Laminitis is a very painful and serious health condition affecting the laminae in horses’ hooves, requiring urgent assistance from your vet and a qualified farrier or trimmer with experience in treating the condition (eg, short trim cycles for horses with laminitis are very important.) The assistance of a qualified horse nutritionist is also recommended.
WHAT IS LAMINITIS?
The laminae are structures located inside the hoof capsule between the pedal bone and the hoof wall which hold the pedal bone in place. When a horse or pony has laminitis the laminae become inflamed, and can also become damaged and their structural integrity compromised.
Laminitis occurs more commonly in the front hooves, but in some cases, all four hooves are affected. In severe cases the laminae may no longer be able to hold the pedal bone in place causing it to rotate downward, resulting in a condition called ‘founder’ which means ‘to sink’.
The greater the angle of rotation of the pedal bone, the more severe the case of founder. Sometimes the terms founder and laminitis are used interchangeably, but strictly speaking a horse with laminitis (inflamed or damaged laminae) can only be said to have foundered if the pedal bone has rotated downward so that the angle of the anterior (front) of the pedal bone is no longer parallel to the angle of the hoof wall. This can only be determined by a vet after taking X-rays of the hooves.
Most horses with laminitis will obviously be in pain, may lie down frequently or put more weight on their hind legs and stand with their front legs camped out in front to take the weight off their front hooves. They will also have a bounding (faster than normal) pulse in the pasterns of affected legs/hooves. Over time there will be changes in the hoof walls as well, eg stress rings which grow down the hooves from the coronet, and white line disease (which are visual evidence of the stretched (damaged) laminae). Horses with metabolic issues like EMS, PPID (Cushings disease) and insulin resistance may present with sub-clinical laminitis, where they will not be in obvious pain, but may show signs like being tender-footed when they walk on very hard ground or on roads, or step shorter than normal, especially when there is a flush of new growth in their pasture. In this case, there may be a thinning and weakening of the laminae without obvious inflammation, and they will also most likely show signs of white line disease.
LAMINITIS AND DIET
Laminitis is most often, but not always, associated with diet. Horses who are more predisposed to laminitis include those that are overweight (‘good doers’ or ‘easy keepers’) with cresty necks and fat deposits, and horses who suffer from metabolic conditions eg PSSM (polysaccharide storage myopathy), insulin dysregulation – insulin resistance and Equine Metabolic Syndrome, and also PPID (Cushings disease), but any horse or pony can potentially be at risk of this condition.
Aside from nutrition-related laminitis, laminitis may be caused by severe stress, sudden changes in diet, infections (eg salmonella infection, pneumonia or an infection caused by a retained placenta in a broodmare) and there are also mechanical causes, eg from riding a horse repeatedly at a fast pace on hard roads.
Laminitis is frequently associated with diets high in sugar and starch, especially in horses or ponies who are overweight or good-doers, or horses who are fed grain-based diets, or those on lush (high sugar) pasture, or pasture which has a flush of growth after rain, or that is stressed due to drought or frost.
High sugar hay, eg oaten, barley, wheaten and rye hay can also be a major source of sugar in the diet. Although cereal hay is lower in sugar and starch than grain it is generally fed to horses in larger amounts so can contribute a lot of sugar to the diet. The fructan level of pasture or hay may also be an issue for horses with or prone to laminitis.
Fructans are polysaccharides that are a form of digestible fibre. There is controversy among some vets and horse nutritionists as to the role of fructans in laminitis, given it is quite different from sugar and starch, as it is a form of fibre rather than soluble carbohydrate, and is digested by fibre fermenting microflora in the hindgut and therefore doesn’t cause insulin spikes or blood sugar regulations (as sugar and starch do), but it does contribute to the total calorie intake of the diet, which may be a definite risk factor for any overweight horses or ponies who have a higher than necessary calorie intake and/or insufficient exercise.
Laminitis is particularly prevalent among horses and ponies who suffer from various metabolic conditions involving insulin dysregulation, eg EMS (Equine Metabolic Syndrome – hyperinsulinemia), Insulin Resistance or Cushings Disease (many horses and ponies with Cushings disease are also insulin resistant) because in these horses the risk of laminitis is linked to higher than normal circulating levels of insulin.
