The Most Underappreciated Performance Enhancer

It’s free too.  Next to air, this is the single most important factor in supporting good performance and maximizing response to training and conditioning.  Water.

The horse’s body is about 70% water.  From brain functioning to the cushion of joint cartilage and deformability of bones, water plays a critical role in the function of every cell. From a performance standpoint, water as sweat regulates body temperature to permit cellular reactions to continue normally.  Water in the blood stream maintains blood volume and pressure to deliver nutrients to working tissues and remove waste materials. Water in and surrounding the cells facilitates nerve transmission and generation of energy.  During recovery from exercise it takes 7 grams of water to replenish just 1 gram of glycogen.

Exercise generates tremendous amounts of heat. Because the horse can only survive with body temperature within a fairly narrow range, cooling mechanisms take precedence over all other functions needing water and the horse will continue to sweat until on the brink of death. Because of the rapid and large loss of water through sweat (minimum of at least 1 gallon/hour for the average horse), other body functions are rapidly compromised.  In fact, inadequate body hydration likely accounts for  more subpar performance than all other causes  combined.

Research has revealed that as little as a 2% loss of body water weight can result in a 10% decrease in performance.

Having clean water available at all times, including as much as they want during and after exercise, is the first step in ensuring hydration is not suboptimal in hot weather.  The horse also has to drink it.

How many times have you been away from home at a competition or ride only to find your horse won’t drink the water there? It’s extremely common. One solution is to bring water from home.  A large picnic carrier filled with half water and half ice will survive even a long hot trip in the back of a truck. Most horses will also readily drink bottled water. Investing in a few 5 gallon jugs is well worth the small price.  Also bring his bucket from home.

If you can’t always have your horse close to your truck and water, get the horse accustomed to a flavored water at home.  Equine flavoring products can be used, preferably sugar free, or use a handful of feed. The advantage of the sugar free flavorings is they won’t support bacterial growth in the heat and are easier to clean out of the bucket.

Getting the water in is only half the battle. To keep it there your horse must have normal electrolyte levels both in the blood and in the tissues.  It is especially important to stay on top of sodium and chloride by remembering to give the horse both his baseline salt requirement and to replace electrolytes lost in sweat. See this recent blog for details:

The next time your horse seems to be flagging in the heat remember the solution may be as simple as a long drink and electrolyte replacement. You will see the results within minutes.

Eleanor Kellon, VMD


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Living with Old Soft Tissue Injuries

Tendon and suspensory ligament injuries plague horses performing in all disciplines.  Even pleasure horses and pasture ornaments may fall victim if they take the proverbial “bad step” over rough ground conditions.

These are every bit as painful as bone or joint disorders and take as much as a year to heal. Even when healing has progressed well these tissues are permanently weakened compared to their uninjured state and always at risk of re-injury.  Minor flare ups are common when horses are back in work. They may not have any serious lasting consequences but they really take their toll in disrupted training schedules.

from Paulick Report

Fortunately, a little extra care can make a huge difference in terms of keeping previously injured areas tight and free of problems.

  • Use boots or wraps when working the horse.  I don’t believe they really do much in terms of “supporting” the horse but they do help hold all the structures in correct alignment. If you have ever had a painful ligament or tendon you know how it is possible to use the involved structures (e.g. a wrist) without pain if you have a proper wrap in place.
  • Always ice the area for 30 minutes after work. Apply as soon as possible after exercise stops, even before removing tack or hosing.  This sounds like a lot of work but once you get into a routine it becomes second nature.  Bring preloaded ice wraps to the barn in an insulated carrier. Just swap them out as the ice melts.  Cold is very effective at curtailing minor inflammation but won’t  interfere with the normal low level inflammatory processes needed for tissue maintenance and remodeling.
  • If the area tends to fill/swell when the horse stands still, use standing wraps when in the stall. The purpose is not to block the appearance of a sign of problems, but to prevent it from interfering with optimal circulation.

The above measures will not mask signs of serious re-injury but they will prevent or minimize discomfort from things like adhesions stretching or breaking down with exercise.

