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Why use a supplement, what to consider?

Supplements can be used for different reasons, such as:

  • The horse is not getting enough nutrients through its diet.
  • Due to health issues, the horse needs more of a specific nutrient than usual.
  • The horse only temporarily needs more nutrients.
  • A nutrient has an extra effect when used at higher dosage.

The first scenario is applicable to almost all horses that are kept on a pasture-only diet. The ground in the Manawatu doesn’t contain enough nutrients to supply our horses with enough. Especially when the pasture has not been fertilized regularly or treated with lime when necessary. For these horses a general supplement should be found that supplies the horse with adequate amounts of quality nutrients that are properly absorbed in the small intestine. 

The horse can make some nutrients on its own, such as vitamin K or certain proteins. However, there are certain nutrients that the horse can’t make on its own, so it will need to receive these through its diet. We call these nutrients “essential”. How much a horse needs of these nutrients depends on its body weight, level of exercise and whether it’s young and growing, pregnant or lactating. Here’s a list of essential nutrients:

  Minerals  Trace elements  Vitamins
  Calcium (Ca)
  Phosphorus (P)
  Potassium (K)
  Magnesium (Mg)
  Sodium (Na)
  Chloride (Cl)
  Sulphur (S)
  Iron (Fe)
  Copper (Cu)
  Zinc (Zn)
  Iodine (I)
  Manganese (Mn)
  Selenium (Se)
  Cobalt (Co)
  Vitamin A
  Vitamin D
  Vitamin E
  Thiamine (Vit B1)
  Riboflavin (Vit B2)

Vitamin K and the B vitamins are produced by the microflora in the hindgut. If the hindgut is healthy, these vitamins don’t need to be supplied in the diet. Only Vitamin B1 (thiamine) and B2 (riboflavin) always need to be supplied through the diet.

Sometimes health issues can cause a higher need for certain nurtients.

Vitamin C for example, is produced in the liver. Under certain circumstances, the horse’s own production can fall short. This happens more often in (older) horses that have decreased liver function. Feeds designed for senior horses often contain more vitamin C.

Horses with hindgut issues have a less balanced or healthy microflora. The horses’ microflora gets shaped when they’re still a foal. After a few weeks of age, the foal starts to eat the mare’s faeces. This helps the process of acquiring the right microflora. When a foal becomes sick and can’t properly develop its gut flora, this can contribute to a sensitive hindgut and hindgut issues, such as being prone to colic, later in life. These horses might be helped by certain “probiotic” live yeast cultures and “prebiotic” fibres (fructo-oligosaccharides, sometimes called scFOS, and pectins). Not every live yeast culture strain is actually part of the normal healthy hindgut and not every live yeast culture ends up in the hindgut alive and well. Probiotic live yeast cells change the hindgut environment in such a way that the good bacteria can grow better. The effect has especially been proven in horses on high concentrate diets. Certain yeast cultures have been tested and proven to 1) belong in the horse’s hindgut and 2) make it there alive. An example would be certain strains of Saccharomyces cerevisiae. When a horsefeed contains the right kind of live yeast culture, there should be a mention of a live yeast brand (such as “Yeasacc©“) or registration number (such as “MUCL 39885CE”) and the amount of live yeast cells that have been added per gram (for example 6×109CFU = ‘colony forming unit’). This CFU number means that they are live yeast cells, not dead ones.

Dead yeast cultures are not probiotics. Some products contain dead yeast or live yeast cultures that have only been tested on ruminants. Dead yeast can be a source of vitamin B and it might increase the flavour of a product, but dead yeast doesn’t have an effect on the hindgut. Live yeast cultures that have been shown to have apositive effect in the rumen of cattle or sheep don’t need to pass the acidic stomach or the enzymes of the small intestine. Fermentation in the horse happens in the hindgut, so this means that these live yeast cultures need to pass the entire intestinal tract unharmed before they’re where they are where we want them to be. If you want to use a supplement that helps your horse’s hindgut, we advise you to use a product that contains live yeast cultures that have been proven to be effective in the horse.

Sometimes a horse temporarily needs extra nutrients.

For example, a horse that’s tying-up will need extra Vitamin E (tocopherol). In these situations, a vet can directly inject a high dose of vitamin E and/or give you a vitaminE supplement to feed. A natural source of vitamin E would be preferred for better absorption in the gut. It’s best to test the horse for Selenium, but not supplement until the results are known, as Selenium is toxic when overdosed. Just like Selenium, vitamin E catches free radicals. These free radicals are a by-product of metabolism and can be produced during muscular activity for example. The damage the body’s cells, so they need to be neutralized as soon as possible. Vitamin E and anti-oxidants do this

A nutrient that can have an extra effect at a higher dose is Biotin.

