Vet students successfully used the Horse Grimace Scale, even without training

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Veterinary students were reliably able to use the Horse Grimace Scale, a system designed to discern pain in equines, even without prior training in its use.

The development of the Horse Grimace Scale by researchers in Italy, Germany and Britain was first reported in 2013, with the scale described in more detail in a journal report the following year.

Six researchers developed the standardized scale of facial expressions to help horse managers discern pain. They did so by monitoring stallions who underwent castration.

Their pain-coding system is based on six Facial Actions Units, which are considered responses to discomfort:

  • Stiffly backward ears;
  • Orbital tightening;
  • Tension above the eye area;
  • Strained chewing muscles;
  • Strained mouth and pronounced chin;
  • Strained nostrils, and flattening of the profile.

The scale was put to the test in a preliminary study by researchers from the University of Milan in Italy.

Their findings are reported in a short communication in the International Journal of Health, Animal Science & Food Safety.

In their preliminary study, Francesca Dai, Emanuela Dalla Costa and Michela Minero set out to evaluate the effectiveness of standardized training in the use of the scale.

Forty-six veterinary student in their second year at the University of Milan and 31 in their fourth year at the University of Teramo were recruited.

Before any training, the students were asked to score 10 pictures of horse faces using the six Facial Action Units.

Then, a 30-minute training session was provided, including detailed descriptions and example pictures of each Facial Action Unit, as well as a discussion of five pictures previously scored by an experienced assessor.

After training, the students scored another 10 pictures.

The students’ reliability was good even before training, the researchers reported, with tension above the eye area and strained nostrils appearing to be the most challenging to be scored reliably.

Reliability improved after the 30 minutes of training. Overall, consistency and reliability was rated as excellent.

“Our results suggest that the Horse Grimace Scale scoring system is easy to apply even without any training,” the researchers reported.

“However, the training method applied proved useful to improve the reliability of Horse Grimace Scale scores.”

Efficacy of a standardized training on horse welfare indicators: a preliminary study
Francesca Dai, Emanuela Dalla Costa, Michela Minero

The original study on the Horse Grimace Scale can be read here.

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