In terms of general management, movement is your friend in keeping all tissues as strong and flexible as possible so minimize stall time.  Even a smallish paddock is better than standing still. Carefully condition the horse for the work you will be expecting and avoid fatigue at all costs.

Whether shod or barefoot, absolutely meticulous attention to hoof trim and balance is critical to preserving the tissue repair.  Working only over manicured surfaces is unrealistic but do avoid heavy going and slow down on uneven natural surfaces.

The common practice of giving a horse with an old injury phenylbutazone or other antiinflammatory/analgesic before work in anticipation of it stressing the area is not a good idea.  If you are doing something that causes a reaction sufficient to require these drugs you shouldn’t be doing it in the first place.  Work up to the desired level of performance gradually and if you consistently run into problems at a certain level of activity you will just have to accept the limitations or risk doing serious damage.

Tendons and ligaments are a specialized form of connective tissue, the most abundant tissue type in the body which also accounts for over 50% of the body’s protein yet little attention is paid to the role of nutrition. Lysine is the major essential amino acid in connective tissue, as well as its derivative hydroxylysine.  Vitamin C is required for that conversion.  Copper, a very common deficiency, is needed for the formation of strong reinforcing cross-links in the structure of tendons and ligaments.  Although its exact role is unclear, magnesium is important to integrity of these tissues. Use of the quinolone antibiotics which can tie up magnesium is associated with side effects of tendon/ligament damage that can be prevented with magnesium.

Necessity of vitamin C supplementation is questionable since the horse can manufacture vitamin C  but making sure lysine, magnesium and copper are adequately supplemented is simply common sense and important to these horses. Couple with some simple management adjustments and you will maximize the chance of enjoying an athletic partnership with the horse.

Eleanor Kellon, VMD


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Plant Pigments and the Immune System

Green drinks are a hot human health craze these days and with good reason. Plant pigments possess a variety of beneficial properties for the immune system.

Green pigment (chlorophyll) is only a piece of the picture.  Flavonoids, carotenes, lycopene, zeaxanthin, anthocyanins, betalains and others are among the wide array of plant pigments.

A primary function for the plant is to capture the energy of light which the plant uses for photosynthesis, the creation of high energy compounds ATP and NADPH, which are then used to produce food sources for the plant, including glucose. The horse can’t use pigments this way but his body interacts with these nutritional substances, especially in the immune system.

Immunity is an incredibly wondrous and intricate function.  It is divided broadly into reactions which shoot first and ask questions later – the innate immune system which responds  immediately to any foreign substance or organism – and the sophisticated/adaptive immune system which targets specific invaders with antibodies and remembers them in stored cells. Inflammation is an inherent part of the immune response to invading organisms or toxins, as well as the method of removal of dead or injured tissues. The immune system also has an intricate set of checks and balances which protects the body’s own tissues from direct attack as well as from collateral damage by friendly fire. Immune system reactions are turned off by a combination of the inciting problem being removed and counter-regulatory messages which control and eventually stop the reaction.

The nature and intensity of immune system reactions is determined by a complex formula involving genetics, the type of threat, the animal’s overall health status, adequacy of basic nutrition (calories, fats, protein, vitamins and minerals) as well as food fractions which normally interact with the immune system. The latter is where plant pigments come into play.

Many plant components interact with the horse’s immune system at the most basic level – gene expression. The study of this is called Nutrigenomics and it is adding tremendously to our understanding of how diet supports health.  Basic research into the functioning of the immune system also shows how diet goes far beyond supplying basic energy sources, vitamins and minerals.

Chlorophyll supports the production of innate immune system cytokines by lymphocytes lining the digestive tract. Chlorophyllin, a sodium copper derivative of chlorophyll, supports the natural healing of open wounds when applied topically and consuming it is associated with higher numbers of all immune system cells.

Chlorophyll and chlorophyllin are also natural antioxidants, as are all plant pigments. Quercetin and other citrus bioflavonoids are naturally occurring dietary participants in counterregulatory gene activity which maintains normal healthful levels of inflammation. Many plant flavonoids also work with the body in maintaining inherent defense systems against the invasion of cells by harmful organisms.

