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:

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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When Joint Nutraceuticals Are Not Enough

In a recent blog,, I talked about the big three joint supplement ingredients – glucosamine, chondroitin and hyaluronic acid. They are components of the joint cartilage and/or synovial fluid that bathes the joint space and interior of tendon sheaths and bursas. These compounds can assist the horse’s body in maintaining a normal homestatic balance between degeneration and repair and many horses do extremely well on them. However, there are exceptions.

The joint nutraceuticals are most supportive in situations of normally encountered stress to the joint and all surrounding tissue – i.e. exercise.  The synovial lining is usually the first tissue to be stressed in the moving joint, with eventual production of thinner joint fluid and compromise of cartilage integrity if the body cannot balance the stresses with healthful and robust regenerative responses.

Joint movement may also strain tendons, ligaments and their attachment to bone (the enthesis).  If degenerative processes in the joint outweigh repair, the synovial membrane becomes thickened and can become pinched between the ends of the bones during exercise, bleeding into the joint cavity and irritating it further.

Cartilage also thins if normal maintenance processes cannot keep pace with the load. As cartilage thins, the cushioning effect is reduced and the joint space narrows. Bone in the area above the joint is irritated. Eventually there can be bone on bone contact rather than the protective cap of  cartilage normally present.  This causes further irritation and bone begins to proliferate in an attempt to stabilize the joint.

Helping the horse’s body to restore homeostasis in the face of all these processes in different tissue types may benefit from more than the usual joint nutraceuticals. There are numerous food components, individual nutrients and plant-based naturally occurring compounds which normally assist in maintaining homeostasis in remodeling and inflammatory pathways.

They accomplish this in several ways. Some, like vitamin C, are necessary cofactors in tissue formation. Others are either direct antioxidants or components of key antioxidant enzyme systems.  Free radical generation is an inevitable consequence of exercise and normal tissue housekeeping but when unbalanced can be harmful.  Still others may normally influence specific pathways or even gene activity.

These useful substances include Yucca, Devil’s Claw, Turmeric, Boswellia, Golden Rod, Astragalus, White Willow, Perna Mussel, Cat’s Claw, Golden Rod, Phellodendron, Fever Few, Egg Shell Membrane, Hydrolyzed Collagen, fatty acids, Silica, Boron, Vitamin C, essential amino acids, B vitamins, copper, zinc, Bioactive Whey, MSM, Resveratrol and other flavonoids abundant in brightly colored fruits.

Horses most likely to benefit from more comprehensive support are animals which are older, previously injured or working heavily. Health and performance are all about  homeostasis. There are many tools in your tool box.

Eleanor Kellon, VMD

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Nutrition for the Senior Horse

I’m old enough to remember when a 10-year-old horse was considered aged. Advances in health care and a growing respect for the value of experience and a mature temperament have changed that. Many horses are now active into their late teens or 20s and may live for a decade or more beyond that.

However, time seems to take an inevitable toll on any species. Are there special nutritional needs for the senior horse?

There is nothing you have to change simply because of the horse’s age.  If he is holding weight well, looking good and has good energy, don’t change a thing.  That said, there are some things to look for as the horse ages.

Dental care is often emphasized for keeping older horses in peak condition but the truth is there are many seniors whose teeth show no obvious issues but they begin to lose weight.  This is likely because the angle of the chewing surface, and the force that can be generated, changes with wear and dental work.  A typical history is that they do fine on pasture, which is soft and easy to chew, but will lose weight on hay.

Some of these horses only need a switch to chopped hay. Others will respond to a diet of pelleted hay and concentrate, preferably fed well soaked or even soupy. Hay should still be fed for chew time, but the horse will need from 50 to 100% of his calories to come from the soaked foods.

Older horses often have a reduced number and diversity of microorganisms in their hind gut. This issue may actually overlap with the chewing problems above since fibrous feeds need to be well processed for fermentation to be efficient. Signs of this issue may include lean body condition, abdominal distention, soft manure or fluid released around fecal balls.

Chopped or ground hays are actually prebiotic since they give the organisms something they can more easily process. Highly fermentable fiber sources such as beet pulp, psyllium husk, soybean hulls and complex plant carbohydrates boost the prebiotic value. High potency probiotic supplements can also help – but only after  their “food” in the form of prebiotics above are already in place.