Biotin is vitamin B8, which is normally produced by the microflora of the hindgut. A horse therefore doesn’t usually need biotin in its feed if it’s eating adequate amounts of fibre. However, an additional daily dosis of biotin has shown to improve the hoof quality of horses with hooves that crack and chip easily. Biotin plays a part in fat- and protein metabolism and in cellgrowth. It has a positive effect on the development of horn- and skincells. Studies have shown that a daily dose of 15-30mg of biotin can improve bad hoof quality. However, this does not happen for every horse with bad hooves, and because hoof growth is very slow, biotin needs to be supplemented for at least 9 months to determine whether there is a positive effect. If there is, it is likely that a horse will need lifelong supplementation to maintain improved hoof quality.

Keep in mind that certain nutrients can become toxic when overdosed, or have a negative effect on the absorption of another nutrient.

When you’re considering to buy a certain supplement, do not forget to consider all other supplements or feeds that the horse is already on.

At the top of the list of things to be careful with not to overdose, is Selenium. Too little Selenium causes health issues, but when overdosed Selenium takes Sulphur’s place in aminoacids, the building blocks for proteins that are used to build bodytissues. This causes problems in the growth and integrity of hoof horn, skin, hair, and other body tissues and can lead to lameness, loss of hair and possibly internal problems. A horse should not consume more than 1mg of Selenium per 100kg bodyweight per day.

Calcium, Phosphorus and Magnesium have an effect on each other’s absorbtion in the gut. Calcium and Phosphorus are necessary for skeletal growth and intergity, and a variety of other bodily functions. A horse should receive enough of these nurtients and their Ca:P proportions should be between 1:1 and 3:1, preferably 2:1. Calcium and Magnesium stimulate each other’s absorption in the gut. There are no guidelines on proportions for optimum absorption, but a horse’s daily nutrient requirements have a Ca:Mg proportion of about 2-3:1. Magnesium plays a role in bone metabolism, muscle contractions (especially the relaxation phase), the immune system and the nerve system. A Phosphorus or Potassium rich diet can decrease the absorption of Magnesium. A Magnesium deficiency can lead to poor performance, decreased growth, getting sick easily and muscle weakness. Unfortunately, Magnesium can’t be reliably tested for in the blood because blood levels fluctuate throughout the day independent of whether tissues levels are adequate. The only reliable measure is Magnesium in urine. The body normally gets rid of Magnesium via urine. If urine levels are too low or absent, we can assume there is not enough Magnesium in the diet or absorbtion in the gut is too low. If a horse has poor kidney-function and can’t cope with an excess of Magnesium, this can lead to Magnesium toxicity (nervousness, sweating, muscle tremors). A study in England showed that when thoroughbred racehorses were fed extra Magnesium supplements on top of a diet that was proficient in Magnesium already, their reaction time on the racetrack became slower.

Some supplements only contain one of these elements and can therefore alter the proportions of these nutrients. Lucerne is rich in Calcium. Cereal grains, such as oats, contain only 1/10th to 1/3rd of Calcium needed for mximum growth, which is especially a problem in pregnant or lactating mares and young horses. Oats have an unfavourable Ca:P ratio, because they’re inherently high in Phosphorus (0.35%) and quite low in Calcium (0.05%). Grass or grass hay will not compensate for this problem, but legume-hay such as lucerne hay, is Calcium-rich and may contribute towards a better ratio. However, without a hay analysis it would be impossible to know whether this is enough. Young, growing horses on a Calcium-deficient diet can be at risk of developing rickets, which is a disease of the bones and joints. Adult horses can develop “big head disease”, which is a bone metabolism disease which causes the bones of the head to become misformed. In many countries “in the old days” horses used to be fed high-grain diets too, but these diseases were no exception even then, and horses were often retired from work in their teenage years because they were incapable of staying sound for consistant, hard work. Fortified horse feeds that contain oats will also contain added vitamins and nutrients that compensate for the unfavourable Calcium and Phosphorus and low protein content of oats and should therefore be safe to feed. Pregnant or lactating mares and young growing horses need a specially designed feed that caters to their specific needs.

If oats are chosen to increase caloric intake, a vitamin-mineral pellet feed would still be necessary to make sure a horse receives proper nutrient levels. Plain oats will not deliver sufficient protein, vitamins, and minerals for maximal growth or performance.

It’s clear that a horse’s entire diet should be evaluated before deciding whether a supplement is needed.

