The Horse | Stone Bruises

The Horse Stone Bruises

I thought this might be of interest to those of you suffering the headache of a horse with a sole bruise.
Dr. C

The Horse | Shoeing in the Frontal and Horizontal Planes

The Horse | Shoeing in the Frontal and Horizontal Planes

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4/28/2010 Equine Melanoma

Vet tip of the Day: Equine Melanoma
Key Words: Melanoma, skin tumor, metastasis, cisplatin, cimetidine, laser

Many of you may have had experience over the years with melanoma in grey horses.  This form of melanoma, the dermal melanoma, is a very common skin tumor, usually slow growing, and usually confined to the site of origin.  Dermal melanomas are tumors of the black pigment cells, melanin cells, that are present in high numbers in the skin of grey horses.  The tumors typically are round, hard, and dense black when cut open.  They occur most frequently around the tail base and rectum, but also are seen in the throat latch region and at the base of the ear, where they most commonly arise in the parotid salivary gland.  While dermal melanomas often are solitary, some horses are afflicted with multiple tumors.  This condition is called dermal melanomatosis, and horses with multiple melanomas are more likely to have metastasis of tumors to remote locations, including lymph nodes, liver, spleen, and skeletal muscle.  Surgical removal of individual tumors in such horses may be locally curative, but the remaining tumors continue to grow and more tumors may develop.
 
There are two less common types of melanomas that occur in horses. The first is the melanocytic nevus, which is a benign tumor that occurs as a single, discrete, nodular mass in young horses. They may arise anywhere on the body and when removed surgically rarely recur.  At the other end of the spectrum are anaplastic malignant melanomas, which occur in older horses (usually over 20 years of age) of any color.  These tumors are uncommon, but usually metastasize to distant sites within a year and carry a poor prognosis.

While most horses with dermal melanomas tolerate them well, occasionally these tumors can be life threatening.  This happens most often when the tumors metastasize and grow in internal organs, or when they become so large that they cause mechanical obstruction to breathing in the throat region or impair defecation by obstructing the anus.

Dermal melanomas present an excellent example of how variable the behavior of tumors can be in different species.  As you probably are aware, melanoma in people often presents as a highly malignant tumor which may carry a poor prognosis for long term survival, even in the face of aggressive treatment.  Similarly, in dogs, oral melanoma is a malignant neoplastic process with a high fatality rate.  Many of you knew my wonderful dog Sticky, who died last year within three months of her diagnosis with malignant melanoma.  Luckily for our horses, this is NOT the case with equine dermal melanoma.  However, the common occurrence of melanoma in horses has made it a useful research tool for scientists investigating treatments for melanoma in other species.

One of the areas of intense investigation is the role of the immune system (immunomodulation) in treating melanomas in humans, dogs, and to a lesser degree, horses.  There is a melanoma vaccine currently under conditional license for malignant melanoma in dogs which I gave to Sticky during her treatment.  There also have been limited investigations using vaccines made directly from tumors removed from a particular horse then administered back to the same horse to control widespread melanomas. However, at this time there is no commercially available equine melanoma vaccine and the use of individual melanoma vaccines is not considered standard therapy.

There are many medications used for other purposes which exhibit immunomodulatory activity in addition to their primary mode of action.  One of these is cimetidine.  Cimetidine is an H2 histamine antagonist which reduces acid production in the stomach and is available over the counter as Tagamet, used in people and horses to treat gastric ulcers.  Cimetidine also acts in several complex ways to alter the body's immune  response to certain neoplastic (cancerous) processes.  It has been used with some success in the treatment of equine dermal melanoma at a dosage of 2.5 mg/kg given orally every 8 hours.  Unfortunately, after some promising initial studies, it appears that the activity of cimetidine against equine melanomas is very variable from horse to horse.  While the medication is unlikely to have adverse effects, its efficacy in each case is unpredictable, and therefore, it also no longer is widely used in the treatment of melanomas.

Dr. Robertson, a veterinarian at the Virginia Tech School of Veterinary Medicine did his PhD research on comparative melanoma (across species) and continues to conduct clinical research using Frankincense Oil as an immunomodulatory agent in the treatment of equine melanoma.  The oil is injected into the tumors and causes their regression.  The overall effectiveness of this treatment is not yet determined, but it is an interesting avenue holding promise for the future.  

