Barefoot Research: What Are the Consequences of Shoe Removal for Trotting Racehorses?

How are the health, comfort and wear of the horse's feet affected when shoes are removed for racing? A research special report from Hippolia Foundation and CIRALE-ENVA

Text and images © CIRALE-ENVA and/or Hoofcare Publishing 

No reproduction or copying without permission

Professor Denoix

Special thanks to researcher Claire Moiroud and Professor Jean-Marie Denoix, who kindly arranged to share this research project with Hoofcare Publishing. This text is an approved, verbatim translation of a French document and is published to coincide with the excitement of the Prix d’Amerique, one of the world’s great trotting races, at Vincennes, France on Sunday, January 25. That race has been won by horses using the methods described in this article.

Introduction
In French harness racing, it is customary for the trainer to remove the shoes of some horses before races. "Relieve the foot, increase the speed"...that is the goal. Perhaps the immediate benefits seem obvious, but no study has addressed the risks to the horse itself in terms of possible discomfort and especially the risk of excess wear to the feet. That has now been accomplished through the work of the CIRALE-ENVA Hippolia team in Normandy, France.

• • • • •

Researcher Moiroud

The practice of “de-shoeing” before a race has become common for French trotters. It may involve all four feet of the horse or only the front or hind pair. Professional trainers contend that the shoe removal allows some horses to improve a gait irregularity, improving the flight arch of the feet during the swing phase. But this practice would mainly be done to increase the horse’s speed.

Statistics published in the professional racing press in France show that horses do tend to perform better when their shoes are removed before a race, and that these performance statistics can influence the betting public. For this reason, since 2009, trainers in France have been required to state in the race entry conditions whether a horse will race shod or unshod.

Previous scientific studies have shown that reducing foot weight, by removing the shoes, allowed an increase in stride frequency (Chateau et al, 2012). However, no study has investigated the impact of this practice on the deep tissues of the foot, and more generally on the horse's comfort. 

Hoof images after a race, shod and unshod

One of the digital record photos for a shod Standardbred foot. The shoes were removed and replaced on the test horses according to the customs of the French trainers who follow the shoe removal practice before races. This photo records the appearance of a test horse's foot after a race when it was wearing a shoe. © CIRALE-ENVA

This "after" photo shows the appearance of the sole of the same horse after racing without shoes; its shoes had been pulled and it had been through a race. Extensive image sessions and measurements were conducted before and after each race simulation, including radiography so that precise measurements of the external hoof capsule in relation to inner structures could be recorded. © CIRALE-ENVA image.

Now it is known that the practice of shoe removal causes wear of the hoof and that if the practice is repeated at short intervals, it may cause a reduction in the protection of the inner tissues by the sole and the wall.

In this context and in order to preserve animal welfare, the Société d’Encouragement à l’élevage du Cheval Français (SECF) tried to find out the best way to control the practice of horseshoe removal at trotting races for several years.

Currently, French race regulations prohibit shoe removal on young trotters two and three years of age. In order to assess whether to regulate the removal of shoes on horses older than three years, the SECF wanted to know the impact of shoe removal on the health of racing trotters.

For this, the Society solicited the aid of equine locomotor pathology specialists Professor Jean-Marie Denoix and the Hippolia team at CIRALE (Center for Imaging and Research on Equine Locomotor Disorders) of the National Veterinary School of Alfort (ENVA) in Normandy, France.

The objective of the study, conducted in the fall of 2013 with funding from the SECF, was to analyze the impact of racing when the shoes were removed from the feet of trotters. (Was there potential harm or pain in the structures of the foot or the lower joints?) The goal was to provide a scientific basis for evaluation by the SECF for a possible change in the regulation of races to avoid endangering the health of the horse.

The route of Cabourg Racecourse, a sand racetrack with righthand turns (horses race clockwise) © CIRALE-ENVA

The study was conducted on six French trotters, aged four and five years, over a period of six weeks with these procedures:

• Each week, the horses performed the same training, with a workout of 2800 meters on Racecourse Cabourg.
• Every 15 days, four of the horses were unshod for their test; their four shoes were pulled. The other two remained shod as normal (control group).
• A standardized clinical examination, focusing on the feet, was performed before and after the test. These tests included a photo monitoring, evaluation tests of the sensitivity of the feet and the evaluation of each horse’s locomotion on a treadmill at 30 km per hour, via high speed video.
• To assess the possible impact of shoe removal on the inner tissues of the foot (bones, joints, tendons and soft tissue), four imaging techniques were used: x-ray, ultrasound, scintigraphy and magnetic resonance imaging (MRI).
• Radiography also allowed the researchers to precisely measure the wear of the hoof horn at the wall and sole.
• Along with studying the impact of shoe removal on the musculoskeletal system, researchers performed an evaluation of the overall comfort of the horse by measuring blood parameters for the main stress markers (cortisol and adrenaline) and monitoring the frequency and rhythm of the heart.

Evaluation of a Standardbred on a treadmill at high speed: 30 km per hour for the analysis of gait and measuring stride length © CIRALE-ENVA

The results of the tests showed that the differences between the two groups of horses were visible from the time of first shoe removal: removing shoes for racing caused sensitivity of the horse’s foot and a discreet bone inflammation of the distal phalanx (P3, coffin bone) developed after the race; sensitivity and bone inflammation increased during successive shoe removals for additional racing tests.

Sole sensitivity evaluation test (digital pressure hoof testers to standardize the pressure force exerted on the foot) © CIRALE-ENVA

Shoe removal also caused a slight increase in the secretion of cortisol; this was coherent with the observed sensitivity of the feet after the training.

The wear of the horn of the hoof wall at the toe, after the shoe removal test, reached an average of 2.6 mm on front feet and 4.2 mm on hind feet. Wear varied, depending on the weeks and between individual horses: the maximum amount of wear of the wall at the toe on a de-shoeing test was 6 mm on a front hoof and 8.6 mm on a hind hoof.

Finally, wear of the sole was more pronounced when the horse raced unshod; it was greater than the wear on the wall in the posterior part of the foot.

Two radiographs superimposed of the right hind foot of one of the trotters for calculating the wear of the wall and sole related to one shoe removal (one unshod racing test between the two radiographs – one week interval between the two radiographs) Average wear on a hind foot was 4.2 mm; the maximum wear on a hind hoof was 8.6 mm. Click on the photo for an enlarged view. French text in white, translated to English in yellow. © CIRALE-ENVA

These results concerned only a small number of test horses and a specific type of track. Further work on the influence of environment, maintenance of the track, the weather and individual variability (quality of hoof horn, gaits) would be interesting to carry out.

The research project described here was led by Claire Moiroud and Professor Jean-Marie Denoix of the CIRALE - ENVA - Hippolia Foundation.

To learn more:

1: Chateau H. et al. (2012) Le Sabot au Travail in Proceedings of the
12th Congress on Equine and Medicine Surgery, Geneva (paper is in French only)

2. To read about the shoe removal practice on trotters in the United States, please read: Shoes, Half Shoes, or No Shoes At All: Swedish-Trained Trotters Ruled Hambletonian Day on The Hoof Blog.

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