Created: September 2007
Last updated: November 2019
Some of what follows is based on current theories and early research rather than well established veterinary practice. As such, anyone following the suggestions contained in this article does so entirely at their own risk.
There are many possible triggers/causes of laminitis (a US study identified around 200 possible triggers), but most of them are rare. The vast majority of laminitis cases (especially if you include Low Grade Laminitis) appear to be caused or at the very least triggered by diet in some shape or form. So it makes sense if we’re trying to either avoid laminitis or get an active attack under control to take a long hard look at the diet of the horse in question.
It’s increasingly becoming clear that by far the most common kind of laminitis in the UK is pasture laminitis where increases in the sugar content of the grass triggers an attack. In this kind of laminitis, the sudden or gradual increase in sugar levels in the diet is thought to be the trigger. It’s likely that the horse already has something wrong with it – otherwise the rising sugar levels wouldn’t cause so many problems. Where laminitis is triggered by rising sugar levels, the horse is likely to either have Pituitary Pars Intermedia Dysfunction (PPID – which used to be incorrectly called Cushing’s Disease) or, more likely, Equine Metabolic Syndrome (EMS). A key feature of EMS and PPID is Insulin Resistance where the horse copes with rising blood glucose levels by using far more insulin than normal. Researchers are currently investigating whether this hike in insulin levels is responsible in some way for the onset of laminitis.
Whilst drugs are increasingly being used to manage laminitis cases, drugs are often not enough on their own to keep laminitis at bay. There are also many cases (especially low grade laminitis cases) that are too mild to warrant drug interventions and, in these cases, good dietary management is critical.
When developing a diet for a horse that has laminitis or is considered to be at risk, there are two goals. The first is to keep blood glucose levels low and reasonably constant so that the horse doesn’t have to produce that sudden increase in insulin. The second goal is to try to reduce the levels of insulin resistance so as to make the horse less sensitive to glucose intake.
Stabilising blood glucose levels
Blood glucose levels increase whenever the horse eats a food that contains forms of carbohydrate that can easily be digested to form glucose. Sugars and starches that enter the digestive tract are broken down into simple sugars such as fructose and glucose. These simple sugars are then absorbed through the gut wall into the blood.
Glucose is found in pretty much every feedstuff but is likely to be at particularly high levels in anything that tastes sweet – so in terms of horse feeds, things like molasses, apples, carrots, etc. Starches are again found in pretty much all horse feeds but in varying quantities. The speed with which starches are broken down into glucose in the gut varies enormously between different feed ingredients.
The majority of a horse’s energy should come from digesting fibre. Fibre is broken down in the hindgut by bacteria to form volatile fatty acids – a source of energy that doesn’t involve blood glucose and hence is safe for insulin resistant horses. Horses can also gain energy from oils and again, because this doesn’t involve being absorbed in the form of glucose, it bypasses the insulin system. As a result, high oil content feeds aren’t thought to be an issue for laminitic horses. This is useful if you need to put condition on a laminitic horse. You can do so safely using feeds rich in oils but low in glucose (such as linseed).
Obviously, the horse needs to get a certain amount of energy per day. What we don’t want to do though is have all that energy come in short bursts that cause the insulin system to have to go into overdrive to deal with them. Instead we want the energy from feeds to be released evenly and slowly over the day. We also want to make sure we don’t give way too much energy-giving food or the insulin system will be in overdrive all day even if it’s released evenly. If the horse is fed entirely on fibre, then we have no problem because no blood glucose is released. Unfortunately sources of fibre available in the UK (such as grass and hay) all have some degree of sugars and starch in them as well and it’s thought that these sugar and starch levels are the real issue in laminitis.
If we feed things like molasses that contain a lot of sugars, the blood glucose will go up suddenly and the insulin level will go up suddenly to sort that out – which is what we want to avoid. So the first rule of feeding a laminitic is to avoid or keep very low anything that contains lots of sugars – and that means fruit, sweet vegetables (e.g. carrots), anything with molasses in it, or anything else that is sweet.
