in energy savings during cooler months when heating is required within swine facilities. This is because results from this project indicate that both non-pregnant and gestating sows would prefer to be housed under cooler conditions than what they are routinely housed under. Therefore, results from this project not only have important implications for raising pigs under high temperatures but may also be applicable to raising pigs in cooler climates where heating barns is an economic concern

Publications

• Type: Journal Articles Status: Published Year Published: 2021 Citation: Robbins, L.R., A.R. Green-Miller, D.C. Lay, Jr., A.P. Schinckel, J.S. Johnson, and, B.N. Gaskill. 2021. Evaluation of sow thermal preference across three stages of reproduction. J. Anim. Sci. 99: 1-10. Doi: 10.1093/jas/skab202.
• Type: Journal Articles Status: Published Year Published: 2022 Citation: Byrd, C.J., B.T. McConn, B.N. Gaskill, A.P. Schinckel, A.R. Green-Miller, D.C. Lay Jr., and J.S. Johnson. 2022. Characterizing the effect of incrementally increasing dry bulb temperature on linear and nonlinear measures of heart rate variability in non-pregnant, mid-gestation, and late-gestation sows. J. Anim. Sci. 100: 1-9. Doi:10.1093/jas/skac004.
• Type: Journal Articles Status: Under Review Year Published: 2022 Citation: McConn, B.R., A.P. Schinckel, L.R. Robbins, B.N. Gaskill, A.R. Green-Miller, D.C. Lay Jr., and J.S. Johnson. A behavior and physiology-based decision support tool to predict thermal comfort and stress in non-pregnant, mid-gestation, and late-gestation sows. J. Anim. Sci. Biotechnol. Accepted.
• Type: Conference Papers and Presentations Status: Awaiting Publication Year Published: 2022 Citation: Pritchett, R.K., V.L. Raber, L.A. Robbins, K.R. Stewart, B.N. Gaskill, A.R. Green-Miller, and J.S. Johnson. 2022. Evaluating the temperature preferences of sexually mature Duroc, Landrace, and Yorkshire boars. ISAE 55th Congress. Ohrid, North Macedonia.