Proanthocyanidins from grape seed extract are one of the most potent antioxidants on the planet and possess all the attributes described above.  They also support the body’s ability to naturally regulate allergic reactions and responses to temporary irritation by environmental toxins.  The pigments of the blue-green algae Spirulina work with the horse’s body in the same way.

Brightly colored foods are as healthful for your horse as they are for you.

Eleanor Kellon, VMD



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Stallion Handlers Should Be Moms

Some mom skills come in really handy – like sensing when things are too quiet and having eyes in the back of your head.  In many ways stallions are like overgrown kids.

This is not to make light of interacting with stallions in any way. They are quick, powerful and no mere human is a match for a stallion in a flat out battle. However, the common perception of stallions as aggressive and inherently dangerous is not accurate.  They are also not sex crazed maniacs that will hurt a mare and kill foals.  Nothing could be further from the truth.  Mares are much more of a threat to the stallion than the other way around and stallions are normally very protective of foals.

Stallions mellow with advanced age to rather stately and dignified gentlemen but in their younger days can be challenging.  It starts early. Colts are more active and physical than fillies, tormenting their dams from an early age with their penchant for mounting.  Rearing and mock fighting with their pasture mates is also a favorite.  As they become sexually mature, feral males form bachelor bands where they peacefully coexist but with an obvious herd hierarchy that is established through posturing and threats much more often than any actual physical contact. The posing is part of their daily interchanges with herd mates.

This behavior carries over to human interactions with domesticated stallions. The dominance  behaviors almost become a form of play where the horse is constantly trying to sneak in a nip, invade your space or keep you from entering his.  Calling his bluff with a sharp word and tap is sufficient to “win” if you are operating from a position of strength – i.e. have adequate restraint on the horse if he is out of the stall or have yourself in a position of power and movement if you are in an enclosed area with the horse loose. These encounters won’t be a once and done phenomenon.

The stallion will continue to challenge you every day and several times a day.  As handler and horse get to know one another, these exchanges can be almost invisible to an observer as a subtle change in body language communicates both the posturing and the response.  Like a mom, an experienced stallion handler can read their minds and convey the don’t-you-even-think-it message with as little as a sideways glance. The horse appears to only be quietly behaved but let someone else try to work with the horse and he can seem to be a different animal, immediately “in your face”.  There is no malice in the behavior though; no intent to inflict harm.

I’m leaving a lot out here, most notably the ground work training of breaking, leading, respecting your space, teaching the absolute zero tolerance for serious behaviors like rearing, striking and aggressive biting and making sure the animal has sufficient exercise and social interaction, with other horses at least visible. However, stallions are trainable just like mares and geldings.  On the whole, dangerous stallions are made not born.  They are a product of poor management and abysmal horsemanship coupled with excessive physical force.

It’s unfortunate that many horsepeople will go their whole lives without ever getting to know a stallion. They are a challenge and keep you on your toes but their unique zest for life is the essence of horse.

Eleanor Kellon, VMD

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Summer Allergies

Nothing ruins enjoying the warm weather with your horse quite like the scourge of allergies.  Manifestations run the gamut from sneezing and snorting to wheezing, runny eyes and agonizing itching.

from Towcester Vets, UK

Allergies are basically a misdirected and unbalanced immune reaction. When the immune system is exposed to a protein that is not a normal component of the body the usual response is to engage both major arms of the immune system (termed Th1 and Th2) to develop antibodies of the IgG and IgA class.  In individuals prone to allergic reactions, IgE antibody is produced and primarily the Th2 type reactions are activated.  When the sensitized immune system is next exposed to the same protein (called an allergen), a reaction is triggered which results in release of chemicals like histamine.

Why some horses are prone to allergy is not entirely clear but studies have suggested a strong  genetic component.  A horse can inherit the predisposition to develop allergies but will not inherit any specific allergy such as to a particular food.

Management of the allergic horse includes minimizing exposure to the trigger as much as possible. Antihistamines may be used to try to prevent the development of new reactions but antihistamines cannot reverse symptoms already present. Corticosteroids are typically prescribed for problems that do not resolve on their own.  They are extremely effective but come with side effects such as reduced immunity and metabolic disorder with chronic use or high dosages.

