Interpretive Summary: Automated collection of heat stress data in livestock: new technologies and opportunities.
By: Dr. Caitlin Vonderohe
Body temperature is a significant aspect of animal health and productivity. Elevations in body temperature may be indicative of a disease challenge. Elevations in ambient temperature that are severe enough to result in elevations in resting body temperature represents a significant stressor that can result in economic losses. It is important for investigators to be able to closely and accurately monitor changes in body temperature. Koltes et al. recently published “Automated collection of heat stress data in livestock: new technologies and opportunities” in Translational Animal Science to review body temperature monitoring technologies that can be used to monitor animal health.
Temperature-sensing ear tags can be mounted on cattle ears and have a temperature sensor that may be placed in the ear canal to measure body temperature. These tags have been used to monitor hyperthermia due to health challenges; they have lights that flash if body temperature exceeds a certain level. These devices may be used to monitor heat stress but need to be correctly inserted in to the ear-canal. Several studies have been conducted to monitor the efficacy of these devices, with inconsistent results.
Rumen-reticular boluses are a sensitive measure for measuring body temperature, but can also be used to monitor rumen pH and rumen activity. However, the temperature recorded by the rumen-reticular boluses may be affected by water volume, feed intake, and rumen microbes, and may run as much as 2°C warmer than rectal temperatures. Rumen boluses also require special equipment to capture data and may only be used once.
Intravaginal thermosensors appear to work well to detect fever (in response to an LPS challenge) and can store large amounts of data. Vaginal thermosensors such as iButtions and Hobo sensors correlate well with rectal temperature. Unfortunately, these sensors do not have the capability to transmit data wirelessly but can be used multiple times and require little additional equipment to download data to a computer. Indwelling rectal temperature probes are the most accurate method for measuring changes in body temperature, but their utility may be limited by their stability and variations in fecal temperature.
Thermosensing microchips have been examined in pigs and tend to correlate with rectal temperature. Temperatures sensed by microchips can be detected with a wand through radiotelemetry. Other implantable devices are available, but implantation is highly invasive.
Thermal imaging represents an opportunity to detect combination behavioral and temperature-related data. However, at present, the interpretation of thermal image data requires significant computation and specialized software. Thermal imaging has been used to detect heat stress in cattle and swine, to varying success. The best places to measure body temperature in swine are the base of the ear and at the eye. Conversely, more accurate results were attained from imaging the forehead of Jersey cattle. In beef cattle, infrared tomography successfully identified heat stressed animals. Unfortunately thermal cameras tend to be expensive and images require a lot of time to review.
When comparing different technologies for evaluating body temperature, it is important to consider the accuracy of the data collected, the ease of data collection and the cost of the technology. It is also important to continue to collect data on multiple animals using these tools to better identify animals experiencing inflammation or heat stress and develop data sets that can further the validation of new technology.
To view the full article, visit Translational Animal Science.