In addition to immunomodulation, chemotherapy has been used in the treatment of equine melanoma. One chemotherapy agent used in horses is cisplatin, which is very effective in the treatment of squamous cell carcinoma (blog coming up on this soon).  Cisplatin has poor effectiveness against melanomas in dogs and people, but has been used with success in at least one clinical trial in horses.  In this study, 13/14 horses with melanoma had a positive response to the implantation of slow release cisplatin beads into the tumor mass.

The definitive treatment for melanomas is wide surgical excision.  With the advent of surgical lasers, it has become possible to remove larger tumors in challenging anatomic locations, such as the parotid salivary gland.
Traditionally, many veterinarians do not recommend the removal of small melanomas when they are first detected.  I disagree with this approach.  Melanomas tend to be very well isolated and complete surgical excision is often possible when the tumors are addressed early and are relatively small.  While excision does not prevent the development of new tumors at other sites, in my experience recurrence of the tumor at the site of excision is rare.

In summary, if you have a grey horse with melanomas, ask your veterinarian to evaluate them. I strongly recommend early surgical removal.  Consider cimetidine as an adjunctive therapy because it is safe, and may be effective.  Cimetidine can be obtained from reputable compounding pharmacies at a reasonable price.   For more advanced tumors, discuss the options of laser surgery and/or cisplatin bead implantation and consider seeking the opinion of a  veterinary specialist, an ACVS boarded surgeon and/or ACVIM boarded large animal internist.


I believe that education is the key to evolution. I believe that animals are the key to compassion. I believe the learning never stops.

4/25/2010 Euthanasia Part III: Making the Decision

 Vet tip of the Day: When is it the right time for euthanasia?

In this final entry concerning the difficult topic of euthanasia, I would like to share with you my views as a veterinarian on the hardest part of the decision for euthanasia: when is the appropriate time?

First and foremost, I respect the right of a horse's owner to use their own judgement in deciding what they believe is best for their horse.  Horses legally are considered property, they do not have legal rights.  There are governing bodies in every state to respond to situations of animal cruelty to protect horses from abuse situations, but elective euthanasia is not considered abuse. I do not agree with every decision for euthansia, and I have refused to perform euthansia in rare cases.  However, the vast majority of owners who come to the decision to end their horse's life do so after careful and painful deliberation, and are acting in the best interest of their cherished animal.

I am frequently asked by clients to help them in making the decision to end a horse's life.  Usually this is in the case of geriatric horses, or chronically lame horses.  I would love to be able to tell you that it is always clear to me when a horse is suffering inhumanely, but it isn't.  The question of quality of life is engulfed in a huge grey cloud. Two things that I offer as factors to consider when you are trying to determine the quality of a debilitated or geriatric horse's life are: 1) progressive weight loss in the face of an excellent plane of nutrition and 2) prolonged periods of recumbency (lying down) to the point that pressure points such as hips develop non-healing sores, and the horse has pronounced difficulty rising.

The subject of euthanasia for practical reasons is really problematic.  Horses live a long time and they are very expensive to care for.  As horses age they typically require more calories and special dietary considerations, as well as nutritional supplements and sometimes medication (such as pergolide for Cushings horses, or anti-inflammtories for musculoskeletal problems) which increase the cost of upkeep for an animal that may no longer be rideable.  I stick very firmly to my respect for each horse owner's individual right to make decisions for such horses.

On the other end of the spectrum are owners who simply do not believe in euthanasia, and feel very strongly that all living beings should die a natural death.  Again, I respect this perspective, as long as the owner is able to provide adequate nursing care and pain medication to support their horse through the process of dying.  I always remember a foal I treated back at the University of Georgia when I was a resident.  The owner had lost a son to a long battle with cancer and absolutely would not consider euthanasia an option for this foal.  The foal suffered from neonatal septicemia, a bacterial infection that circulated throughout the body, seeding infections in multiple sites.  The foal had bacterial endocarditis (a vegetative bacterial growth on a heart valve), pneumonia, an infected umbilical cord, and an infection of the growth plate adjacent to one of the hind fetlock joints.  The bacteria responsible for all these infections was resistant to virtually every antibiotic available.  Statistically the foal's chance of survival was way below 10%, he was extremely lame, had dramatically reduced exercise capacity due to his enlarged heart and leaky mitral valve, as well as the severe pnuemonia.