We can help the horse by providing supplements that support a balanced immune response.  At the most basic level this includes key antioxidant nutrients of copper, zinc, selenium, vitamin E and omega-3 fatty acids.  These are indispensable building blocks for the body’s own antioxidant defenses such as glutathione, EPA, DHA and the superoxide dismutase enzymes.

Vitamin C is a key antioxidant both in its own right and by virtue of its ability to regenerate other antioxidants, like vitamin E, to an active form.  It is abundant in fresh grass but activity is lost rapidly in hays. Vitamin C is particularly important in the respiratory system and the eyes.  Flavonoids (e.g. quercetin) are plant compounds which work synergistically with vitamin C. MSM also has documented antioxidant activity.

Spirulina is an edible algae which promotes normal balance between the arms of the immune system including supporting the production of IgG and IgA antibodies and healthy levels of histamine.

Finally, several herbs have been found to support a normal balance between the Th1 and Th2 arms of the immune system.  These include Astragalus, Siberian Ginseng (Eleutherococcus), Pau D’Arco and Echinacea.  Herbals used topically can also provide soothing relief for temporary irritations.  Ingredients that excel in this include Aloe Vera, Chamomile, Calendula and Chickweed.

There is no question that allergies can ruin your warm weather fun and torture your horse but there are several nutritional and herbal approaches that can be used to support normal function of the immune system and provide temporary relief for skin involvement.

Eleanor Kellon,  VMD

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Electrolyte Supplements

If you are thinking ahead to the imminent summer heat by looking at electrolyte supplements, good for you.  Horses lose massive amounts of electrolytes (and water) in sweat, putting them at high risk for dehydration, impaired performance, heat stroke, GI issues and impaired organ function.

An electrolyte is simply a mineral present in the blood in a charged electrical state, positive or negative.  The major electrolytes of nutritional importance are sodium, potassium and chloride.  In addition to the sweat losses with exercise, requirements also include sweat losses at rest in the heat and baseline losses in urine and manure (digestive tract secretions).

Sodium is most problematic because dietary levels are usually very low. In hot weather the baseline requirement is at least 20 g/day for a 500 kg horse which is equivalent to approximately 2 oz of salt.  Salt, sodium chloride, is the best choice for a sodium supplement since chloride level in the diet is highly variable and could also be low.  Levels in grass hay range from a low of 0.169% to 1.035% in the Dairy One database which contains over 40,000 samples.

After meeting the baseline requirements you need to compensate for sweat losses. Sweat contains approximately twice as much chloride as sodium and twice as much sodium as potassium. Your first step in selecting a supplement is to find one that approximates these electrolyte ratios although if your horse is not exercised heavily in the heat you can allow lower levels of potassium since the equine diet always has excess potassium. In other words, sodium can be greater than 2X potassium.  The relative electrolyte amounts in horses is very different from human sweat so using human products like powdered Gatorade is not advisable.

If the product label only lists salt rather than sodium and chloride separately you can calculate the amounts using figures of 40% sodium in salt and 60% chloride in salt. For example, if the % salt is 50%, sodium would be 0.4 x 50% = 20% and chloride 0.6 x 50% = 30%.

Once you have found a product with the correct ratios of sodium, potassium and chloride the next step is to figure out how much you would have to feed.  Product labels don’t always make this easy!  Law requires they always be listed as a %.  A product that is 10% potassium will provide 0.1 x 28.4 (28.4 g/oz) = 2.85 g of potassium per oz. You will need to know the weight of the serving size in grams (g) if it is different from 1 oz.  A half ounce serving would be 14.2 g (28.4/2) and at 10% potassium would provide 0.1 x 14.2 = 1.42 g of potassium.

A horse that is sweating only lightly will lose about 5 grams of potassium an hour  but if sweating heavily loses over 20 g/hour.  There is a HUGE variation in the levels of electrolytes provided in a  manufacturer’s recommended “dose”.  For example, potassium ranges from less than 1 g to over 9 g/serving so you have to do your homework and compare your horse’s actual needs to what each serving of the various products provides.