You may hear that older horses need more protein but their requirements are actually not different. It’s their ability to utilize the protein that may change. In other species, age may come with reduced production of stomach acid which is called achlorhydria. Stomach acid plays a key role in the first step of protein digestion. Production of digestive enzymes by the pancreas may also drop with age.

None of this has been specifically investigated in the horse but provision of digestive supplements with protease activity and adding vinegar to meals may help a horse that seems to be losing muscle mass. It is also important to regularly check for PPID – pituitary pars intermedia dysfunction, aka Cushing’s Disease – because this is a common disorder of older horses and muscle loss is a hallmark.  Additionally, regular exercise has been found to be protective against the muscle loss that naturally accompanies aging.

Correct mineral nutrition may be as important for the senior horse as the very young horse. While issues such as decreased bone strength and waning immunity have their roots in hormonal changes and DNA decay, they can be greatly worsened by mineral deficiencies and imbalances. Of all the factors, this is the one that is completely within our control.

Aging appears to be accompanied by a reduction in all the body’s basic ‘housekeeping’ functions such as production of vitamins, enzymes and antioxidants. A well rounded vitamin supplement is therefore cheap insurance and of more importance for older horses.

There’s no reason today’s horse cannot enjoy good health well into his second decade. Nutrition plays an important role in this and gives us a powerful tool for supporting the senior horse.

Eleanor Kellon, VMD


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How Joint Supplements Work

The first joint supplement for horses came out in the 1980s and was a chondroitin sulfate only product, followed by products containing Perna (green-lipped mussel). In the early 1990s, a patent was granted for the first equine combination joint supplement containing glucosamine, chrondroitin sulfate and manganese.  The market has grown tremendously since then, and with good reason.

It would be amazing if an animal the size and weight of a horse didn’t develop joint stress with what we expect of them. The stress is also cumulative so that even horses that are not upper level athletes can eventually develop joint issues over time. Things like being overweight, poor/imbalanced hoof care and less than perfect conformation also contribute.

Fortunately, the horse’s body is equipped with ways to balance these normal challenges to the joint and we can support efforts to do so by providing the correct nutrients.

Joint health begins with providing the young horse the materials needed to develop strong bones and joints. This requires correct levels and ratios of minerals including ultratrace minerals like boron and silica and good protein intake with adequate essential amino acids as the base. Whey and hydrolyzed collagen are rich sources of key amino acids for connective tissue such as joint cartilage and for bone. Methylsulfonylmethane (MSM) may assist in maintaining a balance between cytokines involved in breakdown, remodeling and repair. Vitamins C, D and K play pivotal roles in cartilage and bone formation.

The three most familiar ingredients in joint support supplements are glucosamine, chondroitin sulfate and hyaluronate (hyaluronic acid). All three are naturally occurring components of healthy joint fluid, cartilage and the connective tissue matrix of bone. In addition to being structural elements in these tissues, they also serve important homeostatic functions.

Glucosamine has been found to support the expression of enzymes synthesizing hyaluronic acid as well as components of cartilage and help maintain balance between the activity of cells which break down versus build bone. Glucosamine also facilitates a healthy balance between cytokines favoring tissue destruction and those which repair and build.

Chondroitin sulfate has a similar action in supporting a healthy anabolic (builds) catabolic (breaks down) balance.  In fact, the actions of glucosamine and chondroitin complement each other.

Hyaluronic acid is a major contributor to the slippery, lubricating properties of joint fluid and it has many other functions, including the support of cell division and participating in normal clean-up and repair activities. Its presence in the joint cartilage gives it fluid holding capacity and resilience.

Vitamin C is critical to health of both bone and cartilage as well as soft tissues of all types because it plays an essential role in the formation of collagen, the basic protein of all these structures. Horses can manufacture vitamin C but it is unknown how well they compensate when requirements are high.

A number of herbs have been used for joint support, including Devil’s Claw, Boswellia and Yucca.  They all have in common antioxidant actions and support of a healthy homeostasis between anabolic and catabolic activity.

Your horse’s skeletal system takes a pounding every day. Supplementing the nutrients which support his ability to deal with these inevitable challenges and maintain healthy bones, joints and connective tissues is one of the best decisions you can make.

Eleanor Kellon, VMD



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Mini Nutrition Quiz

As promised, here are the answers to the nutrition quiz.

1. The first thing calculated in designing a diet is the calorie requirement. Once you know that, you determine how much of each element of the diet to feed. After you know how much you will be feeding you can calculate how much protein, fat, minerals and vitamins that is providing.

