Thermocline design for thermal preference testing in piglets

Housing animals within their thermoneutral zone can have positive impacts on productivity and animal well-being. Based on the Guide for the Care and Use of Agricultural Animals in Research and Teaching, piglets between the weights of 3 kg to 15 kg prefer temperatures between 26°C to 32°C. However, this preferred range is based on 30 year old data from individually-housed animals. Therefore, a thermal gradient apparatus, or thermocline, was designed to re-evaluate the thermal preference of group-housed piglets. The thermocline was a rectangular chamber that maintained a steady thermal gradient. The cool end sourced ambient air from the room and incrementally heated the air as it traveled the length of the thermocline to the opposite end. Ceramic radiant heating bulbs were placed along the length of the thermocline to heat the air. Prior to piglet testing, the chamber was evaluated to verify that the target temperatures (20°C to 40°C) could be achieved and maintained over the course of several days. Results revealed that a constant thermal gradient of 22°C to 40°C could be maintained if the ambient room temperature was between 17°C to 18°C. At ambient room temperatures around 21°C, the gradient was shifted 3°C to 5°C higher. Group-housed piglets appeared to show a preference for the coolest temperatures (22°C to 26°C), which is lower than the 26°C to 32°C listed in the Ag Guide. Furthermore, results indicated that the thermocline could maintain a desired temperature range to test the thermal preference of group-housed piglets.