What a horse’s top line says about its welfare status

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The top line points used in the study. Photo: Sénèque et al, https://doi.org/10.1371/journal.pone.0211852
The top line points used in the study. Photo: Sénèque et al, https://doi.org/10.1371/journal.pone.0211852

The top line of a horse’s back can reveal telling insights into its welfare status, the findings of recent research suggest.

Descriptions by Darwin in 1872 of the expression of emotions in humans and animals indicated that postures and emotions are interrelated.

For example, humans are familiar with the postures in dogs and cats and other domesticated animals that suggest fear, anxiety or other challenging situations, although they are not always easy to describe.

“The measurement of postures is especially important when considering animal welfare issues,” Emilie Sénèque and her colleagues wrote in the open-access journal PLOS ONE.

It is possible that ongoing stressful situations may lead to chronic states. So, in such cases, could postures known to be associated with stress likewise become chronic?

Findings of a few recent studies suggest that this is indeed the case. The backs of pigs reared in social isolation were rounder (that is, more tensed) than those of pigs reared with company.

Horses living in more natural conditions and subjected to less strict riding techniques have been shown to have a more optimistic outlook and an overall “rounder” body posture than horses living in restricted conditions.

Also, it has been shown that the roundness of a horse’s neck reflects the state of the horse’s back.

The University of Rennes research term used photographs of 85 riding school horses from 11 riding schools for their study.

Photographs of two types of riding school horses. Those marked A show riding school horses presenting characteristic elements of posture associated with poor welfare. They expressed stereotypic or abnormal repetitive behaviours and show a "depressed-like" posture too. The images marked B are of riding school horses which showed no such behaviors, and did not have characteristic elements of posture associated with poor welfare. Images: Sénèque et al, https://doi.org/10.1371/journal.pone.0211852
Photographs of two types of riding school horses. Those marked A show riding school horses presenting characteristic elements of posture associated with poor welfare. They expressed stereotypic or abnormal repetitive behaviours and show a “depressed-like” posture, too. The images marked B are of riding school horses which showed no such behaviors, and did not have characteristic elements of posture associated with poor welfare. Images: Sénèque et al, https://doi.org/10.1371/journal.pone.0211852

They analysed the top line of the animals using precise geometric morphometric measurements to determine if posture was linked to each animal’s welfare state.

The assessment of the welfare state of each animal was based on the prevalence of stereotypic behaviors such as weaving and cribbing; other abnormal repetitive behaviors such as repetitive biting and teeth chattering; evidence of depressed-like posture; and ear position.

They also factored in other matters that have a bearing on welfare, such as the number of hay meals each day, the time spent at pasture, whether they were kept with other horses, and the time spent in work.

Analysis showed that horses showing stereotypic or abnormal behaviours, and, to a lesser degree, horses with depressed-like postures, tended to have a flatter, or even hollow, back profile, especially around the neck and croup.

“These altered profiles could represent an additional indicator of poor welfare, easy to use in the field or by owners,” they wrote.

They said the study delivered surprisingly consistent results.

“Overall, stereotypic or depressed horses living in restricted conditions are characterized by a flat or hollow back, neck and croup shape with a prominent withers. These findings show that poor welfare is also associated with chronic alterations of posture, erasing the natural curves of the horse’s spine.”

The flat croup in depressed horses may be due to the repetition of “depressed-like” postures where the horse puts most of its weight on the forelegs, thus lowering muscle activity at the croup level. It was also possible that back problems at the croup level induced depression in horses.

“The results suggest that the depressed state, associated with flat croup and back, may be more related to work quality.”

They said the absence of a clear relationship between postures and chronic ear positions further suggests that postural alterations are due to specific problems, while repeated backwards ears reflect a more general impaired welfare state.

“In conclusion, the finding, based on precise geometric morphometric measurements, that a riding school horse’s flat or hollow dorsal profile is related to a compromised welfare state and associated management conditions provides a first clear profile of individuals with risk factors of at least a ‘depressed’ or ‘abnormal’ psychological state.

“These profiles may however be related to the particular population considered (riding school horses).”

Further studies will have to consider larger, more diverse horse populations, they said.

The full study team comprised Emilie Sénèque, Clémence Lesimple and Martine Hausberger, all from the University of Rennes; and independent biostatistician Stéphane Morisset.

Sénèque E, Lesimple C, Morisset S, Hausberger M (2019) Could posture reflect welfare state? A study using geometric morphometrics in riding school horses. PLoS ONE 14(2): e0211852. https://doi.org/10.1371/journal.pone.0211852

The study, published under a Creative Commons License, can be read here

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