But we also want to avoid any feeds that have high quantities of starches that are quickly digestible into glucose. So, for example, feeding wheat in large quantities would be bad idea. In fact as a general rule, feeding any significant quantity of grains to a laminitic horse is a bad idea.
You may have heard of the low GI diet for humans. GI stands for Glycemic Index and is a measure of how much glucose the food releases when digested and how rapidly it is released. Essentially, the diet we want for our laminitic horse is a low GI diet with a slow release of energy. The ideal is a forage based diet where the sugar and starch levels in the forage are reasonably low. A high fibre foraged-based diet also ensures that the horse is getting most of its calories from fermentation of fibre and hence blood glucose levels aren’t affected. Any sugars and starches in a forage also tend to be released more slowly than with high-sugar bucket feed ingredients so reducing the likelihood of insulin spikes. To be suitable for a laminitic horse, the total of the ethanol soluable carbohydrate (ESC) plus starch in a grass, hay or haylage should be under 10%.
Quite often we want to feed some sort of bucket feed on a daily basis. This might be to ensure the horse agrees to be caught in the field, it might be because the horse doesn’t maintain condition on a forage-only diet, or it might be as a way of feeding supplements that the horse needs. Whatever the reason, these bucket feeds need to be suitable for a laminitic. As with the forage, we want something that is low sugar and slow release.
As a general rule, I don’t assume that just because a feed says it’s suitable for laminitics on the bag that it is suitable for any laminitic horse. I find that at least some of the ‘laminitis freindly’ feed stuffs available are too rich for the typical laminitic. Some of these feeds are only really appropriaite for laminitis prone horses that are in seriously high levels of work (e.g. endurance, eventing, etc.).
Another point to bear in mind is that the typical 500kg horse’s stomach is only able to hold a couple of kilograms of feed at a time. If the horse eats more than that at a sitting, the excess gets pushed through before it’s been fully digested and ends up in the caecum (the hind gut). There’s some evidence that starches that make it to the caecum undigested cause incorrect fermentation there which releases toxins that can poison the horse and cause laminitis. So it’s important that the overall size of feeds is kept small.
Getting to the root causes of Insulin Resistance
There is still a very large amount of research to be done before we truly understand what causes insulin resistance. Until recently, we had few tools with which to tackle insulin resistance. In the last few years however, it has been suggested that the balance of minerals/vitamins in the diet may either cause or exacerbate insulin resistance in at least some cases. We’re not sure currently whether the laminitic horse’s diet is low in these nutrients or whether some underlying illness in the horse causes them to be absorbed, synthesised or utilised less well – it may well be that both are true in at least some horses.
There are a number of nutrients that have been suggested as having a role in insulin resistance, but for most of them, we have too little research to be able to say categorically that they are involved. One nutrient that does seem to be involved is magnesium. Supplementing magnesium in horses seems to help both with the level of insulin resistance and with the susceptibility to laminitis. Supplementing with magnesium is still somewhat controversial, but this approach is now being used by increasing numbers of owners of laminitic horses and the anecdotal evidence of it’s effectiveness is mounting up despite the lack of formal scientific trials. I’ve used magnesium supplementation extensively in my practice and have found that it helps the majority of laminitic horses and seems to fully control laminitis in a good number.
There is much discussion about exactly why the magnesium helps, but until we have more research in this area, it’s only really possible to speculate. Magnesium is certainly very important for the correct functioning of the metabolism. Magnesium is used in every cell in the body as part of the process of converting blood glucose into usable energy within cells. As such, it’s possible that a deficiency in magnesium might cause glucose metabolism to be impaired – could this be one factor in insulin resistance? Or it could be something entirely different… magnesium is normally fed as magnesium oxide, which is alkaline. Feeding significant quantities of magnesium oxide may well change the acid/alkali balance of the gut and that in turn may be beneficial.
