USING HAIR AND WOOL TO MONITOR ANIMAL WELFARE

Stress in animals is not only a matter of behaviour or veterinary health. Understanding how much an animal is exposed to stressful conditions means improving its quality of life and, in the case of livestock, ensuring a more sustainable and welfare-oriented production. It is valuable information for owners, veterinarians and those involved in agricultural and environmental policy.

Measuring stress, however, is not straightforward. The hormones that regulate it, such as cortisol, fluctuate rapidly in blood or saliva, providing only a snapshot of the immediate situation. The picture changes when looking at tissues such as hair and wool, where these hormones accumulate over time, offering an overview of long-term exposure.

This was the focus of a study published in Scientific Reports by the Food Chemistry and Drug Residues of the Istituto Zooprofilattico Sperimentale dell’Abruzzo e del Molise (IZSAM), in collaboration with the Universities of Milan and Urbino. The researchers developed two new methods to measure, with great precision, four hormones linked to the stress response (cortisol, cortisone, DHEA and DHEAS) in samples of horse mane and sheep wool.

“We used – says Giorgio Saluti, senior chemist at IZSAM – a precise and selective analytical technology, liquid chromatography coupled with high-resolution mass spectrometry (LC-HRMS/MS), together with a strategy known as surrogate analyte approach, which allows us to overcome technical issues related to the lack of hormone-free reference samples.”

The surrogate analyte approach makes it possible to address a common problem in measuring substances that are naturally present in the body. For pollutants, measurements can be made on animals that have not been exposed to them, which then serve as reference samples. But with hormones, there is no such “blank” sample for comparison. To overcome this limitation, researchers add artificial molecules designed to mimic the hormones being measured.

These molecules are almost identical to the natural ones but contain small markers (such as stable isotopes) that make them distinguishable. By comparing the instrument’s response to the “real” and the labelled hormones, highly precise measurements can be obtained, even in complex matrices such as hair or wool, where many interfering substances may be present.

“The method – continues the chemist – was developed and validated using samples collected from animals living in marginal areas of the Apennines. Its sensitivity is remarkable: it can detect even very low concentrations of these biomarkers, a key feature for assessing animal welfare in real-life contexts such as farms or natural environments.”

“One of the most important aspects of this work – adds Saluti – is the possibility of analysing several hormones at the same time, thus obtaining a more complete picture of the animal’s condition. The ratios between different hormones, such as cortisol and DHEA, can provide more reliable information than measuring a single parameter.”

 Analyses of this kind can help determine whether an animal has experienced stress related to management, environment or interaction with other individuals, and can therefore guide potential improvements. For this reason, the study is part of a growing field of research that brings together veterinary science, animal welfare and sustainable farming practices.

The work is part of the project “Towards a fair and sustainable production in marginal areas: novel indicators to improve animal welfare”, funded by the Italian Ministry of Health under the “Ricerca Finalizzata” programme - Young Researcher (under 40) section, with Giorgio Saluti (IZSAM) as Principal Investigator.