To summarize correct electrolyte supplementation:

  • Meet baseline sodium and chloride requirements first, using 2 oz of salt per 500 kg of body weight
  • Look for a product that provides approximately twice as much chloride as sodium and at least twice as much sodium as potassium
  • Once you have a supplement with the correct proportions of electrolyte ingredients, calculate how many servings you need using the guideline of 5 g of potassium for every hour of light sweating up to 20 g/hour with profuse sweating (500 kg horse).  Note: Because you made sure the proportions were correct first you only need to calculate servings for one of the electrolytes.  The others will follow along in correct amounts because the ratios are right.

Eleanor Kellon, VMD

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No Quick Fix for Laminitis Risk

It’s perfectly natural to want a silver bullet that will instantly remove the threat of devastating health problems like laminitis but it’s just not that simple.

         The classical laminitis stance is something you never want to see.

The latest proposed silver bullet currently popping up in mail boxes and on groups is a magazine article from 2016 regarding a vaccine developed in Canada.  The headline was “Laminitis Vaccine Offers Horse Owners a Preventive Tool”.

The vaccine is against two exotoxins produced by Streptococcal bacteria which proliferate in the hind gut when there is an overload of grain starch or fructan. These exotoxins are believed to trigger the enzymatic cascade that breaks down the laminar connections in hind gut associated laminitis.  In an experimental model the vaccine prevented laminitis in 20 out of 24 horses and reduced the severity in the remaining 4 animals.  Formal testing for regulatory approval has not been done.

Sounds really promising so far but there’s one big problem.  The vast majority of laminitis cases are caused by insulin resistance, not hind gut carbohydrate overload.  Streptoccal overgrowth and exotoxin absorption are not involved so obviously protecting against those exotoxins isn’t going to work.

There is no guaranteed protection against pasture laminitis with an IR horse. There are times of the day, weather conditions and grass growth stages that are more likely to be safe than others but no guarantees because grass is a living tissue with sugar and starch levels in constant flux.

Well controlled IR horses are more likely to escape without problems if they accidentally get pasture access, or if you roll the dice and allow grazing when sugar and starch levels should be safe.

Good control requires hormonal normalization if the horse has Cushing’s disease/PPID (pergolide) and an IR appropriate diet with sugar and starch intake at less than 10% of the analyzed nutrients.  Correct mineral amounts and balancing are also very important.  Common deficiencies and imbalances which are involved with normal functioning and hormonal activity include magnesium, phosphorus, copper, zinc, selenium and iodine.  If your hay was grown on alkaline soils, common in the mid West, adding chromium can be of benefit since uptake of this mineral is impaired in alkaline soil.

Acetyl-l-carnitine is a metabolite normally present in the body that supports insulin sensitivity in other species when supplemented.  Jiaogulan is a Chinese herb that also participates in insulin responsiveness and supports normal blood flow to the foot in the face of the high vascular tone induced by IR.

It’s not as easy as a shot in the neck but correct nutritional support for an IR horse is your best defense against laminitis.

Eleanor Kellon, VMD

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Myth Busting

It’s easy for opinions or hypotheses that are repeated often enough to eventually morph into what passes as a fact and from there to a myth that’s difficult to eradicate. These are three commonly repeated, but wrong, horse feeding myths.

Constant access to hay buffers stomach acid/Feeding grain increases stomach acid.  Damkel et al in a 2015 study fed horses either free choice hay, limited hay plus grain or the hay and grain diet with a pectin and lecithin supplement (75 g/100 kg of body weight). The horses had electrodes implanted in their stomachs to monitor pH.  Diets were fed for 14 days before starting the experiment.  Horses on the free choice hay had significantly lower (more acidic) pH values with a median pH of 2.69 over 24 hours compared to the the hay/grain diet (3.35) or the hay/grain diet with the supplement (3.4).  Similarly, Nadeau et al 2000 found much lower pH in horses fed a grass hay diet than in those receiving corn and alfalfa. As a corollary myth, it has also been widely stated that alfalfa will reduce ulcers and buffer stomach acid but Vondran et al 2016 fed grass hay, alfalfa pellets or alfalfa chaff to weanlings and found no difference in ulceration in most areas but greatly increased ulceration at the pylorus in the weanlings fed alfalfa chaff.