HIGH SUGAR & STARCH DIET AND LAMINITIS
There are three main reasons why a diet high in sugar and starch is a major risk factor for laminitis:
If too much high sugar pasture or grain (or other feed high in sugar and/or starch) is consumed by horses and ponies it may overwhelm the capability of the small intestine to digest all of it and it will then continue along the GI tract into the large intestine where it will be fermented by acid producing gut microflora. The large intestine is designed for fermenting large amounts of fibre, which is healthy for horses because it boosts the fibre-fermenting gut microflora and they provide positive benefits to immunity, and general health and wellbeing. Sugar and starch, however, should ideally be digested in the small intestine, and if some or most of it arrives in the large intestine undigested or semi-digested this boosts lactic acid-producing sugar and starch fermenting microflora. The result of this is that the pH level of the large intestine is reduced (becomes more acidic) and this causes the die-off of the fibre-fermenting microflora which require a higher pH level in the hindgut. The effect of the proliferation of lactic acid producing microflora and decimation of the fibre-fermenting microflora causes an imbalance in the gut microflora which leads to a cascade effect that leads to inflammation in the hindgut lining and also laminitis, when (according to scientific theory) toxic by-products from the mass die-off of gut microflora enter the bloodstream from the hindgut and inflame and damage the laminae in the hooves.
High fibre feeds that are low in sugar and starch, on the other hand, boost the beneficial fibre-fermenting microflora and also act as food for these microorganisms, allowing them to proliferate, and maintain a slightly alkaline environment in the hindgut, which is healthy for the horse.
- Feeds high in sugar and starch cause a rise in circulating insulin, because insulin is required to allow glucose (from the sugar and starch) into every cell for energy required for metabolic processes. Too much sugar and starch (or even relatively low to moderate levels of sugar and starch in horses with insulin dysregulation issues) results in insulin spikes and fluctuating blood sugar levels. Horses with metabolic issues like Insulin Resistance and EMS have higher circulating levels of insulin than healthy horses because the cells become resistant to the uptake of insulin and because more than normal amounts of insulin are released in horses with these conditions. The connection between insulin and laminitis occurs when higher than normal levels of circulating insulin damage the laminae, resulting in thinner laminae with a weaker connection between the laminae and the hoof wall.
- Sugar and starch are both high in calories, so for horses that are ‘good doers’ or ‘easy keepers’, or are overfed and/or aren’t exercised sufficiently, or have metabolic issues (as discussed above) sugar and starch from lush pasture, grain, grain by-products, high sugar types of hay etc contribute calories to the diet which can lead to fat deposits, cresty necks and an associated increased risk of laminitis. This is especially likely in the case of pony breeds, but many horses are also at risk.
For horses that need higher calorie diets because they are underweight or in hard work it is healthier to provide calories in the form of feeds high in digestible fibre than feeds high in sugar and starch, because digestible fibre boosts beneficial gut microflora and immunity, and provides sustained slow release energy that doesn’t result in blood sugar level fluctuations and insulin spikes. Horses in heavy work though may require some added sugar and starch, eg in the form of oats for quick-release energy, especially if they are doing hard or fast work requiring sudden bursts of energy, but if the horse is predisposed to laminitis or insulin dysregulation metabolic disorders then grain should always be avoided.
FEEDS TO AVOID
The diet should be 10% or less combined sugar and starch for a horse or pony with or prone to laminitis. Any type of feed that is moderate to high in sugar and starch should be avoided.
This includes pasture that is moderate to high in sugar, especially when it is growing quickly in spring or after rain (or irrigation); or is stressed; or is a species known for being high in sugar and starch, eg clover or rye, or any species deliberately grown for fattening cattle or sheep.
Cereal grains (rice, oats, barley, corn, wheat, rye) are high in sugar and starch, as are grain by-products (pollard, rice bran, wheat bran, millrun/millmix) and cereal hay (eg oaten, wheaten, barley). If the horse or pony has a metabolic condition like insulin resistance or EMS or if the horse is overweight then the diet should also be low in fat, so feeds high in fat even if they are low in sugar and starch (eg copra) should be avoided for these horses.
Linseeds, cold-pressed linseed oil, fish oil and chia seeds are the exception because they are high in omega 3 which has been shown to reduce insulin resistance and is also healthy for hooves, however, it should not be fed in large amounts.
Molasses (which is high in sugar) should be avoided for any horse with or prone to laminitis, as well as treats like apples, most other types of fruit and bread.
