Category Archives: Medical

Top Equine Medicine Studies of 2016 – from THEHORSE.COM

I found this article on THE HORSE (the  Very interesting… Good to know what the top vets thought were the most interesting equine medical studies of 2016!

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Top Equine Medicine Studies of 2016

 Top Medicine Studies of 2016

PENS–a minimally invasive neuromodulatory treatment–could be a new solution to headshaking in horses.


Around the globe veterinary scientists investigate equine health issues in a search of new treatments and diagnostics or to substantiate conventional wisdom.

Each year during the Kester News Hour, part of the annual American Association of Equine Practitioners Convention, three esteemed veterinarians offer their top picks from current published studies in their respective specialty areas of surgery, reproduction, or medicine in a popcorn-style research roundup.

At the 2016 meeting, held Dec. 3-7 in Orlando, Florida, Rob MacKay, BVSc, PhD, Dipl. ACVIM, a professor at the University of Florida, in Gainesville, presented his selection of research topics in medicine, ranging from equine herpesvirus to headshaking.

Heparin for EHM Prevention

Equine herpesvirus myeloencephalopathy (EHM) is the dreaded neurologic form of equine herpesvirus-1 (EHV-1). During outbreaks, infection control and treatment are paramount, but the virus still confounds veterinarians for one reason: No reliable and tested medication is available for treating or preventing the disease.

Enter a research team from the University of Zurich, in Switzerland, and an EHV-1 outbreak that involved 61 horses. The veterinarians hypothesized that the drug heparin, a blood thinner/anticoagulant, might help manage EHM infection spread during outbreaks because of the virus’ procoagulant nature. So, beginning on Day 10 of the outbreak, the team administered heparin to 31 EHV-1-infected horses on the first day of fever, before the onset of neurologic signs. Thirty horses infected with EHV-1 before Day 10 of the outbreak were not given heparin.

The researchers analyzed results after the outbreak and found that the heparin-treated horses showed a lower EHM incidence (one out of 31) than did the untreated horses (7 out of 30). Results indicate that heparin might be useful in managing EHM spread during an outbreak, MacKay said, but because important controls were not possible during this study, the work needs to be confirmed by additional studies.

Walter J, Seeh C, Fey K, et al. Prevention of equine herpesvirus myeloencephalopathy – Is heparin a novel option? Tierärztl Prax 2016;44:313-317.

Diet and Omeprazole to Control Equine Gastric Ulcers

Veterinarians who treat horses with equine gastric ulcer syndrome (EGUS)—and owners who manage them—know that keeping EGUS under control is a balance between medication, feed type, and feeding schedule. In an effort to provide “real world” data on the efficacy of omeprazole for suppressing gastric acidity in the horse (which is related to the formation and recurrence of EGUS), Australian and British investigators took a closer look at diet and drug treatment for affected horses.

In the study, a group of horses consumed two different diets, one a free-fed (at liberty) “all-hay diet” and the other a concentrate-based (high-grain, low-fiber diet) “racehorse diet.” MacKay noted that veterinarians often recommend high-forage, low-concentrate diets to manage EGUS by simulating the horse’s natural grazing tendencies. Conventional wisdom for treating EGUS would say that horses on an all-hay diet would do better than horses on a concentrated, grain-based feed.

In addition to the two diets, the study horses also received omeprazole treatment.

Researchers then measured the horses’ stomach pH on Day 0 for a baseline and recorded their stomach pH for continuous 23-hour cycles. Ideally, EGUS treatment with omeprazole raises stomach pH (making it less acidic), allowing existing ulcers to heal.

The seemingly surprising study result? The “racehorse diet” group fared better, with their stomach pH improving the most after omeprazole administration, MacKay said.

But don’t throw out your slow-feeders just yet. Rather, MacKay said, the study simply suggests omeprazole works best when administered on an empty stomach, and veterinarians should consider making minor feeding schedule adjustments to accommodate drug treatment times. “Withhold hay for two hours before and after dosing,” Mackay suggested.

