Influence of workload and weather conditions on rolling behaviour of horses and mules

Highlights

• Horses rolled frequently more after the most intense exercise.

• Mules frequently rolled in both the null exercise and intense exercise.

• Horses and mules rolled frequently after bathing, regardless of the level of exercise.

• Only mules rolled more often by influence of weather conditions.

• While rolling, mules frequently exhibited leisure, self-care and scent marking.

Abstract

We evaluated the influences of workload intensity, bath handling and environmental conditions in the rolling behaviour of horses and mules. For this purpose, animals were observed after being exposed to different levels of workload and the rolling behaviour was recorded and described. During all testing procedures, the weather condition (temperature and humidity) was registered by a Black globe and Wet Bulb apparatus. Horses frequently rolled after intense exercise and after bath handling, independently of the weather condition. Mules frequently rolled after control (no exercise) and intense exercise in warmer and wetter days and after bath handlings in colder and drier days. Rolling behaviour characteristics were slightly different between species. While mules exhibited more frequently the behaviours of rest, self-care, yawn, tail swishing, complete spins, snort vocalization and use of the same spot to roll, horses exhibited more frequently the behaviours of paw, sniff, head and neck rubbing movements and incomplete spins to the right and left. This findings evidence that rolling is an important and frequently exhibited behaviour by domestic horses and mules, but animals may express it differently and may have their own motivations. In this sense, we believe that domestic equines, mainly those raised in more intensive livestock, should have the opportunities to freely express the rolling, as a way to improve their welfare conditions and with agreement with a more rational handling practice.

Introduction

Rolling behaviour occurs in various species of the Equidae family (Equus caballus: McDonnell, 2003; E. asinus, E. kiang: Kannan and Parsons, 2017; Moehlman et al., 1998; E. zebra, E. bruchelli: Joubert, 1979; Penzhorn, 2010) and plays an important role in the wellbeing and comfort of these animals when free-ranging (Waring, 2002). By lying down in the sternal recumbency position, performing backward and forward rubbing movements of the body over the ground, with incomplete or complete spins, rolling animals maintain efficient self-care against ectoparasites. Rolling is also important for thermoregulation, as it allows heat to dissipate towards the ground and a protective layer of dust to form on the animal's coat (Fraser, 1992; Joubert, 1979; Moehlman et al., 1998; Kannan and Parsons, 2017). Although rolling has already been described for almost all equines, its functions in domestic conditions have not yet been fully described. Recent research has demonstrated that rolling behaviour can also be displayed in horses (E. caballus) as a play pattern (Maglieri et al., 2020) and in domestic male donkeys (E. asinus) as a sexual behaviour to court jennies in oestrus (Henry et al., 1998). Regarding mules (E. asinus × E. caballus), which result from artificial crossbreeding, rarely occurring in natural environments – a full description of their rolling patterns and other behaviours are scarce in the literature (Matsui et al., 2009; McLean et al., 2019).

Considering the variety of functions of rolling behaviour on free-range equines, it is very likely that such behaviour is also important for the welfare of domestic equines, such as horses, donkeys, and mules kept under more intensive systems of activity and/or living conditions. Such conditions may compromise the natural rolling pattern, as limited stall space mostly does not allow its complete execution, increasing the risk of injury to animals attempting to roll (Hansen et al., 2007). Many equine owners make a range of modifications to the stalls, such as rounded walls, gutters, and attachments, to prevent harmful situations during rolling movements (D’Agosta, 2000). These measures may be effective in preventing accidents, but they disregard the relevance of rolling behaviour to animals’ physical and mental welfare, especially for animals with a constant training and work schedule.

A large number of horses, donkeys, and mules are raised to perform some kind of physical effort with some additional weight on their back (Pritchard et al., 2005). In more socioeconomically developed countries, equines are mainly used in sports and leisure activities; in contrast, equines in underdeveloped countries are mainly used for pack transport and heavy activities. Although the number of mules used for sports and leisure practices has grown substantially, the largest proportion is still found in underdeveloped countries, where they are used for various traction and transportation work (Pritchard et al., 2018; Mclean et al., 2019). For these equines that perform heavy work in warmer weather, rolling behaviour probably has important thermoregulatory, comfort, and self-care functions. Instead of restricting the ability of equines to roll, we should provide them with conditions to naturally perform rolling behaviour, especially after a working day and on hot days.

In this context, we aimed to characterise the rolling behaviour of horses and mules under working conditions. Thus, we expected that more intense exercise and higher weather temperatures would increase the frequency of rolling behaviour in horses and mules. We also expected mules to exhibit rolling behaviours specifically related to their hybrid nature.