Hay fed to the horse should be tested and shown to be around or lower than 10% combined sugar and starch. Soaking hay for half an hour to an hour reduces the sugar content by up to a third so hay that is a little over 10% sugar and starch should be soaked and drained before feeding it out. It shouldn’t be soaked for longer than an hour though because minerals will leach out of the hay, and there is also the opportunity for mould and bacteria to proliferate in the hay while it’s soaking. Soaking hay for the prescribed time that is relatively high in sugar and starch, eg oaten hay and some types of grass hay which are around 20% sugar and starch, won’t reduce the sugar levels sufficiently to make the hay safe for a horse or pony with laminitis and should be avoided.
SUITABLE FEEDS FOR HORSES
Native species of Grass hay, Rhodes hay and Teff hay are usually low in sugar and are suitable for horses and ponies with or prone to laminitis, but it should be noted that all types of hay are higher than usual in sugar in certain conditions: if the hay is harvested when it is stressed (eg grown in extra dry conditions), or if it is cut earlier in the growing season (spring as opposed to summer), after rain, or if the hay is cut in the afternoon, especially late afternoon or early evening (as sugar builds up in grass, hay crops and other plants during the day when they photosynthesize), or in the morning if there has been a frost the previous night, so even if hay types are available which are commonly low in sugar, any hay fed to a horse with laminitis should be tested and shown to be around or under 10% combined sugar and starch.
If horses are on pasture that is higher than 10% combined sugar and starch then they should be removed from the pasture and fed suitable low sugar (tested) hay, or should wear a grazing mask under the direction of a vet or equine nutritionist. Pasture is lowest in sugar from about 2 am till about 10 am, providing there hasn’t been a frost the previous night (not exactly a practical time to be putting a mask on a horse, unfortunately!) Track systems in paddocks (where most of the interior of the paddock isn’t available to the horse for grazing) which encourage movement around the perimeter and limit pasture intake can also be very helpful for horses or ponies with or prone to laminitis.
Forage is very important in the diet of all horses, as their digestive tracts are designed to have large amounts of fibrous material moving through almost constantly, so pasture and/or hay that is low in sugar and starch is the most important consideration when devising a diet for a horse or pony with or prone to laminitis (or any horse or pony for that matter). For overweight horses, or those with EMS or who are insulin resistant it is best to feed no more than around 1.5% of the horse’s weight per day in (tested) low sugar forage. Slow feed hay nets are very useful for horses or ponies that are overweight. If the horse requires more weight or doesn’t have a metabolic condition, low sugar (tested) grass hay (with the addition of some lucerne hay for horses that tolerate it well) may be able to be fed ad lib with no issues (or up to 2.5% of the horse’s body weight per day).
Other feeds suitable for horses with laminitis include beet pulp (but it must not have molasses added), legume hulls, and legumes, eg lupins (although lupins are high in calories so are not always suitable for overweight horses, unless fed in small amounts). Beet pulp is quite high in calories from digestible fibre despite being low in sugar and starch so should only be fed in small amounts, if fed at all, to overweight horses. Pre-mixed and pelleted feeds are only suitable if they are free of grain and grain by-products and any other ingredients that are moderate to high in sugar and/or starch (eg molasses) and are 10% or preferably less than 10% combined sugar and starch.
Lucerne hay is nutritious and is relatively low in sugar and starch and is suitable for some (but not all) horses with or prone to laminitis, as a significant number of horses who have insulin dysregulation issues do not tolerate the protein in lucerne well and/or it is too fattening for them and it shouldn’t be fed to those horses, and lucerne is quite high in calories from protein and digestible fibre so is likely to be too fattening for overweight horses or ponies unless fed in relatively small amounts with low sugar grass hay.
It is recommended that anyone owning a horse or pony with or prone to laminitis should consult with a qualified equine nutritionist to develop a healthy balanced diet for their horse.
A well-balanced diet with macro minerals and trace elements in the correct ratios, vitamins, high-quality protein, balanced omega 3 and 6, and most importantly, plenty of fibre is crucial for supporting the metabolism and hooves through the stress associated with laminitis, and for healing and recovery.
Written by Elizabeth Funnell
Equine Nutrition Educator
Sub-editor Bryan Meggitt (BMedSc. PGCrtMedSc.)
Senior Scientist and Co-founder of CEN Horse Nutrition
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- Soaking Your Horse’s Hay – University of Minnesota Extension
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