Sykes BW, Underwood C, Greer R, et al. The effects of dose and diet on the pharmacodynamics of omeprazole in the horse. Equine Vet J 2016; DOI: 10.1111/evj.12630.

Liver Failure Related to Supplement

An otherwise healthy 8-year-old Holsteiner gelding presented to the University of Pennsylvania School of Veterinary Medicine’s (Penn Vet) New Bolton Center, in Kennett Square, colicky, off his feed, listless, and jaundiced. Ultimately veterinarians euthanized the horse, but subsequently found that he had a small, flaccid liver and Alzheimer-like cells in his brain.

All signs pointed to liver failure and consequent brain disease related to toxicity. But what caused the horse’s acute illness? No other horses in his barn showed signs of sickness, and veterinarians found no evidence of hay or feed contamination or potential exposure to toxic plants. The research team started sleuthing to uncover the cause, ultimately testing an oral supplement containing C-phycocyanin that the horse’s owner had purchased to support his joint health.

C-phycocyanin is derived from blue-green algae (cyanobacteria), and research shows it might have anti-inflammatory and antioxidative properties that help osteoarthritis is horses, dogs, and humans. However, blue-green algae can also produce microcystins, which are highly toxic and often associated with algal blooms.

In this case, tests confirmed that three containers of the supplement purchased for the horse—including one that was open and had been fed to him—contained the toxins. The veterinarians concluded that consuming the toxic supplement had likely sickened the horse, leading to his death.

MacKay’s takeaway: Despite professional-looking label and marketing claims “supplements are not always safe,” he said. Furthermore, he pointed out that blue-green algae harvesting and processing for supplements is not regulated.

Mittelman NS, Engiles JB, Murphy L, et al. Presumptive iatrogenic microcystin-associated liver failure and encephalopathy in a Holsteiner gelding. J Vet Intern Med 2016;30:1747-1751.

Effect of Rifampin on Clarithromycin Absorption in Foals

Veterinarians commonly use the antibiotic rifampin in combination with a macrolide antibiotic such as clarithromycin to treat Rhodococcus equi infections in foals. A team of German researchers compared the pharmacokinetics (how drugs move through the body) of clarithromycin (CLA) given orally with rifampin to data from foals given CLA alone. They found that CLA concentrations lowered by more than 80% in foals’ blood and bronchoalveolar cells when rifampin was co-administered with CLA.

Although CLA absorption was improved by giving the rifampin four hours after CLA, rather than at the same time, this effect was slight, and the investigators did not consider it clinically significant.

The research team found that rifampin suppressed CLA absorption by upregulating the actions of P-glycoprotein, an “efflux protein” that actively pumps the antibiotic back into the gut’s lumen.

For MacKay, the study’s main take-home is that rifampin likely severely reduces uptake of all macrolides used for R. equi treatment (i.e., CLA, azithromycin, erythromycin). Notwithstanding this effect, the CLA/rifampin combination remains a clinically effective R. equi treatment.

“More work is needed to discern whether the perceived advantage of rifampin outweighs the negative effects on macrolide absorption,” MacKay said.

Berlin S, Spieckermann L, Oswald S, et al. Pharmacokinetics and pulmonary distribution of clarithromycin and rifampicin after concomitant and consecutive administration in foals. Mol Pharm 2016;13:1089-1099.

Retrospective Look at Lyme Neuroborreliosis

The neurologic form of Lyme disease in horses—or more accurately, equine neuroborreliosis (NB)—is as difficult to describe as it is to diagnose, in part because little literature on the subject exists. That’s why a research group at Penn Vet delved into a retrospective study of equine NB cases in hope of providing a detailed description of the disease’s clinical signs, diagnostics, and pathologic findings.

