The Truth About Hoof Abscesses

The Truth About Equine Hoof Abscesses.

Hoof abscesses can be much more serious than most of us realize.  Abscesses usually are misunderstood, misdiagnosed, mistreated and cause our horses unnecessary suffering, loss of use and too often loss of life.

The following is a brief explanation of White Line Abscesses of the hoof wall and White Line abscesses of the hoof bar (sub-solar).

White line Abscesses of the Hoof Wall:  It’s commonly believed that a horizontal crack appearing in the hoof wall is caused by injury at the hairline (coronary ridge) that treks down the hoof with the wall growth.   

However, a crack or rather split in the wall that develops as a result of trauma at the hairline will typically be “vertical” and will nearly always become a permanent fixture of the wall to some degree.

Conversely, horizontal cracks in the hoof wall are most often caused by abscesses (affecting the white line - WL) that rupture at the hairline and migrate with wall growth to the ground where it should be trimmed off.  

Abscess rupture sites may be any width; from a hole the size of a match head, to several inches wide, as often seen in draft hooves. Multiple abscesses can affect the same hoof at the same time or in very close succession.  More than one hoof can be affected at the same time due to a duplication of the conditions that lead to abscessing.

Cause:   WL abscesses generally affect hooves that have been neglected, or that are trimmed regularly, but incorrectly, shod or unshod.

 

The hoof wall, if allowed to flare creates leverage on the connective tissue (lamina/white line) between the wall and the sole which can cause stretching of the white line.  Laminitic connection stretches to a point, and then separation ensues. 

WL separation (the primary and secondary layers of connective tissue detach interrupting life support of one to the other) causes death of the lamina.  Once necrotized, that tissue mixes with bacteria and debris and entire pocket of inflammation causing pus begins its ascension up the wall into the narrowing space between the wall and bone below the hairline.  Pain will increase due to the increased pressure as the pocket continues to become more inflamed and makes its way to sensitive nerves near the coronary ridge.  The abscess is most painful just prior to rupture.  At some point in the process lameness is usually presented in varying degrees.  

It’s important to understand that as the pus pocket treks up the inside of the wall to the soft hairline where it finally and painfully ruptures, a channel of dead lamina is left in its wake.

The abscess channel will eventually dry up leaving an area of disconnection (a tunnel) behind the wall from the ground to the hairline.                                                                                                                                                                                                                            

Lameness soon subsides after rupture. As the wall grows, new/well-connected lamina develops (grows down) above the descending “crack” and takes the place of the damaged tissue. Lameness soon subsides. As the crack (rupture site) treks closer to the ground, the detached wall below the crack may snap off.

White line Abscesses of the Bars:  Bar abscessing is more serious and painful than wall abscesses.  That is because affected areas of the WL may also migrate to the sub-solar connection (papillae) causing eventual detachment of sole (and frog) and in severe cases can cause permanent damage to the solar papillae. 

Mistaken assumptions are made that abscesses of the sole (bars) are caused by trauma to the sole. Sharp objects may impact the sole of a soft-soled hoof, but the result generally will be a localized wound.  Abscesses and injuries to the bottom of the hoof are different conditions and we need to distinguish between sole trauma and white line abscess to avoid confusion.

The bars of the hoof are an extension of the hoof wall.  Which means abscesses can develop in the white line of the bars, tracking up connective tissue to rupture at the hairline of the heel bulb. 

The lameness that the horse incurs is often described as “mystery lameness.”   The resulting rupture sites appear as horizontal splits in the back of the hoof and are typically misinterpreted as injuries caused by forging and other misstep type injuries.

Cause:  When hooves are neglected or the bars left unattended during trimming, the same stretching of the white line of the bar will result - just as we see in the white of the hoof wall.

In a hoof affected by bar abscess, a section(s) of white line of the bar will become blackened where stretching and invasion takes place.  The main difference we see in bar abscess is that its affect is not limited to the lamina.  But also invasion of solar connective tissue (papillae) often occurs. 

Left in the aftermath of a processed sub-solar abscess is profuse dried, blackened, necrotized residue in place of the once healthy connective tissue.  This disconnection will eventually lead to complete detachment of sole material from the hoof as well as the frog in severe cases.

Symptoms:  Usually we notice varying degrees of lameness.  Horses suffering abscess have been observed lying on the ground, unwilling to stand except to eliminate -- or no observable lameness at all.  When an abscess takes place in the hind we often don’t observe lameness.  Or a horse can process numerous abscesses that no one notices essentially because no one was observing the equine.

Treatment for both types of WL abscess: There is no actual treatment for an abscess once the white line has been invaded. The condition has to run its course. Epsom salt or vinegar soaks may help soften the coronet band, while pain meds and padded boots can offer relief post rupture.

Don’t Do This:  Digging openings into the sole or white line is a common approach to relieve pressure.  However, by the time the horse displays pain, the abscess is close to rupturing at the hairline. Therefore, that procedure most often only causes further trauma to a hoof, rather than relieving pain.  Poultices sometimes may help drain a bar abscess if caught soon enough, but the pain and rupture will still take place.

However, when veterinarians or farriers increase the opening of an abscess entrance site in the hoof as a treatment, they do offer the owner a means to feel like they are contributing to the horse’s rehabilitation.  Typically prescribed aftercare includes hoof packing (needed to treat the enlarged hole) along with hoof soaks, and ridiculously extended periods of stall rest.  Most horses would tell you they don’t appreciate any of the above recommendations.  

