Cracks in horses’ hooves are always a bit of a worry. But while some are fairly benign, others can be serious. In this blog, one of our equine vet bloggers takes a deeper look at horse’s hooves and the reasons for those frustrating cracks and fissures.

Table of contents

Structure and function of the hoof

The hoof wall or horn is made of keratin; a tough protein, with a low water content, that is incredibly strong and also insensitive, much like our nails. Its main function is to bear the weight of the horse while protecting the sensitive structures that lie beneath it. Such as the pedal bone as well as tendons and soft tissue.

The inside of the hoof wall is lined by sensitive laminae which act as a type of biological Velcro to attach the pedal bone to the hoof as well as acting as a pathway or conduit along which the new horn grows. The horn is produced by specialised cells called papillae at the top of the hoof wall, the coronary band. The hoof wall grows on average at a rate of 6-10mm a month. This means that it takes approximately 9-12 months for a hoof to grow from the coronary band to the sole.

Types of crack

The hoof wall is subject to huge forces when the horse is at rest and even more so at exercise or whilst jumping. Overgrown or weakened hooves, or those subjected to abnormal stresses, can be more prone to splitting or breaking. 

The two most common types of cracks seen in the hoof are usually referred to as grass cracks and sand cracks. Grass cracks are those that originate at the bottom or sole of the foot. While sand cracks are those that start at the top of the hoof, or the coronary band. Either of these may be complete or incomplete. 

In general, grass cracks occur when the hoof wall is overgrown and begins to flare at the sole

These are rarely involved in severe lameness unless infection is present. 

Sand cracks are present at the front of the hoof, extending from the coronary band. Those that occupy the side of the hoof wall are usually referred to as quarter cracks. 

Sand cracks are most commonly caused by poor foot balance

Quarter cracks are usually associated with a mediolateral (side to side) foot imbalance or with sheared heels. If you watch your horse walking, it may be possible to see if the foot lands evenly on the ground or not. If one side of the hoof wall lands first, it is likely that there is a mediolateral foot imbalance. Sand cracks are not always painful, particularly if they are superficial. But they are a good indicator that there is a problem with foot balance. 

Horizontal cracks in the hoof wall are sometimes seen following the rupture of a foot abscess at the coronary band, or trauma to the hoof wall. These will usually grow out without too much concern, unless they are very large. 

What to do when you notice a crack

The first thing to do is to clean the foot well so that you can inspect the damage properly and to reduce the risk of further dirt reaching into the defect. Watch your horse walk to see if the crack widens as the horse bears weight on the affected leg. This is an indication that the crack is unstable and may worsen over time. Any signs of lameness or discharge from the crack may indicate the involvement of deeper structures. 

If possible, move the horse to dry, hard standing, especially if the field is muddy. Cover the damage with a clean, dry dressing. Call your vet or farrier as soon as possible to arrange a visit. While it is not always an emergency, hoof wall damage should be assessed promptly before any further damage or complications arise.

All cracks may lead to instability of the hoof wall, And as such, even if the crack is not causing a lameness, if left untreated, they may lead to more serious complications. It is also important to determine the cause to treat the problem correctly. 

Treatment

Hoof cracks will not resolve without intervention, the earlier the better. In addition to treating the defect itself, removal or resolution of the underlying cause is essential both to aid healing and to prevent recurrence. 

In the first instance, the hoof should be examined by your vet or farrier 

They will assess the depth of the crack and to ascertain if any sensitive structures have been affected. This will include walking the horse or using hoof testers to check for pain or lameness the presence of which may indicate a more serious condition. Your vet or farrier will also clean and debride the crack to remove any contamination. This is often followed by corrective farriery to balance the foot. A shoe may be needed to stabilise the foot and prevent the crack worsening. In some cases, a clip or groove above the crack is used to stop it advancing upwards towards the coronary band. Your farrier may also remove some hoof wall at the sole below the crack to reduce any pressure on the crack which may drive the sides apart. 

Severe sand cracks may need to be stabilised with materials such as fibreglass or acrylic

Some farriers will use wire or metal plates to achieve this. The method used will depend on the shape of the hoof, the depth of the crack and your farrier’s preference. It is important to remember that the treatment does not stop with stabilisation of the hoof, since these cases will need frequent visits from the farrier to ensure that the foot remains balanced and stable, with minor adjustments made if necessary. 

As mentioned earlier, it takes on average 9-12 months for the hoof wall to grow from the coronary band at the top to the sole at the bottom, so it will take a long time as well as regular farriery and a lot of patience for the fissure to disappear. 

Prevention

Whilst some horses are more prone to cracks than others, the importance of hoof care cannot be emphasised enough. Feet should be checked at least once daily to monitor for early signs of damage. In winter, this does mean hosing off any mud to inspect the feet. 

An area of hard ground to stand on, while sometimes difficult to find, is hugely beneficial in providing good hoof care. Horses that are kept on deep litter or in muddy conditions are more prone to developing diseases such as thrush or white line disease and standing for prolonged periods of time in damp conditions may lead to reduced horn quality. Although we cannot control the weather, if at all possible, during prolonged periods of wet weather, horses should have access to hard standing or clean dry stabling.

Regular farriery will help to keep feet trimmed and balanced to reduce the risk of traumatic cracks

A trimming interval of six weeks is average, but some horses may need more or less frequent visits to keep their feet in good condition. Occasionally, it may also be necessary for your vet and farrier to work together and use radiographs to guide the shoeing process, particularly in cases with a foot imbalance.

Some horses have poor foot conformation which can predispose them to damage. Breeding for good hoof conformation may help to increase horn and foot quality and biomechanics in future generations. 

Try to avoid excessive or fast work on hard ground 

This may lead to traumatic fractures of the hoof wall, particularly if your horse is overdue for trimming. 

Supplementation may help to improve horn quality in some horses

Biotin may be valuable in some horses, but it can take up to a year to notice a significant effect as the hoof quality will improve from the coronary band down. Supplementation with vitamins and minerals such as methionine, zinc and calcium as well as omega-3 fatty acids may also be beneficial in addition to a balanced diet. It is always advisable to ensure that your horse’s body condition is within the correct range to reduce the load on the hooves and to ensure optimal overall health. Bear in mind that not all horses will need dietary supplements. Speak to your vet about the available supplements to choose which one is right for you.