Recent Advances in the Treatment of Equine Stereotypic Behaviour
Daniel Mills
Animal Behaviour Cognition and Welfare Group
University of Lincoln
Caythorpe Campus, Lincs NG32 3EP UK
Voice 01400 275629    Fax 01400 275686
dmills@dmu.ac.uk

Introduction

Stereotypic behaviour has been defined as behaviours, which are “repetitive and invariant with no obvious goal or function” (Mason, 1991a) and can be indicative of a situation in which the animal lacks a certain degree of control over its environment (Winskill et al, 1995; Fraser and Broom, 1990). Over 15% of domesticated horses have been reported to exhibit what are commonly termed ‘stereotypies’ (Luescher et al, 1991). Four behaviours are most commonly described as stereotypic in the horse: weaving, an obvious repetitive lateral swaying movement of the head, neck, forequarters and sometimes hindquarters; box walking, circular route tracing within the stable; crib-biting, grasping of a fixed object with the incisor teeth and engulfing air with an audible grunt; (McGreevy et al, 1995a) and windsucking a similar behaviour in which no object is grasped before the characteristic grunt made. Because of their similarity, the latter two behaviours are commonly classed together in many studies. Mills et al (2002) in a review of declarations of animals presented at sales found that the risk of having oral and locomotor stereotypies were independent of each other, but not the two forms of locomotor stereotypy. Nicol (1999) also suggests that wood chewing may be functionally related to the oral stereotypies described, as it often appears to be a precursor to them. In her review of the various epidemiological surveys of these behaviours she reports that in the surveys, the mean rate of each reported in these studies were 4.13% for cribbing, 3.25% for weaving, 2.20 % for box walking and 11.78% for wood chewing. The figure varies with management and individual factors (McGreevy et al, 1995b), but even so this generalisation is probably an underestimate of the true prevalence as the only longitudinal study reported to date has generally found much higher rates (10.5%, 4.6%, 2.3%, 30.3% respectively).

Commonly Reported Techniques and their Reported Efficacy

These behaviours are of welfare concern (Mason, 1991b) and cause problems for owners and managers, who often believe the behaviour can be learned, and can harm the horse, resulting in the use of many techniques aimed at preventing the behaviour. Crib-straps and anti-weaving bars are used most frequently in this regard, by an estimated around 60% and 70% of yards in the UK respectively (McBride and Long, 2001). Other less common techniques include the removal of surfaces on which cribbing may occur, electrification of cribbing surfaces, the hanging of obstacles at the front of the stable to prevent weaving, tying up and obstructing the path of box walkers, (McBride and Long, 2001). It is however, important to consider the welfare implications of these techniques, and prevention in the case of stereotypy is a cause for concern (Cooper and Mills, 1997; McGreevy and Nicol, 1998; Mcbride and Cuddeford, 2001). A variety of other management changes have been suggested and these appear to vary in their reported efficacy, (Table 1) but there have been few experimental studies into these techniques. 

Recent Innovations in the Management of Weaving

Several epidemiological surveys (McGreevy et al, 1995a; Redbo et al, 1998) have found that weaving tends to be more common in horses with lower levels of social contact. However, it is impossible to determine whether this relationship is a causal one from this type of study, and given the concern owners have in these behaviours being copied, isolation might reflect a management decision in response to the identification of the behaviour in an individual. Our own group at the University of Lincoln  (Cooper et al, 2000; Mills and Davenport, 2002; McAfee et al, 2002) has however examined this relationship between social contact and weaving experimentally. Current results are summarised here. 

Initial studies (Cooper et al, 2000) found that horses allowed social contact with a conspecific through a 1 metre square barred window reduced their weaving by 97% on average, head-nodding in the stable was also reduced. Comparison of the effect of a mirror in the same location with social contact found no significant difference in the two treatments, with on average an 85% reduction achieved by the increased social contact and a 77% reduction with the mirrors (Mills and Davenport, 2002). However in all of these studies treatment was relatively short (1 week) and so a novelty effect could not be ruled out. McAfee et al (2002) examined the effect of a mirror over a more prolonged period in a greater variety of settings. All horses had been known to weave for at least two years, and a consistent reduction in weaving (by around 97% on average) was again found throughout the five weeks of treatment. There was also a decrease in repetitive head nodding and head threats, which has not been reported previously. It is possible that these effects are related since both stereotypy and aggression are believed to be a common consequence of frustration (Duncan and Wood-Gush, 1971).

Implications. The efficacy of the treatment in a population in which the behaviour has clearly become established, also questions whether these behaviours become emancipated as has been suggested for stereotypic behaviour in other species (Cooper et al, 1996). Two types of repetitive, relatively invariant behaviour are commonly recognised in man, those, which relate to the persistent triggering of a specific motor pattern (stereotypy) and those which relate to attaining a recurrent goal (obsessive-compulsive behaviours). It may be that this distinction needs to be made when considering apparently stereotypic behaviour in the horse, since they may share more with the latter than the former, being less of a fixed behaviour and more of a fixation, which can be treated by satisfying the goal. Recently we have examined the nature of the significant factor further through the use of poster images, and preliminary results suggest that it is the image of the horse which is the significant  factor producing the effect, further reinforcing the hypothesis, that weaving occurs as a result of social frustration. These results will be discussed further at the meeting. Preliminary feedback from case studies, also suggest that the mirror is effective in reducing box walking, which is not surprising given the interaction between the behaviours reported by Mills et al (2002).

