Sheep’s eye reveals how much stressed out they are

Subtle changes detected in eye temperature can indicate animal stress.


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Eye temperature measured using infrared thermography (IRT) can be used as a non-invasive measure of autonomic nervous system (ANS) activity in cattle. A new study by the AgResearch aimed to evaluate ANS activity in sheep using infrared thermography.

The technology is non-invasive and can effectively detect the presence of disease or inflammation in animals that may require further investigation.

After demonstrating that infrared thermography could be used to measure stress in cattle, scientists undertook similar research to understand the stress level sheep may be experiencing.

Twenty, 2 to 4-year-old Romney ewes were randomly assigned to the study. Scientists focused on temperature changes of the eye region as a measure of stress and activation of the autonomic nervous system. 

By comparing ewes injected with epinephrine (also known as adrenaline) and those without, they were able to detect a subtle difference in temperature change as measured from the eye.

AgResearch senior scientist Dr. Mhairi (pronounced Vaa-ree) Sutherland said“We focused on the eye region of the sheep given that it is free of wool and can, therefore, provide an area to measure that is not obstructed, 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.”

“At this stage, infrared thermography is being used primarily as a research tool in this area, but there is certainly potential for this technology to be integrated into farming systems, where animals may, for example, be directed to pass by an infrared thermography device checkpoint to take measurements relating to stress or health. Once you have the tools to measure stress levels in animals, you can, of course, then look at what situations or circumstances are causing more stress for the animals, and how you can adapt farming practices to reduce this and enhance their welfare.”

“Our experience is that farmers want the best for their animals and are open to how to evolve their practices, and we know those good welfare standards are also an important factor for consumers of food and fiber produced in New Zealand.”

Journal Reference:
  1. Mhairi A. Sutherland et al. Evaluation of infrared thermography as a non-invasive method of measuring the autonomic nervous response in sheep. DOI: 10.1371/journal.pone.0233558