Skilled veterinarians have been known to drill tiny holes in the outer wall in the path of the abscess causing discharge and instantaneous relief from pressure and pain.   Done correctly, this is one of the only methods that can provide instant and actual relief to a horse suffering from a wall abscess.  However, this method isn’t practical for an abscess of the bar.  Also, many veterinarians aren’t aware that the abscess doesn’t trek straight up the wall, but treks at the same angle of the angle of the growth of the horn tubules.   Numerous holes drilled into the hoof wall in an attempt to find the abscess track could cause secondary problems.

Anytime I have introduced this technique at conferences, the first question is always, “How do you know when to stop drilling?”  The answer: When you hit pus!  The important bit is to follow the angle of the horn tubules from the entrance site and you’ll find the abscess channel.

What to Expect: For horses that have been processing white line abscess chronically for some time, expect it to take several hoof growth cycles before the horse stops processing abscesses or at least less often.  

Rehabbing an abscessing hoof requires trimming at 4 week intervals. It can take many months, or

years to grow out new hoof material to replace the involved connective tissue.

 For the sake of your horse, please be patient with the rehab process.  It will take as much or more time for your horse to make his way out of this condition as it took to get into it.

Prevention: Preventing abscesses of the white line is as simple as making sure that your horse’s

hooves receive correct trimming at regular and frequent intervals, removing and controlling flare.  

For optimum hooves, trim scheduling should be at 4 to 6 intervals.  Trimming strategies should produce healthy hoof horn (no flare) and well maintained bars with tight, connecting tissue (lamina/white line).  This strategy will reduce and eliminate abscesses. 

Common Misunderstandings of Hoof Abscesses:  Lameness caused by WL abscesses is frequently misdiagnosed because it’s difficult to identify an abscess until rupture at the hairline takes place followed by “gradual” relief.  Even then, the condition remains a mystery when we hear the owner state that “The lameness simply went away.”

Radiology and even MRI usually will not pick up the abscess channel.  This lack of obvious cause of the observable lameness often leads to a search for alternative causes.  The use of this technology can show us different hoof anomalies that otherwise would never be discovered, that have always been a part of the hoof internal structures, and have no relevance to the horses current discomfort, but will receive the blame.   Such as "navicular syndrome" which in most cases isn't a syndrome at all.

The above isn’t always the case, but it is not an uncommon scenario that leads to mistreatment, usually an unorthodox shoeing strategy, which may not produce an obvious, permanent and/or “immediate” cure.  So the only consideration for the horse at some point is to euthanize. 

Thermal Imaging does at times illuminate abscess inflammation.

Founder can result in more than one hoof caused by the severe inflammation in the abscessing hoof or hooves.  It’s not unusual for a horse to be diagnosed with founder, but the initial cause (abscess) miht never be detected.  That’s when horses who have never had an issue with “grass” are often pulled of pasture indefinitely, but needlessly.

Once a horse has been pronounced with the “f” word – founder.  It’s thought that the cure is troublesome and expensive, or worse, there is no hope at all.  That simple isn’t true in most cases.

Important Notes

Abscess pain often mimics colic pain before obvious lameness is displayed. I wonder how often horses are treated for colic, that would love to be able to say, “The pain is in my foot!” 

Founder can result in more than one hoof caused by the severe inflammation in the abscessing hoof or hooves.  The cause of the founder is mechanical in this case and not organic.

In severe cases a hoof can be fully engulfed in several abscesses at one time causing severe pain and lameness and founder. If left untreated (untrimmed) the hoof may eventually lose most of its attachment material.

Shoes can stall out the process of abscess and should be pulled during rehab.  Lameness in a shod hoof is frequently caused by abscesses located at the junction of the bar/heel (seat of the corn) which can be difficult to locate until the hoof has been indefinitely unshod and trimmed correctly and regularly. 

Abscess discomfort may not cause a horse to display obvious lameness all the time or at all.  Lameness may be off and on.  Not appearing at the walk, but obvious at the trot or canter.  A horse may seem fine until the weight of the saddle/rider is added. 

Even if we can drain an abscess, it will still rupture at the hairline in most cases.  

One hoof growth cycle (HGC) takes about one year so patience is required.  The horse will improve with frequent corrective trimming.

Creating craters in an abscessing hoof will only add further healing time and will allow pebbles and debris to invade the hoof that wouldn’t otherwise be an issue.  This procedure creates a secondary problem in the hoof.

Because no obvious signs of pain can be detected initially when a hoof is processing an abscess, very often riders will comment that their horse is lazy because their horse is fine in the pasture, but has learned that if he starts to limp when being ridden he will get out of work.  First, that is ridiculous.  Second, that is exactly how abscess pain is often presented.  Off and on!  Those horses are often referred to as “heartbreak horses.”  As if the horse is at fault!

The more we know - the better we understand the cause, prevention and cure of hoof abscesses, the more years of soundness our equines will experience.  Thank you for taking the time to read and understand this important information about a very common, yet commonly misinterpreted hoof ailment.

Patricia Morgan Wagner

Hoof Rehabilitation Specialist

Rainier, Washington

Revised: 1-2015