Early kinetic activity

Simple movements initiated by the developing fetus can be detected from only a few months old and include limb stretching, becoming more complex and coordinated as it matures. Once born, the foal becomes mobile through a series of stages described by Fraser (1992) that result in teat seeking and sucking. Foals differ in their ability to achieve each stage of mobility, but usually they are stable on their limbs within hours of birth (Fig. 16.2). Its interesting that although most foals are able to walk, canter and suckle very soon after birth, they need a few days to develop the skills needed for lying down and standing up. Many foals will literally fall asleep on their feet, during their first days of life, illustrating that even in precoccial species, complex locomotory movements need to be learned and practiced. It is worth considering how much the intensive housing of foals at this early stage may hamper the development of many behaviors, including locomotion.

One of the primary activities foals engage in is stretching, which seems to be of greatest importance during the first few weeks after birth. Foals have been observed to perform this activity 40–60 times each day (more than sucking) (Fraser, 1992). It is suggested that both recumbent and upright stretching are important for athletic development, growth and joint formation. Especially in the first 10 days of their life, foals are engaged in many short bouts of solitary locomotory play around their dams, allowing their muscles to develop.

Grazing

During the first week of life the mare and foal spend approximately 90% of their time within 5 m of each other (Waring, 2003). During these early weeks, the mare repeatedly leaves the foal and moves a short distance away, and the foal follows. This following behavior is an instinctive tendency in a foal, refined through learning during the first week of life. Over time, the mare and foal will spend more time apart, until by the age of 1 year the youngster may be grazing for approximately 44 min/h alongside the rest of the herd. Grazing involves moving whilst foraging, an activity that horses in their natural state will perform for around 16 h each day depending on their physiological and reproductive state, the time of year, available forage and weather conditions. Thus horses have evolved to spend much of their time moving slowly with their head and necks lowered, whilst selecting suitable forage. In the natural environment, horses may travel up to 80 km during grazing and for water, and even when kept on restricted pastures, horses are estimated to move around 20 km each day (McGreevy, 2004). Increased locomotory activity has been found in horses kept socially isolated from others in which case they will walk and trot three times more frequently than horses kept in groups or in visual contact with another horse (Houpt & Houpt, 1989), apparently to try to get into more close contact with conspecifics.

Play

Apart from movement associated with following and grazing with the herd, the foal engages in various locomotory activities described as play (Fig. 16.3). There appears to be no universally agreed function or homogeneous character to define play, but it is apparent that play has survived the pressures of natural selection and is an almost universal trait in mammals. There are a number of proposed functions which include development of social skills (Fraser, 1992); motor strength and co-ordination; behavioral flexibility (Spinka et al., 2001) and cognitive training. In horses, play occurs most frequently in younger animals, with colts performing more than fillies (Kurvers et al., 2006). When the spontaneous locomotion activity of foals kept under various management conditions was compared (Kurvers et al., 2006), it was found when foals were kept for 24 h/day at pasture, they exercised at a level comparable with feral foals. Interestingly the total observed daytime workload in the first month of life was approximately twice that of the following months, while locomotion activity decreased with increasing age. Foals that were stabled for some portion of the day appeared to engage in compensatory locomotion activity. However this was insufficient to reach the level of locomotion of foals kept continually outside (Kurvers et al., 2006).

There have been relatively few studies of play in non-domestic equids and where recorded this has generally been anecdotal, but social and solitary-locomotor play have been recorded in Hartmann’s zebra foals (Joubert, 1972) and also in captive juvenile Przewalski horses (Zharkikh, 1999) as well as in free-ranging and feral horse populations in the UK and USA (Tyler, 1972; Berger, 1986). In these groups, the majority was social play behavior with activity patterns including: play fighting, neck wrestling and chasing and with solitary-locomotor play including gamboling, high speed turns and sudden stops (see Goodwin & Hughes, 2005). During play, absolute force values as exerted on the developing tissues are probably not substantially different from those created by cantering, but play activities result in other loading directions, including eccentric loading and loading in the sagittal plane, which might be important for the development of musculoskeletal structures (Kurvers et al., 2006) (see Chapter 13).

