Picky Eaters

Most horses are good examples of what it means to “eat like a horse”.  The few that don’t dig in as well can drive their owners nuts.

To make things worse, Murphy’s Law often kicks in so the pickiest horses are those that have restricted diets or really need the supplements or medications you are trying to get them to eat.

Like people, individuals vary in their preferences for specific flavors as well as textures. Most healthy horses will eat just about anything but the picky ones can pose a real challenge in finding something they will accept, especially if you have to add supplements or medications to it.

Even horses with robust appetites usually object to having powders puff up their noses when they eat. To prevent this, wet the feed lightly with water or oil (best is CocoSoya which also smells wonderful). This also prevents powders from sifting through and being left in the bottom of the bucket. Mixing powders into the feed thoroughly works for some horses but there are others that prefer to have them top dressed without mixing. I never could come up with a reasonable explanation for why that would be the case but nevertheless it’s true!

If the horse absolutely refuses to eat something you can try a few things:

  • Start by putting just a tiny amount in the meal, increasing slowly
  • Syringe it all directly into his mouth
  • My favorite, a hybrid, is to syringe most of the dose into the horse before feeding then feed the meal with progressively larger amounts of the offending substance in the meal. This method has the taste of the supplement or drug in his mouth already before feeding.
  • Some owners report the horse will accept things better when placed on the hay. This can work if you make sure the entire dose is actually sticking well to wet or oiled hay, and that the horse is truly eating and swallowing all of the hay, not spitting it out or sorting through it.

Sprinkling small amounts of the supplement or drug around the stall, on ledges as well as the floor, can also help desensitize the horse.

Texture can make a difference. You need some water or oil to make sure there is good adherence but too much water may cause the horse to refuse the meal.  Others like it more soupy. You have to experiment.  Also be aware that water may actually enhance the taste or odor of whatever you are adding, while oils tend to mask it.

Some horses are remarkably picky even when nothing is added to their basic meals.  This is a common problem when trying to switch from sweet feeds to low molasses options, or from high starch to low starch items. Important: If the horse is refusing to eat something that had previously been well accepted, suspect a problem with the feed even if you can’t tell anything is off, dental issue causing pain or some other illness. Refusal of concentrates and preference for hay is highly suspicious for gastric ulcers. Involve your veterinarian.

Otherwise, first try to wait out the boycott by not allowing any hay or turnout until the meal is cleaned up. If the horse has more staying power than you do, you’ll need to ramp up the appeal.  My three  favorite options are:

  • CocoSoya oil – even barn cats have trouble resisting it!
  • Crumble the horse’s favorite dry herbs or treats on top of the meal
  • Stevia-based flavorings (don’t use other artificial sweeteners).  Some people use Stevia sweetened pancake syrup but there are other options in horse agreeable flavors like apple, banana, peppermint, fenugreek and cherry.

It may take a lot of trial and error but with persistence you can overcome the picky eater problem.

Eleanor Kellon, VMD



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Do Feeds and Supplements Go Bad?

They sure do – but the labeling laws don’t make it easy for you to figure out which ones may be out of date.  To be fair, a big part of the problem is determining when “out of date” (best not to feed) is likely to be.

Human supplements are clearly labeled with both a lot number and an expiration date.

When we buy fresh dairy or meat products, canned or boxed foods, we expect to see “best by”, “expiration” or “use by” dates. These are based on expected room, refrigerator or freezer temperatures. With horse feeds, there’s no such thing as a standard room temperature. Feeds are stored under a huge range of temperatures and humidity depending on geographical location, time of the year and the facility itself. Another complicating factor is the composition of the feed and how it was manufactured.

Properly dried whole plain grains and very dry ingredients like beet pulp retain their nutrition and have low risk of molding for about a year but processed/broken grains, added fat or added molasses decrease the safe storage time to as short a period as 90 days.  High heat and humidity also lead to loss of vitamin potency.

For best nutritional value and safety it is best to only use commercial feeds that are less than 3 months old. You will never find an expiration date on a feed bag, or even a clearly marked date of manufacture.  However, you will likely find a code on the tag or bottom of the bag that includes a Julian date format, or some variation of it, for date of manufacture.  Never assume a feed is fresh just because it’s on a store shelf.

