The Right Way to Supplement Electrolytes

Once you know the basics, it’s not that difficult to supplement electrolytes correctly but many people don’t know how and it’s taking more of a toll than is realized.

Even mild dehydration can have a major effect on performance

Electrolytes are minerals that exist in the body in their free, ionized form –  i.e. carrying an electrical charge. Cations like calcium, potassium and sodium have positive charges. Anions like chloride, bicarbonate and sulfate are negative.

Much like in a battery, movement of electrolytes makes excitatory activity possible, such as muscles contracting, nerves firing and the heart beating. Electrolyte concentrations and gradients  also allow the body to hold normal amounts of water (hydration) and the kidney to adjust the concentration of urine.

Sweat is a major avenue of loss for sodium, potassium, chloride and to a lesser extent calcium and magnesium but it’s not the only avenue.

The horse also has daily endogenous losses in urine, sloughed cells, mucus and the digestive tract. Those losses must be met by the diet on a daily basis. Failure to do that is one major reason why even horses getting electrolyte supplements are often deficient and dehydrated.  These baseline daily losses (not including sweat) are 10 grams sodium, potassium 25 grams, chloride 40 grams for a 500 kg horse.

Hay takes care of baseline potassium needs at an intake as low as 1% of body weight. Chloride requires closer to  2% of body weight but some will also come from salt (sodium chloride). Sodium requirements have to come from salt. The baseline requirement for sodium can be met by approximately 2 oz of salt in hot weather = one stall size salt lick per month. Salt may also come from supplements, commercial feeds or be added to feed or sprinkled on hay.

Once the baseline requirements are adequately met you can work on replacing sweat losses. At low rates of sweating, the horse will average losses of approximately 10 grams of sodium, 5  grams of potassium and 20 grams of chloride per hour.  That’s a ratio of 2:1:4 for sodium, potassium and chloride. Check to see that your replacement supplement has those correct ratios or you may be making things worse. Low levels of  calcium and magnesium (typically 200 to 300 mg/hourly dose) may also be used. Magnesium losses in particular may be important since many diets are borderline to deficient already.

To determine dosage, calculate average sweat losses as above then look at the amount per dose on the label.  For example, an hour of light sweating needs 10 grams of sodium so if the product provides 5 grams (same as 5,000 mg) per dose you need 2 doses.  Do not rely on manufacturer’s suggestions alone.

Horses already showing signs of electrolyte deficiency and dehydration such as weakness, muscle trembling, thumps or poor gut motility may also benefit from use of a paste that has a higher amount of potassium as well as additional magnesium and calcium. Potassium in blood is depleted quicker than sodium despite being lower in sweat. This is because sodium is pulled from tissues to replace blood sodium and also because the kidney will substitute potassium for sodium in urine when blood sodium is low.

It isn’t particularly difficult to figure out how much electrolyte supplementation your horse needs. Just takes a few minutes. It’s time very well spent and you will quickly see how much easier and better your horse performs in hot weather.

Eleanor Kellon, VMD

 

 

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Ketogenic Diet for Horses? Pass

Everyone has heard about the ketogenic diet by now, “keto” for short. It’s basically a reinvention of the Atkins diet with more emphasis on eating fat.   Fasting, starvation and no or low simple carbohydrate diets trigger a higher rate of fat oxidation to spare glucose. In  omnivores and dogs, a by-product of fat oxidation is the production of ketones – hence the name.

Even starvation, when body fat is the only fuel, fails to produce significant ketosis in horses

The best diet for EMS horses is similar to ketogenic in that simple carbohydrate intake is very low. However, carb and fat calories are replaced by fiber calories. That very basic fact of equine nutrition and physiology is ignored by a proposal to treat EMS with a ketogenic diet.

Ketones are a by-product of burning fat for energy. The mitochondria can burn either glucose or fat. Fat oxidation is a very slow process compared to glucose. When it can keep pace with energy demands most of the fat is efficiently burned in the Krebs cycle in the mitochondria with very little ketone body production. Ketone production increases proportionate to how quickly fats are being presented to the mitochondria compared to how quickly they can be processed so levels go up when carb intake is low – but not in horses.

Multiple studies such as Rose and Sampson 1982 and Hardy 2003 established a long time ago that ketone generation is not important to horses in a variety of circumstances where ketones rise in humans and mice, from fasting to endurance exercise.  The reason for this is multifactorial, including very efficient gluconeogenesis and glucose recycling as well as adaptation to direct burning of acetate in horses.