Another nutrient that is worth looking at is sodium. Sodium, like magnesium, is an essential element – without suitable quantities of it in the diet, the horse will die. In the west, we tend to be concerned about sodium content of our food because high sodium levels in human diets (e.g. from too much salt) are associated with heart disease. However, it’s important not to assume that the same is true of horses. While the typical human diet in the west is high in sodium (we eat lots of meat and dairy produce and put salt on our chips), the typical horse’s diet is usually moderately low in sodium. Most forages should provide enough sodium for a horse that is not in work, but once the horse starts to work hard, sodium requirements go up and we may need to provide additional sodium. Too much dietary sodium is just as harmful to a horse as it is to a human, but horses are generally starting from a much lower level so there’s much more room for an increase without hitting danger levels.
A recent discovery is that, in at least some horses, providing a little extra sodium seems to make magnesium supplementation more effective. The level of supplementation involved is quite low and, while it pushes the horse noticeably above the minimum level of sodium needed for health, the levels involved are still well below those that would be considered harmful to the horse’s health. It is interesting to note that traditional approaches to feeding horses included throwing a small amount of salt in every feed – a practice which seems to have largely disappeared over the decades. As with the magnesium, it’s not known why slightly higher levels of sodium help. One suggestion is that the ratio of potassium to sodium in the diet is important. If the potassium:sodium ratio is too high, the body requires more magnesium. So if the diet is high in potassium and low in sodium and magnesium, the horse may end up deficient in magnesium.
Most forage is extremely high in potassium. This is because, in the west, we generally fertilise our fields with chemical fertilisers that contain, amongst other things, high levels of potassium. As a result, the level of potassium in virtually all western agricultural soils is way higher than it would be in the lands where horses evolved. The use of high levels of fertiliser increases the productivity of grassland significantly, which in turn takes more trace elements out of the soil. Anything that is not put back will tend to drop. We typically add potassium, nitrogen and phosphate to the soil, but we don’t add magnesium. As a result, the potassium levels stay high and the magnesium levels tend to drop. A few years ago, a UK government study found that 40% of men and 70% of women had diets that were deficient in magnesium… it’s not unreasonable to assume that our horses are also deficient.
So if typical western forage is very high in potassium and slightly low in magnesium, then that might explain why adding a little sodium and quite a bit of magnesium to the diet helps. But as ever, much of this is just speculation. Of course the ideal would be to source low potassium forage, but that is extremely difficult, at least in the UK.
Indications for feeding supplementary magnesium/sodium
It is probably safe to feed any horse extra magnesium and a little extra sodium, however if the horse is healthy, there is probably no point in doing so. You also need to be careful to take account of the magnesium and sodium content of any supplements already being fed. Magnesium is very safe to supplement because the levels at which it becomes toxic are way higher than the minimum levels required for health – this gives us a good ‘headroom’ into which to increase magnesium intake. Sodium has a smaller headroom, so supplementation with additional sodium needs to be done with more caution.
I would generally consider supplementing with magnesium/sodium any horse that:
- has had acute laminitis within the last year
- shows signs of Low Grade Laminitis
- shows signs of Insulin Resistance
Copper, zinc, iron and manganese
Another aspect of mineral balance that is increasingly looking significant in the battle against EMS is the ratios of copper and zinc to iron and manganese. In UK soils, copper and zinc are commonly a touch low and iron and manganese are frequently quite high. It turns out that high iron and/or manganese levels in the feed will tend to block the uptake of copper and zinc. And it is suggested that copper and zinc are required for optimal glucose metabolism. So it’s possible that the combination of high iron and/or manganese alongside low copper and/or zinc may be contributing to EMS in the UK. Of course if you add a supplement to the bucket feed that has any significant quantity of iron or manganese in it, that may well make the problem worse.
There is increasing interest in ‘intelligent balancers’ that are designed to improve the unhelpful mineral ratios present in typical UK forages. These products typically have little or no iron or manganese and have higher than normal levels of copper and zinc (to compensate for poor absorption as a result of high iron/manganese in the base forage). Anecdotal evidence seems to suggest that these products can prove highly beneficial for a significant proportion of EMS cases.
