Why do so many ex-racehorses have bad feet? This very interesting question was asked to me recently and the answer is complexed. There is no denying that farriery plays a huge role in the answer to this question, but it goes well beyond simply good or bad shoeing, there are many factors, macro and micro conformation, shoeing cycles, work load, type of work and management to name a few. Aside from the fact that racing is tough on the musculoskeletal system and past injuries are almost inevitable in an ex racehorse, what factors cause specifically weak feet?
Firstly, lets establish the normal life, farriery wise, for a racehorse in a professional yard and look at some studies that have quantified the effects on the thoroughbreds hoof and musculoskeletal system.
They are broken in at around 18months old and already would have been shod, they are then shod on average once every 4 weeks and often more, they are, in general, very well managed, with clean stables that they spend the majority of their time in when not working. They wear light shoes with small nails and spend most of their time cantering or galloping the same way round a track on surfaces specifically for racing. Studies into the effect of this life on the horse and its hoof have been extensive, effects of the training on musculoskeletal development higher up have been examined, Watson et al (2003) showed 76% of thoroughbred racehorses to have a larger right third metacarpal perhaps due to the continued work around the track in one direction, hinting at asymmetries effecting coordination and balance and Pearce et al (2005) questioned whether common femoral asymmetries were congenital or acquired through workload, these skeletal asymmetries could perhaps point at why many thoroughbreds have high-low hoof conformation.
Peel et al (2010) expressed a reduction in hoof angle as a result of gallop training, this is significant in understanding why “flat” feet are ubiquitous in the ex-race horse population, Labuschagne et al (2017) added to the power of this statement by indicating “flat feet” are a “typical presentation of thoroughbred feet” also complimenting the theory of asymmetrical pairs of hooves being caused by one directional training.
This image shows a comparison between a common thoroughbred hoof and a cob hoof. The thoroughbred inherently has a much steeper angle and in this case is broken back, proportions were restored with a duo ellipse graduated shoe. The cob foot is much more upright and is stronger all round.
The effects of race training go well beyond the hoof and effects the entire musculoskeletal system, we know that the hoof morphs according to the forces acting upon it, so all these effects of training will have influence on hoof morphology to varying degrees.
We must of course remember that thoroughbreds are bred for speed, and what lends itself to speed often doesn’t lend itself to durability, the micro conformation of the thoroughbred perhaps favours acceleration and maintained speed but smaller feet, thinner walls, less digital cushion and thinner lateral cartilages will inevitably fail sooner than more heavy weight structures. Read my article on conformation for further info.
Brown (2017) discussed this subject and eluded to the short shoeing cycle of race horses plus their management exacerbating the deterioration of the hooves, the author, while not disagreeing with this, would offer the thought that the shoeing cycle actually helps to mitigate and go some way to controlling the effects of the thoroughbreds hoof conformation and training. We know from studies that hoof growth effects the forces acting on the hoof and its internal structures (Van heel et al 2004,2005, moleman et al 2006) creating the potential for negative hoof morphology from the moment the foot is placed on the ground after shoeing, so more regular shoeing may help stop this factor playing a role in hoof deterioration by keeping the biomechanics more optimal.
This picture expresses how a low angled hoof will gain a greater proportional amount of base length for every unit of height removed from the heel, conversely this shows how the low angled feet of thoroughbreds will grow out of balance comparatively quicker in the dorso-palmer plane than a more upright foot for the same amount of hoof growth. This highlights the importance of much shorter shoeing cycles with thoroughbred feet, often once removed from the racing world owners and their farriers will use the phrase “he doesn’t grow much foot, he can go longer.” Or something of the like, but understanding hoof morphology we can see that this is contraindicated, something eluded to in Moleman et al (2006) which stated that low hoof angles had a larger increase in moment force around the distal interphalangeal joint (DIPJ) from hoof growth over 8 weeks.
Shoeing cycle is one of the factors that causes the poor hoof morphology once these horses are no longer in that world, once they leave the racing industry they enter a world of relative chaos! Shoeing cycles range from 5 weeks to 8 weeks and depend on budget, work load and misconceptions on hoof growth, turnout becomes random and often inappropriate, feed changes, work load becomes inconsistent, sometimes hacking daily, trotting down the hard road in their now much heavier shoes with a heavier rider, just to name a few variables! The flat, weak feet inherent of the breed and exacerbated by the training which have low elastic moduli are now suddenly becoming overloaded.