Ketone bodies are formed from acetate generated during fat metabolism and the first step in their reutilization is to convert them back to acetate. Acetate is also the main product of fiber fermentation in horses and horses can get 60+ % of their energy from acetate. Horses may therefore be burning the extra acetate before it is converted to ketones or very efficiency recycling ketones back to acetate and fat – or both.

Like many descriptions of the human ketogenic diet, the equine keto diet proposes ketones are some highly beneficial metabolic fuel so the more the better. In fact, as above, they are only an indicator of incomplete fat oxidation. It is also claimed as ketones go up insulin goes down because high levels of one inhibit the other. This is not true.

In the ketogenic diet, high levels of ketones indicate high fat oxidation because glucose intake from starch and simple sugars is low. Ketones do not directly inhibit insulin. In fact, a high ketone production from a meal high in medium chain triglyceride fats [see below] lowers glucose but increases insulin.  Severe ketosis in diabetic ketoacidosis also induces life-threatening insulin resistance.

The equine keto diet involves feeding  timothy, Orchardgrass or alfalfa hay, claiming they are more “nutrient dense”, lower carbohydrate and higher fiber than fescue, brome or bermuda (which is not true), no grain or other supplements except an antioxidant sold by the company proposing this. They found, not surprisingly given the normal physiology of the horse, that horses fed this diet don’t have elevated ketone levels. To correct this they also sell a supplemental direct source of ketones and an oil containing medium chain triglycerides –  MCTs (although suggested dose is less than for a human). MCT intake causes higher ketone levels because it does not require a carrier to enter the mitochondria so more gets wasted as ketones. Did I mention these three supplements are also expensive?

A far better approach that has been working well for 20 years now is to feed a low sugar and starch hay with adequate calories from fiber, adequate but not excessive protein, and vitamins and minerals to match. See http://www.ecirhorse.org. Ketones have nothing to do with it.

Eleanor Kellon, VMD

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Taurine – The Most Important Amino Acid You Never Heard Of

Taurine is a sulfur-containing amino acid derivative. Unlike typical amino acids, it is not used to synthesize proteins. However, it has a wide variety of roles to play in the horse’s body.

                            The equine vegetarian diet provides no taurine.

The only dietary sources of taurine are meat/fish, milk or eggs. The horse must synthesize all the taurine needed. This is done from the methionine breakdown product homocysteine or from the amino acid cysteine.  As problems with low sulfur levels in soils increase https://wp.me/p2WBdh-qX , levels of these taurine precursors also drop.

Taurine directly interacts with genes and the endoplasmic reticulum where proteins are assembled to support normal metabolism and energy generation.

Taurine is a prime osmolyte, meaning it is a regulator of fluid levels in cells. It is also a critical antioxidant and detoxifier. Taurine is essential for the production of bile in the liver, a major avenue for removal of harmful substances from the body.

Taurine is important for the support of proper nerve transmission and muscle function, and promoting calmness in horses by aiding in balancing levels of excitatory neurotransmitters in the brain. It assists in nerve impulse generation and helps stabilize cell membranes by modifying neurotransmitter uptake. Taurine also helps modulate the stress hormones cortisol and adrenalin to maintain normal emotional balance.

Taurine is found in high concentrations in electrically active tissue such as the brain, retina, heart, and muscle. It supports the stability of membranes and assists in the movement of electrolytes including calcium ions in and out of cells, which is critical for proper nerve transmission and muscle contraction.  Taurine also normally stabilizes the generation of energy in mitochondria, the powerhouses of cells.

Research in experimental animals has found taurine may even assist the body in normal glucose regulation, insulin excretion and lipid levels in the blood.

All of these things make taurine a vital player in normal mood, metabolism, energy generation and exercise performance.

Eleanor Kellon, VMD

 

 

 

 

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The Real Cause of PAL – Pasture-Associated Laminitis

It isn’t fructan.  It isn’t hind gut acidosis.  Here’s the science.

The AAEP’s Laminitis Working Group did a four year study with the goal of identifying laminitis risks. Other than diet, EMS pattern obesity, known EMS or PPID and use of corticosteroids within 30 days were identified. All relate to equine metabolic syndrome [EMS] and elevated insulin.

A 2006 field study performed by a group from Virginia Polytechnic followed a herd of 106 mixed breed ponies on pasture for a year, performing pasture analyses and monitoring the ponies using proxies of insulin resistance they had developed from the results of intravenous testing. They found both prior laminitis and development of acute laminitis correlated well with indicators of insulin resistance. There was no increase of  fructan in the pasture when laminitis cases appeared, no indication of diarrhea or hind gut upset.

