Comparison of a non-contact infrared thermometer with a rectal digital thermometer for use in ewes

The aim of this study was to assess the accuracy of measuring body temperature in sheep using a noncontact infrared thermometer on the inguinal area and the eye cornea in comparison with a rectal digital thermometer. The trial for the first comparison was conducted in the milking parlor in 52 ewes in full lactation and 15 dry ewes and for the second one in 51 ewes. The body temperature measured with the noncontact infrared thermometer in the inguinal area, although significantly lower, was strongly linearly correlated with that of the rectal digital one in both ewes in full lactation and dry ewes. In lactating ewes, besides the high precision, the highest accuracy was also recorded and the plotted differences were within clinically insignificant levels. The corneal temperatures were highly correlated but were significantly lower compared to the rectal ones. Due to these differences the cut-off point of 37.9 °C was estimated to be adopted for the detection of the hyperthermic animals when noncontact infrared thermometers are applied to the eye cornea for the measurement of body temperature. In conclusion the inguinal area of the dry ewes and the eye cornea cannot be recommended as appropriate sites for body temperature measurement because the temperatures recorded are biased by external factors. The noncontact infrared thermometer evaluated is sufficiently accurate for the measurement of body temperature in sheep only when applied in the inguinal area of sheep in full lactation.