When date of manufacture is straightforward it is likely to look like day-month-year, e.g. 5Feb2018 would be February 5, 2018.  In the Julian system, month and date of the month are replaced by day of the year (first through 365th or 366 in a leap year). A manufacturer may use year-Julian day so 2018043 where year is 2018 and day of the year is 43.  Still others use a format that starts with a number or letter code of varying length to identify the mill where the feed was made, followed by a Julian date code.  This gets very complicated as you go through the decades of a century and have to figure in leap years https://landweb.modaps.eosdis.nasa.gov/browse/calendar.html. Bottom line is if your feed doesn’t have an easy to read date on it, call the manufacturer to get details on their coding system.

For the very freshest feed possible, look for a local mill that makes their own feed. These small mills have limited storage space, know their market and often make fresh feed every week.  Large barns that can quickly use up a minimum order of half ton to a ton of feed can often contract with the mill to have a custom formula of their choice made – usually for half what it would cost to buy the same feed from a large feed company.

Supplements are even more of a mine field than feeds. You will never see a clear manufacturing or expiration date. Even lot numbers are not required on the label but you may see one there or elsewhere stamped on the package. It may or may not be identified as a lot number. Before you buy a supplement, contact the manufacturer, ask where the lot number is located and if you can be told the manufacturing date if you call with the lot number.

The longest shelf life is for inorganic minerals, e.g. oxides, sulfates, chlorides, phosphates, that have no flavorings or organic base such as alfalfa or flax seed. These will not support bacterial or fungal growth, keep potency virtually forever and the only issue may be clumping over time. Because they have an organic base, organic minerals do support organism growth and their shelf life is around 2 years.

Liquid supplements of all types, including liquid fats, have the shortest shelf life unless preservatives are added. Supplements with a flax seed base may also go rancid in as short as 6 months depending on storage conditions. Horses can detect, and refuse to eat, levels of rancidity that are not obvious to us.

Whenever possible, it is best to buy directly from a manufacturer rather than at the local level or even through a distributor. The more middle men are involved, the more likely the supplement may have had periods of improper storage conditions or have been in inventory too long. The manufacturer will have a vested interest is not selling old product – distributors often do not.

If despite your best efforts you end up with a feed or supplement with obvious molding, an off or “old” odor, excessive crumbling or one that your horse does not want to eat – take or send it back. Such a product is high risk of making your horse sick and has little chance of doing him any good.

Eleanor Kellon, VMD



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Vitamin E and Selenium Are Powerful Protectors

Vitamin E and selenium are nutrients familiar to most horsepeople.  They are among the most common deficiencies in unsupplemented animals – and also the only two where deficiency diseases are still routinely seen.  Suboptimal levels also impact health and performance at levels below those that will trigger full blown deficiency syndromes.

Vitamin E and selenium are powerful protectors of muscle as well as immune function.

E and Se are often supplemented together but contrary to popular belief they do not actually work together, nor is their absorption from the intestinal tract interrelated in any way. However, they complement each other to provide broad spectrum protection to the body’s cells.

E and Se are both important antioxidants. E works to prevent fats within membranes from oxidative damage.  Se, as part of the glutathione peroxidase enzymes, works to protect the internal watery portions of cells from free radical injury. Free radicals are a by-product of cells generating energy for work or cell division and of immune system activity.

Vitamin E and selenium status is documented to significantly impact:

  •  The nervous system
  • Muscular function
  • Fertility/sperm quality
  • Antibody levels in colostrum
  • Immune function
  • Red blood cell integrity in exercising horses
  • Heart health
  • Cancer surveillance

Selenium is also integral to the enzyme which converts the inactive form of thyroid hormone (T4) to the active T3.

In most areas of the US and Canada, selenium is barely adequate to frankly deficient.  https://wp.me/p2WBdh-ha.  Horses not being maintained on pasture have extremely low levels of vitamin E in unsupplemented diets. E added to feeds or multi-ingredient supplements often acts more like a natural preservative than a supplement because even stabilized forms of the vitamin can breakdown easily.

Horses absorb inorganic selenium (e.g. sodium selenate) well but absorption of this form may be reduced by high levels of competing minerals in the diet. For this reason, some or all of the selenium supplement should be in the form of high selenium yeast.

As above, vitamin E can be unstable. I prefer to supplement it separately. Because this is a fat soluble vitamin it is best given dissolved in fat.  If your supplement is powdered,  mix it into some oil or sprinkle it on top of oil top dressed on the feed.

