Having been shovelling dirt on this hot and sunny afternoon, it brought to mind thoughts about the “conditioning” of horses’ feet.
In physical medicine, ‘conditioning’ refers to an improvement of the physical state with a program of exercise and ‘work conditioning’ refers to a physical exercise program designed to restore specific strength, flexibility, and endurance for return to work following injury or disease. ‘Work hardening’ includes activities designed to improve overall physical condition, including strength, endurance. Central to all work hardening programs is the reproduction of a work-like environment where tasks are designed to improve the patient's tolerance for productive work.
It is not just when a horse has its shoes removed to work without shoes (which some people refer to as ‘transitioning’) when this is relevant, but also needs to be considered when a shod horse lives and works on different surfaces.
Initially, when a horse’s shoes are removed for it to go barefoot, it may not be comfortable enough to be worked, or the horse may even be lame. There are a number of possible reasons for this, including the state of the hoof, the sole and the frog, the type of surface the horse is on and the work that it is required to do.
It has been suggested that the nature of the hoof horn has to adapt when shoes are removed, with the implication that the hoof may not be able to cope with the transition until a full growth cycle has occurred (till the wall has grown down from the coronary band). Certainly for horses with poor white line integrity, as with chronic laminitis or white line disease, particularly if they have nail-hole damage, are very likely to lose sections of the wall, but in many cases, the hoof wall is able to maintain its integrity.
Although the hoof wall is likely to wear more rapidly once the shoe has been removed, if it is healthy it will be able to withstand the forces that act on it, however, the sole and frog have a different structure and will often be sensitive to stony and uneven ground. These structures that make up the palmar (ground) surface of the foot have sensory nerve endings that not only tell the horse that it has trodden on something large or sharp, but also have a role in letting the horse know the position of the foot on the ground (proprioception).
Both the owner and his ass are barefoot (photograph from my grandfather’s trip to Egypt in 1910). At least the owner does have the advantage of being able to ride if his feet get sore.
Relaxing at home without my shoes on and realizing I need something from the car, anyone seeing me walk barefoot over the driveway might consider me ‘lame’, but I am just walking carefully, not fully loading my foot till I know there is no large stone under it, and not doing so if there is. This is what horses that have just had their shoes taken off are likely to do, until the feet have become conditioned, but they (and I) are still able to run around freely, and soundly, on soft and even surfaces. Horses that are still sensitive on these more forgiving surfaces will almost certainly have some pathological changes going on to cause lameness.
Horses that are sensitive when walking on stony or uneven ground (shod or unshod) may have a sole that is too thin or the horse has been stood in mud and the sole is moist and flexible, and this is likely to be worse for those with chronic laminitis or ‘distal descent’ of the coffin bone. For horses that are in a dry environment, if the superficial dry layer of sole is removed at the time of shoe removal, this will leave the moist more flexible ‘live sole’ exposed, and this is likely to make the horse more sensitive during transitioning.
With the shoe removed, it was found that large areas of white line disease had weakened the integrity of the wall, pieces of which are already breaking away. The feet were trimmed and the shoes were left off so that the white line could be treated and to avoid further nail damage.
Exercise will probably help to ‘condition the feet’ and is likely to be beneficial, from increased stimulation and blood circulation that should produce greater growth, thus increasing the thickness of the sole, although there, of course, may be more wear also. Exercise is also one of the main means of controlling insulin resistance, which can cause ‘weakening ‘of the laminae. This weakening of the laminae can lead to ‘low-grade-laminitis’ (or even clinical laminitis), which can affect the integrity of the hoof/corium junction, and make the horse more liable to sensitivity of their feet.
Some people suggest that stabling on pebbles (pea-gravel) and then increasing the size of rock, as well as walking the horse on stones and rocks, to mimic the ground surface the horse will meet will help to condition the feet. Again, I feel this will be of benefit by increasing stimulation and circulation, but I think that there is something more important that helps to condition the feet.
It is some time since I went on a ‘beach holiday’, but I recall that when I removed my shoes on that first day I would have to walk very carefully over pretty well any surface, but by the end of the holiday I could cope much better and walk relatively easily on pretty well any surface. My soles were more resilient, not because I had been walking a lot on different terrain (which I did not) or taking more exercise (which I certainly did not), but, I believe, was due to a combination of sand and sea-water.
On the lateral side, the hard outer layer of the sole has been removed and the wall taken down to the level of the sole. On the medial side, the wall is above the level of the sole, which is still covered by a hard protective layer. A barefoot horse will not cope nearly so well if the foot is trimmed as the lateral part of this foot has been.
When I was shovelling that dirt on the hot day, what made me think about conditioning of the horses’ feet was the surface of the dirt I had dealt with the previous day. I had sprayed the surface of the dirt to stop the dust flying around, and this ground had a nice hard crust on the surface, produced by the combination of dirt and water. In the wild, a horse has to stand in water in order to drink (having no water buckets available), and this moist foot picks up dirt afterwards. Even in hot and very dry environments, the domestic horse is going to have moisture on its feet from morning dew. The crust that is produced helps to protect the ground surface of the foot by becoming embedded in the surface, filling the ends of the tubules in the distal hoof as well as the sole. It helps to limit abrasion and, for the sole, helps to prevent cracking of the superficial, dry layer, which is therefore retained, and sole thickness increases. Studies of wild horses’ feet have demonstrated that they have thicker soles than generally found in the domestic population. I believe that it is due to this combination of dirt and moisture.
When a horses’ shoes are removed, and the horse is not comfortable on hard and uneven surfaces, an owner may decide that the horse is unable to cope and may well have shoes put back on. Modern alternatives to this are to apply hoof casts (Equicast) or hoof boots. The casts will be particularly useful if the wall is compromised, and this will help to maintain the integrity of the wall until a healthier wall grows down. Hoof boots can be used on the newly unshod horse, allowing the horse to be maintained in work, and removed when not. These boots allow the horse to have more exercise, and when un-booted, the palmar structures can receive more stimulation, but it can still take some time before these horses can cope with rough ground. In order to shorten this transition time, I suggest that the feet of these horses in dry conditions should be wetted daily and in wet conditions should be given the opportunity to dry out.