Joint supplements are the most widely used supplements in the equine industry. Usually, these supplements contain active constituents such as glucosamine, chondroitin, methyl-sulphonyl-methane (MSM) or hyaluronic acid (HA). It’s helpful to know more about what the roles of these constituents in healthy joints are.

Glucosamine, chondroitin, MSM en HA are building blocks for cartilage and synovial fluid. The theory of joint supplements is that extra supplementation of these ingredients helps prevent (sporthorses) or recover from joint damage . Studies conducted on tissues in the lab (not on an animal) show positive results. However, studies on live horses show variable results and have not been able to reach consensus. It is very difficult to conduct a good long-term study. For example, to determine whether joint supplements have a protective and preventative effect, one would need enough horses, give them all the same exercise for a decade, while half gets supplemented and the other half doesn’t, and hope that nothing else happens to them that would exclude them from the study… not very practical. It’s easier to see whether a joint supplement has an effect on horses with joint issues such as osteoarthritis or decreased joint lubrication due to old age. However, even then it’s impossible to see what the effect is on the joint itself without euthanizing the horses at the end of the experiment to look at the joint tissues under a microscope.

We get great feedback about some products, more so in some horses than in others. This means that results vary, just like in the studies that have been done. Sometimes improvement is not very obvious, but may become more obvious when an owner stops using the product. Sometimes the products don’t seem to have an effect at all. What causes these differences and whether the improvements are real is hard to say. Some supplements might only mask pain without actually improving joint quality. An example of this is Devil’s claw, which is sometimes added to joint supplements. Horses often show improvement because of the painkilling effects. Depending on what you’re after, this might or might not be enough. Another phenomenon that can play a role in the results is the placebo effect. The placebo effect describes a situation where someone is given a fake, ineffective treatment, but nontheless perceives a positive treatment effect. For example, someone thinks they’re taking a painkiller, but the pill doesn’t actually contain active ingredients, and the person still starts to feel less pain. The placebo effect can happen in animals too, in which case their owner plays a role as well. A good example is given by a study that looked at the effects of vitamin E supplements on back pain in horses. The back pain in these horses was not diagnosed by any vets, but just noticed by the owners themselves. One group received actual vitamin E, while the other received a fake supplement that didn’t contain any active ingredients. The interesting thing was that the results were equally positive in both groups. Almost all owners were convinced that the back problems in their horse had improved. A possible explanation could be that when people supplement their horses they also become more aware of a problem and therefore maybe handle their animal differently, which might have a positive effect. There are several studies that have proved the placebo effect in animal-owner groups. Whatever the explanation of the placebo effect might be, the effect in a therapy setting is positive. The placebo effect is therefore generally seen as a valid therapy approach.

Back to joint supplements… Because results are not equivocal, and more research is needed, it may just be a case of trial and error. The products that Totally Vets uses have had positive feedback. We have oral supplements and we have products that are injected in the muscle or vein so that digestion is not a limiting factor. We have found better results with some products compared to others, so depending on your (horse’s) situation and goals we can help you find a product that suits your demands. From there on the horse will have to tell us whether it’s a success.

Omega 3

Omega 3 has been known for its anti-inflammatory effects. It also helps create a healthy and shiny haircoat. How does this work? Omega 3 (linolenic acid) and omega 6 (linol acid) are both fatty acids that play a role in recovery from cellular damage. Omega 6 stimulates inflammatory processes and omega 3 inhibits inflammatory processes (lowers them). They are each other’s counterparts, and they’re both equally important in maintaining healthy tissues. Sometimes the amount of omega 3 and omega 6 can get out of balance. When a diet predominantly provides a lot of omega 6, addition of omega 3 supplements can tip the balance back to normal to prevent inflammatory processes from having the overhand. Optimal levels of omega 3 reduces the inflammatory state of the body, supports immune function. This may specifically work for horses with alergies, skin conditions, respiratory issues, joint issues or reproductive issues.

Grass has a very low fat content, but in that, the proportion of omega 3 is relatively high. A diet based on hay and hardfeed (especially cereal feeds) will contain more omega 6. Vegetable oils also contain more omega 6. If the omega 6 – omega 3 balance is a concern with your horse, replacing vegetable oil with canola or soy oil will help. Fishoil is the biggest and best source of omega 3. There are different kinds of omega 3 fatty acids, with docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) having the best biological activity. Fishoil is rich in DHA and EPA. If oil isn’t part of the diet, a supplement such as EO-3, developed by Kentucky Equine Research (KER), is a good option. It has marine derived omega 3. Fish oil has an omega-3:omega-6 ratio of 6:1. How much omega 3 a horse exactly needs in its diet on a daily basis is unfortunately unknown. Keep in mind that oil is a high-energy source for horses. Make sure your horse doesn’t become overweight.