Progress 05/15/18 to 05/14/22

Outputs
Target Audience:During the course of the project,target audiences included academic and goverment researchers, swine industry researchers and facility managers and institutional animal care and use committee members. These audiences were reached via scientific conference presentations, extension outreach presentations and articles, scientific publications, popular press articles, and personal communications. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?The PhD student, the postdoctoral research associate, and the undergraduates employed to work on this project have been given several training opportunities including learning new laboratory techniques, data analysis skills, data interpretation skills, and the ability to present data at scientific conferences. In addition, the PhD student and postdoctoral research associate have been given the opportunity to mentor undergraduate researchers. As a direct result of participation in this project, both the PhD student and postdoctoral research associate gained valuable skills which assisted in gaining employment following their training. How have the results been disseminated to communities of interest?Results from this project have been disseminated to academic and government scientists as well as industry representatives at scientific conferences, producer meetings, and through the publication of scientific and popular press articles. In addition, researchers involved in this project have given several presentations to swine industry groups and have disseminated results via personal communications. What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? An increase in the frequency and intensity of heat stress events negatively impacts swine health, productivity, and welfare. Management practices to alleviate heat stress in swine populations depend on an updated and accurate understanding of what constitutes heat stress in swine based upon life stage. Unfortunately, current recommendations for sows are based upon outdated data and may not be relevant for modern swine. Furthermore, there is limited information on how gestation stage influences temperature preferences or heat stress thresholds. Therefore, this project sought to accomplish three primary goals: 1) To determine temperatures that are preferred and those that are aversive, for sows at three reproductive stages (e.g., non-pregnant, mid-gestation, and late-gestation), 2) to evaluate the temporal pattern of the physiological response of sows to heat stress using thermoregulatory, productive, and blood biomarker data when sows at three reproductive stages are exposed to increasing ambient temperatures ranging from the low end of a sow's thermoneutral zone to just above the upper critical temperature as currently defined by the Guide for the Care and Use of Agricultural Animals in Research and Teaching, 4th Edition (AgGuide),and 3) to create a decision support tool based on updated and scientifically sound behavioral, thermoregulatory, and physiological data from objective 1 and 2 to predict heat stress in modern commercial sows at three reproductive stages. A summary of major accomplishments for each goal is provided below. Goal #1: Sow temperature preferences In the completion of this 1st goal, we developed and built two identical thermal gradient apparatuses (thermoclines) that would allow for the evaluation of temperatures that were preferred and temperatures that were avoided by sows at three reproductive stages (non-pregnant, mid-gestation, late-gestation). In general, thermoclines have been used in rodent models and this was the first attempt (to our knowledge) by researchers to scale up thermoclines to be used in large mammals. The thermoclines were built (12.2 m x 1.52 m x 1.86 m) to provide the recommended space per sow and create a desired thermal gradient (10.35 ± 0.42ºC to 30.49 ± 0.45ºC) that encompassed the low (10 ºC) and high (25ºC) ends of current thermal recommendations (10 to 25ºC) for sows. For testing, sows were given a 24-hour acclimation period and then were continuously video recorded for an additional 24 hours to compare location within the thermocline with environmental conditions of that specific location. Following data analysis, it was determined that late gestation sows preferred a slightly lower temperature (14.0ºC) and temperature range (12.6 to 15.6ºC) than the preference temperature (14.8ºC) and preference temperature range (13.2 to 16.4ºC) of non-pregnant or mid-gestation sows. The conclusions from this experiment were that 1) the thermal preference range of sows differed by reproductive stage, and 2) the thermal preference range was lower and narrower than what is currently recommended (10 to 25°C) for sows. Therefore, it is possible that swine producers may be causing thermal discomfort in their gestating sows if they are housing them at higher than preferred ambient temperatures. Furthermore, we concluded that there may be economic benefits to housing non-pregnant and gestating sows at lower temperatures during winter months due to the associated energy cost savings of reducing facility heating. Goal #2: Sow physiological response to increasing temperatures In the completion of this 2nd goal, we exposed non-pregnant, mid-gestation, and late-gestation sows to gradually increasing temperatures (19.84 ± 2.15 to 35.54 ± 0.43°C) over a 400 min period and closely monitored body temperature, heart rate, respiration rate, blood gasses and pH, skin temperature, and water consumption. This was done in order to determine heat stress thresholds. It was determined that the heat stress threshold was similar when comparing non-pregnant and mid-gestation sows, but that the heat stress threshold for late-gestation sows was lower than non-pregnant and mid-gestation sows. Furthermore, the temperature threshold that caused heat stress was lower than what is currently recommended (>25°C). Results from this experiment indicated that heat stress likely occurs at lower temperatures than are currently recommended and that this threshold can vary depending on the sows' reproductive stage. Goal #3: Development of a behavior and physiology-based decision support tool to predict thermal comfort and stress in sows. In the completion of this 3rd goal we developed a behavior and physiology-based decision support tool to predict thermal comfort and stress in non-pregnant, mid-gestation, and late-gestation sows. This decision support tool integrated data collected from goal #1 and #2. Thermal preference data from goal #1 were used to establish the temperature ranges that sows consider to be cool, comfortable, and warm. Physiological heat stress data from goal #2 were used to develop thermal prediction equations that described temperature ranges that were considered mild heat stress, moderate heat stress, and severe heat stress in non-pregnant, mid-gestation, and late-gestation sows. To improve usability by swine producers, this tool has been integrated into a smartphone application named "HotHog" that is currently undergoing beta testing and then will be made freely available to producers, researchers, and the general public through both the Apple App Store and Google Play. It is expected that this decision support tool will provide swine producers with more accurate knowledge of thermal comfort and thermal stress for their non-pregnant, mid-gestation, and late-gestation sows. Knowledge of temperatures that pigs find comfortable and stressful can assist swine producers in more effectively managing the environments pigs are raised in. Furthermore, from an economic standpoint, greater knowledge of the temperature ranges pigs should be housed at may result in energy savings during cooler months when heating is required within swine facilities. This is because results from this project indicate that both non-pregnant and gestating sows would prefer to be housed under cooler conditions than what they are routinely housed under. Therefore, results from this project not only have important implications for raising pigs under high temperatures but may also be applicable to raising pigs in cooler climates where heating barns is an economic concern Other Accomplishments: In addition to the work described in the project goals, we have also completed similar work in boars, nursery and growing-finishing pigs, and pre-nursery pigs with the goal of developing similar decision support tools for those populations for integration within the HotHog smartphone application. Thermal preference testing has been completed for all swine categories (pre-nursery, nursery, growing-finishing, boars) and physiological heat stress testing is ongoing. These data will be used to develop a behavior and physiology-based decision support tool for swine producers to improve the health, performance, and welfare of their swine herd.