2. Iron is by far the mineral present in greatest excess in most diets. I’ve never seen a diet where iron needed to be supplemented.

3. There are many nutritional issues that may show up as poor hoof quality but the most common is trace mineral imbalances and/or deficiencies. The healthier, tighter growth at the top of this horse’s hoof occurred after mineral balancing with no other changes.


4. Sulfur-containing amino acids are the most important source of sulfur in the diet. The horse can also absorb and utilize sulfates. Contrary to popular opinion, sulfur from MSM does not become incorporated into body tissues. It is absorbed easily but the sulfur it contains is all excreted.

5. None of those listed factors will cause inflammation. Inflammation only occurs in reaction to something like an injury or illness. The diet may cause an imbalance in the homeostatic mechanisms the horse’s body uses to balance inflammation but it can not actually cause inflammation.

6. The answer is False. Balancers may or may not provide enough supplementation to make sure individual requirements for nutrients are met, thus avoiding primary deficiencies, but secondary deficiencies often remain. A secondary deficiency is when the ratios between minerals are off, allowing minerals present in high amounts to essentially crowd out those in low amounts.

7.  Chloride is the electrolyte deficiency which causes alkalosis. Alkalosis is an excess of bicarbonate ions. To maintain electrical neutrality, the body strives to balance this equation: sodium + potassium = chloride +  bicarbonate. As chloride drops, bicarbonate must go up. This causes more binding of ionized calcium which interferes with muscle and gut function or can cause “thumps”.

8. The answer is all of the above. Fresh grass has more water, vitamin E and vitamin C than hay. If it is a fructan producing species, it also has more fructan when live pasture as the grass continues to metabolize fructan stores after being cut.

9. Again, the answer is all of the above. Deficiencies of iodine, selenium, copper and zinc are very common.

10. Horses differ in the way they absorb calcium. In other animals, calcium absorption is hormonally regulated but the horse freely absorbs calcium and excretes any excess in the urine.

11. Lactating mares have a higher dietary protein requirement than any other age, class or use. Failure to provide it compromises her muscle mass but she can also break down key tissues like tendons and ligaments to free up the protein she needs to make milk.

Eleanor Kellon, VMD

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Test Your Nutrition Knowledge

Nutrition is a specialty like any other scientific field. Despite this, it’s common for people with no qualifications to offer nutrition advice. Many things you hear or read over and over again can be wrong.  Take this mini quiz to test your own equine nutrition knowledge. I’ll post the answers tomorrow.

When building a diet and deciding how much to feed, the first thing to be calculated is always:

  1. calorie needs
  2. protein needs
  3. fat requirements
  4. starch and sugar levels
  5. minerals

The mineral most likely to be present in any diet at levels far exceeding requirements is:

  1. calcium
  2. phosphorus
  3. chloride
  4. iron
  5. copper

The most common nutritional factor contributing to poor hoof quality is:

  1. low protein
  2. fatty acid deficiency
  3. trace mineral deficiency
  4. too much sugar
  5. silicon deficiency

Bioavailable sources of sulfur in the diet are:

  1. MSM
  2. sulfur containing amino acids
  3. flowers of sulfur (inorganic sulfur)
  4. sulfates
  5. Both 2. and 4.

What can cause inflammation in the horse’s body:

  1. High omega-6 fatty acids
  2. High sugar/starch intake
  3. High copper intake
  4. Both 1. and 2.
  5. None of the above

True or False.   If you feed the recommended daily amount of a balancer or fortified feed, vitamin and mineral  deficiencies or imbalances are impossible.

Deficiency of which electrolyte causes alkalosis in endurance horses:

  1. sodium
  2. potassium
  3. chloride
  4. bicarbonate
  5. calcium

Compared to hay, fresh pasture always has higher levels of:

  1. vitamin E
  2. vitamin C
  3. fructan
  4. water
  5. all of the above

The most common trace mineral deficiencies in hay are:

  1. iodine
  2. selenium
  3. copper
  4. zinc
  5. all of the above

Horses differ from humans and small animals in the way they absorb:

  1. calcium
  2. protein
  3. fats
  4. iodine
  5. chromium

Assuming an equivalent adult body weight, which of these horses has the highest protein requirements:

  1. mare in late pregnancy
  2. a 2-year-old in race training
  3. yearling
  4. mare in early lactation
  5. horse recovering from surgery

Eleanor Kellon, VMD



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