Evaluating the temperature preferences of sexually mature Duroc, Landrace, and Yorkshire boars

Authors: RABER, VICTORIA - US Department Of Agriculture (USDA); Pritchett, Rebecca; ROBBINS, LINDSEY - Purdue University; STEWART, KARA - Purdue University; GASKILL, BRIANNA - Purdue University; GREEN-MILLER, ANGELA - Purdue University; Johnson, Jay

Submitted to: Translational Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/22/2023
Publication Date: 5/29/2023
Citation: Raber, V.L., Pritchett, R.K., Robbins, L.A., Stewart, K.R., Gaskill, B.N., Green-Miller, A.R., Johnson, J.S. 2023. Evaluating the temperature preferences of sexually mature Duroc, Landrace, and Yorkshire boars. Translational Animal Science. 7(1). https://doi.org/10.1093/tas/txad060.
DOI: https://doi.org/10.1093/tas/txad060

Interpretive Summary: Recent research in sows, pre-nursery and nursery pigs indicates that their temperature preferences are lower than currently established guidelines. However, it is unknown whether temperature preferences of boars have changed from the current guidelines that were established based on >50 year old data. Additionally, current guidelines do not differentiate by breed. Therefore, the study objective was to determine the temperature preferences of sexually mature Duroc, Landrace, and Yorkshire boars. Based on previous data in sows, pre-nursery, and nursery pigs, we hypothesized that boar temperature preferences would be at the lower end of currently established guidelines. Contrary to our hypothesis, it was determined that, regardless of breed, boars preferred temperatures at the upper end of current guidelines. These data provide new information on appropriate temperatures to house boars under commercial production conditions to improve welfare.

Technical Abstract: An accurate understanding of boar temperature preferences may allow the swine industry to design and utilize environmental control systems in boar facilities more precisely. Therefore, the study objective was to determine the temperature preferences of sexually mature Duroc, Landrace, and Yorkshire boars. Eighteen, 8.57 ± 0.10-month-old boars (n = 6 Duroc, 6 Landrace, and 6 Yorkshire; 186.25 ± 2.25 kg) were individually tested in thermal apparatuses (12.20 m x 1.52 m x 1.86 m) that allowed free choice of their preferred temperature within an 8.92 to 27.92ºC range. For analyses, the apparatuses were divided into five thermal zones (3.71 m2/thermal zone) with temperature recorded 1.17 m above the floor in the middle of each zone. Target temperatures for thermal zones 1 to 5 were 10, 15, 20, 25, and 30ºC, respectively. All boars were given a 24 h acclimation phase followed by a 24 h testing phase within the thermal apparatuses. Daily feed allotments (3.63 kg/day) were provided to each boar and all boars were allowed to consume all feed prior to entering the thermal apparatus. Water was provided ad libitum within the thermal apparatuses with one waterer per thermal zone. During testing, boars were video recorded continuously to evaluate behavior (inactive, active, or other), posture (lying, standing, or other), and thermal zone the boar occupied. All parameters were recorded in 15-min intervals using instantaneous scan sampling. Data were analyzed using GLM in JMP 15. For the analyses, only time spent lying or inactive were used because they were observed most frequently (lying 80.02%, inactive 77.64%) and were deemed to be associated with comfort. Percent time spent active (19.73%) or standing (15.87%) were associated with latrine or drinking activity and were too low to accurately analyze as an indicator of thermal preference. Breed did not affect temperature preference (P > 0.05). A cubic regression model determined that boars spent the majority of their time inactive at 25.50ºC (P < 0.01) and lying (both sternal and lateral) at 25.90ºC (P < 0.01). These data suggest that boar thermal preferences do not differ by breed and that boars prefer temperatures at the upper end of current guidelines (10 to 25ºC).