Sixteen equine cases qualified for the research paper based on basic selection criteria, which included location in areas of the northeastern United States known to be at high risk for Lyme disease and post-mortem histologic findings consistent with previous reports of NB without evidence of other disease. Study candidates came from New Bolton’s own caseload, as well as other referral clinics in the northeast.

The study found variable clinical signs, including:

  • Muscle atrophy/weight loss;
  • Cranial nerve deficits;
  • Incoordination;
  • Changes in behavior;
  • Difficulty eating or swallowing;
  • Muscle tremors;
  • Neck stiffness;
  • Episodic respiratory distress;
  • Uveitis;
  • Fever;
  • Joint swelling; and
  • Heart irregularities.

Of the 16 horses, only six tested positive for Borrelia burgdorferi (the causative agent of Lyme disease) infection via standard immunodiagnostic testing of blood or cerebrospinal fluid. PCR testing on cerebrospinal fluid for exposure to the tick was negative in all seven cases that were tested.

MacKay’s takeaway: There’s still a lot we don’t know about Lyme disease in horses.

“Signs are nonspecific and numerous, routine bloodwork is unhelpful, and tests such as the Lyme multiplex are not diagnostic,” MacKay said.

Johnstone LK, Engiles JB, Aceto H, et al. Retrospective evaluation of horses diagnosed with neuroborreliosis on postmortem examination: 16 Cases (2004–2015). J Vet Intern Med 2016;30:1305–1312.

PENS for Treating Horse Headshaking

Headshaking in horses is a frustrating chronic problem—likely a response to nerve pain—that has no consistent, effective treatment. Managing cases can, in turn, leave veterinarians and horse owners shaking their own heads.

But there’s a promising new treatment that’s recently been tested by researchers from the University of Bristol, in Somerset, U.K.: percutaneous electrical nerve stimulation (PENS) therapy. This is a minimally invasive neuromodulatory (the physiological process by which a given neuron uses one or more chemicals to regulate diverse populations of neurons) treatment used to manage human neuropathic pain.

Researchers looked at seven horses diagnosed with headshaking that showed clinical signs at the study’s onset. They sedated and treated the horses with a PENS probe following a protocol developed for managing nerve pain in people. The horses each received a series of three or four treatments, with researchers repeating treatments as headshaking signs recurred.

The results had MacKay shaking his head yes, calling the treatment protocol both “safe and promising.” All horses tolerated the treatments well, according to the paper. Two of the horses had increased headshaking for up to three days after the initial treatment session. Six of the study’s horses responded positively to their first treatment and returned to ridden work at the same level as prior to onset of headshaking. Five of the seven horses continuing to respond to subsequent treatments, gaining up to 20 weeks of relief from headshaking after the fourth treatment.

Roberts VLH, Patel NK, Tremaine WH. Neuromodulation using percutaneous electrical nerve stimulation for the management of trigeminal-mediated headshaking: A safe procedure resulting in medium-term remission in five of seven horses. Equine Vet J 2016;48:201-204.

About the Author

Michelle N. Anderson, Digital Managing Editor

Michelle Anderson serves as The Horse’s digital managing editor. In her role, she produces content for our web site and hosts our live events, including Ask the Vet Live. A lifelong horse owner, Anderson competes in dressage and enjoys trail riding. She’s a Washington State University graduate (Go Cougs!) and holds a bachelor’s degree in communications with a minor in business administration and extensive coursework in animal sciences. She has worked in equine publishing since 1998. She currently lives with her husband on a small horse property in Central Oregon.


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What do you know about MAGNESIUM and your horse? Some say that magnesium is VITAL to your horse’s MENTAL AND PHYSICAL CONDITION!

I came upon this article about magnesium.  To be honest, I haven’t paid attention to how much magnesium my horses are getting…

…but Wrigley sure fits into the model for a deficient horse.


I am going to research my local feed store and see what they have in bagged magnesium supplements.  It is said to be inexpensive and easily excreted.

