The horse population in the UK is currently reported to be around 1 million (Anon, 2005), from this the annual number of journeys undertaken can be estimated at over 2 million, and it is reasonable to assume that there are;
- A large number of horses who do not travel well.
- Owners that are prevented from attending events by horses unable to tolerate travel.
- Competition horses under-performing on arrival due to the ill-effects from and/or energy expended during a stressful journey.
- Horses that do not travel well when alone – but have no available companion.
Although some of the physiological and behavioural responses during transport can be accounted for by the journey itself, it is known that during isolation herd animals exhibit a stress response as part of their coping mechanism, manifested by an abnormal or extreme adjustment in behaviour or physiology (Kiley-Worthington and Wood-Gush, 1987; Boissy and Le Neindre, 1997; Broom et al., 2002; McDonnell, 2003). In non-transportation situations previous investigations into the effects of isolation in horses have documented both physiological and behavioural effects (Sweeting et al., 1985; Alexander et al., 1988; Houpt and Houpt, 1992; Jezierski and Gorecka, 1999, 2000; Strand et al., 2002), and tachycardia has been documented in horses transported alone by Erichsen and Rootwelt (1994). Maintenance of visual contact with other horses inside a vehicle could therefore influence these effects.
Measurement of such adaptive responses can provide some idea of the extent to which a horse has been challenged by a journey. Because the degree of stress encountered can have a deleterious effect on the horse’s capacity to grow, reproduce, train, and maintain health in the long term, identifying and minimising stressful situations could protect the performance and economical potential of the horse (Baucus et al., 1990; Stull, 1997; Broom et al., 2002).
In situations where herd animals must be handled individually, environmental modifications such as a mirror-image could possibly be used to reduce isolation stress. If effective, this may improve the welfare of an isolated animal by reducing the level or fear or stress experienced (Piller et al., 1999). It is known that increasing visual horizons and creating surrogate companionship can reduce the incidence of stereotypies in the horse (Cooper et al., 2002; Mills and Davenport, 2002; McAfee et al., 2002), and exposure to a mirror has been documented to reduce the stress response during isolation of cattle (Piller et al., 1999) and sheep (Parrott et al., 1988; Parrott, 1990).
Because surrogate companionship in the form of a mirror has elicited a positive result in the stable, mirrors for use during transportation are now commercially available. No published studies however, have been carried out to support or refute the effectiveness of these products. Isolation from herd mates and the effect of creating surrogate companionship during transportation are the two factors that are investigated during this study. Studies by Ingram et al. (2002), Lowe et al. (2005) and Yu and Blessing (1997) suggest that changes in ear-pinna temperature can be used as a sensitive, non-invasive measure of activation of the defence reaction in prey species. As little is known about peripheral temperature changes in response to stress in horses, this parameter in addition to heart rate and behaviour are measured during this study.