New technology allows us to “see” stress levels in chickens

Herborn, K. A., Graves, J. L., Jerem, P., Evans, N. P., Nager, R., McCafferty, D. J., & McKeegan, D. E. F. (2015). Skin temperature reveals the intensity of acute stress. Physiology & Behavior, 152, 225–230

A recent study by the University of Glasgow has found that the intensity of stress in animals can be detected using thermal imaging technology. They used this technology to record the skin temperature of chickens in response to different levels of handling stress, and found that more severe handling led to bigger changes in temperature.

All warm-blooded animals experience a phenomenon called Stress-Induced Hyperthermia. This is the process when, during stressful events, the “core” temperature of the body rises and the skin temperature falls, as blood rushes away from the skin to the vital organs. This means that skin temperature could potentially be used to monitor and quantify stress. To test this, the Thermal Ecology Group at University of Glasgow has been investigating how domestic chickens respond to different stressful situations. Using a new technology called infrared thermography (IRT), or ‘thermal imaging' they were able to measure changes in the chickens’ skin temperature and investigate, for the first time, whether this was proportional with stressor intensity.

More severe handling techniques led to a greater drop in skin temperature

This study used two common handling techniques to represent different severities of acute stress in chickens, cradling (mild stressor) and side-pinning (more severe stressor). The stress intensity of these handling methods were measured by hormonal and behavioural responses, and the results validated side pinning as a more severe stressor than cradling. To see if thermal imaging would mirror these findings, the researchers then measured the temperature at the comb and wattles of commercial laying hens (n=57) following either of these handling methods, by using continuous thermal video footage to record the level of skin temperature change.

The results showed that side-pinning, the more severe handling method, led to a greater drop in skin temperature in both the comb and the wattles. This suggests that skin temperature can be used to quantify stress intensity, and ergo indicates that thermal imaging could be useful in the future for stress assessment in animals. This is highly beneficial as it can be done from afar without direct interference with animals, therefore providing a potential “non-invasive” alternative to other invasive measures (such as blood sampling or core temperature measurements) which can compromise welfare. The continuous measurement of temperature over long periods could also allow scientists to better understand the nature of the stress response across numerous species.

World Animal Protection’s view

Animals are sentient beings, capable of experiencing pain and suffering, as well as joy and excitement. This applies equally whether the animal is a family pet, on a farm, or in a laboratory. Studies like this are vital to help us understand their emotional states, and to enable us to measure stress using non-invasive methods.

World Animal Protection is opposed to all experiments or procedures which cause unnecessary suffering to animals. Where these experiments increase our understanding of animal sentience, we will continue to report them in the long term interest of all animals. World Animal Protection is committed to advancing the field of animal sentience and advocates for humane research to continue to improve our knowledge and understanding of sentience.