First investigations to refine video-based IR thermography as a non-invasive tool to monitor the body temperature of calves

Abstract

In this study, a video-based infrared camera (IRC) was investigated as a tool to monitor the body temperature of calves. Body surface temperatures were measured contactless using videos from an IRC fixed at a certain location in the calf feeder. The body surface temperatures were analysed retrospectively at three larger areas: the head area (in front of the forehead), the body area (behind forehead) and the area of the entire animal. The rectal temperature served as a reference temperature and was measured with a digital thermometer at the corresponding time point. A total of nine calves (Holstein-Friesians, 8 to 35 weeks old) were examined. The average maximum temperatures of the area of the entire animal (mean ± SD: 37.66 ± 0.90°C) and the head area (37.64 ± 0.86°C) were always higher than that of the body area (36.75 ± 1.06°C). The temperatures of the head area and of the entire animal were very similar. However, the maximum temperatures as measured using IRC increased with an increase in calf rectal temperature. The maximum temperatures of each video picture for the entire visible body area of the calves appeared to be sufficient to measure the superficial body temperature. The advantage of the video-based IRC over conventional IR single-picture cameras is that more than one picture per animal can be analysed in a short period of time. This technique provides more data for analysis. Thus, this system shows potential as an indicator for continuous temperature measurements in calves.Keywords: calves, health control, IR thermography, non-invasive, temperature Implications A tool that continuously measures body temperature in calves can improve the health and welfare of the animals and therefore holds implications in calf housing. This could serve as an early warning system to support the farmer in monitoring the health of his calves, particularly in critical periods and subclinical cases. A video-based IR thermography system could represent a fast and non-invasive method that can be installed in a calf feeder to automatically measure the body temperature of each animal daily. IntroductionThe rectal temperature is one of the most important disease indicators in livestock production. The procedure itself, however, is time consuming and requires direct contact with animals.In contrast, IR thermography represents a non-invasive, contactless method to measure body surface temperature, which can be used as an indicator of core body temperature in cattle (e.g., George et al., 2014). Using rectal temperature is a common method used by veterinarians and farmers; however, there are limitations to this method. Investigations showed that both the technique used when administering a digital thermometer and the thermometer type can affect the measured values (Burfeind et al., 2010;Naylor et al., 2012). Other technologies have been developed to continuously record body temperature in cattle, for example, boluses to measure the rumen temperature (Rose-Dye et al., 2011) and sensors to measure the milk temperature in automatic m...

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“…Our study used a fixed time point, single image thermographic assessment. Previous studies have provided evidence that video‐based infrared cameras have the advantage of producing greater than a single image per animal in a short period of time, which is suitable for continuous monitoring of surface temperature in calves …”