Despite my repeated explanations of the foal's condition and poor quality of life, the owner refused to consider euthanasia, and instructed me to continue treating the foal, regardless of cost or prognosis.  Well guess what?  That foal lived to race as a 3 year old - he only raced once, and not very well, but he managed to overcome his heart infection, and although he never was sound, he was retired after his one race and lived out his life in a beautiful pasture. It is not our place to judge the decisions of others regarding their horses, unless cruelty or neglect are evident.

So when is it appropriate to choose euthanasia for your horse?  Only you can make that decision.  Listen to your veterinarian's assessment of your horse's condition and prognosis, then search your heart and mind and make your decision based on your own personal ethical code.  It is never easy, and it never gets easier, but it is part of the responsibility of horse ownership. 
















I believe that education is the key to evolution. 
I believe that animals are the key to compassion.
I believe the learning never stops.

4/22/2010 The mechanics of euthansia

Vet tip of the Day: Euthanasia - What really happens
Key Words: Barbiturate, gunshot, cerebral cortex

Yesterday's euthanasia stories came straight from the heart.  Today I'd like to take a step back and discuss this difficult topic from a more detached perspective. Much of what will be included in todays' blog was taken directly from the American Veterinary Medical Association Guidelines on Euthanasia published in 2000.  If you want to read them in more detail, they are available on line.

The word euthanasia is derived from two Greek words.  The first, "eu" means "good" and the second, "thanatos" means "death".  Thus the word means "good death" or the act of inducing humane death in an animal.  One of the greatest concerns expressed by owners with respect to euthanasia is their animal's state of consciousness during the transition from life to death.  The AVMA makes it very clear that any appropriate form of euthanasia should result in a rapid loss of consciousness and that the loss of consciousness should occur before, or simultaneously with, loss of motor control.  In most cases, equine euthanasia is performed with an injectable barbiturate, usually sodium pentobarbital.  This drug acts very rapidly, causing central nervous system depression beginning in the cerebral cortex.  The cortex is the center of consciousness, so the first thing that happens when a horse receives a large dose of sodium pentobarbital is an immediate loss of awareness.  The drug then rapidly depresses the lower brain centers, resulting in apnea, or failure to breathe, and cardiac arrest. 

The horse may sink quietly to the ground after the euthanasia injection is administered, but this cannot be guaranteed.  Sometimes the animal becomes rigid and may even fall over backwards.  It can be very disturbing to watch such a large animal hit the ground, but REMEMBER THAT THE HORSE IS UNCONSCIOUS AND UNAWARE.  The physical process of dying may include several gasping breaths, muscle trembling, and voiding.  These activities are natural physical processes that accompany the shutting down of body systems and even though they involve motor activity, or physical movement, they occur AFTER the cortex has stopped functioning and the animal has lost consciousness.

Sometimes owners request that their horse be sedated prior to euthanasia.  If the horse is extremely excited or difficult to handle, this is appropriate.  However, in general I try to avoid sedation if possible.  Sedatives slow the heart rate and decrease cardiac output, thereby slowing the delivery of barbiturate to the brain.  Euthanasia is most often performed on very sick or very old horses, which may already have impaired cardiovascular function.  The goal is to get the largest amount of barbiturate into the horse's brain as quickly as possible to achieve immediate and complete loss of consciousness.  Sedation can compromise this process.

Finally I'd like to address the issue of using firearms to perform euthanasia.  The following is quoted directly from the AVMA Guidelines on Euthanasia (note the term "physical methods" includes firearms and captive bolt pistols):

"When properly used by skilled personnel with well-maintained equipment, physical methods of euthanasia may result in less fear and anxiety and be more rapid, painless, humane and practical than other forms of euthanasia.  Some consider physical methods of euthanasia aesthetically displeasing.  There are occasions, however, when what is perceived as aesthetic and what is most humane are in conflict."

The term "physical methods" includes captive bolt pistols and gunshot.  Most of us have a natural fear of guns and are very upset by the violence associated with the act of shooting an animal, especially one we have loved and cared for. Horses do not share this aversion.  When performed safely and correctly, death by a bullet into the brain is instantaneous and therefore, painless.  It should never be considered unless the person handling the firearm is skilled not only with the weapon, but also absolutely understands the anatomy of the horse's head and how the shot should be placed. 