In a 2016 study, Menzies-Gow at al followed 446 animals on pasture over a period of 3 years. They found the most reliable indicator of risk of laminitis was basal insulin levels. Also significant were low adiponectin and high insulin response to dexamethasone. Fructan does not increase insulin. There was no indication of  diarrhea or hind gut upset.

A 2019 study by de Laat et al looked at 301 cases of naturally occurring laminitis and found EMS and/or PPID in 94%. They were also careful to point out those that did not have elevated insulin at time of testing may have been reflecting their  current diet rather than their state at the time of acute laminitis. No diarrhea or other indication of hind gut distress was reported.

There are many other studies and they all come back to insulin. Very large doses of pure fructan by stomach tube can experimentally cause laminitis by resulting in extreme hind gut acidity, damage to the intestinal lining and absorption of bacterial products in the same way gorging on grain can. This hind gut upset is accompanied by diarrhea, septicemia and fever. These horses are clearly sick. None of that happens with naturally occurring PAL.

Not only are there zero documented cases of high fructan in pasture causing laminitis, the levels of fructan naturally found in a whole day’s worth of eating pasture grasses almost never come even close to the amount needed to cause laminitis. Could laminitis prone horses be more sensitive to fructan?

Nope. Borer et al 2012 found virtually no insulin response to fructan in ponies whether predisposed to PAL or not.  Crawford et al 2007 fed a moderate fructan dose to normal and laminitis prone ponies and looked at the changes in fecal pH and fermentation products. They found pH and fermentation products did change but none of that was reflected in blood levels so wasn’t absorbed. There was also no difference in documented changes between normal and laminitis prone ponies.

Only simple sugars (ESC fraction on analysis) and starch can increase insulin. Those two things should be less than 10% combined [ESC + Starch less than 10%] for at risk horses.

The greatest danger in perpetuating the fructan myth is that owners will rely on supplements designed to control pH or alter hind gut fermentation to protect their horse or pony from PAL.  They won’t help if your animal is in the high risk group with endocrine disease that accounts for 94+% of PAL cases. Not all horses or ponies at risk will develop obvious laminitis every year, but time is not on your side. Unlimited pasture access is Russian roulette.

Eleanor Kellon, VMD

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Beware Trendy Cures for Equine Metabolic Syndrome/IR

The time is ripe. Horses with undiagnosed metabolic syndrome or those not being managed appropriately are coming down with laminitis from grazing.  It’s no coincidence that PR for new cures is ramping up at the same time.

The two I’m aware of (so far) are using one of the oldest tricks in the book that has worked extremely well in small pet care markets –  jump on what’s trending for human nutrition.  In the case of EMS, it’s avoiding lectins and a ketogenic diet.  Spoiler alert – thumbs down.

Over the next few weeks we’ll look at the claims being made and explain why they are flawed. In the meantime, caveat emptor (buyer beware) and consider relying on real science-based information that has a 20 year track record of good results without charging you anything – http://www.ecirhorse.org.

There are no silver bullets with EMS.  Correct management is, as they say, a life style change.

Eleanor Kellon, VMD

 

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Nitric Oxide Isn’t Laughing Gas

Laughing gas is nitrous oxide, N2O. Nitric oxide is a very simple gas with just one nitrogen and one oxygen molecule, NO, and is a free radical with a half-life in the body of only seconds. This unassuming little compound is of profound physiological importance in life forms from bacteria to elephants.

Gynostemma pentaphyllum (Jiaogulan) is a potent NO inducer

In 1998, the Nobel Peace Prize in Medicine/Physiology was awarded to  Louis Ignarro and Ferid Murad for their discovery of the role of nitric oxide as a signaling molecule in the cardiovascular system.  Since its discovery there have been almost 170,000 scientific publications on nitric oxide and in a mere 20 years it has its own journals: Nitric Oxide – the journal of the Nitric Oxide Society; the Open Nitric Oxide Journal; and Nitric Oxide Biology and Chemistry. Nitric oxide is a super star. In 1992 it was named “Molecule of the Year”.

With good reason too. Unlike other discoveries that hold the spotlight for just a short time, there have been over 3000 professional publications referencing NO just in 2019 to date.  The effects of nitric oxide are felt throughout the body systems. There are two inducible enzyme systems producing nitric oxide on as as-needed basis only – iNOS and nNOS – serving the immune and nervous systems, as well as an eNOS enzyme, endogenous nitric oxide synthase, which works 24/7 to maintain key function such as keeping blood vessels open, dilating airways and triggering cellular healing, growth of new blood vessels and other responses of tissues to stress and exercise.