E and  selenium are two of the most important and the most often deficient nutrients in the horse’s diet.  Make sure your horse’s intake is adequate.

Eleanor Kellon, VMD

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Salt to the Rescue

I do some version of this post every year for good reason.  At the least it will safeguard your horse’s well being and performance in the heat.  At best it could save his life.

Sweating is the horse’s major mechanism for cooling off.  Human sweat has the same concentration of electrolytes as plasma but equine sweat is much higher.  Sodium and chloride, which together make salt, are by far the major electrolytes lost in sweat.  Even a lightly sweating horse will double his  sodium requirement with one hour of work.  When sweating heavily for an hour, the sodium requirement goes up 500%.

Every cell in the horse’s body works like a mini battery. It performs its functions by maintaining a gradient between the concentration of sodium outside versus inside the cell. Electrolyte fluxes are involved with everything from absorption of nutrients in the gut to brain, heart and muscle function.   Sodium and chloride are also the major electrolytes in blood and the fluid around cells.  Without sufficient sodium, the body tissues cannot hold normal levels of water and the kidney is unable to conserve water. Dehydration rapidly ensues.

The consequences of salt and water depletion begin before you can even tell that the horse is dehydrated by common tests like the skin pinch.  Reduced performance is the first sign. Muscle cramping is common. Humans report experiencing nausea (? colic or gut motility changes in a horse).  This is followed by more obvious weakness and “hitting the wall”.

Exercising a horse with suboptimal salt and water levels greatly increases the risk of heat stroke.  To prevent this, and make sure your horse performs comfortably and up to his best potential in the heat, you must understand what your horse’s needs are and make sure you meet them.

Before even worrying about sweat losses, the average horse has a basic salt (sodium chloride) requirement of approximately 1 oz/day.  An average size horse weighs about 450 kg. You can estimate sweat losses for moderate sweating at about 10 mL/kg/hour so 4500 mL each hour.  This is the equivalent of about 1 1/4 gallons of water and another 1 oz of salt.  This takes care of the sodium. There is also a large loss of chloride, which will be replaced partially by the hay/grass and partially by the salt.  Potassium losses also occur but are covered easily by the hay/grass as long as sodium needs are being met.

Adding only more salt will work for horses exercising up to 2 hours. Beyond that you will also want to use a balanced electrolyte supplement to make sure potassium is covered as well.  A supplement balanced to sweat will have twice as much chloride as sodium and about twice as much sodium as potassium. When deciding how much you need to feed, don’t rely on product instructions.  Find out how much sodium is in the product and figure on giving 11 to 12 grams of sodium for each hour. For example, if the product is 30% sodium, to get 12 g you need to feed 12/0.3 = 40 grams (1.4 ounces) of the product.  This is on top of the 1 oz basic salt requirement and 1 oz/hour for the first 2 hours of exercise.

Timing is important. Water should be freely available at all times. Horses that have water restricted after work do not drink sufficient amounts. It does no good to give extra salt/electrolytes several hours before work  because they will end up in the urine. You can give the first hour’s dose within 30 minutes of starting exercise and the rest during or after exercise. Mix in food or syringe in after the horse eats and drinks.

The hardest part about supplementing electrolytes correctly is ignoring all the bad information out there.  If you follow these guidelines you will help protect your horse from the heat and will likely be pleasantly surprised at how much better he performs.

Eleanor Kellon, VMD

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Thiamine for Horses

Thiamine (B1) is a member of the water soluble group of B vitamins.  Following absorption it is metabolized to its active form, TPP – thiamine pyrophosphate. TPP is an essential cofactor in multiple reactions involving energy generation from carbohydrate (glucose) and branched chain amino acids.

Specifically, TPP is involved in steps needed to get energy sources burned by aerobic metabolism.  For example, TPP is required for the pivotal enzymatic reaction that sends pyruvate from glucose into aerobic metabolism instead of conversion to lactate. In fact, elevated lactate is one sign of thiamine deficiency, as is impaired muscular function.

Since the primary and preferred fuel of the brain and nervous system is glucose, thiamine also is critical to their normal functioning.  Thiamine deficiency has been linked to a host of neurological conditions – confusion, weakness, gait abnormalities, impaired thinking are among the signs of severe deficiency. Thiamine status has also been linked to depression or anxiety in times of stress.

Other signs of deficiency noted specifically in horses include loss of appetite, poor growth, low heart rate, even death.

