Estimating the body temperature of groups of pigs by thermal imaging.

Measurements on 28 pens of pigs containing 384 animals to be slaughtered at a commercial abattoir showed that the mean ear temperatures of the pigs in each pen, measured with a thermal imaging camera, were significantly correlated (r=0.71, P<0.001) with the mean temperature of the blood the pigs lost at exsanguination. In measurements on 220 pigs in 16 of the 28 pens, the mean activity of serum creatine kinase was positively correlated with the mean ear temperature (r=0.55, P<0.05) and the mean concentration of serum cortisol was positively correlated with the mean blood temperature (r=0.50, P<0.05), suggesting that the hotter pigs were suffering from a higher level of stress.