PEMC Equine Healthline
May 2008

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EQUIOXX ® (Firocoxib) adds to NSAID choices for therapy and USEF competition

Non-Steroidal Anti-Inflammatory Drugs (NSAIDS) are commonly utilized in equine medicine for their anti-inflammatory, antipyretic (fever treatment), and analgesic (pain relieving) effects. The biological mechanism of NSAIDS stems from their ability to interfere with the body's production of prostaglandins via the inhibition of COX (cyclooxygenase) activity. These effects upon COX are primarily therapeutically beneficial by the inhibition of the COX-2 (inducible inoform), however the typical adverse effects of NSAIDS such as gastrointestinal tract ulceration's are largely attributable to their inhibition of the 'good' COX-1 component. For years, the routine NSAIDS utilized both for therapy and permitted for showing have included: phenlybutazone, banamine, arquel, naproxen, and ketoprofen. All of the NSAIDS have significant inhibition of the "good" COX-1 as well as their desired inhibition of the "bad" target COX-2 production. EQUIOXX ® manufactured by Merial, is the first highly selective COX-2 inhibitor to be introduced specifically for use in horses, and it has been shown in clinical studies to be very effective in controlling pain and inflammation associated with osteoarthritis and post-operative procedures without many of the previous side effects associated with other NSAIDS.

Recent clinical studies, in which PEMC participated, found EQUIOXX ® to be essentially equivalent to Bute (phenylbutazone) in treating pain and inflammation associated with chronic osteoarthritis based upon lameness scoring. Its application to management of lameness conditions is based upon these comparative effects.

The issue of safety is always important in NSAID usage, and studies showed EQUIOXX ® to be well-tolerated for the 14 day study period without side effects. In terms of toxicity, EQUIOXX ® was not associated with GI disturbances at recommended doses and the incidence of transient, low level side effects characteristic of other NSAIDS were only detected with doses of 3-5 times the recommended which were administered for 30-92 days. Our conclusion is that EQUIOXX ® is a safe and effective alternative to phenylbutazone and other traditional NSAIDS, and has special application in horses who currently have or are predisposed to GI ulcers and irritation.

EQUIOXX ® was approved by USEF last fall as one of the permitted medications for horse show administration and is palatable and packaged in an easily dosed and administered paste syringe. These factors coupled with the specific COX-2 characteristics make EQUIOXX ® a valuable new addition to the therapeutic arsenal of products at our disposal to cope with pain and inflammation in our performance and pleasure horses. As always, these decisions should be discussed with your veterinarian to determine their applicability to your specific horse's problems.

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Healthcare Guidelines

Muscle Disorders in Warmbloods & Draft Horses
By John Fling, DVM

Equine athletes who suffer from poor performance, painful back and hind quarter muscles, reluctance to collect or engage the hindquarters, poor rounding over fences, gait abnormalities that are difficult to define by standard diagnostics, and muscle atrophy may have a higher than normal probability for being candidates for "Polysaccharide Storage Myopathy" (PSSM).

How does PSSM affect your horse and what is it?

PSSM is a common cause of exertional rhabdomyolysis (tying up), muscle soreness, and weakness. It is basically a defect in tissue metabolism which manifests in individual horses and has a genetic origin. Glycogen (the main form of storage of glucose) accumulates in abnormally high concentrations in the muscle fibers due to an enzyme defect. Research on the genetic basis of different forms of PSSM in Warmbloods and other specific breeds is ongoing.

How is PSSM Diagnosed?

Horses exhibiting clinical signs of PSSM should have a thorough physical and lameness evaluation including the following:

• Blood work for evaluation of their muscle enzymes and Vitamin E/Selenium levels
   
  
• Muscle biopsy to exclude PSSM
   
  
• A thermographic exam may hone in on "hot" spots in the affected muscle region, giving further evidence of an existing myopathy. This imaging modality may be restricted to cooler times of the year where environmental artifacts are minimized.

It is not uncommon to live with the status quo in poor performing horses that have "known" chronic osteoarthitis, but further investigation beyond the known joint/tendinous issues may lead to the knowledge that PSSM is a major factor affecting your horse.

What's next if your horse is diagnosed with PSSM?

Owners need to be aware that any horse diagnosed with PSSM will always have an underlying predilection for muscle soreness. The best that can be done is to manage horses in the most appropriate fashion to minimize clinical signs. With adherence to both diet and exercise recommendations, at least 80% of the horses show notable improvement in clinical signs, and many return to normal levels of performance.

There is, however, a wide range in the severity of clinical signs shown by horses with PSSM. Those horses with severe or recurrent clinical signs will require more stringent adherence to diet and exercise recommendations to regain muscle function. Researchers have demonstrated that 54% of Warmbloods showed improved clinical signs if diet and exercise modifications were followed.

Consistent low level exercise, and a diet that is low in starch (less than 20%), and high in fat (greater than 10%) were the two most important factors in mitigating PSSM.

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Joint Disease
Part One

This month we will begin a 3-part series on Joint Disease. First we will begin by discussing the anatomy of the joints, Next we will discuss the causes of joint problems and how they present to horse owners. And finally, we will review the treatments and therapies available, how they work and how they are implemented. But, as is always the case, each horse is different and each joint injury is different. Because there is such a wide spectrum of solutions, horse owners should always be aware that it is important to keep in mind that what may have worked in one horse may not necessarily work in another. Also, there is a very large gray area of treatment, That is, the level of treatment can begin with small increments of therapy and based on the horse's response to therapy it can be accelerated as needed.

Types of Joints

To begin, there are three different types or classifications of joints:

• Fibrous Joints
  Fibrous joints are the least likely to be afflicted with disease because they are pretty much immobile. These include joints in the skull and those between the shafts of some long bones.
   