Depriving horses of 24 hour access to hay causes cortisol to rise from the extreme stress.  Gordon et al 2009 fed overweight horses a diet of either a high calorie pellet or reduced calorie, low carbohydrate weight control feed with 1% of their body weight in hay.  Hay was only fed once a day, in the afternoon. Grains were fed twice a day.  Some of the horses on weight control and restricted hay were also exercised.  The unexercised weight control horses lost significant weight and also had a large drop in their cortisol levels from 11 ng/mL down to 1.8 ng/mL.  Exercised also dropped from about 10.6 to 6 ng/mL (note: exercise increases cortisol naturally). The control horses that did not lose weight because of the high calorie grain had no significant change in cortisol with this feeding pattern (although it dropped a little in them as well.)  Two other studies also found a drop in cortisol when feeding was restricted.

Feeding high glycemic index diets (i.e. grain) causes insulin resistance.  Suagee et al 2013 fed nonobese horses feeds of 10%, 20% or 60% non-structural carbohydrate (primarily starch) for 90 days.  They found no change in insulin sensitivity with the high carbohydrate diet. This study was important because other work looking at the effect of diet was done with horses that were obese or were deliberately overfed and became obese. Bamford et al 2016 also showed that feeding 1.5 g/kg body weight of glucose every day for 20 weeks did not alter insulin sensitivity even though it caused the horses to gain weight. In fact, feeding glucose actually improved insulin sensitivity in these non-IR horses.

Even if it seems to make sense it is always good to question what you think you know – and what other people think they know too.

Eleanor Kellon, VMD


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Can We Prevent Arthritis?

Oral joint supplements/nutraceuticals have been with us for a quarter of a century. It didn’t take long after their appearance for the question to be raised regarding the potential to actually prevent arthritis.

                      Few active horses escape the bane of arthritis.

There are now hundreds of studies looking at the ability of oral supplements to prevent the development of arthritis or slow its progression. For example, positive results have been found for Boswellia in mice (Wang et al 2014), mussel extract in rats (Chakraborty et al 2010),  quercetin in rats (Gardi et al 2015), glucosamine in rats (Aghazadek et al 2014), glucosamine in overweight women (Runhaar et al 2016) and long term chondroitin sulfate in humans (Kahan et al 2009) just to list a few.

The situation in horses is a bit more complicated.  Being natural athletes they often make whatever they are doing look easy but the sheer size of the horse means tremendous forces are generated on his joints.  These are further magnified by obesity, work on uneven ground, pre-existing OCD or traumatic damage, any hoof imbalances, conformation imperfections, rider weight, rider errors and quite possibly genetics.  Preventing arthritis will never be as simple as giving a supplement. Nevertheless, there is reason to think we can have a significant effect.

In one of the earliest equine studies, White et al 1994, it was found that a commercially available chondroitin and glucosamine supplement did not protect against arthritis induced chemically by injection into a joint.  However, Vidella and Guerreo 1998 did find significant protection by both oral and injected chondroitin sulfate in a similarly induced condition.  The only difference between injected and oral was the injected chondroitin worked faster.

A small unpublished study by Dr. Smith at Rood & Riddle in Kentucky looking at Thoroughbreds in training with and without supplementation with hyaluronic acid oral gel for 59 days found statistically significant decrease in the number of horses evaluated for lameness when supplemented. HA greatly reduced postoperative joint swelling following surgery for OCD lesions in the hock, Bergin et al 2006.  Prevention of postoperative joint degeneration was also confirmed by a study looking at supplementation with ASU (avocado soy unsaponifiables) in a situation where damage was created surgically, Kawcak et al 2007.  They found no effect on pain but greatly improved cartilage quality.