The well known human cardiac medication, nitroglycerin, works by releasing nitric oxide. This relaxes spasms of blood vessels in the heart which cause chest pain/angina. Nitric oxide has also been found to be a key regulator of tendon and ligament healing. In human studies, nitroglycerin assists in the management of degenerative tendon and ligament problems where healing is stalled.

Inhaled nitric oxide is used to assist people with pulmonary hypertension or babies with premature lung issues. Inhaled nitric oxide also improves oxygenation in horses undergoing surgery and general anesthesia.

Nitric oxide is of particular importance in hoof health. Imbalances between endogenous nitric oxide from eNOS causing dilation and effects of the potent vasoconstrictor endothelin-1 can restrict blood flow to the foot. Carbohydrate sensitive horses can have such imbalances.  Restoring homeostasis between the two allows for optimal health and growth.

As mentioned, nitroglycerin is one way of increasing nitric oxide but overdoing it causes drops in blood pressure and humans report severe headaches. The amino acid L-arginine and its byproduct L-citrulline are needed for nitric oxide production but play no significant role in actually promoting it. Several herbs and natural substances are known to support NO production, including Hawthorn which is a popular human cardiac supplement, but the most effective is Gynostemma pentaphyllum, aka Jiaogulan.

Jiaogulan is a vine indigenous to a remote area of China where it often is used as a tea or vegetable. The leaves are used for endogenous nitric oxide support.  At the same time it supports regulation of inflammatory nitrous oxide production. It has a mild, pleasant odor and horses seem to enjoy the taste. For best effects, give between 2000 and 5000 mg twice a day, mixed into a paste and fed 20 minutes before a meal. It can also be added to the food but higher dosages are usually needed.

Eleanor Kellon, VMD

 

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Whole Food for Horses

The “whole food” claim is being used to market some feeds and supplements for horses but what is a whole food and are these products really superior?

Does this look like whole food to you?

The term whole food is not currently regulated so it can mean anything the company using it wants it to mean. “Whole food” was originally coined in the 1940s and referred to produce “without subtraction, addition or alteration”, harvested and eaten fresh, raised without pesticides, herbicides or chemical fertilizers – in other words, both unprocessed and organic.

Whole food in horse products is definitely not the same as organic. If you don’t see the USDA seal of certification, it’s not organic. Non-GMO is not the same thing as organic either and no guarantee the product does not contain chemicals even far more dangerous than glyphosate.

If you don’t see the USDA seal, it’s not organic.

Whole food is supposed to mean not processed in any way – like eating an apple or peach. Reference might be made to minimal necessary processing. This should include things like peeling a banana to eat it, rinsing dirt off a carrot or cracking open a nut. However, in one prominent feed that plays the whole food card the only actual whole food in it is oats. Everything else has been ground, skinned, pelletized, dried, heat dehydrated (and possibly preserved with sulfur dioxide), dehulled, cleaned, exposed to strong magnetic fields, steamed (split peas), polished, or solvent extracted.

The reality is that very few whole foods will escape rotting inside a feed bag without processing or preservatives. Even drying and grinding leads to loss of some vitamins and fragile fatty acids. What starts out as a whole food loses some critical portions of its nutrition by the time it goes into a bag and really isn’t a whole food any longer.

Whole food supplements have another problem. In addition to not really being whole  foods after they are processed into a powder or bar, the levels of nutrients they provide falls far, far short of being helpful. For example, one “multi” type whole food supplement made from fruits, vegetables, nuts (and some most definitely not whole foods like oils, bran and processed yeast) provides the following amounts of nutrients per daily serving:

  • Protein: 6.2 grams versus requirement of 630 grams (500 kg horse at maintenance)
  • Calcium: 0.8 grams versus requirement of 20 grams
  • Copper: 0.4 mg versus requirement of 100 mg
  • Zinc: 1.35 mg versus requirement of 450 mg

Those are only the rock bottom bare minimum requirements in health. Actual optimal requirements can be much higher. Are these numbers misleading because nutrients in foods are much more bioavailable?  No. That’s a myth. In fact, research has shown minerals in foods are far less bioavailable than minerals in supplements, including inorganic minerals from rock.