Should you supplement?  How much?

Full blown, potentially life threatening, thiamine deficiency has never been reported in horses eating typical diets.  The minimum requirement to sustain life has been set at 3 mg/kg of dry matter in the diet – about 30 mg/day for the average horse not in significant work. Exercising horses need about 50 mg/day.  There is also evidence that growing horses have more efficient growth and weight gain when fed diets that have twice the density of thiamine as the adult minimum requirement.

These are the bare minimum requirements. Do they differ from optimal intake?  The answer is most likely yes.  A 2017 paper in the Israel Journal of Veterinary Medicine (Laus et al) found that horses given intravenous supplementation in the form of TPP (the active form of thiamine) produced significantly less lactate on a standardized exercise test compared to horses of identical fitness.

This is similar to findings in human athletes where oral thiamine supplementation in higher than typical recommended minimums reduces lactate, ammonia and fatigue to an even greater extent than formal endurance training.  Supplementary thiamine has also been found to support performance and mood under stressful conditions.

Thiamine is virtually nontoxic, with the only noted side effect of even massive doses being nausea. Horses at maintenance or in light work may not need any supplemental thiamine.  Horses in heavier work schedules and/or under stress could benefit from supplementation of between 300 and 1000 mg/day for the average size horse for maximal support of metabolism and the brain.

Eleanor Kellon, VMD


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Parasite Resistance – Where Do We Stand

The doomsday scenario of parasites resistant to all deworming drugs has not materialized but we are facing some challenges.  This will give you current information on resistance, your treatment options and future directions.

Note: I have deliberately not used any brand names. There are several brands associated with the same active ingredient in dewormers and it’s a good idea to get in the habit of actually looking at the active ingredient rather than the brand name to be sure you are getting what you need.

From bots in the stomach (above) to pinworms at the anus, the horse is home to many    different parasites, many of which have developed some dewormer resistance.

Ascarids (Parascaris, roundworms).  This is a major health threat for young horses. Healthy adults are rarely infected but aged horses may lose their ability to resist.  These are large worms and can even obstruct the intestine in foals.  Their immature forms migrate through the liver and lungs. They are a common cause of “snots” in young horses.

Ascarids in many areas are resistant to ivermectin, moxidectin and in some instances also pyrantel pamoate. They are still sensitive to the benzimadazoles (e.g. oxibendazole, fenbendazole) and piperazine.

Small Strongyles (Cyathostomin sp.).  These parasites of the large intestine are the major parasite of adult horses.  The immature forms can go into a dormant cyst in the wall of the intestine and cause considerable damage when they emerge.

The small Strongyles are resistant to all drugs except the macrocyclic lactones ivermectin, abamectin and moxidectin.  Even these drugs don’t work like they did in the past. Fecal egg counts are reduced for approximately 30 days in contrast to the several months previously obtained with these drugs.

Pinworms (Oxyuris).  Pinworms occupy the most distal portions of the intestinal tract and emerge from the anus to lay eggs around the anal area. This produces intense irritation and itching.

There are multiple reports, both anecdotal and formal research, of macrocyclic lactones failing to remove pinworms. However, there are other reports showing the expected effectiveness. It is unclear at this time whether there is emerging resistance or if some issues may be related to inaccurate dosing. Resistance of pinworms to other dewormer drug classes has not been reported.

There are no known resistance problems with tapeworms, Strongyloides westerii (a problem in young foals), lungworms or large Strongyles (Strongylus species). However, large Strongyles are relatively rare since the introduction of the macrocyclic lactones and may actually share the resistance profile of the small Strongyles.

So far these problems are troubling but surmountable. However, there are no new drugs on the horizon to come to the rescue if issues worsen. There is another solution though, and it’s ready to break onto the scene.  Duddingtonia flagrans.

I first wrote about the potential for predatory fungi to assist in parasite control about 20 years ago. D. flagrans is a fungus naturally found in the environment which feeds on the infective larval stages of multiple parasites including large and small Strongyles, roundworms, threadworms (Strongyloides) and pinworms (although it would not help with roundworm larvae since they don’t hatch in the manure, and pinworm larvae are rarely in the manure). D. flagrans traps and consumes the larvae before they can infect the horse.  They are fed to the horse in an inactive spore state and remain inactive until passed in the horse’s manure.