An unfortunate reality is that ex racehorses are relatively cheap to acquire but their conformation, working history, acquired and congenital weak feet, mean they are, or perhaps should be, expensive to keep. Aside from being higher maintenance than other breeds we must appreciate that their feet will also need more involved care. The findings of Peel et al (2010) and the micro conformation eluded to in Labuschagne et al (2017) mean they will be prone to weak heels, thin walls, thin soles, broken back hoof pastern axis’, prolapse of bulbs, frog and sole and these all predispose to pathologies such as navicular, bruised soles, abscesses etc, therefore farriery intervention needs to mitigate as many of these as possible.
This image shows a common radiographic presentation of an ex-racer with poor feet. A broken back hoof pastern axis, long toes, low heels and flat pedal bone, this strongly predisposes to navicular which is a very common pathology affecting these horses. Farriery intervention is vital in longevity of working life. Caldwell (1987) debated the existence of pre-navicular syndrome expressing the conformation in the above image, it stated poor hoof morphology perpetuates due to the sub-optimal forces acting on the hoof over time leading to the development of the pathology. Caldwell (1987) expressed the lack of recognition and inappropriate farriery intervention as being exacerbating factors, it also outlined the environmental factors adding to the deterioration. It discussed the interruption of blood flow due to standing in for the majority of the time, showing the routine during racing life perhaps being a contributing factor but also outlined excessive moisture being a negative factor, showing the importance of sensible management with these feet. These findings correlate with the authors experience that many ex-racers are bordering on, if not showing, signs of pre-navicular syndrome due to conformation, training and environmental factors.
The important factors in the authors experience in shoeing ex-racers are
A short shoeing cycle – As hoof growth in low angle hooves increases the moment arm around the DIPJ and moves the centre of pressure caudally toward the heels which will cause crushing of the heels due to the low elastic modulus.
Shoeing around the centre of rotation (COR) – Poor hoof morphology often means long toes and low heels and poor dorso-palmer balance, the biomechanical forces need to be optimised to create an environment for positive morphology. Long toes need controlling and weak heels need support.
Frog/solar support – When putting a rim shoe (on a weak hoof) the load is borne peripherally leading to further prolapse, padding will spread the load over a larger area reducing the pressure on weak structures. Padding will also create protection to thin soles and support the internal structures.
Using padding also engages the haemodynamic system which plays an important role in concussion dampening, blood perfusion and supporting the weight of the horse. This is one of the most important factors in hoof health.
https://www.theequinedocumentalist.com/post/haemodynamic-mechanism-the-key-to-hoof-health
Mechanical shoeing – Often ex-racers will need work to create ideal hoof proportions, this can include different types of shoes and modern materials, roller motion shoes, ellipse shoes (flat or graduated), timeline shoes, graduations etc. creating ideal proportions of the foot creates ideal forces acting on that foot encouraging positive hoof morphology.
Owner management – The inherent fragility of thoroughbred feet means they are often more susceptible to environmental factors such as anaerobes which can break down the feet/frog and in the authors experience can be more readily affected by changes in environment such as wet-dry. The fact that they often need heel support means lost shoes can be a factor. These points put a responsibility on the thoroughbred owner to play their part, to perhaps create an environment more closely resembling a professional racing yard, of course in balance! as the author doesn’t wish to take away the fact that many prefer to allow their animals a more free existence.
All of this lends itself to possibly an expensive and regular maintenance routine and unfortunately farrier and/or owner ignorance can lead to very negative hoof morphology very quickly. However in the authors experience with patience and conscientiousness thoroughbreds can respond very well to going barefoot! So in conclusion, bad feet in ex-racers can be somewhat attributed to their breeding, their training during their working life, and their management after, they can’t be treated the same as a cob who is shod every 8 weeks and only needs basic shoes, they inherently have a different hoof angle and different hoof conformation in general, meaning different shoeing cycles and more involved farriery and management.
References
The effect of gallop training on hoof angle in Thoroughbred racehorses
First published: 10 June 2010
Influence of different exercise regimes on the proximal hoof circumference in young Thoroughbred horses
First published: 05 January 2010
Laterality in stride pattern preferences in racehorses
A Cross-Sectional Survey of Forelimb Hoof Conformation and the Prevalence of Flat Feet in a Cohort of Thoroughbred Racehorses in New Zealand
Shoeing the racehorse… after training
Published Online:13 Sep 2017https://doi.org/10.12968/eqhe.2017.37.21
M. Caldwell, 1987, Pre-navicular syndrome, personal correspondance