Evaluation of Non-Contact Device to Measure Body Temperature in Sheep

Abstract

Non-contact devices have been used in the measurement of body temperature in livestock production as a tool for testing disease in different species. However, there are few studies about the variation and correlations in body temperature between rectal temperature (RT) and non-contact devices such as non-contact infrared thermometers (NCIT) and thermal imaging/infrared thermography (IRT). The objective of this work was to evaluate the accuracy of non-contact devices to measure the body temperature in sheep, considering six body regions and the possibility of implementing these systems in herd management. The experiment was carried out at the experimental farm of the Catholic University of Valencia, located in the municipality of Massanassa in July of 2021, with 72 dry manchega ewes, and we compared the rectal temperature with two types of non-contact infrared devices for the assessment of body temperature in healthy sheep. Except for the temperature taken by NCIT at the muzzle, the correlation between RT vs. NCIT or IRT showed a low significance or was difficult to use for practical flock management purposes. In addition, the variability between devices was high, which implies that measurements should be interpreted with caution in warm climates and open pens, such as most sheep farms in the Spanish Mediterranean area. The use of infrared cameras devices to assess body temperature may have a promising future, but in order to be widely applied as a routine management method on farms, the system needs to become cheaper, simpler in terms of measurements and quicker in terms of analyzing results.

Keywords: infrared thermography; infrared thermometers; manchega ewe; rectal thermometry; thermal imaging.

Figure 1

Testo 868 infrared thermography camera (Barcelona, Spain). (a) EA measurement; (b) LC measurement.

Figure 2

Correlation matrix between measured parameters. Upper triangle corresponds to the significance level (*** = p-values < 0.0005; ** = p-values < 0.005; * = p-values < 0.05; NS—not significant). Lower triangle corresponds to the values of the correlations. Diagonal shows the parameters (RT—Rectal thermometer, NCIT—Non-contact infrared thermometers, IRT—Thermal imaging/infrared thermography, LC—lachrymal caruncle, VL—vulva, MUZ—muzzle, EA—ear, NE—neck, BL—back leg). Blue color corresponds to positive correlations and red to negative ones. The intensity of the color depends on the value of the correlation, being fainter close to zero.