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Managing older horse lameness (Proceedings)

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Apr 01, 2009

Management of pain in older horses, especially brood mares and stallions, can be challenging. There are several levels of expectations for older horses and the management style oftentimes needs to be dictated by the animal's use. Therefore the goal of management is to use various local and systemic therapies in order to allow the horse to perform its duties with a minimal amount of pain.

There is no better example of this than in broodmares. The effectiveness of management is often dictated by the breed. For instance, in Thoroughbred racehorses the mares must undergo live cover and carry to term and facilitated breeding techniques cannot be used. This places more weight and stress on the mares and consequently makes management more difficult. With these mares aggressive oversight of their feet, fetlocks, suspensory apparatus and carpi are needed especially if they have a racing history. However mares that can undergo facilitated breeding techniques such as Quarter Horses can be managed more effectively. In Quarter Horse mares embryo transfer can be used. In addition, with the use of shipped semen some mares can live their lifetime at a single farm without much transportation. Some breeding managers are uncomfortable if the mares don't periodically carry to term; however that must be weighed against the potential negative complications of carrying on their musculoskeletal system.

Stallions can also have limitations due to musculoskeletal pain. Again, in Thoroughbreds this is significant as they must live cover and aggressive pain control is needed. In other breeds such as Quarter Horses, in which artificial insemination can be used the collection techniques can be modified to enhance the horses comfort. Breeding dummies can be manipulated, such as being lowered, or the horse can sometimes be collected standing. In addition, horses that are euthanized can have semen stored for later use.

Several types of diseases can influence the musculoskeletal system in these older horses. Systemically, things such as Cushing's disease or metabolic syndrome can have effect on the horse's feet. Laminitis consequently is a common sequela of these diseases and periodic systemic screening of these horses is needed. In addition, nutrition can have a large influence on these horses especially if their carbohydrates are not adequately monitored.

Hoof disease is very common in older horses especially if they have had any lameness history. Laminitis is common in older horses for various reasons and it is often our recommendation to do yearly radiographs to be sure that the angles remain normal and the stresses are minimized on the feet. There are some horses that benefit from a lifetime in shoes and that oftentimes is dictated by the horse itself as well as the condition. Navicular syndrome is also very common and in the advanced stages can be very limiting to the horses comfort. In some instances when aggressive medical therapy and shoeing fails, a palmar digital neurectomy is needed to maintain comfort. However care must be taken that the flexor surface of the navicular bone is closely analyzed as those horses with neurectomies could suffer from complete rupture of the deep digital flexor tendon requiring euthanasia or heroic efforts to fuse the distal interphalangeal joint. Many older horses are maintained of isoxsuprine which oftentimes can maintain an improved level of comfort. Even though this is a contentious approach in some horses it does have a significant impact.

Joint disease is common and needs to be managed based on common principles. The problem with using intraarticular corticosteroids in older horses is that even normally accepted doses of these steroids could potentially have a negative effect on the horse systemically especially if they suffer from Cushing's disease. Therefore it is not uncommon to evaluate the horse's metabolic status prior to recommending intraarticular corticosteroid administration.

Diseases of the suspensory apparatus are not uncommon especially in retired racehorses. It is now recognized that degenerative suspensory desmitis can occur and that there may be a genetic link. This is not uncommon in the hind limbs of western performance horses such as cutters and reiners who have had a significant amount of stress in their hind limbs. It is difficult to properly support these horses. Sometimes extended heel shoes can help however not in all cases. It does seem that if the horses are comfortable turn out and light exercise can be beneficial to maintaining muscle tone and strength and hence compensating for suspensory apparatus loss.

In general several things need to be kept in mind when making recommendations for orthopaedic pain in the older horse. If the horse is comfortable enough to be turned out this is often beneficial and in some cases in chronic joint disease horses can actually do better when turned out as apposed to being confined. Systemic treatments such as supplements isoxsuprine and occasional anti-inflammatory medications can also be beneficial. Local application of medication can also be beneficial and various different types of shoeing schemes can be beneficial depending on the horse. It's important to remember that the breeding scheme and the plan can also have an influence on the horses comfort and that to must be taken into consideration.

In summary, managing the older horse can often times be difficult and the horses can often show a large variation in comfort even in a small amount of time. It is this authors opinion that the goal is often to find a steady course of comfort and not to overreact to short durations of increased pain. This commonly occurs and shoeing recommendations made when in fact the original shoeing scheme may have been more appropriate.