There’s nothing wrong with the ingredients that go into these feeds and supplements but the suggestion they are superior to other products does not stand up to scrutiny. For example, I would much rather feed processed wheat bran with its high protein, minerals and vitamin-packed wheat germ intact than the whole wheat grain which is loaded with high glycemic index starch/flour.  The supplements have nice ingredients and are yummy but they’re treats, not supplements.

As much as I favor whole foods like whole oats, it’s not the answer to optimal nutrition for the management scenario of today’s domesticated horse.

Eleanor Kellon, VMD

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Should You Feed Probiotics?

The World Health Organization definition of probiotics is live organisms which, when administered in adequate amounts, confer a health benefit on the host. This usually refers to oral ingestion but they may also be used for health of the skin or the female reproductive tract.

                Populating the gut begins in the birth canal.

The term microbiome describes the population of organisms that inhabit a specific location. Foals are sterile in the uterus but they begin to populate their bodies with organisms during the birth process. Everything their muzzle touches introduces more organisms that could take up residence in their intestinal tract.  They have to survive stomach acid and be able to thrive in the pH and low oxygen tension in the bowel, on the type of food the animal is ingesting. However, there is no lack of diversity in the environment and this process proceeds uneventfully.

Amazingly, the precise microbiome makeup is different for every horse but they are often similar in terms of the families of organisms present and their percentages. The relative number of species shifts predictably with diet changes. This isn’t surprising since the major determinant of which organisms can thrive is whether or not they have a food source.

If the organisms are so abundant and adaptable, why would you ever have to feed probiotics? For healthy horses with normal intestinal function and holding weight as they should, you don’t have to routinely feed probiotics but there are situations where they can be helpful, including:

  • After antibiotic use
  • In horses performing extremes of speed or endurance exercise, or after long distance shipping
  • Older horses having trouble holding weight
  • Horses with suboptimal hind gut fermentation

These are all situations when we know there can be compromise of the microbiome of the intestinal tract.

Once you have identified candidates for probiotic supplementation, you need to pick products most likely to be helpful, including those with equine specific strains in the formulation. Saccharomyces cerevisiae yeast have proven their beneficial effects in multiple studies with a wide spectrum of diets. Saccharomyces boulardii yeast are helpful after antibiotic use and in imbalances involving harmful organisms.

Lactobacilli are found throughout the intestinal tract and are the dominant species in the stomach and small intestine where they help digestion of sugar and starch. Equine specific strains include L. salivarius, L. equi and L. reuteri. In addition to the Saccharomyces yeasts, the hind gut can benefit from Bacillus subtilis, Enterococcus faecium and Propionibacterium as well as Bifidobacterium species.

For routine use after antibiotics or shipping, a basic probiotic product which has a high dosage of S. cerevisiae is a good choice. Horses with weight problems will benefit from a product which also has high digestive enzyme activity documented. For horses with evidence of irritation to the lining of the intestinal tract, the addition of ingredients like Slippery Elm Bark, sodium copper chlorophyllin, Marshmallow Root, Glutamine and Aloe Vera can be soothing and support a healthy mucosa.

Digestive supplements aren’t needed for every horse but when you are stressing the GI tract or the horse has obvious signs of difficulty, probiotics and other support supplements can help.

Eleanor Kellon, VMD

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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How to Get Rid of Pinworms

Tail rubbing is a term that hardly does justice to the devastation a horse can do to their tail hair and skin when they start violently trying to scratch the area. Insect irritation is one cause and Culicoides can be hard to spot. They also don’t mind regular fly sprays so try essential oils of mints and thymol in an ointment or petroleum jelly base. Another possible cause is a dirty sheath or build up of sweat, cells and dirt in the crease between the thigh and the sheath or udder. If none of these apply, think pinworms.

Adult Oxyuris equi – Pinworms

Pinworms (Oxyuris equi) live in the terminal portions of the intestine. The females exit the anus at night to lay their eggs on the perianal skin. Eggs are encased in a sticky fluid which helps them adhere to the skin. It also causes irritation, making the horse rub its tail and  in the process deposit eggs on any surface it rubs against. Eggs also eventually drop off.

Cases where O. equi was resistant to treatment with moxidectin or ivermectin have been reported so this is one instance where you probably should stay away from those drugs. They are still sensitive to fenbendazole and the pyrantel family of dewormers.

There are also anecdotal reports of inability to clear pinworm infections with any dewormer. However, pinworms have a 5 month life cycle and the dewormers only get adults and very late stage larvae so the drugs may well be effective but they are seeing the younger larvae mature to egg laying after the drug is gone.