For detailed safety information see this document from the EPA:  https://www.federalregister.gov/documents/2018/05/07/2018-09647/duddingtonia-flagrans-strain-iah-1297-exemption-from-the-requirement-of-a-tolerance.

D. flagrans has been approved for use in horses in the USA, New Zealand and Australia. It is set to hit the market in New Zealand and Australia very shortly. Although already approved by the EPA, USA use will require approval by the individual states before it can be marketed.

Smart control of intestinal parasites requires a knowledge of the species threatening your horse, how various parasites respond to each dewormer class and environmental control to limit exposure.  D. flagrans will make the job of limiting exposure much easier.

Eleanor Kellon, VMD

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Common Issues of the Older Horse

With a lifetime of good care there is no reason a horse can’t remain active and useful well into their 20s or even longer. However, just like us, there are some health issues that become more common as a result of the passage of time.  Joint disorders and digestive complaints are two of the most common.

When thinking about joint health, our tendency is to focus on the cartilage but many other tissues can be involved.  The horse’s body is equipped with mechanisms to repair damage as it occurs.  It doesn’t just pile up over time.  Problems can occur when the damage overwhelms the healing  capacity (e.g. serious trauma, very hard work) or when regenerative capacities slow down due to age. Most horses fall in the second category.

The big three of joint support supplements – hyaluronate, chondroitin sulfate and glucosamine – are involved in helping to maintain the homeostatic mechanisms that protect chondrocytes (cells producing cartilage) from things like oxidative stress. MSM and hydrolyzed collagen have similar properties.  They also help with maintaining a normal balance of potentially damaging enzymes in the joint fluid.

Regular antioxidant supplementation benefits the older horse by working with the body’s own antioxidant defenses to help alleviate potentially harmful free radicals. Ingredients in this category include grapeseed, bromelain, olive extract, Devil’s Claw, Curcumin and Boswellia.

Older horses are likely to benefit from additional support for soft tissue/connective tissue and bone from silicon (as the bioavailable orthosilic acid), vitamin C, copper and hydrolyzed collagen. Key nutrients for both collagen and hooves are L-lysine and L-methionine. Hooves also benefit from zinc and biotin.

Older horses may face several challenges in digesting their food. Natural wear and overaggressive dentistry can lead to loss of the enamel ridges on their chewing surfaces. There is also a change in the angle of the chewing surface which reduces the force of chewing. Although not investigated in horses, ageing can result in decrease in stomach acid production and pancreatic digestive enzyme activity. Older horses also often have reduced numbers and diversity of microorganisms in their intestinal tract.

When chewing is an issue, switching the diet to one based on hay cubes/pellets and/or a complete feed, fed thoroughly moistened or even as a “soup”, is highly beneficial.  Adding psyllium to every meal improves ease of swallowing and is also prebiotic.  You can leave hay available to keep the horse busy unless choke is a problem, but don’t count on it to supply significant calories.

Digestive support from digestive enzymes can help with small intestinal absorption of nutrients. These may come from enzyme preparations such as Pancrelipase and pepsin.  Bacterial and yeast fermentation products are also rich sources of digestive enzymes as well as growth factors for beneficial organisms.  The best probiotics are a blend of bacterial strains and yeast.  The number of live organisms is extremely important.  One  CFU = 1 colony forming unit = 1 live organism.  You need to think in terms of tens of billions to have an effect.

Ageing has its challenges in some key areas but the correct choice of supplements can help the horse maintain more youthful normal functioning.

Eleanor Kellon, VMD

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When is That Pasture Safe to Graze?

It seems counterintuitive that the very food our horses have evolved to eat as their primary diet could in any way be harmful to them. Despite this, some horses do have trouble with spring  grass. How can this be?  It’s complicated.

This succulent pasture with a mix of young grasses and clover will more than meet the    nutritional needs of any horse, but for some it’s too much of a good thing.

There are risks in trying to draw parallels between feral horses and today’s domesticated horse.  The problem is the horse’s well being is determined by more than simply the diet.  There are critical interactions between diet and exercise level.  The specific type of grass available also matters, as do differences in requirements between breeds.

The first thing to realize about high quality pasture early in the growing season is that it’s like a 10 course French meal with a decadent dessert all day, every day. This may mean salvation for a feral horse coming off a brutal winter in poor body condition, or a thin pregnant mare in late pregnancy with a rapidly growing foal and needing a high nutrient supply for lactation but for a well fed domestic horse unlimited access can, and will, at least result in a rapid weight gain.

