Infrared thermography: Variability and correlations of measured temperatures in cows

Abstract

The use of a thermal imaging camera is a reliable, non-invasive method of assessing compressive stress. The emissivity given by the body surface in cattle ranges from 0.93-0.98, which makes infrared thermography an extremely suitable method. By measuring the temperature of different anatomical regions, it is possible to determine the thermal load as well as their mutual variability in relation to external temperatures. With the thermal imaging camera, it is possible to make maximum, medium and minimum IRT (infrared thermograms). It is also possible to evaluate which thermograms are the most accurate for assessing heat load. Correlation analyzes on thermograms show a significant relationship between the external ambient temperature and the temperature of different body regions in cows under heat stress. The coefficient of determination averaged 94.27%, indicating a very high correlation between body surface temperature and ambient temperature. In our experiment, we dealt specifically with the temperatures of the abdomen and the temperature of the head region. The average, maximum and positional temperature values of these two regions correlate significantly with each other so that the coefficient of determination is 96.33% for averages, up to over 98% when it comes to the maximum temperature values of a given region or the positional values of pixels along the longitudinal axes of the region. The next important region is the udder region, and a significant correlation was found between the maximum temperature of the udder with the maximum temperatures of the head region (determination coefficient 93%) and the abdomen region (determination coefficient 98%). The limb region does not show significant correlations with the head region, while the correlation with the abdomen was at the level of 82%. And finally, there was a significant correlation between the temperature of the left and right sides of the body with a coefficient of determination of 97%. All of the above confirms that it is possible to determine heat stress in cows using data from thermograms. In this paper, a detailed overview of various correlational researches in infrared measurement is given.