Putting the dewormer dose into the rectum instead of orally has been tried. This is safe but hasn’t been effective. Consider trying a combination of Strongid paste (pyrantel pamoate) or fenbendazole plus daily pyrantel tartrate (Strongid T or Equi Aid CW) using the daily pyrantel for 3 to 4 months. The daily pyrantel will kill younger forms before they mature to egg laying stages.

Fecals are usually negative but you can check for eggs on the skin by applying a strip of clear tape to the skin and examining this under a microscope. If you get some microscope slides you can put the tape sticky side down on the slide and take it to your vet’s office.

Also start daily gentle washing of the underside of the tail, anal area and surrounding skin with Dawn dish soap in warm water to help remove eggs without irritating the skin. Do this in the morning since they lay eggs at night. Another washing in the evening won’t hurt. Try coating the skin with baby oil, Vaseline, Desitin, etc. at night to reduce egg packets sticking to and irritating the skin. Skip that step if you are going to check for eggs on the skin the next morning. The oil may also help you identify areas where the horse is rubbing and depositing eggs in the environment. Eggs may also come off on bedding or ground where the horse lies down to sleep so don’t feed anything off the ground.

Trying to decontaminate the premises may be futile! When egg packets dry and fall to the ground they can land anywhere. Eggs survive for about 8 to 10 weeks so you should be clear by the time you finish the treatment protocol.

Eleanor Kellon, VMD

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Vitamin C – Friend or Foe

Vitamin C [ascorbate/ascorbic acid] is a water soluble vitamin which functions as an important antioxidant and is needed for the synthesis of L-carnitine, catecholamines like epinephrine and dopamine, as well as collagen, the major protein in all connective tissues, including tendons and ligaments, even blood vessels.  Deficiency causes a disease called scurvy, beginning as weakness and muscle pain, progressing to bleeding gums, loose teeth, poor healing and eventually mental changes and death.

Fresh, live grass in an excellent source of Vitamin C.

Unlike humans, the horse can synthesize enough vitamin C in its body to prevent the development of a full blown deficiency state (scurvy). However, the ability of this synthesis
to maintain normal vitamin C levels and the role of dietary C is poorly understood. We do know that heavy exercise and chronic disease, especially lung disease, lead to decreased vitamin C blood levels in unsupplemented horses, as does stabling versus pasture access. Low blood levels have also been linked to poor wound healing in horses.

Although information is limited, a “conditionally essential” status may best describe the need for additional vitamin C in the diet of horses that are recovering from illness or surgery, or exercising heavily, when requirements may exceed the body’s ability to make it. The NRC states that information about vitamin C levels in common feedstuffs is lacking but a study from 1938 measured ascorbic acid in many common feeds, hays and references levels in grasses.

The figures are presumably on a dry matter basis and they report 20 to 136 mg/100 gram in fresh pasture; 1.3 mg/100 g in 50:50 alfalfa/grass hay; 0.9 mg/100 g in grass hay; 1.3 to 1.8 mg/100 g in alfalfa; 0.7 mg/100 g in beet pulp; about 0.6 mg/100 g in grains (this would only apply to whole grains). A stabled horse on a grass hay based diet would be taking in less than 1 gram of C from its diet daily while an average horse on pasture is getting a minimum of 20 grams/day (quite possibly part of the value of “Dr. Green”!).

In the early 1970s, Dr. Linus Pauling was recommending megadoses of vitamin C for maximum health and disease prevention. As usually happens, many of these claims were debunked and the pendulum actually swung so far to the other side that megadosing was proposed to be toxic.  Once again, the truth is somewhere in between.

With specific reference to the horse, toxicity in the form of diarrhea usually begins with dosages of 20 grams/day and above. This may be more of a local irritation than a toxicity.  There are two other properties of vitamin C that would dictate caution in horses known or suspected to be iron overloaded. One is that vitamin C increases iron absorption in the intestine. It also can act as a pro-oxidant rather than anti-oxidant in the presence of excess iron in the circulation or tissues.

A reasonable level of supplementation is 3 to 10 grams/day for an average size adult horse, keeping to the lower levels with iron overload.  For additional antioxidant support vitamin C can be combined with other antioxidants such as resveratrol from grapeseed, citrus bioflavonoids, MSM, herbals with good antioxidant activity such as Jiaogulan or Spirulina and vitamin E for fat soluble coverage.

Eleanor Kellon, VMD

 

 

 

 

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