Relationship between piglets skin temperature measured by infrared thermography and environmental temperature in a vehicle in transit : a preliminary study

The thermal state of pigs during transport is particularly hard to assess because it depends on the mixed of production of heat and humidity, of external environmental conditions and of the vehicle ventilation. The measure of body temperature has a particular relevance for the welfare assessment of pig during transport, but this parameter is difficult to detect during transit. In the last two decades, infrared thermography (IRT) has been already applied on pig in order to detect their superficial body temperature, but not during a journeys. Infrared thermography does not require any contact and is therefore a completely non-invasive technique that allows to record temperature of hardly approaching or moving subjects. The purpose of this study was to detect, continuously, a thermometric profile of piglets skin during a long journey and to evaluate its relationship with the temperature inside the vehicle. Two journeys of 14 hours were carried out on July and September 2009 respectively and skin temperature variations were measured by infrared thermography on a total of 12 piglets, six for each trip. Average weight of piglets transported was 10.88 ± 1.97 kg in the first trip and 8.08 ± 0.74 kg in the second one. A thermocamera Avio TVS 500 was placed in front of and above the pen, in the first and in the second journey respectively. Environmental temperature and humidity inside the compartment housing piglets were continuously recorded. Relationship between piglets skin temperature max value and environmental temperature in the vehicle during the two transports was examined by regression analysis. During the second trip, camera location above the pen led to higher values of skin temperature reducing also the variability of thermal measurements, compared to the first one. In both journeys relationship between skin temperature and environmental temperature inside vehicle was linear (P <0.001). The R2 value was equal to 0.44 and 0.57 in July and in September, respectively. Thus, in the range of temperatures recorded during these transports, an increase of one degree in temperature inside the vehicle matched an increased of 0.2°C in piglets skin temperature. In our knowledge, this is the first study on using infrared thermography to measure continuously changes in skin temperature on pigs during transport. This technique, coupled with deep temperature recording systems, will help to better understand adaptive efforts of piglets to extreme environmental conditions experienced during transport.