Electrolytes are often used to rehydrate a horse after strenuous exercise or in hot weather. Electrolytes are minerals such as Sodium, Potassium, Chloride, Calcium and Magnesium. The blood always tries to keep levels of these electrolytes between certain limits. When a horse gets dehydrated, the water content of the blood goes down, which means that there’s relatively more electrolytes per ml of blood. This gives a signal to the brain that makes the horse want to drink water, which corrects the water content of the blood. The restored blood fluid now has a normal electrolyte:water ratio again. A horse’s sweat contains water and electrolytes, mainly Sodium, Chloride and Potassium. This means that when the horse sweats a lot, it doesn’t just lose water, it also loses these electrolytes. The blood now contains not only less water, but also less electrolytes, which means that the electrolyte:water ratio stays relatively similar, so there’s no signal going to the brain to tell the horse to drink more water. By giving a horse electrolytes after strenuous exercise, the electrolyte:water ratio in the blood becomes skewed again, which gives off a signal to the brain to make the horse want to drink more water. This is how electrolytes can make a horse rehydrate faster. A tube of electrolytes does supply some electrolytes for the body, but when a horse has sweat a lot, it won’t replenish all that the horse has lost. To do that, the horse needs to eat its regular feed, supplemented with extra salts if necessary. Giving a horse electrolytes after exercise is just meant to make a horse rehydrate itself (which is very important for good recovery!).

When should you add extra salts to the diet? Firsty, a horse’s diet should contain enough salts for maintenance requirements. The amount of exercise that you do with your horse can increase the daily requirements due to loss of sweat. For example, a 500 kg horse would normally need about 10 grams of Sodium a day. When the horse is exercised, the daily requirements could go up to 30 to 60 grams a day. Horses that don’t get enough salts can start licking objects, eat sand or dirt, have a dry skin or food- and faecal passage in their gut can slow down. If your horse sweats during regular exercise, but there’s no salt in the diet and it’s not interested in a salt block, you can add 5-10 grams of kitchen salt a day.

If you have a strenuous weekend of competitions or exercise planned during hot weather, than it could be that your horse’s regular diet won’t have enough salts to replenish the extra losses through sweat. For multiple day events, endurance rides or high performance during hot weather start adding some salt two days in advance and continue till a day after. If you’re using kitchen salt, than depending on how big your horse is and how much your horse will sweat, you can add 20-40 grams a day for a 600kg horse. If you’re giving too much the horse will start to drink more and urinate more. This means you have to immediately reduce (half) the amount of salt you’re giving. Too much salt can damage the stomach. A horse usually doesn’t like eating overly salty feeds. When you you’re your horse salts, always make sure there’s anough fresh water available.

There are also pre-made electrolyte solutions available. These often contain more than just Sodium and Chloride to cater to a horse’s losses a bit better. There are drenches, which can be handy because you control the amount your horse is consuming and you can give it even when a horse isn’t drinking on its own. There are also solutions that you can add to water. This means that your horse does need to want to drink water to consume it. If you’re using a product like that, make sure your horse has access to plain water as well. Too much salt and not enough water can lead to salt intoxication.


Some herbs are believed to have a positive effect on health. Some examples:

  • Yucca contains saponins that have an anti-inflammatory, anti-oxidant and anti-muscletension effects. Yucca also contains resveratrol and yuccaols, which have a slight painkilling effect. However, yucca has not been studied in horses, so its positive effects haven’t been confirmed in horses.
  • Valerian has a calming effect in people. There have been no studies to the effect in horses. Valerian can be picked up in drug tests in performance horses, so we don’t advise using such products in performance horses.
  • Devil’s claw as mentioned before has pain killing effects. It contains the active ingredient harpagophytum. Devil’s claw also can be picked up in drug tests in performance horses, so we don’t advise using such products in performance horses.
  • Primrose has slight anti-inflammatory effects. Primrose oil contains high concentrations of omega 6 and some omega 3. A study looked at the effect of 150ml per day in horses of 500kg bodyweight, which showed anti-oxidant effects.

If you would like to supplement your horse, but you’re not sure how to do this safely or which product to use, give us a call so one of our vets can help you out.

Graph 1

Graph 1: Comparing three different feeds. This is just an example, and in reality we may advise a combination of things. To know the horse’s daily requirements, we need to know the horse’s breed, weight, age, gender, type of exercise and whether there are any complaints.

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