Publications

• Type: Conference Papers and Presentations Status: Published Year Published: 2019 Citation: Robbins, L., A. Green, J.S. Johnson, and B.N. Gaskill. 2019. Evaluation of sow thermal preference. International Society for Applied Ethology. Bergen, Norway. August 5-9, 2019.
• Type: Conference Papers and Presentations Status: Published Year Published: 2019 Citation: Robbins, L., A. Green-Miller, J.S. Johnson, A.P. Schinckel, and B. Gaskill. 2019. Evaluation of sow thermal preference. ISAE 53rd Congress, Bergen, Norway. August 5-9, 2019.
• Type: Theses/Dissertations Status: Published Year Published: 2020 Citation: Robbins, L. 2020. Into the comfort zone: Understanding swine thermal preference. PhD Dissertation. Purdue University
• Type: Conference Papers and Presentations Status: Published Year Published: 2020 Citation: McConn, B.R., A.W. Duttlinger, K.R. Kpodo, J.M. Maskal, B.N. Gaskill A.P. Schinckel, A.R. Green-Miller, D.C. Lay Jr., and J.S. Johnson. 2020. Thermoregulatory and physiological responses of sows at different reproductive stages exposed to increasing ambient temperature. J. Anim. Sci. 98 (Suppl. 3): 7. Doi: 10.1093/jas/skaa054.011.
• Type: Conference Papers and Presentations Status: Published Year Published: 2019 Citation: McConn, B.R., A.W. Duttlinger, K.R. Kpodo, J.M. Maskal, B.N. Gaskill A.P. Schinckel, A.R. Green-Miller, D.C. Lay Jr., and J.S. Johnson. 2020. Effects of increasing ambient temperature on the thermoregulatory and physiological response of gestating sows. National Pork Board Pig Welfare Symposium. Minneapolis, MN. November 13-15.
• Type: Journal Articles Status: Published Year Published: 2021 Citation: Robbins, L.A., A.R. Green-Miller, J.S. Johnson, and B.N. Gaskill. 2021. One is the coldest number: How group size and body weight affect thermal preference in weaned pigs (3 to 15 kg). Animals. 11: 1447. Doi: 10.3390/ani11051447.
• Type: Journal Articles Status: Published Year Published: 2021 Citation: McConn, B.R., B.N. Gaskill, A.P. Schinckel A.R. Green-Miller, D.C. Lay Jr., J.S Johnson. 2021. Thermoregulatory and physiological responses of non-pregnant, mid-gestation, and late-gestation sows exposed to incrementally increasing dry bulb temperature. J. Anim. Sci. 99: 1-8. Doi: 10.1093/jas/skab181.
• Type: Journal Articles Status: Published Year Published: 2021 Citation: Robbins, L.R., A.R. Green-Miller, D.C. Lay, Jr., A.P. Schinckel, J.S. Johnson, and, B.N. Gaskill. 2021. Evaluation of sow thermal preference across three stages of reproduction. J. Anim. Sci. 99: 1-10. Doi: 10.1093/jas/skab202.
• Type: Journal Articles Status: Published Year Published: 2022 Citation: Byrd, C.J., B.T. McConn, B.N. Gaskill, A.P. Schinckel, A.R. Green-Miller, D.C. Lay Jr., and J.S. Johnson. 2022. Characterizing the effect of incrementally increasing dry bulb temperature on linear and nonlinear measures of heart rate variability in non-pregnant, mid-gestation, and late-gestation sows. J. Anim. Sci. 100: 1-9. Doi:10.1093/jas/skac004.
• Type: Journal Articles Status: Under Review Year Published: 2022 Citation: McConn, B.R., A.P. Schinckel, L.R. Robbins, B.N. Gaskill, A.R. Green-Miller, D.C. Lay Jr., and J.S. Johnson. A behavior and physiology-based decision support tool to predict thermal comfort and stress in non-pregnant, mid-gestation, and late-gestation sows. J. Anim. Sci. Biotechnol. Under Review.
• Type: Conference Papers and Presentations Status: Accepted Year Published: 2022 Citation: Pritchett, R.K., V.L. Raber, L.A. Robbins, K.R. Stewart, B.N. Gaskill, A.R. Green-Miller, and J.S. Johnson. 2022. Evaluating the temperature preferences of sexually mature Duroc, Landrace, and Yorkshire boars. ISAE 55th Congress. Ohrid, North Macedonia.

