What do ears positions tell us about horse wellfare ?
Résumé
Developing approaches to measure welfare states as objectively as possible, particularly by non-invasive and easily applied methods, remains a scientific challenge. Ear positions, a postural element easily recordable, have been shown to reflect acute stress in several species, and one may wonder if it could also reflect chronic stress. Here we tested the hypothesis that ear position could be a reliable indicator of chronic poor welfare in horses, comparing horses’ ear positions in their box to several welfare indicators. Observations were performed on 59 adult horses from riding schools. Ear positions were observed while foraging on the ground only at quiet times in the stables, outside feeding times by a silent experimenter, walking slowly and regularly in the stable, on 2 days at 15 min intervals until 10 scan samples of ear positions were obtained per horse. Chronic welfare state was assessed by chronic health disorders, vertebral problems and behavioural observations of stereotypies. It appeared that 34% of the horses suffered from chronic health disorders, 73% were severely affected by vertebral problems and 66% showed stereotypic activities, evidencing poor welfare states for some of these 59 horses. Interestingly, the 31 horses displaying mostly a backward ear position (i.e. ≥ 50% of the 10 scan samples) were prone to suffer from health disorders, to be affected by vertebral problems and to display stereotypies (Fisher, Mann Whitney & Spearman correlations, P<0.05). Conversely, the more time spent with forward ears, the less health-related problems and number of stereotypies (Spearman correlations, P<0.05). These results both confirm earlier findings in horses, reporting a backward ears position in acute aversive situations and go beyond by showing that a similar backward ears position could be observed more permanently in horses experiencing chronic poor welfare. Conversely, forward ears may also reflect good welfare. At the time where the need has appeared to include both negative and positive emotions in welfare assessment, this study clearly shows that posture may be of great help in both directions.