Please read the below articles.  I had no idea!

Original article linked here.

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Magnesium: The Mineral Superhero

Very few people are aware of the enormous role magnesium plays in a horse’s body. After oxygen, water, and basic food, magnesium may be the most important element needed to maintain health. It is vitally important, yet hardly known.   Magnesium is by far the most important mineral, regulating over 325 enzymes in the body.  Magnesium supplementation has been shown to improve performance and allow human athletes to reach exhaustion later in their exercise routine. It increases oxygen delivery to muscle tissue; it promotes muscle strength, endurance and relaxation. Magnesium also activates enzymes necessary for the metabolism of carbohydrates and amino acids which lead to protein synthesis.

Magnesium is often the most neglected mineral in horse feeds.   Spring grass is typically deficient in magnesium due to the fast growth rate and at this time of year many horses seem hotter and more difficult to ride.  Owners often attribute this to too many carbohydrates in the grass.  While this may be part of the story, what is often overlooked is that these horses may be deficient in magnesium.  Magnesium deficiency has varying effects on the horse population.  Some horses do not suffer any signs while others are almost unrideable due to their apparent silliness and hyperactivity.  Adding magnesium to their diet may have a dramatic calming effect.  To understand why magnesium affects the horse in a calming manner, it is important to know what is happening in your horse’s body on a cellular level when there is a magnesium shortfall.

Calcium and magnesium work closely with each other.  Calcium needs magnesium to assimilate properly however magnesium does not need calcium.  Calcium is in charge of contracting the muscle and magnesium looks after the relaxation or release of the muscle much like a gas pedal and a clutch work together.    When a muscle cell is triggered, the cell membrane opens, letting calcium in and raising the calcium level in the cell setting off a reaction and the muscle contracts.  When the contraction is done, the magnesium inside the cell helps to push the calcium back out of the cell releasing the contraction.  This happens very rapidly.    When there is not enough magnesium in the cell, calcium can leak back in causing a stimulatory effect and the muscle cannot completely relax. This can put the body into a continually stressed state.  Low magnesium makes nerve endings hypersensitive thus exacerbating pain and noise.    Magnesium is required for proper nerve and muscle function.

The use of magnesium today is often incorrect.   One reason is this: Calcium needs magnesium in order to assimilate into the body. However, when too much calcium is consumed, it inhibits the body’s ability to absorb and utilize magnesium efficiently.  To maintain proper levels in the blood, the body will borrow magnesium from bones and soft tissue to make up for the shortfall in order to assimilate the calcium.   Over time, this creates an accumulative negative reaction in the body that actually triggers the body to release adrenaline adding to the excitatory behavior we see in deficient horses.    To correct a deficiency, magnesium needs to be offered by itself, not with calcium.  Only approx 1% of magnesium is stored in the blood, the rest is stored in soft tissue and bone and the body is very efficient at maintaining that level in the blood stream to facilitate organ function.  This is why blood level magnesium tests are rarely indicative of an animal’s true magnesium status.  A horse would be severely deficient and would be very ill by the time a blood test would indicate a shortfall.

Horses with magnesium deficiency may have all or only a few of these signs so it is important be aware of them.    They may be borderline and only exhibit signs during competition or stress.  For instance, horses with magnesium deficiency often have very sore tight backs in spite of excellent saddles and pad, proper fit, conditioning and training.  They don’t respond well to chiropractic adjustments and massages or these treatments don’t last more than a couple days and the tension and soreness return.  They often resent or even act afraid of being touched leading the owner to ask themselves, ‘Is someone abusing this horse when I am not around?’  Their response to outside stimuli is over reactive and they tend to become fractious, worried, fearful or resistant to training.