Progress 05/15/20 to 05/14/21

Outputs
Target Audience:During this reporting period, research presentations were given to academic and government scientists as well as industry representatives at scientific conferencesregarding project results. In addition, peer reviewed scientific research articles were published and made available to the scientific community, stakeholder groups, and the general public. Finally, popular press articles related to research efforts from this project were published by the USDA communications office and independent news sites and were openly available to the public. In each incidence, appropriate credit was given to USDA-NIFA. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?The PhD student, the postdoctoral research associate, and the undergraduates employed to work on this project have been given several training opportunities including learning new laboratory techniques, data analysis skills, data interpretation skills, and the ability to present data at scientific conferences. In addition, the PhD student and postdoctoral research associate have been given the opportunity to mentor undergraduate researchers. How have the results been disseminated to communities of interest?Results from this project have been disseminated to academic andgovernment scientists as well as industry representatives at scientific conferences, producer meetings, andthrough the publication of scientific and popular press articles. What do you plan to do during the next reporting period to accomplish the goals?In the next period we plan to finish publishing results from Objective 1 and Objective 2 and then fully complete Objective 3. We will complete the integration of the decision support tool into the smart phone application and the website for dissemination to swine producers.

Impacts
What was accomplished under these goals? Climate change has resulted in an increase in global temperatures, which can negatively impact swine health, productivity, and welfare. Although swine producers have a variety of technologies and management practices available to combat the negative effects of heat stress, these practices are dependent on an accurate analysis of what constitutes heat stress for pigs based upon life stage. Unfortunately, the most up to date recommendations for thermal stress in swine were determined over 35 years ago and since that time pigs have become more heat stress sensitive due to genetic improvements in productivity. In addition, no information is available regarding the thermal preference or heat stress threshold of sows at different gestation stages. Therefore, in order to combat the negative effects of heat stress in modern production sows, the overall goal of this research project is to develop a decision support tool for swine producers based upon scientifically validated data. This will allow swine producers to make an informed decision regarding what constitutes heat stress and can allow them to make a more informed decision about the use of their cooling management procedures and technologies. Project goals from objective 1 and objective 2 have been completed and outcomes from those objectives were described during the previous reporting period. During the current reporting period, we have completed the majority of objective 3 by developing the decision support tool. This tool is currently being integrated into a dedicated website and smartphone application that will be beta-tested and then made freely available to producers, researchers, and the general public. It is expected that this tool will provide swine producers with more accurate knowledge of pig temperature preference and heat stress thresholds which are important factors to consider when raising pigs. This knowledge can determine how the animals are managed under variable environmental conditions and can also have an impact on energy use in the barn. In addition, understanding the temperature ranges pigs should be housed at may result in energy savings during cooler months when barn heating costs rise because results from this project indicate that gestating sows would prefer to be housed under cooler conditions. Therefore, results from this project not only have important implications for raising pigs under high temperatures but may also be applicable to raising pigs in cooler climates where heating barns is an economic concern.

