Effects of enrichment items on activity and social interactions in domestic horses (Equus caballus)

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Abstract

The aim of this study was to investigate the use of items intended to provide enrichment during turnout, both for individual and group kept horses in an attempt to reduce the amount of passive behaviours. The study was divided into two parts, where study 1 involved eight horses rotated through eight individual paddocks, each containing one of seven enrichment items and one paddock being kept without item, functioning as a control. The horses’ item-directed behaviours; passive behaviours or other non-item related activities were scored using instantaneous sampling, every minute for 1 h at the beginning and the end of the turnout period. Study 2 involved six horse groups (3–6 horses) and the same scoring methods and ethogram as in study 1. The four items that the horses interacted the most with during study 1 (straw STRA, ball filled with concentrates CBALL, branches BRAN and scratching pole POLE) are investigated in study 2. In addition, the amount of social interactions was recorded.

Both horses kept individually (P < 0.05) and in groups (P < 0.0001) performed significantly more item-directed behaviours towards edible items like STRA and CBALL than other objects. There was, however, no overall relation between the numbers of item-directed behaviours and the number of passive behaviours observed, indicating that the enrichment items did not alone reduce the amount of passive behaviours during turnout periods. Such a reduction was, however, only apparent when horses spent more time eating green leaves growing on the paddock surface (R = −0.97 study 1, R = −0.67 study 2, P < 0.0001). Access to STRA in group kept horses also seemed to reduce the amount of agonistic behaviours (P < 0.0001). In conclusion, if grass is not available in paddocks, the provision of roughage reduces the amount of passive behaviours in singly kept horses and it also reduces the risk of agonistic interactions between horses kept in group.

Introduction

Turnout is generally regarded as positive for horses, as it gives opportunity for fresh air and voluntary exercise which is important for developing strong bones, joints and improving long term health in general (e.g. Dykgraaf et al., 2008, Rogers et al., 2008). However, experiments have shown that horses’ activities in such paddocks are rather limited and mostly linked to feed (Jørgensen and Bøe, 2007a). Longer periods of confinement increases the horses activity when turned out (Chaya et al., 2005), and when horses are actively exercised they become more passive during turnout (Jørgensen and Bøe, 2007a). Interestingly, horses display significantly more active behaviours when turned out in social groups compared to when kept individually (Jørgensen and Bøe, 2007b). Barren environments and social isolation have also been linked to many equine behavioural problems (Luescher et al., 1991, Waters et al., 2002) and stereotypies (e.g. weaving: Cooper et al., 2000). Despite this, the most common way of housing horses is still in individual tie-stalls or boxes inside barns (Bachmann and Stauffacher, 2002, Søndergaard et al., 2002). Welfare regulations in several countries demand that horses are given daily access to an outdoor paddock (e.g. Norway: Landbruks og matdepartementet, 2005), Denmark even recommends that young horses are kept in groups until they reach sexual maturity (Søndergaard et al., 2002). Even so, many horse owners prefer to keep their horses individually in paddocks during turnout, probably due to an unwarranted fear of injuries from social interactions (Grogan and McDonnell, 2005, Jørgensen et al., 2009).

Several studies have linked low reactivity and passive behaviours to a passive coping strategy and apathy that is probably related to high rather than low stress sensitivity (Koolhaas et al., 1999; review: Koolhaas, 2008, Nagy et al., 2009). In horses this means that passive horses might be prone to developing stereotypic behaviours like crib-biting (Nagy et al., 2010). In an attempt to reduce boredom, apathy and the risk of developing stereotypic behaviours, different objects, toys or feedstuffs are now commercially available. Only a few of these have been scientifically tested and only individually stabled horses where then used (Winskill et al., 1996, Henderson and Waran, 2001). A study on horses’ use of the “Edinburgh Foodball” revealed a reduction in concentrate ingestion, movement, nosing of bedding material and standing compared to control observations (Winskill et al., 1996). A significant reduction in time spent performing stereotypic behaviours was also found when testing the same feeding device on stabled horses displaying some form of stereotypic behaviour (Henderson and Waran, 2001). Newberry (1995) defined environmental enrichment as: “an improvement in the biological functioning of captive animals resulting from modifications to their environment”. There is, however, no standard criteria for assessing whether access to an object or item functions as enrichment for the animal in question. Studies on environmental enrichments for other domestic animals emphasize that such enrichments should stimulate foraging and exploratory behaviour (e.g. pigs: Van de Weerd et al., 2003) and further studies on pigs report a higher degree of manipulation of edible items like straw compared to other commercial objects like a “Bite Rite” chewing toy (Van de Weerd et al., 2005, Van de Weerd et al., 2006).

Environmental enrichments could be divided into four sub-categories: foraging opportunities, structural complexity, sensory stimulation/novelty, and social companionship (Newberry, 1995). In addition to provision of forage, the complexity of diets are important (Thorne et al., 2005) and objects could be provided that enable animals to groom or scratch in places they cannot reach themselves, as shown by the use of mechanical brushes for cattle (DeVries et al., 2007).

The aim of this experiment was to investigate the use of enrichment items during turnout, both for singly and group kept horses. We hypothesized that horses would react differently to edible items compared to other non-edible items. From this we predicted that:

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    Horses would show more item-directed behaviours towards edible items.

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    Horses would display less passive behaviours when given edible items.

We also hypothesized that horses in groups would react differently to items of “enrichment” than individually kept horses, and predicted that:

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    Horses in groups would pay less attention to items than horses kept individually.

Section snippets

Materials and methods

Two different studies were performed. The first and preliminary study aimed to discover which items individually kept horses would interact with, while in study 2 the four most popular items from the preliminary study were tested in six different groups of horses.

Item-directed behaviours

The horses spent significantly more time (in average 13.2% vs. non-edible items: 0.9% of tot. obs.) performing item-directed behaviours when exposed to edible items like straw (STRA), the ball with concentrates (CBALL) and branches (BRAN) (Table 4). The other items, however, were rarely touched by the horses, but this was probably not related to horses being afraid of the items since no events of “Keeping distance to items” were seen.

In the CBALL-treatment the horses spent most of the time

Discussion

Both horses kept individually and in groups performed more item-directed behaviours when given access to edible items like straw (STRA) and a ball filled with concentrates (CBALL). There was, however, no overall relation between the numbers of item-directed behaviours and the number of passive behaviours observed, indicating that the enrichment items did not alone reduce the amount of passive behaviours during turnout periods. Horses kept individually paid more attention to non-edible items

Acknowledgements

This experiment was funded by the Research committee at the Norwegian Equine Centre. We would like to thank Guro Vasdal for valuable comments on earlier versions of this manuscript. We would also like to extend our gratitude to Hallkjell Jensen and all participating horses and stable owners.

References (36)

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