Other signs:

  • Unable to relax physically or mentally
  • Muscle tremors, twitches, flinching skin, or all over body trembling especially after exertion (not related to outside temp)
  • Body tension
  • Does not tolerate long periods of work– often becoming more excited instead of working down
  • Has difficulty with collection or picking his back up under saddle, moves hollow
  • Random spooking, running through the bridle, inconsistent from one ride to the next
  • Angry about being brushed, blanketed or touched or palpated on either side of spine
  • History of tying up
  • Fatigue
  • Painful heats in mares
  • Bucking or rearing 20-30 minutes into a ride for no apparent reason
  • Requires long periods of lunging before being able to focus on work
  • Would be described as ‘thin skinned’ or over sensitive to sound or movement
  • Massage and chiropractic adjustments do not have lasting affects
  • Teeth grinding
  • Irregular heartbeat or pounding heart- endurance horses often experience this at vet checks

Magnesium is assimilated quickly in times of stress, such as traveling or heavy training.  Horses lose magnesium through sweat and urine.  Many performance horses can become deficient as the season progresses as they are using the available magnesium more rapidly due to stress, travel and competition. Horses with low magnesium status will often crave salt, which exacerbates the shortfall.  Calcium-rich diets can create an imbalance.

These horses are often difficult to work with, so riders tend to over exercise in an effort to manage behavior.  They are worked harder and for longer periods of time in an effort to wear them down which only adds to the shortfall thus creating a vicious cycle.  This causes more sweating and muscle cramping while contributing to fatigue, soreness, post competition pain and a negative association to work.  Behavior gets worse with more work and exposure to stress, not better. Subsequently, horses begin to resent the show arena often developing gate issues.

There are many factors that affect magnesium absorption and utilization.   Working horses require 10-30% more magnesium for light to moderate exercise, respectively, due to sweat losses.  Horses who sweat heavily will lose magnesium at a more rapid rate as well.

Magnesium toxicity is rare because excess is naturally excreted.   Magnesium should be split between morning and evening feedings to increase absorption and decrease its occasional laxative effects. Once a horse becomes low on magnesium, it is very difficult for them to catch up without supplementation.

What kind of magnesium should I use?   There are injectables, oral supplements and transdermal applications.  The most popular is oral magnesium oxide.  It is the least bio-available form of magnesium but it is the most available and inexpensive to feed.  Some horses do not like the powdery texture so picky eaters may turn up their noses to it.  It can also act as a buffer in the horse’s stomach which can help horses who tend to develop ulcers.  There are many oral forms of magnesium; the best form of which is Di-magnesium malate.  It is highly absorb-able, bio-available and has the least potential laxative effect.   Horse owners need to be aware that magnesium is in different forms such as citrate, oxide, ascorbate, which is the secondary ion.  Horse owners should avoid magnesium sulfate because of its laxative effect.  We recommend feeding 6 to 10 grams daily or to bowel tolerance, for working horses exhibiting mild to moderate signs of magnesium deficiency.  Horses showing severe signs of deficiency respond may require more.    Every horse is different and will have its own individual maintenance dose. This will also fluctuate depending on times of stress, showing, weather and pasture content.   When signs of deficiency begin to subside, the dosage can be tapered off.

Transdermal magnesium (delivered through the skin) is an efficient way to deliver magnesium to muscle tissue as it bypasses the digestive system all together and can be taken up by the muscles rapidly.  Transdermal application can be very therapeutic prior to athletic competition especially for the nervous horse and also post work out helping the body to recover and relax muscles.   It is available in sprays, lotions and a magnesium chloride salt form that is dissolved in warm water, sponged on the horse and rinsed off after 20 minutes.   This is the most economical of choices.

How do you know how much magnesium your horse is getting?  It’s very difficult without analyzing every bale of hay.  Many feed supplements only give you a percentage of mineral content, not a gram total.  One thing you can do to insure your horse is not deficient is to familiarize yourself with the signs of possible deficiencies in your horse.  If you think you may have a shortfall, it’s a very safe mineral to give in any case.   Toxicity is extremely rare.    Horses with reduced kidney function should not be supplemented with magnesium without vet supervision.   Make sure your horse has access to water.

