In a previous article, the Hoof Blog described a study conducted in New Zealand to survey the way sport horses in that country are shod, and what management aspects may affect the condition of feet. (Please see the article "Research: farriery and hoof care trends for dressage, showjumping sport horses in New Zealand".) Now the New Zealand hoof researchers move on to the racetrack.
This month, the Journal of Equine Veterinary Science is publishing the next in the Massey University (New Zealand) foot research series; it is a survey of Thoroughbred racehorses and the incidence of flat feet. The abstract of "A cross-sectional survey of forelimb hoof conformation and the prevalence of flat feet in a cohort of Thoroughbred racehorses in New Zealand" can be viewed online now with library or subscription access. A summary is provided here.
Also this fall, the Equine Veterinary Journal published a related abstract, “Centre of Pressure Between the Forelimbs in a Cohort of Thoroughbred Racehorses.”, which was presented at the International Conference on Equine Locomotion this summer. The full abstract may be viewed online at no charge.
For the conformation study, the researchers collected data from 75 Thoroughbreds in training ranging from two to five years old; most had been shod two to three weeks before the data was collected. They also measured hooves from the lateral, dorsal and solar aspects.
|Dorsal view of the quantitative measurements that were taken. MWH= medial wall height, LWH= lateral wall height, CS= coronary span. (Image from research document)|
Although conformational deviation was noted in only 20 percent of the horses, more than half the horses in the study had uneven sulci in at least one foot and/or some degree of higher medial hoof wall. In addition, the researchers found that 28 percent of the horses had at least one flat foot, usually the left front.
Conclusions of the study included that:
• Many racehorses presented uneven sulci depth
• Flat feet were commonly the left (front) foot
• Mild deviations from the ideal may still be a functional foot in the racing Thoroughbred
"The study identified that while most feet were 'within normal bounds', there was a strong trend for a larger and flatter left (front) foot," research Chris Rogers, PhD, shared via email. "All the horses in our region train counter-clockwise, or left handed (track turns, as in the USA)."
"In an earlier study, we found some very interesting differences between the medial and lateral bone mineral density profile of the left and right forelimbs of horses trained counter clockwise," he continued. "So we have a working hypothesis that this (flat foot) observation may be due to the loading of the limb when racing and training – rather than a farrier effect.
"We think there is a training-related asymmetry in bone response and possibly hoof response to training (as the hoof is a dynamic tissue). Leading on from this, we have been using a Footscan® pressure plate to prospectively follow a cohort of racing Thoroughbreds to observe any changes in center of pressure oscillation and limb loading.
"We are using this technique as human medical trials have shown this technique can pick up the early signs of knee osteoarthritis (OA) before clinical signs are present – i.e., before that patient if fully aware they have OA in their knees – so, theoretically, it is a very sensitive technique. We found that there are training-related changes in the size and the frequency of the oscillations of the centre of pressure associated with increasing training load (so shorter and faster shuffles when standing still).
“We also found that when standing still the loading of the limb is the exact opposite of what we saw with CT scans (in a previous study) – so these horses are offloading the regions that were under the greatest strain when race training.
“In short, we think we are developing a non-invasive way to work out what is happening with the limb during race training and now want to link this with what we see is occurring with the hoof.”
A typical Footscan® image from Massey University. The right (on the left) foot shows brighter color, indicating greater loading, even when at rest.
Read the original research papers:
Lichtenauer E., Fitch G., Colborne G.R., Reid K., Back W. and Rogers C.W.(2016), Centre of Pressure Between the Forelimbs in a Cohort of Thoroughbred Racehorses. Equine Vet J, 48: 14. doi:10.1111/evj.19_12595
Wilna Labuschagne, Chris W. Rogers, Erica K. Gee, Charlotte F. Bolwell, A cross-sectional survey of forelimb hoof conformation and the prevalence of flat feet in a cohort of Thoroughbred racehorses in New Zealand, Journal of Equine Veterinary Science, Available online 5 December 2016, ISSN 0737-0806, http://dx.doi.org/10.1016/j.jevs.2016.11.013.
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