These are difficult things to think about, but I believe that understanding the process is an important part of making the decision to end a life.  This decision, when you face it, is about the quality of your horse's life.  It is painful, and sad, but it also is part of the responsibility of owning animals.  Now that we have examined the physical realities of euthanasia, tomorrow I will conclude this topic with some more philosophical thoughts on reaching the decision for euthanasia of your horse.


I believe that education is the key to evolution.
I believe that animals are the key to compassion.
I believe the learning never stops.

4/21/2010 Euthanasia

 Vet tip of the Day: Thinking about Euthanasia

I would like to introduce the topic of euthanasia with a few stories.  The first is one about an experience I had as a resident, and the second is about PipSqueak, a wonderful patient of mine

I completed a large animal internal medicine residency at the University of Georgia School of Veterinary Medicine.  I was on call to receive emergency patients into the hospital every 3rd weeknight and every other weekend for 5 consecutive years.  That's a lot of emergency admissions.  The sad reality of referral equine medicine is that we see a lot of very sick horses and many of them don't make it out of the hospital.

One weekend early in the first year of my residency I didn't sleep for 48 hours.  During that time I received 8 emergency patients.  Four of them were critically ill and over the course of two days I administered a lethal dose of sodium pentobarbital (euthanasia) to all four when it became clear that they had no hope of survival. Right there you come up against one of the more difficult concepts in the decision for euthanasia: no hope.  We all know that there always is hope, we just choose under certain circumstances to consider that hope too small to warrant the continued suffering of the really sick or the really old.  And let's face it, economic concerns and practical concerns influence the decision to end animal's lives as well.

That particular weekend in 1989 when I was a resident was very difficult for me. In the five subsequent years I never had to face the death of some many horses in such a short period of time.  I was exhausted, I was a new resident and I didn't have a lot of experience coping with the grief, guilt and confusion often experienced by owners when making the decision for euthanasia of an animal they love. At that stage of my career I also didn't have a lot of experience pushing the plunger on the syringe of "blue juice" that ends an animal's life.  I don't really remember all the details of that weekend.  I do remember that moment, just before performing each injection, when I wondered if perhaps there was hope, if perhaps I had misinformed the clients, if in fact the horse might survive if I could just do one more thing to turn its condition around, if I was making a terrible mistake.  None of these things was true, but the thoughts ran through my head nevertheless.  And I remember on Sunday afternoon, after I had humanely destroyed the fourth horse, sitting on the floor of the recovery stall outside the equine surgery suite and thinking, if one more horse comes in and requires euthanasia before tomorrow morning, someone else is going to have to push the plunger, I just can't take any more life today.

The second story is about PipSqueak.  PipSqueak was a grey arabian gelding who I took care of for 13 years, from the time he was 14 until his death.  Over these years PipSqueak belonged to 4 different owners, all of whom he taught the skill of riding after hounds, or foxhunting.  PipSqueak was a remarkable horse, an outstanding athlete, and a very wise soul.  Toward the last years of his life he was retired and turned out to pasture by his then owner.  His care was not adequate and he lost weight and began to have trouble getting up.  One of his previous owners, who by now was a teenage girl, saw PipSqueak's condition and reclaimed him.  She had owned PipSqueak when she was 8-12 years old and had ridden him all over the desert of Northern Nevada.  Now 15 years old, she brought PipSqueak home and fattened him up and took great care of him for another 9 months.

Although he was back in great body condition, PipSqueak's degenerative joint disease progressed to the point that he sometimes struggled for as long as 20 minutes attempting to rise, raising himself on his front legs but unable to lift his hind end to a standing position.  He was treated with joint supplements and anti-inflammatories, his hocks were injected, he was put on special footing and had special foot care, but his condition continued to deteriorate.  Finally his owner's grandmother called me one day to schedule an appointment for PipSqueak's elective euthanasia.

I arrived at the appointed time to find the entire family waiting with PipSqueak.  The horse had been bathed, his mane and tail brushed to a shimmering white, hoof dressing applied to all four feet, and he wore a beautiful new halter.  We all walked out with PipSqueak to the area where he was to be buried.  PipSqueak walked comfortably because his owner had given him one last whopping dose of bute that morning along with a bucket of grain so that he would be comfortable and feel especially spoiled in his final hours.  As we walked we shared stories of PipSqeak's many exploits over the years.