Young pasture with high sugar, low fiber and high protein is also a significant diet change.  Even horses that live on pasture may be unprepared when warmth and rain combine to produce rapid growth. Most horses at least show the typical bright green and slightly soft manure.  Others have obvious bloating, discomfort and frank diarrhea.

High simple sugar levels (plus starch in clovers) pose a laminitis risk for horses with metabolic syndrome.  It has been well established that high insulin levels are the best predictor of pasture laminitis risk.  Since pregnancy induces a degree of insulin resistance in all breeds, heavily pregnant mares are also at increased risk.

The solution for digestive tract issues is a combination of restricted grazing time with a muzzle and dry lot confinement with hay to “dilute” the grass. With very dense pastures the muzzle is usually necessary because horses will gorge themselves on the pasture in the time they have allotted.  They can cram a full day’s intake into as little as 6 or 7 hours of grazing.

For the horse with hyperinsulinemia, any time on spring pastures is inviting laminitis. A well controlled metabolic syndrome horse on a rigorous exercise program may tolerate some hand grazing in the first hour after exercise but otherwise it best to completely prevent access.  If turning the horse out for exercise, use a sealed muzzle.

It can be very frustrating to have a  beautiful pasture at your disposal but not be able to use it freely. If our horses were being exercised 20 miles per day it might be a different story but even then the composition of well maintained pastures bears little resemblance to BLM lands in Nevada or even West Coast states.  Most horses can benefit from our improved pastures if introduced slowly.  For the rest, nothing is worth the risk of  laminitis.

Eleanor Kellon, VMD

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Keeping a Spring in Your Older Horse’s Step

Horses are living much longer today and spending many more useful years under saddle.  Even so, age does take a toll on even the healthiest senior. I want to share a few things I have found to make an obvious difference in energy levels and feeling good attitudes.

Social Security.  No, I’m obviously not talking about a monthly check! Horses are social creatures and change in their social network can have serious consequences. Loss of a companion, moving and a drop in status within the herd are examples of common social stressors for older horses.

Horses have different sleep patterns and requirements than people but they definitely can become sleep deprived. They need to feel secure to sleep well so this is one area where issues often develop in older horses. If you notice your senior is never lying down to sleep, there’s a problem.  Try making sure he gets quiet time alone in a stall or with a trusted companion in a small pen with shelter.

When a horse’s position on the social totem pole drops, so does their chance of successfully competing for food within the group. What they do have access to may be lower quality foods (e.g. stemmy portions of hay) that others left behind. Eventually this leads to weight loss but long before that the horse becomes fearful and anxious. Their frustration may surface as aggression toward humans or resistance to work.  Keep a close eye on herd dynamics. If you see your senior being bullied around food be sure to give him enough time to eat by himself in a safe area.

Adaptogens.  Ageing in all species inevitably comes with reduced “vigour”, decreased capacity for work, lower energy levels, reduced immune function and less mental clarity in several areas.  Ageing is a complex process and at this point we have a better understanding of consequences than causes but in essence it is a blunted capacity of homeostatic processes to maintain a more youthful balance.

Adaptogens are nontoxic, naturally occurring plants that have the ability to support the body’s homeostatic responses to stressors of all types.  For example, the horse’s body reacts to the physical stress of regular exercise by adaptations in levels of key hormones like growth hormone and cortisol.  Within a certain physiological range, these changes enhance resistance to stress.  If levels fall above or below that optimum, resistance is lost and cellular damage can occur. Hormonal and DNA changes with normal ageing further erode adaptive capacities. Adaptogens assist the ageing body in keeping hormonal shifts within the resistance range and preserving key cellular functions like mitochondrial energy generation.

There is a long list of adaptogens to choose from. One that I particularly like for senior horses is Jiaogulan.  This is a vine from southern China which is widely used locally as a tea or vegetable. It is free of the extreme stimulation that often occur with Ginsengs but has a clear energizing effect in the older horse. It is highly palatable and supports a normal appetite, healthy gastric lining and good circulation.

Antioxidants. One of the major theories of ageing is that it is caused by cumulative damage from oxidative stress. Oxidative stress arises both externally from toxins, harmful metals, even the sun, and internally from metabolism, exercise, immune system activity. As the horse ages, this issue is compounded by a decrease in the ability to produce key antioxidants like vitamin C and glutathione, as well as the cumulative effects of a lifetime of suboptimal intake of key nutrients like vitamin E, selenium, copper and zinc.