Publications

• Type: Journal Articles Status: Published Year Published: 2021 Citation: Robbins, L.A., A.R. Green-Miller, J.S. Johnson, and B.N. Gaskill. 2021. One is the coldest number: How group size and body weight affect thermal preference in weaned pigs (3 to 15 kg). Animals. 11: 1447. Doi: 10.3390/ani11051447.
• Type: Journal Articles Status: Accepted Year Published: 2021 Citation: McConn, B.R., B.N. Gaskill, A.P. Schinckel A.R. Green-Miller, D.C. Lay Jr., J.S Johnson. 2021. Thermoregulatory and physiological responses of non-pregnant, mid-gestation, and late-gestation sows exposed to incrementally increasing dry bulb temperature. J. Anim. Sci. In press. Doi: 10.1093/jas/skab181.

Progress 05/15/19 to 05/14/20

Outputs
Target Audience:Target audiences: Scientists, college faculty, undergraduate students, graduate students, animal agriculture industry representatives, swine producers, and government scientists Efforts: Formal presentations of experimental results, write-ups of experimental objectives and results, informal teaching of students in a one-on-one setting, and laboratory instruction. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?The PhD student, the postdoctoral research associate, and the undergraduates employed to work on this project have been given several training opportunities including learning new laboratory techniques, data analysis skills, data interpretation skills, and the ability to present data at scientific conferences. In addition, the PhD student and postdoctoral research associate have been given the opportunity to mentor undergraduate researchers. How have the results been disseminated to communities of interest?Results from this project have been disseminated to academic and government scientists at scientific conferences, producer meetings, through the publication of scientific articles. What do you plan to do during the next reporting period to accomplish the goals?In the next period we plan to publish results from Objective 1 and Objective 2 and then complete Objective 3. We will complete the development of the decision support tool and implement these results into the smart phone application and the website for dissemination to swine producers.