Feeding suggestions for laminitics
The following suggestions are based on my experience both with my own horses and those of my clients. They come with no guarantees of effectiveness or safety – if you decide to follow these suggestions, you do so at your own risk. For horses prone to laminitis, if these feeding suggestions work, then the horse is likely to need to stay on this diet for life in order to minimise risk (or at least until we work out how to cure laminitis properly). These suggestions do not represent a cure for laminitis… just a diet that helps to reduce the risk of laminitis in susceptible horses. This diet does not tend to fully work for every laminitic horse, but certainly seems to help the vast majority in my experience.
The ideal forage for laminitic horses is hay. Hay contains most of the goodness of grass but because of the drying process after it is cut, the sugar levels tend to be lower. It also doesn’t suffer from sugar levels that fluctuate during the day unlike grass. Unfortunately hay varies a lot depending on what field it has come from and unless you’re an expert in identifying grasses, it can be very difficult to know the difference. Ideally, hay from old-fashioned wildflower meadows is the best as this tends to have far more species in it (which helps to increase the levels of trace elements) and tends to have lower levels of potassium and sugars. Sadly such hay isn’t easy to find, but if you can get hay from a field that hasn’t been fertilised in the last few years, this is usually better than nothing.
In an ideal world, you should get your hay analyzed for sugar content and for essential minerals. The degree of insulin resistance will dictate how low the sugar content needs to be. The current recommendation is that any forage with an ESC + Starch content under 10% should usually be safe, but for more sensitive horses, it may be necessary to source hay with lower levels (which is not easy).
Where the sugar/starch level in a batch of hay is too high for a laminitic horse, soaking it for half an hour in clean water will reduce the sugar levels. This is good for short periods of time – especially as a first aid approach for a horse that has just had an attack. However, it also reduces some of the nutritional value of the hay so when using soaked hay for a long period, it may be necessary to provide a broad spectrum mineral/vitamin supplement.
Although some laminitic horses cope well on haylage (especially the drier forms), it appears to be better to use hay if possible. This may be because the fermentation process by which haylage is made makes the hay digest more easily and hence increases the risk of blood glucose spikes.
I tend to avoid specialist bagged forages. They tend to be produced using intensive farming practices that will result in higher levels of potassium and as such I am concerned that they may cause problems. Many also have some added molasses and so may not be low enough in sugars for the more sensitive laminitics. That said, a minority of horses seem to do better on these products than on grass or hay and bagged haylage taken from ‘meadows’ is increasingly becoming available and suits some laminitis cases because it is very consistent in sugar/starch levels.
Ideally forage should be provided on an ad-lib basis. It is important that the horse’s gut is never allowed to empty. Unlike humans, horses constantly produce stomach acid (they have evolved to eat pretty much constantly). If a horse is starved for more than a few hours, the gut empties and the levels of stomach acid build up. This can upset the balance of gut bacteria and can also cause stomach ulcers – both of which are thought to contribute to the risk of laminitis. A lot of insulin resistant horses will tend to overeat if given free access to forage so it may well be necessary to find ways of slowing the horse’s eating down such as double haylage nets or feeding a proportion of oat straw.
Bucket feeds – bulk ingredients
There are many possibilities for bulking bucket feeds and I don’t intend to list them all here. The basic principle is again to avoid anything that’s high in sugars or starch. The potassium levels are less important in bucket feeds as they shouldn’t make up more than a small percentage of the overall diet. I typically like to keep each bucket feed below 2 kg for a 500kg horse and many cases will need a lot less than that. Where more feed is needed (e.g. where the horse loses condition easily), it should be provided as two or more smaller meals.
I tend to avoid anything that contains cereals – especially in horses that are recovering from laminitis.
Good feed ingredients include:
- Sugar beet. This is a great feed for providing protein and energy. Be sure to used unmolassed sugar beet as the majority of beet products on the market have added molasses. Speedibeet is good, as is Simple Systems Purabeet.
- Alfalfa. This is high in calcium and protein and, in small quantities (i.e. not as a main forage) seems to be good for hoof growth. The high calcium content can prove a problem for horses with low magnesium status, so I tend to only use alfalfa where the horse is getting supplementary magnesium. Even then, a small number of horses react badly to alfalfa – in which case it needs to be removed from the diet. Good sources of Alfalfa include Simple System Lucienuts and Alfa A Lite.
