63. The best article i found on how to treat a hoof abscess...

FOOT ABSCESSES

  A relatively common after-hours emergency call sounds something like this: " I think my horse has broken its leg. It can barely even touch its toe to the ground and doesn't want to walk on it al all. I think you're going to need to come out and probably have to put him down." These calls often are accompanied by the owner holding back tears as they tell the news about their 'broken-legged' horse.
More often than not, what they are describing turns out to be a hoof abscess and fortunately these are typically easy to diagnose relatively simple to treat.

Hoof abscesses are literally bacterial infections within the hoof capsule. Another name for this condition is called ‘subsolar abscesses’ and this simply describes a common location for the infection, i.e. just inside the sole of the hoof. The cause of hoof abscesses can also be simplified; they are caused by :
a puncture,
or separation in the outer, non-living hoof wall or sole which allows dirt, manure, and bacteria to gain entrance into the inside, living tissue of the hoof.
Once contaminants are inoculated into the sensitive tissues of the hoof, and abscess forms. An abscess is an accumulation of pus and cellular debris as bacteria, tissue cells, and white blood cells die in their attempt to fight off the infection. 

The hoof capsule is quite non-yielding when a pocket of pus forms on the interior. This means that tremendous pressure is created within the hoof as a result of this expanding infection. Since the hoof can not ‘give’, the sensitive tissues within the hoof, such as the lamina, become compromised. The laminae are the soft tissue attachments between the outer hoof capsule and the inner sensitive soft tissue structures of the hoof. There are a tremendous amount of pain receptors, or nerve endings, in this tissue; this explains why subsolar abscesses are so exquisitely painful. In addition to that, imagine all the weight a horse bears on their small hooves and how that pain would be amplified tremendously when they attempt to walk on an infected foot.

When the vet arrives at a case such as this, the first thing they will do is examine the digital pulse. They are checking for a bounding or strong pulse when compared to the other legs. If the lame leg has a bounding pulse, that is a good indication that there is a problem within the foot. It does not mean specifically an abscess, as a broken coffin bone or an infected joint could produce a similar strong and bounding pulse. A pulse is not always detected if the abscess is very deep or a puncture has just occurred.
They would then produce hoof testers to apply pinpoint pressure to specific parts of the sole and frog. This is done to localize a specific portion of the sole that causes a pain response. The horse may flinch mildly or may rear up and explode as the veterinarian applies pressure over the abscess. It unfortunately is necessary, however, to use this crude diagnostic tool since our patients can not talk and tell us exactly where it hurts. Once the specific location of the pain is determined, a hoof knife (or abscess probe) is used to carefully pare away (or drill into) and examine the nature of the sole and hoof wall deep to that area. Sometimes sedation may be needed if the process is too painful for the horse. Often the shoe will need to be removed.
Often a black tract is seen which can then be followed through careful and conscientious dissection directly to the pocket of pus. When this is accomplished, the pressure is relieved, sometimes with pus squirting several feet from the hoof due to the great pressure. As you can imagine, this produces almost-instant relief to the horse.
    So the cure for a hoof abscess is drainage of the pus. This is not always as easy as described above. Many times there is not just one focal area of pain, but the entire hoof hurts. In those cases, it is difficult to know where to dig a hole to drain the infection. Other times, there is no black tract to follow and the veterinarian can not just unscrupulously dig various holes in the horse’s sole hoping to get lucky and find the correct spot. In those difficult cases, many times vets will recommend soaking the hoof once or twice daily in epsom salts and wrapping the hoof with a poultice bandage in attempts to draw the infection out. This should be followed up in 48 hours with a re-check examination to attempt locating and draining the abscess again as this will be the quickest method to achieve soundness in your horse and avoid other more serious complications.

    When the abscess is located and drained, half of the battle is over. The horse should regain soundness over the next 5-7 days assuming proper follow-up care is given. Your horse now literally will have a hole in its hoof that must be kept clean to prevent more contamination from setting up shop in there. So the key is to keep the drainage hole and sole cleaned regularly, and apply an antiseptic medication to the area to prevent re-infection while the horse’s body heals the defect in its hoof. This requires a bandage to be maintained on your horse’s hoof until it is sound and the drainage hole has healed to the point that re-infection will not occur. A tetanus toxoid immunization should also be administered at this time if it has been longer than 9 months or it the horse has a questionable vaccine history.