Impacts
What was accomplished under these goals? Average summer temperatures and temperature extremes are increasing, which can have a detrimental impact on the productivity, health, and welfare of pigs in commercial production systems. Swine producers have a variety of technologies available to cool pigs under hot weather conditions, and their use is dependent on an accurate analysis of what constitutes heat stress for pigs based upon life stage. Unfortunately, the most up to date recommendations for thermal stress in swine were determined over 30 years ago and since that time pigs have become more heat stress sensitive due to increased productivity. In addition, no information is available regarding the thermal preference or heat stress threshold of sows at different gestation stages. Therefore, in order to combat the negative effects of heat stress in modern production sows, the overall goal of this research project is to develop a decision support tool for swine producers based upon scientifically validated data. This will allow swine producers to make an informed decision regarding what constitutes heat stress and can allow them to make a more informed decision about the use of their cooling management procedures and technologies. The first step in the development of a decision support tool for the prediction of heat stress in sows was to determine their thermal preference range and this was addressed in Objective 1 of the project. In the completion of this 1st objective, we first developed and built an apparatus (thermocline) that would allow us to evaluate which temperatures were preferred and which temperatures were avoided by sows at three reproductive stages (not pregnant, mid-gestation, late-gestation). In general, thermoclines have been used in rodent models and this is the first attempt (to our knowledge) by researchers to scale up thermoclines to be used in large mammals. The experiment was successful, and we determined that 1) the thermal preference range of sows differed by reproductive stage, and 2) the thermal preference range was lower and more narrow than what is currently recommended (10 to 25°C). We determined that not pregnant and mid-gestation sows preferred a similar temperature range (13.2 to 16.4°C) that was higher than the temperature range preferred by late-gestation sows (12.6 to 15.6°C). In addition, these temperature ranges were lower than what is currently recommended to swine producers and therefore is it likely that swine producers are inadvertently causing discomfort in their gestating sows by housing them at higher than preferred ambient temperatures. Following the completion of Objective 1, the next step was to complete Objective 2 and determine the heat stress threshold of sows at three different reproductive stages. This experimental objective was performed so that a thermal index could ultimately be developed in Objective 3 (a process that is ongoing). During the course of this experiment, we exposed sows to gradually increasing temperatures and closely monitored body temperature, heart rate, respiration rate, blood gasses and pH, skin temperature, and water consumption. Following data analysis, it was determined that the heat stress threshold was similar when comparing not pregnant and mid-gestation sows, but that the heat stress threshold for late-gestation sows was lower than not pregnant and mid-gestation sows. Furthermore, the upper temperature limit (e.g., heat stress threshold) was lower than what is currently recommended (>25°C). Results from this experiment indicated that heat stress likely occurs at lower temperatures than are currently recommended and that this threshold can vary depending on the reproductive stage of the pig. Data generated by Objectives 1 and 2 are currently being used to develop a decision support tool for swine producers. This tool will be available as both a smart phone application and a dedicated website and both will be freely available. Accurate knowledge of pig temperature preference and heat stress thresholds are an important factor to consider when raising pigs as this can determine how the animals are managed under variable environmental conditions and can also have an impact on energy use in the barn. In addition, understanding the temperature ranges pigs should be housed at may result in energy savings during cooler months when barn heating costs rise because results from this project indicate that gestating sows would prefer to be housed under cooler conditions. Therefore, results from this project not only have important implications for raising pigs under high temperatures but may also be applicable to raising pigs in cooler climates where heating barns is an economic concern.

Publications

• Type: Conference Papers and Presentations Status: Accepted Year Published: 2020 Citation: McConn, B.R., A.W. Duttlinger, K.R. Kpodo, J.M. Maskal, B.N. Gaskill A.P. Schinckel, A.R. Green-Miller, D.C. Lay Jr., and J.S. Johnson. 2020. Increasing ambient temperature alters the thermoregulatory and physiological response of sows at different reproductive stages. J. Anim. Sci. In press.
• Type: Conference Papers and Presentations Status: Published Year Published: 2019 Citation: McConn, B.R., A.W. Duttlinger, K.R. Kpodo, J.M. Maskal, B.N. Gaskill A.P. Schinckel, A.R. Green-Miller, D.C. Lay Jr., and J.S. Johnson. 2020. Effects of increasing ambient temperature on the thermoregulatory and physiological response of gestating sows. National Pork Board Pig Welfare Symposium. Minneapolis, MN. November 13-15.
• Type: Conference Papers and Presentations Status: Published Year Published: 2019 Citation: Robbins, L., A. Green-Miller, J.S. Johnson, A.P. Schinckel, and B. Gaskill. 2019. Evaluation of sow thermal preference. ISAE 53rd Congress, Bergen, Norway.
• Type: Theses/Dissertations Status: Submitted Year Published: 2020 Citation: Robbins, L. 2020. Into the comfort zone: Understanding swine thermal preference. PhD Dissertation. Purdue University

Progress 05/15/18 to 05/14/19

Outputs
Target Audience:Results from Aim #1 were submitted and accepted as an abstract to the 2019 International Society for Applied Ethology meeting in Bergen, Norway. Data will be presented to academic and government scientists, post-doctoral research associates, graduate and undergraduate students, and agriculture industry representitives. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?During the course of this project numerous students have been provided with training opportunities. For example, three undergraduate research assistants from Purdue University have been involved with the project and have been able to assist with data collection, animal handling, and data analysis thereby improving and developing their research skills. In addition, a postdoctoral research associate and graduate student were hired onto the project and have been responsible for running the day to day operations of the project. At the completion of the project, these students (postdoc and graduate student) will be given the opportunity to present their research at national and international scientific meetings to a peer group which will improve their professional development. How have the results been disseminated to communities of interest? Nothing Reported What do you plan to do during the next reporting period to accomplish the goals?1.) Complete writeup of the results from objective #1 2.) Complete live animal work, data analysis, and writeup of data from objective #2.