• Cartilaginous Joints
  Cartilaginous joints don't have a high propensity for disease because they too have limited movement. These are the joints of the pelvis and vertebrae as well as growth plates which extend a bone's length during the horse's growing years.
   
• Synovial Joints
  Synovial joints are the ones most likely to suffer disease and injury because they are the most active joints in the horse's body. They consist of two bone ends covered by articular cartilage. This cartilage, within the joint is so smooth and resilient that, when properly lubricated allows for frictionless movements of the joint.
   
  Synovial joints include the shoulders, hips, knees, hocks, fetlocks, pasterns, and coffin joints but the most commonly seen joint problems are seen in the knee, the hock, the pasterns, and the fetlocks. This is because these joints are placed under the most stress during horse sports such as dressage, eventing, cutting, reining and hunters/jumpers. It is the accumulation of this type of work that breaks the joints down and causes lameness.

Components of Joint Health

There are two components to the joint's health:

• Stability
  The joint's stability is maintained by a fibrous joint capsule, which attaches to both bones and collateral ligaments. Collateral ligaments are located on either side of most joints which are the key components of the fetlock, knee, elbow, hock, pastern, and stifle joints. Other ligaments such as the cruciate ligaments in the stifle help stabilize some joints. Ligaments that are outside the joint capsule also lend support. The distal sesamoidean ligaments and suspensory ligaments that, together with the sesamoid bones, make up the suspensory apparatus and hold the fetlock in its correct position.
   
  
• Flexibility
  The joint's flexibility is provided by the joint capsule, which acts like a bubble around the joint and contains an inner lining called the synovial membrane. This lining secrets the synovial fluid that lubricates the joint. The key ingredient in this fluid is hyaluronic acid, also known as sodium hyaluronate or hyaluronan, which lubricates the synovial membrane. The other ingredient of the synovial fluid is a protein called lubricin, which is the primary lubricant of the cartilage. In some cases of joint disease there is a depletion of this necessary fluid which causes friction and pain of the horse's joint.
   
  Another factor, important to maintaining healthy joints are the components of the articular cartilage, which are chondroitin sulfate, hyaluronic acid, and glycosaminoglycans. These substances help the cartilage retain its resiliency and density. When these substances are lost in response to inflammation within the joint-joint problems are magnified.

In PART TWO of this series we will discuss in more detail the actual process of joint injury.

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Tip of the month

Changing feed should be done carefully!

Changing feed should be done carefully! With the increasing influences placed upon agricultural producers by decreased rainfall, consumer demand, and economics, there are going to be more fluctuations in hay availability ahead this year. As hay provides the largest component of your horses diet, inconsistent hay availability can impact their health and performance. Changes in hay type (alfalfa, oat, grass, timothy, etc) should be introduced gradually over 10-14 days to allow for microbial changes (which aid in digestion) within the bowel to accommodate. Many hays are high in fiber (i.e. limited digestibility) and the horse relies upon its microbial flora in the bowel to convert fiber to a more utilizable form. Alfalfa hays also vary greatly in nutrient content depending upon season (i.e. number of cuttings previously in the season), with later cuttings being very leafy and less "stemmy" which results in increased protein content and digestibility.

In addition to nutritional concerns, many horses have developed allergies to various hays or supplements. These allergies can become intermittent depending upon feed products available at the time.

Bottom Line: Nutritionists and horse owners agree that equine nutrition is more important and more complicated than the old slogan "he eats like a horse"! Therefore, among the many factors we consider in optimizing our horse's health and performance capabilities, an individualized nutritional program is a critical component!

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Meet the Staff - Sinead Devine, DVM

I was born in Drogheda, Ireland just 6,000 miles away from the Emerald Isle! Summers spent on my Uncle's farm prompted my early love of animals and my decision to become a vet.

I went on to study Veterinary Medicine at University College, Dublin, and spending summer's externing in California at UC Davis & Peninsula Equine. After graduating I spent 4 years working in Portlaoise, but not just with horses but dogs, cats, sheep & plenty of cattle!

This is my second year working here and it is great getting paid to work with horses everyday! The variety of horse breeds & riding disciplines in this area is a constant source of fascination to me.

In Ireland I hunted the incredible "Joker" a ¾ thoroughbred and ¼ Irish Draft with the Laois Foxhounds. We were devoted members of the Dunamaise Riding Club and also competed at hunter trials and show jumping. Now my free time is spent riding, practicing yoga, biking and some choir singing!

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Upcoming events

•  5/5 - Gilroy Gaits equestrian facility grand opening
•  5/23 - 5/25 - Woodside Spring Horse Trials
•  6/19 - 6/29 - Bay Area Summer Festival - H/J
•  7/19 - 7/27 - Reining by the Bay

From the office

PEMC provides a means for you and those who take care of your horses to be prepared for unexpected emergencies. Complete the Absentee Owner Authorization Form online.

Having this form on file with PEMC will allow you to be confident that everyone involved in your horse's health care is prepared for the unexpected. Some important informational aspects of this form include: listing authorized persons you've empowered to contact you or to make a decision if you are unavailable; if insured, who is your insurance carrier and policy information; and what are any specific criteria you might have which would guide our staff at PEMC to best provide your horse with emergency treatment. These forms are very helpful, whether problems which might arise are minor or major, in assuring owners that they can be absent or on vacation without worrying about unforeseen emergencies back at home! The staff at PEMC hope you all have a great and worry free summer of showing, vacationing, and otherwise enjoying both family and horses!

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Peninsula Equine Medical Center
(650) 854-3162 | peneq@yahoo.com
100 Ansel Lane, Menlo Park, CA 94028

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