If there is one time you want to keep your horse as oxidative stress free as possible, it’s as they age. This has to start with a balanced diet with adequate intake of all key antioxidant nutrients listed above.  Add vitamin C to the list, especially if the horse is not on pasture. Other nutrients of benefit are the antioxidants alpha lipoic acid and N-acetyl-cysteine which is also a precursor for glutathione. On the plant antioxidant side of things, benefit is derived from resveratrol/grape seed extract, bioflavonoids including quercetin, Boswellia, Turmeric, Ginkgo biloba (also a good pick me up for seniors) and Oregon Grape root.

While ageing brings its challenges, there is much you can do to support the horse when you understand what those challenges are. Seniors often respond dramatically to the correct supplements and there are few things more rewarding to witness.

Eleanor Kellon, VMD

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Lyme Disease in Horses

The number of human Lyme Disease cases is steadily increasing, with the CDC estimating there are at least 10X more cases than get reported. For every human case there are likely many more equine since they live outdoors and finding the tiny nymph stages responsible for most transmissions is extremely difficult on a horse even with meticulous grooming. Lyme Disease is most common in the Northeast (Maryland and Delaware and states north of there) and in the midwestern states adjoining the Great Lakes but has also been reported virtually anywhere except in the most arid desert regions.

The nymphal tick stages most likely to be transmitting Lyme Disease are much smaller than adults, about the size of a poppy seed.

Multiple studies have described antibody confirmation of equine infections with the Lyme organism, Borrelia burgdorferi. What we don’t know is how many infections actually produce symptoms. Researchers have been unable to experimentally produce symptoms even when it is confirmed several months later that the horse was successfully infected.

The most well documented consequence of Lyme in naturally occurring infections is neurological disease. Signs mimic other causes of meningitis or encephalitis and include anything from cranial nerve problems and sensitivity to touch to gait changes, ataxia and muscle loss. Borrelia can also invade the eye and produce a picture identical to “moonblindness”/periodic ophthalmia. The development of skin nodules has been reported at sites of bites from infected ticks. These are all issues that develop weeks to months after infection.

Signs of recent infection, fatigue and mild fever, are likely to be missed in horses and we can’t see the skin rash that is typical in people. Lyme may be treatable with a single dose of antibiotic in these early stages but horses are never diagnosed early. Additional signs that have been described in chronically infected horses include a shifting lameness, weight loss, depression, behavior changes and muscle pain.

Laminitis may also be seen in Lyme positive horses. It is often severe and when insulin elevations are detected they tend to be on the low end and disproportionate to the severity of the laminitis. These horses do not respond as expected to the usual dietary modifications.

The best diagnostic option available today is Cornell University’s Multiplex assay. This test can detect both early and late stage infections. Idexx Laboratories SNAP test is also accurate but may take up to 8 weeks after infection to become positive.

Treatment of Lyme disease in horses is complicated by the fact the infection is not detected until the late stages.  It is known from human medicine this makes treatment more difficult. Oral doxycycline or minocycline is usually prescribed but treatment may need to be repeated. Research has shown the best results with 28 days of intravenous tetracycline.

Prevention is always preferable but options are limited. Ticks can be discouraged in areas where horses are kept by keeping them dry/well drained, mowing grass, eliminating brush and piles of trimmings, avoiding wooded areas and fencing out deer.

All common ingredients in equine fly sprays have some tick repellent activity, with permethrin best against the species which transmit Borellia burgdorferi. However,  repellents and grounds keeping will never be able to protect the horse 100% from tick bites.

There is no vaccine commercially available for horses. It has been documented that horses develop antibodies in response to canine vaccines, and that antibody levels are better when the dose of vaccine is doubled, but antibody levels only persist for about 16 weeks. Horses would have to be vaccinated at least twice a year to keep their titers up and even then we don’t know for sure if those titers are protective. The safety of vaccinating a horse that is already infected is also unknown.

The threat of Lyme disease is likely to grow before it lessens. If you live in an area at risk for Lyme, always keep it on your radar. Positive antibody tests alone do not confirm the B. burdorferi infection is causing your horse’s issues but this puts it squarely on the list of possibilities for your veterinarian to consider.

Eleanor Kellon, VMD

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