The findings of various studies suggest that (24 h) pasture-based management systems for foals may be superior to more intensive management systems due not only to the recognized advantages of social interaction with other mares and young foals but also the physical gains due to increased and varied locomotion in early development. One of the impacts of the pressures of producing horses as early in the season as possible, as is the case in the Thoroughbred racing industry and many sports horse registration schemes, is that in some climates, it is difficult to persuade breeders of the social, mental, physical and thus welfare advantages of the pasture-based system, when their foals are being born during the coldest months of the year.

Development of laterality (sidedness)

Equine laterality (or sidedness in horses) has been investigated in relation to equine performance and training as well as trying to understand the underlying factors that lead one horse to favor a left lead over a right leading leg. In a series of studies, (van Heel et al., 2006; Kroekenstoel et al., 2006; van Heel et al., 2010) healthy jumping bred KWPN foals were born and raised outside at the same location, and were then followed weekly for a year to observe the development of laterality (Fig. 16.4).

They were assessed at 3, 15, 27 and 55 weeks of age for pressure distribution under their feet (to determine the Centre of Pressure), external and internal development of the foot including phalangeal development and ‘handedness’ (or side preference). In addition several conformation measures were made such as relative leg length and head size, heel height and toe angle. It was shown that about 50% of the foals developed a significant preference for protracting the same limb systematically while grazing, which resulted in changes to the balance of their feet and subsequently uneven loading patterns. There was no overall preference for either left or right sidedness, with an even distribution between the two sides. However it appears that foals with relatively long limbs and small heads were predisposed to develop laterality and, consequently unevenness (van Heel et al. 2006, Kroekenstoel et al. 2006).

Seventeen of these horses were tested again when 3 years old, after they had only been handled for normal management procedures like trimming and de-worming (van Heel et al., 2010). The assessments revealed that the laterality as well as the unevenness still existed, but the relationship between the body conformation and the unevenness had weakened. In addition when these horses were also assessed in free trot to canter transitions and free jumping, laterality and unevenness were strongly related to incorrect transitions (either disunited canter or counter-canter) (Fig. 16.5).

Since in ridden horses there is a preference for left sidedness (McGreevy & Rogers, 2005; McGreevy & Thomson, 2006), the results of studying 3-year-olds suggests that left sidedness can be induced by the human interaction with the horse, which, in most cases, is predominantly from the left side of the horse. Apart from the concern that horses with strong lateral preferences might be more prone to overloading injuries of the distal limb it is also interesting to note that this could relate to performance problems later in life. For example: horses may be less balanced when running around racetracks that run to the left or right, or have problems with picking up the correct lead in canter when under saddle. There is a need for more applied work in this area to determine how motor laterality can be influenced through breeding, environment and training.

Feeding

The effects of diet on equine locomotory responses has received surprisingly little scientific attention, despite the fact that many sports horses are fed high-energy diets in order to boost performance. A study by Nicol et al. (2005) examined the effect of different feeds on the behavior of foals aged from 2 to 40 weeks. Each foal received either a starch and sugar (SS) diet, or a fat and fibre (FF) diet, and their behavior was monitored immediately after weaning. The results showed that horses receiving the FF diet cantered less frequently and for a shorter duration and the authors described the foals receiving the fat/fiber diet as more settled. This suggests that at least during a stressful time such as occurs at weaning, high-energy diets appear to be associated with increased locomotion. However, inappropriate or over-feeding high-energy foods to horses is also known to be associated with unwanted locomotory responses, such as explosive reactions to signals (aids), and this is particularly the case for horses housed in stables (Riveria et al., 2002). Hyperactivity responses, including shying, pulling, bolting, and rushing could all be considered to be the result of a restricted environment, lack of exercise and too much sugar/starch in the diet. It is likely that the behavioral problems often experienced by horse owners and that lead to poor owner–horse relationships, and thus lower equine welfare, could be prevented through improved understanding of the effect of food and feeding on horse behavior and by providing the horse with a more natural time-budget including access to an area to enable it to perform a normal locomotion pattern.