In the most recent study, Leatherwood et al 2016 treated young Thoroughbreds with 30 mg/kg/day of glucosamine sulfate for 84 days before injected a carpal (knee) joint with lipopolysaccharide, a bacterial product which induces inflammation.  A matched control group was not supplemented.  The glucosamine group showed reduced markers of inflammation and cartilage breakdown, increased marker of regeneration compared to the injected control group. That dosage produced a blood level of glucosamine very similar to what was reported to be preventative in laboratory animals.

What to use at what dosage is the million dollar question. Firm answers just don’t exist but the evidence points to keeping at the high end dosages for at least one of the three major joint ingredients – 10,000 to 15,000 mg glucosamine, 2500 to 3500 mg chondroitin, 100 to 200 mg hyaluronic acid.

That’s what I’ve been doing with our racing Standardbreds for the last quarter century, starting when they are broken.  The difference in the incidence and severity of joint problems compared to the days before these supplements were available is undeniable. I’ve been around long enough to see both first hand!

Eleanor Kellon, VMD

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Do Horses Have Food Allergies?

Your immediate response would probably be – Sure, why not? That may well be true but you could be surprised to find out that a true food allergy has never been formally proven in a horse.

Seeds, nuts and grains are among the most common food allergies in other    species

A food allergy is defined as an unpleasant or dangerous reaction to the ingestion of a food. It can range from life-threatening immediate anaphylactic reactions to hives or swelling and tingling in the mouth or lips.  People may develop eczema and dogs often have itchy and inflamed ears, faces and/or paws.

Gastrointestinal symptoms may also be involved, such as abdominal pain, bloating/gas, vomiting or diarrhea although these may be symptoms of food intolerances rather than true allergy. For example, horses may be particularly susceptible to food intolerances because of the extensive fermentation in their hind gut.  The microflora of each horse is unique so the way they handle fermenting things may be different.

For all the horses you hear about  that are supposed to have feed allergies you would think that someone would have published on the problem by now.  A major difficulty is diagnosis. In humans and dogs it is well established that skin testing by scratch, patch or intradermal testing has at best 60% accuracy while blood testing for IgE levels is even worse. You might as well go through the list of possible allergens flipping a coin.

Despite this, blood testing for equine feed allergy is widespread and of course the companies claim it is useful. Are horses really different?  A 2016 study (DuPont et al) used a commercial testing service to do blood IgE allergy testing on 17 healthy ponies and tests were repeated twice to look at consistency of results.  They found 10 of the 17 tested positive for one or more food allergy but only 3 tested positive twice and only 1 tested positive twice for the same allergy.

Ponies with positive IgE tests were further tested with the “gold standard”, a challenge test where they were fed the identified offending food for 14 days and serum amyloid A levels were also monitored. Serum amyloid A is a very sensitive marker of inflammation.  There were no abnormalities in blood work or symptoms during the provocative trial.

Two studies have reported that intradermal testing can sometimes provoke signs of enteritis (intestinal inflammation) and hives in horses with food allergy confirmed by alleviation of signs when the food is removed from the diet.

A 2001 study (Lorch et al) looked at horses with known skin or lung allergic disease and compared reactions on intradermal testing to 3 different blood allergy assays. They concluded “None of the 3 serum allergy tests reliably detected allergen hypersensitivity compared with the intradermal testing”.  Morgan et al 2007 also confirmed IgE testing was not worthwhile for skin allergies and Tahon et al 2009 found the same for RAO/”heaves”.

If only by chance, the blood IgE tests are bound to get it right sometimes but research really does not support their use as a diagnostic tool.  Too many people are unaware of this and agonizing unnecessarily over what to feed their horse based on a host of positives on IgE testing.

The horse cannot be allergic to a food he has never been exposed to so if you see positives for things you never fed you can write that off.  Also realize that when showing the signs you suspect are a food allergy it has to be something he is eating then.  The best way to get to the bottom of it is list hay/grass type(s) and food ingredients for all feeds and supplements. Start the horse on a hay only diet of a hay type he has never eaten before. If symptoms resolve, start adding back individual foods (e.g. oats only) one at a time allowing 2 weeks between additions.  If you add an item the horse is allergic to or does not digest well, symptoms will return.

Eleanor Kellon, VMD

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