Recent Innovations in the Management of Crib-biting

Both McGreevy and colleagues (1995a) and Redbo and colleagues (1998) have also reported that cribbing appears to be associated with the feeding of concentrates, which supports the observation of Fitzwygram (1911) who reported that the condition “most commonly … arises from some form of acidity …of the stomach”. In 1888, Mayhew suggested that the condition could be prevented if treated in the early stages with “ a lump of rock-salt in the manger; (and) a large piece of chalk; should these be unavailing, always damp the food, and, at each time of feeding, sprinkle magnesia upon it, and mingle a large handful of ground oak-bark with each feed of corn.” This observation appears to have been forgotten and not tested experimentally on subjects of any age until recently. In 1997 a pilot study (Mills unpublished data) was conducted using a commercial antacid preparation (Rennie, Laboratoires Roche Nicholas SA, France) (Fig 1). This suggested that treatment with antacids might have the potential to significantly reduce cribbing. Coincidentally at around the same time, Nicol (1999) was suggesting that these oral behaviours, including wood chewing, might be an attempt to increase alkaline saliva flow to reduce the increased acidity associated with feeding concentrate rations. Thus providing a potentially sound scientific basis to the mechanism behind the effect seen. Crib-biting in foals has subsequently been found to be associated with gastric ulceration (Nicol et al, 2001) and we have recently completed a double-blind placebo-controlled field study into the use of antacids for the control of cribbing in adult horses (Mills and Macleod, manuscript submitted). The results of this study will be presented.

Table 1 Management changes for the control of equine stereotypic behaviour and their reported success, (data from McBride and Long, 2001)

Fig 1. Effect of six “Rennie” tablets at feeding time on the rate of cribbing immediately post feeding in a single subject

References

Cooper JJ, McDonald L, Mills DS (2000) The effect of increasing visual horizons on stereotypic weaving: Implications for the social housing of stabled horses. Appl Anim Behav Sci 69: 67-83.

Cooper JJ, Mills DS (1997) Welfare considerations relevant to behaviour modification in domestic animals. In Mills DS, Heath SE, Harrington LJ (Eds), Proceedings First International Conference on Veterinary Behavioural Medicine, Potters Bar: UFAW, pp 164-173.

Cooper JJ, Odberg F, Nicol CJ (1996) Limitations on the effectiveness of environmental improvement in reducing stereotypic behaviour in bank voles (Clethrioonomys glareolus). Appl Anim Behav Sci 48: 237-248.

Duncan IJH, Wood-Gush DGM (1971) Frustration and aggression in the domestic fowl. Anim Behav 20: 500-504.

Fitzwygram F (1911) Horses and Stables 5^th ed., Longmans, Green and Co London, p 99.

Fraser AF, Broom DM (1990) Farm Animal Behaviour and Welfare. Bailliere Tindell, London.

Luescher UA, McKeown DB, Halip J (1991) Reviewing the causes of obsessive-compulsive disorders in horses. Vet Med 86: 527-531.

Mason GJ (1991a) Stereotypies: A critical review. Anim Behav 41: 1015-1037.

Mason GJ  (1991b) Stereotypies and Suffering. Behav Proc 25: 103-115.

Mayhew E (1888) The Illustrated Horse Doctor 16^th ed. WH Allen and Co, London, pp 168-171

McAfee LM, Mills DS, Cooper JJ (in press 2002) The use of mirrors for the control of stereotypic weaving behaviour in the stabled horse. Appl Anim Behav Sci.

McBride SD Cuddeford D (2001) The putative welfare-reducing effects of preventing equine stereotypic behaviour. Anim Welf 10: 173-189.

McBride SD, Long L (2001) Management of horses showing stereotypic behaviour, owner perception and the implications for welfare. Vet Rec 148: 799-802.

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McGreevy PD, French NP, Nicol CJ (1995b) The prevalence of abnormal behaviours in dressage, eventing and endurance horses in relation to stabling. Vet Rec 137: 36-37. 

McGreevy PD, Nicol CJ (1998) Behavioural and physiological consequences of short term prevention of crib-biting in Thoroughbred horses. Physiol Behav 65: 15-23.

Mills DS, Alston RD, Rogers V, Longford NT (2002) Factors associated with the prevalence of stereotypic behaviour in Thoroughbred horses passing through auctioneer sales. Appl Anim Behav Sci, in press.

Mills DS, Davenport K (2002) The effect of a neighbouring conspecific versus the use of a mirror for the control of stereotypic weaving behaviour in the stabled horse. Anim Sci 74: 95-101.

Mills DS Macleod CA (manuscript submitted) The response of crib-biting and windsucking horses to dietary supplementation with an antacid mixture. Appl Anim Behav Sci

Nicol CJ (1999) Stereotypies and their relation to management. In Harris PA, Gomarsall GM, Davidson HPB, Green RE (Eds), Proceedings   BEVA Specialist Days on Behaviour and Nutrition, pp 11-14.

Nicol CJ, Wilson AD, Waters AJ, Harris PA, Davidson HPB (2001) Crib-biting in foals is associated with gastric ulceration and mucosal inflammation. In Garner JP, Mench JA, Heekin SP (Eds), Proceedings 35^th International Congress of the ISAE. UC Davis California, p 40. 

Redbo I, Redbo-Tortensson P, Odberg FO, Hedendahl A, Holm J (1998) Factors affecting behavioural disturbances in race horses. Anim Sci 66: 475-481.

Winskill LC, Waran NK, Young RJ (1995) Stereotypies in the stabled horse: Causes, treatments and prevention. Curr Sci 69: 310-316.