The use of infrared thermography for assessing thermal condition of pigs during unloading at slaughterhouse

Infrared Thermography is a completely non-invasive technique that allows recording measurements of animal skin temperature on subjects difficult to reach or to approach, or moving subjects. The use of this technique is particularly interesting at the slaughterhouse, where there is a need to detect the temperature increase in response to the pre-slaughter handling. In order to evaluate the use of thermography at the slaughterhouse for assessing pig’s surface temperature, a survey was conducted during 10 deliveries occurred from February to June 2014 involving 1400 subjects supplied by one farm. Distance from farm to slaughterhouse was 15 km, corresponding to a journey time of about 30 min. The deliveries were carried out using double trailer lorries with three hydraulic deck. The lorries had natural and mechanical ventilation system, with fans placed on the left side of the trucks. Unloading at the slaughterhouse was carried out by a platform (m 2.7x9.3x0.9) adjustable at the level of the lower deck. The vehicle was always offloaded firstly and then the rear trailer. Maximum surface temperatures of dorsal region and ears were recorded by Avio Nec G120 EX thermocamera on pig’s groups of each unloaded deck drove along the platform. Images involving at minimum of 20 subject on the total of 23-24 pigs held in each deck were examined by software NEC InfRec Analyzer and Grayess IRT Analyzer. A total of 7000 thermal images involving 1222 pigs were analysed to determine the maximum temperatures in repere areas. Environmental temperature and relative humidity were recorded during the unloading of each deck. Data of surface skin temperature recorded by thermocamera was analysed using PROC MIXED of SAS using a model including the fixed effect of the truck deck, the random effect of day of slaughter and their interaction. This latter affected significatively (P<0.05) both temperatures of dorsal surface and ears. Irrespectively of the environmental temperatures, pigs loaded into the middle deck of both vehicle and lorry showed the highest surface temperatures on the dorsal area at unloading for the majority of slaughter days.