Impacts
What was accomplished under these goals? Heat stress mitigation and management practices have become increasingly advanced in recent years; however, heat stress continues to reduce animal welfare and compromise the efficiency and profitability of animal production for the U.S. swine industry. Losses due to heat stress are estimated to cost U.S. pig producers >$300 million annually, and global estimates exceed $50 billion/year. In addition to postnatal production losses (i.e., reduced growth, reproductive efficiency, mortality), the effects of prenatal heat stress on postnatal welfare and pig productivity is just beginning to be characterized and it has been suggested that these effects could substantially increase economic losses for producers above current estimations. While the swine industry has made major improvements to swine productivity due to genetic advances, this has increased the susceptibility of pigs to heat stress. Although it is well-reported that heat stress susceptibility has likely increased in modern sows, our current definition of thermal strain may not accurately characterize the thermal condition of the sow due to out of date recommendations (i.e., recommendations based on sows from >30 years ago). Furthermore, despite the widespread development and use of thermal indices and decision support tools available for cattle producers, there is limited information and no scientifically proven tool specific for swine producers to predict thermal strain in modern commercial sows at several reproductive stages, and no standardized swine heat stress recommendations for research scientists and Institutional Animal Care and Use Committee members to refer to. Therefore, there is an urgent need to re-evaluate ambient temperature thresholds that result in heat stress in modern production sows and develop a decision support tool to assist swine producers with management decisions, scientists with experimental design, and provide Institutional Animal Care and Use Committee members with a metric to determine what constitutes heat stress in modern swine. Successful completion of this research project will update the current recommendations for heat stress in modern commercial sows at different reproductive stages and provide swine producers with a decision support tool to determine when to provide management interventions during times of heat stress. This tool could be easily adopted by both commercial and small-scale swine producers both in the United States and internationally to reduce to detrimental effects of heat stress on swine welfare. Furthermore, we will make this tool available to the general public as a smartphone application and through a dedicated website. In addition, data generated by this research project will provide academic researchers with standardized information as to what is considered heat stress in modern sows when performing heat stress experiments and will be a valuable tool for Institutional Animal Care and Use Committees to decide what temperatures will cause distress in modern production sows. The goals of the project are to 1) Determine from the sows' perspective what temperatures are preferred and what temperatures are avoided, 2) Evaluate the biological response of the sows to increasing ambient temperature, and 3) Incorporate these data into a new thermal index that swine producers, scientists, and animal care and use committees can use to determine what constitutes heat stress in modern sows. Currently, project goal #1 has been completed and thermal preference has been established for modern commercial sows. We have determined that modern sows prefer temperatures that are at or below the lower end of the currently published thermoneutral zone. This finding is in agreement with our hypothesis that modern commercial sows would prefer lower temperatures than are currently recommended and these data are being written up for publication. Project goal #2 is in progress and the live phase animal experiment will be completed by Fall 2019. Once these data have been collected, they will be analyzed and incorporated into the new thermal index for modern commercial sows. Project goal #3 is also in progress and currently the smartphone application and website designers are working on the project. Once the animal data are collected and analyzed, they will be incorporated into the application and it will be made available to the general public.

Publications

• Type: Conference Papers and Presentations Status: Accepted Year Published: 2019 Citation: Robbins, L., A. Green, J.S. Johnson, and B.N. Gaskill. 2019. Evaluation of sow thermal preference. International Society for Applied Ethology. Bergen, Norway. August 5-9, 2019.