Disclaimer: The information in this article in not intended to replace a one-on-one relationship with a qualified health care professional and is not intended as medical advice. It is intended as a sharing of knowledge and information. We encourage you to make your own health care decision for your horse based upon your own research and in partnership with a qualified veterinarian.


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Is your horse nervous?

Is he highly anxious in numerous situations?

Do you wish there is something you could do?

There might be an easy fix…

One of the most common signs of magnesium deficiency is extreme nervousness.

Read on below to find out more about this essential mineral…

Nervousness is a sign of magnesium deficiency.

Magnesium (Mg) plays a number of important roles in your horse’s body.

In his muscles, it attaches to ATP so that the ATP can be used by the muscle cells. If the Mg is not present, the ATP cannot be used, and the muscle would not be able to generate energy to carry out any functions.

It also plays roles in your horse’s blood, as well as acting as an activator for many enzymes throughout the body. It is necessary for many of the enzymes that work with ATP.

Almost 60% of the Mg in your horse’s body is in his skeleton, while another 30% is found in his muscles. The other 10% is found in various areas, including the blood and liver.

Mg is one mineral that the absorption of is not highly influenced by other minerals. Calcium, phosphorus, potassium, and aluminum all have little, if any effect on the absorption of Mg. It is also good to know that neither oxalate or phytase affect the absorption either.

Likewise, exercise appears to have little effect on the absorption rate.

Dietary Sources

Mg that your horse gets naturally from his diet is absorbed at a rate of about 40-60%. With most feeds containing around 0.1-0.3% Mg, it can be hit or miss whether or not a horse meets his daily needs.

However, inorganic forms that are often supplemented — Mg oxide, sulfate, or carbonate — appear to have a higher absorption rate at around 70%.

Magnesium Deficiency in Horses

Horses that are deficient in Mg show a variety of symptoms, including:

  • Nervousness/Flightiness
  • Muscle tremors
  • Ataxia (incoordination and unsteadiness)

Diets low in Mg also cause mineral clots to form in the aorta, the main blood vessel that carries blood from the heart to the body.

Magnesium Toxicity

Mg toxicity has not been studied in the horse. However, at normal dietary concentrations of varying Mg sources, it appears that there is little likelihood of toxicity being a problem.

The only time toxicity might be an issue is if Mg sulfate is used as a laxative to clear a blocked intestine. If it is overdosed, it can cause a toxic reaction, which has symptoms of kidney insufficiency, calcium deficiency, and intestinal damage.

Supplementing Magnesium to Horses

Many horses are supplemented Mg to try to calm them. There are a number of products on the market, including Ex-Stress:

Magnesium supplement for horses.

Sold by Jeffers Equine

Another popular supplement for Mg is Quiessence. These (and other commercial Mg supplements) are all good magnesium supplements, and work for many horses.

If you don’t want to spend that much money, another option is simply to buy magnesium oxide from your local feed mill. It is straight Mg oxide, which is what is the main ingredient in most Mg supplements anyways.

This usually is sold under the name of MagOx or FeedOx, and is a supplement that cattle owners use to mix into their cattle rations.

As a result, its usually not displayed on the floor, and you will have to ask an associate for it.

You’ll also probably have to specify that you want a cattle product, as the associate will probably be confused if you tell him or her that you are buying it for a horse.

In my experience it comes in a non-descript brown bag, usually in 50 pounds. Last time I bought it (sometime last year) it cost me $12 for the bag.

The great part about using MagOx is that it is so inexpensive…it is fed at a rate of tablespoons per day, so that bag lasts forever!

To use it as an insulin resistance treatment, supplement 3 tablespoons/day for the first month, then reduce that to 1 tablespoon/day for maintenance.

I supplement all my horses with Mg, as it is so inexpensive and it is thought that many horses today are probably Mg deficient to some degree.


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