- Straw Chaff. Any of the ‘lite’ forms of straw chaff (e.g. HiFi Lite) are usually good for laminitics. They provide bulk and fibre without excessive sugar levels. Again, some horses react badly to these products and there are some concerns that a lot of UK straw is now contaminated with herbicides as a result of modern farming practices – so it may be worth specifically asking the manufacturer what steps they take to minimise herbicide contamination.
- Linseed. Linseed (in its whole form rather than as oil) is another good source of protein and is also really useful for putting condition on underweight horses and (in smaller quantities) putting a shine on the coat. Raw linseed needs to be boiled before feeding which is something of a faff, but there are pre-prepared forms available (micronized linseed).
There are various ways of getting magnesium into a horse. Some off-the-shelf products contain added magnesium – if you are using any of these, you will need to reduce the amounts specified below.
The easiest way to supplement magnesium is in the form of magnesium oxide. There are various products available, but you’re unlikely to find pure magnesium oxide on the shelves of your local tack shop. A search on the internet will pull up various small businesses selling magnesium oxide for horses, although prices and quality of product seem to vary wildly, so it’s worth shopping around.
Ideally you want pure magnesium oxide that’s in the form of a very finely divided powder. The finer the powder is, the more easily it’s absorbed in my experience. This best versions are usually termed ‘light magnesium oxide’. ‘Heavy magnesium oxide’ can also work so long as it is a high standard of purity (look for pharmaceutical grades).
There’s still very little real research into ‘correct’ doses, but anecdotal experience of horse owners has provided some guidelines for magnesium supplementation. For a 500kg horse, a dose of 10g/day of magnesium oxide seems to be a good starting point. This will provide around 5g of extra magnesium per day. The daily requirement for a 500kg horse is now thought to be around 15g and most forages seem to provide between 10g and 12g so this should ensure that the horse is getting enough magnesium. For smaller/larger horses, you need to scale the dose pro-rata.
Some horses seem to need higher quantities to get the benefits of magnesium. Some owners have increased doses to as high as 20g/day of magnesium oxide for a 500kg horse without ill effects. I would not recommend this unless the lower dose shows some benefit and the higher dose shows an increase in benefit. If increasing the dose doesn’t show a benefit, then the horse is unlikely to need that increase and it’s safer to reduce the dose again. I wouldn’t currently advise feeding more than 20g/day of magnesium oxide for a 500kg horse as we really don’t know how safe that would be.
As with any supplement, magnesium oxide should be introduced gradually into the diet. Watch out for any signs of loose droppings as excessive levels of magnesium in the diet have a laxative effect.
The daily requirement of sodium for a 500kg horse that is not in work is around 10g/day. Most forages will provide something like 20-25g/day (assuming a 500kg horse that eats 10kg of forage per day). For horses in significant work (i.e. more than just the odd hack now and again), the requirements can go up to as much as 30g/day, so these horses may well need some additional sodium even if they don’t have laminitis. The level at which sodium becomes toxic is around 300g/day so clearly you want to keep total intake well below that. The level of additional sodium that seems to help laminitic horses use the magnesium supplements is around 10g/day extra. Adding this to the typical 20-25g/day provided by forage gives 30-35g/day which is still well clear of the 300g/day danger level. Bear in mind though that adding salt to the diet of a horse that is not working is still controversial.
The easiest way to supplement sodium is to use table salt. I wouldn’t recommend using sea salt or other ‘natural’ salts as these contain all sorts of impurities that may not necessarily be beneficial. Also don’t use lo-salt as this is potassium chloride rather than sodium chloride and the last thing the typical laminitic horse needs is more potassium!
Table salt is 40% sodium, so to get the 10g/day extra sodium for a 500kg horse, you need to feed 25g/day of table salt (roughly a level tablespoonful). As with the magnesium, for smaller/larger horses you need to scale the dose pro-rata.