Question: My four-year-old TB has a sand crack in one of her hooves. This crack has been there quite some time and has almost grown to the bottom of the hoof. While the coronet appears healthy and I never noticed any injuries, my main concern is that the hoof is still growing with a split. She has also started to get horizontal splits and I have found a split in one hoof that appears in the centre of the hoof wall touching neither the coronet nor the bottom of the hoof.
Could you tell me what could be causing these splits? Is there any way to promote healthy growth with the sand crack and how best can I minimise the damage from the sand crack?
Answer: Sandie, it sounds like your horse has quite a few cracks and splits and you are quite right to be concerned about these. I think we should firstly explain the terminology of cracks so we can understand what we are talking about. A sand crack is a crack or fissure on the outer surface of the hoof wall that extends from top to bottom of the hoof (that is, from the coronet to the ground surface). These can be superficial and not causing lameness or a deep sand crack that has the complication of movement or interference of the sensitive structures within the hoof.
Grass cracks more commonly start at the ground surface of the outer wall and extend a certain way up the hoof but do not reach the coronet. As with sand cracks, grass cracks can also be deep and cause lameness depending on the severity.
We also commonly describe cracks by their location and direction. For example, toe or quarter cracks to describe where the crack or split is occurring and horizontal cracks can also be labelled as an expansion crack. Expansion cracks are sometimes seen in shod horses when the hooves have outgrown the shoe or the shoe is ill fitting. These are often seen towards the heel area on the outer wall and commonly start off to be 1-2cm in length. Sometimes, expansions cracks can occur in horses that have had a change in their conditions (weather conditions for example) and the hoof undergoes a change in moisture content causing a crack to form where the hoof is placed under the most force from the change (that is, towards the heel area).
Horizontal splits are most commonly caused by an unsuitable balance of forces and pressure placed onto the hoof capsule. For example, conformational faults, when the hoof has been trimmed inappropriately or the feet have been left too long in between trimming. These will all cause too much pressure on one part of the hoof opposed to the ideal situation when the pressures are evenly spread around the foot. When this occurs, the forces become too great for the hoof wall and it starts to crack under the abnormal pressure. The area that will split first will depend on which is the weakest part of the hoof and/or under the most pressure.
Forces that occur within the hoof include those from the ground, those from above (including the stationary weight of the animal, the rider) and the greater forces that are generated when the horse is in motion or being ridden. For us to help reduce the occurrence of cracks and splits (and so many of the other conditions of the hoof) it is vital to have a level and balanced base for the horse to stand and walk on. Hoof balance and suitable trimming is so very important for us to achieve as much as is possible with our horses including the treatment of cracks.
From what you have told me, it appears that your horse is having more problems with vertical cracks than anything and these are more difficult to remedy. You mention that you would like to promote healthy horn growth as the hoof appears to be split as soon as it has been formed from the coronet. An injury to the coronet area can very often cause an imperfection in the growth of horn that will be seen as a crack. If you are sure there has been no damage to the coronet then I suggest that rather than the newly produced horn being grown with the split already present, the crack below is actually encouraging the new horn to split almost immediately after formation. So rather than spending time and money trying to further improve the quality of horn that is growing, I would suggest that you work on a solution to reduce the movement and forces that are allowing the crack to continue up the hoof. As we have already mentioned, having the ground surface of the hoof balanced suitably for the horse above is most important. Employing a farrier that understands and is able to remedy these issues will be vital. The conformation of the horse, the workload and environment should always be taken into account when performing a suitable trim.
When the feet are optimally balanced, your farrier may want to attempt to stabilise the hoof thus reducing movement in the crack and allowing new horn to grow without itself becoming compromised. Stabilisation methods include shoeing (various methods and remedial work), the application of patches, plates or material to the outside of the hoof wall and the affected area and so on.
After you have trimmed suitably and attempted remedial efforts to stabilise the crack, you may then consider promoting healthy horn growth. This could be in the form of providing a balanced diet and if required, a supplement such as Kevin Bacon’s Hoof Formula
David Hankin Dip.WCF
This question and answer originally appeared in NZ Horse & Pony magazine and has been re-edited for this blog