Thermal imaging can detect subtle changes in temperature in a sheep’s eye that help researchers understand the levels of stress the animal is feeling, according to a study by researchers with AgResearch in New Zealand.

Research in which thermal imaging technology is focused on sheep as a potential tool to help assess and enhance welfare was published recently in the international PLOS ONE journal.

“For some years now at AgResearch, we’ve been looking at how infrared thermography (using a thermal imaging device that detects the amount of infrared energy an object radiates) can help us gain a better understanding of the stress levels livestock may be experiencing, and, therefore, their welfare,” AgResearch senior scientist Dr. Mhairi Sutherland said. “A key advantage of this technology is that it is non-invasive when, clearly, the aim is not to add to the stress of the animal in the course of trying to take these measures. The technology has also been used to detect the presence of disease or inflammation in animals that may require further investigation.

“After demonstrating that infrared thermography could be used to detect stress responses in cattle, we undertook similar research in ewes where we focused on temperature changes of the eye region as a measure of stress and activation of the autonomic nervous system,” Sutherland said. "By comparing ewes injected with epinephrine (also known as adrenaline) and those without, we were able to see subtle temperature changes in the eye. We focused on the eye region because it is not obstructed by wool, but we did look at other areas of the body such as the ear, where there may also be the potential to detect changes in temperature that relate to stress."

She explained that infrared thermography is currently used primarily as a research tool to detect stress responses in animals, but there is "potential for this technology to be integrated into farming systems, where animals may be directed to pass by an infrared thermography checkpoint to take measurements relating to stress or health."

Being able to detect stress responses in animals, researchers and producers can then look at the situations or circumstances that could be contributing to the stress for the animals and how to best adapt farming practices to reduce this and enhance animal welfare, she added.