PipSqueak stood patiently while everyone said their goodbyes.  As I injected the sodium pentobarbital PipSqueak's family stood close by, speaking to him gently.  As soon as he fell to the ground we followed his descent, everyone keeping a hand somewhere on his neck or head.  We were very quiet,  his young owner began to cry and arms encircled her in her grief.  PipSqueak passed from life to death very swiftly, in the company of humans who loved and respected him, and who took the responsibility of ending his life squarely on their own shoulders, with compassion and grace.

I find the topic of euthanasia very complex, and will discuss it in more theoretical, and practical terms, over the next few days.  Please feel free to comment on this blog entry with your own thoughts and experiences concerning this topic.


I believe that education is the key to evolution.
I believe that learning never stops.

4/20/2010 Spring Breeding - the Transitional Period

Vet tip of the Day: The Mare's Transitional Period

It's the time of year when I get lots of calls regarding breeding mares.  In the past week I've also had several  about performance mares exhibiting unusual behavior and brood mares showing irregular heat cycles.  Both of these problems are related to the seasonal nature of mare's reproductive cycle, and may be particularly evident this year because of our unusual weather patterns. Today I am going to briefly review the mare's estrous cycle with emphasis on the transitional period that affects many mare's between January and April.

Seasonal variation in the duration of daylight has a profound influence on mare reproductive performance.  The horse is a seasonal breeder - increasing daylight improves the mare's reproductive efficiency while shortened days results in poor reproductive regulation.  Daylight is believed to act by stimulating the production of melatonin by the pineal gland, located within the brain.  This melatonin in turn causes the hypothalamus to release GnRH (gonadotropin releasing hormone).  GnRH acts on the pituitary, causing production of FSH (follicle stimulating hormone) and LH (luteinizing hormone) which influence the ovaries to develop and release follicles. In order for successful conception to occur, a mature follicle, or egg, must be fertilized by healthy sperm and then arrive in a uterus which is ready to accept and nourish it as it develops into a budding embryo. 

The transition from the short days of winter when most mares stop cycling all together, to the long days of June, when fertility is at its highest, is a gradual, progressive process.  During the spring and fall, mares enter a period of anovulatory receptivity, or the transitional period.  At this time, they often exhibit erratic estrus behavior, and while they appear to be in standing heat and accept a stallion, there often is not an associated ovulation of a mature follicle.  Even if a transitional mare does ovulate appropriately, it is also likely that the hormonal sequence necessary to maintain the early critical days of pregnancy will not be in place and the conceptus is lost.  Particularly in the spring, this transitional period is characterized by long, erratic heat cycles without ovulation. 

During the transition period performance horses often exhibit irritable behavior and are difficult to train.  It is during this time that trainers are often looking for ways to suppress reproductive activity so that their mares will behave appropriately in the show ring.  There are many oral supplements available over the counter which claim to improve the demeanor of irritable mares. The effectiveness of these supplements is debatable.  The only way to know if one will help your cranky mare is to try.  For years people have used cattle subcutaneous hormonal implants to control mare's heat cycles, but multiple research trials have been performed using these implants and no one has ever been able to show that they have any real effect on the mare's hormonal regulation.  Injectable progesterone in olive oil can be used intramuscularly to prevent mare's from cycling during the transitional period with variable success.  The only truly reliable means of controlling a mare's reproductive system and preventing cycling is the daily administration of  oral Regumate liquid (a synthetic progesterone).

Once the transitional period is over and mare's are cycling regularly, reproductive efficiency rapidly improves.  The "normal" mare has a 21 day heat cycle.  She is not receptive for 14-15 days (diestrus), then comes into heat for 4-7 days (estrus), ovulating 12-24 hours before behavioral signs of estrus disappear. Regarding performance horses, some mares continue to be difficult during the days close to ovulation, but in general the number of days when undesirable behavior is exhibited are markedly reduced, and can be predicted based on following the heat cycle.

So, when your mare is acting like a maniac and its February or March, remember that part of her behavior may be attributed to the "raging hormone" condition that we all recognize in each other from time to time.  Mares, just like people, are very individual in their reaction to their own internal chemistry.  Some have placid dispositions and do not seem affected by the ups and downs of hormonal transitions while others are truly distressed during these transitional phases and should not be punished when they are at the mercy of Mother Nature's nasty tricks.  If you own a mare you are trying to breed in the early spring, or a performance horse with seasonal behavior problems, speak with your veterinarian about management practices that may improve your breeding success or help your mare's disposition. 

I believe that education is the key to evolution.
I believe that animals are the key to compassion.
I believe the learning never stops.