Laminitis
Common stance of a horse with laminitis (founder)
Laminitis (Founder) Laminitis, also often called founder, is a condition of the hoof, caused by incorrect feeding. Similar in cause and effect to laminitis and founder in equines, it is the result of too much high protein feed or grass – often damp, new grass – which causes the laminae in the hoof to break down, hence the name, ‘laminitis’.
Laminitis in horses is becoming a very common condition these days, mostly due to the lush pastures that more and more horses and ponies are being grazed on.
Horses are actually classed as foragers/grazers which means that their digestive systems are designed to cope with a continuous supply of small amounts of roughage at a time. Wild horses have to travel great distances to get enough food to keep them alive as most wild grasses are low in nutrients. In comparison domestic horses are given huge amounts of high nutrient grasses and confined to much smaller areas. This results in a horse who consumes more sugars than it's body can handle - as it's not burning them off with movement - and this is often the main cause of laminitis in horses.
Also many stable kept horses are given large amounts of grain in one feeding and then left for many hours with nothing in their stomach. This is also very disruptive to the digestive system and can contribute to laminitis.
Definition of Laminitis in Horses
Laminitis is inflammation of the sensitive structures in the hoof called the lamellae. The lamellae are the means by which the coffin bone is held tight within the hoof capsule. When viewing the sole of a healthy hoof you can tell how good the connection is by looking at the white line. If the white line is tight (narrow in width) then there is a strong connection. If the white line is stretched then the connection is compromised - see diagrams below. Untreated laminitis often leads to Founder which is where the bone becomes detached from the hoof capsule and in severe cases will penetrate through the sole. Laminitis in horses is referred to as acute when it is in the early stages and chronic when it has been present for a long time.
Laminitis is inflammation of the sensitive structures in the hoof called the lamellae. The lamellae are the means by which the coffin bone is held tight within the hoof capsule. When viewing the sole of a healthy hoof you can tell how good the connection is by looking at the white line. If the white line is tight (narrow in width) then there is a strong connection. If the white line is stretched then the connection is compromised - see diagrams below. Untreated laminitis often leads to Founder which is where the bone becomes detached from the hoof capsule and in severe cases will penetrate through the sole. Laminitis in horses is referred to as acute when it is in the early stages and chronic when it has been present for a long time.
Healthy hoof with tight white line
Laminitis in horses occurs when the lamellae become inflamed and produce a secretion full of toxins which weakens the connection between the coffin bone and the hoof wall. This leads to a stretched white line which is visible when looking at the sole of a horse with chronic laminitis.
Laminitis in Horses - hoof with stretched white line
Laminitis - The condition, symptoms and treatment.
Laminitis affects so many horses and ponies that it is now the most researched aspect of lameness worldwide. This research continues to explain why certain horses and ponies do not respond to correct dietary management alone and also tells us more about how we should manage susceptible horses and ponies.
Symptoms of Laminitis in Horses
- Less activity and a reluctance to move when led
- Lying down more than is normal
- Depression
- Reluctance to turn
- Tight muscles
- Hooves warmer than normal
- 'Bounding' digital pulses in affected legs.
- Blood in the white line
- Fever rings visible on hoof wall
- Pain response when pressure is applied to sole
- Standing a typical laminitic stance - hind feet further under the body with weight rocked back and front feet further out in front of the body
Most horses and ponies can recover from laminitis but the extent of their recovery depends on many factors including how severe the problem was when it was first spotted, and how soon treatment commences. The very mildest (sub-clinical) nutritionally-triggered, cases can often be nipped in the bud by changes in management, notably feeding. Clinical cases need the urgent attention of a vet. Acting quickly and using the combined skills of a vet, farrier and nutritionist lays the foundation for the most successful recoveries.
What is Laminitis?
Laminitis is a disease of the foot that can vary in severity from the merest hint of lameness to a situation described as 'sinking', which can be fatal.
As laminitis develops the attachment of the pedal bone to the hoof wall starts to fail, leaving the pedal bone to rotate and point towards the sole, and in the worst cases to sink right through it.
International research has made it abundantly clear that laminitis is multi-factorial that means there is normally more than one factor involved before a pony is 'tipped over' into laminitis. It may be helpful to think of a threshold over which laminitis is triggered. A pony may have trotted too fast down a rough, stony track causing mechanical damage; this will raise his 'at risk' line towards the threshold. He may also be genetically predisposed to insulin resistance; this will raise his 'at risk' line further. Finally he may have access to too much high sugar grass and suddenly his 'at risk' line is pushed over the threshold and he goes down with laminitis.
When we think about the nutritional causes of laminitis our first thought is to an overload of carbohydrate (mainly starch) into the hindgut. Over the years a huge amount of research has built up to demonstrate the consequences of such an overload on firstly the microbial balance in the hindgut and ultimately the weakening of the support given to the pedal bone in the foot by the laminae.
More recently researchers have demonstrated that obesity not only adds to the mechanical weight that the laminae have to support but also has a direct negative effect through the hormonal activities of the fat cells within fatty tissue, especially around the stomach (omental) and in the crest.
However the latest research points to an even greater role for nutrition because it has long been known that increasing amounts of glucose entering the bloodstream from the small intestine, that is before the hindgut, cause a rise in the level of insulin. The most recent research shows that high levels of insulin in the blood directly precipitate laminitis.
Adding all this research together means that not only must we be careful not to feed horses prone to, being treated for or recovering from laminitis a diet that could lead to a carbohydrate overload in the hindgut, for example one containing too much starch, but we must also be careful to avoid feeding a diet providing too much sugar in the form of, for example, molasses. Whereas we used to consider that because molasses had a high glycaemic index, that is it was virtually all digested in the small intestine and absorbed through the intestinal walls, it did not reach the hindgut unless fed in excessive amounts and therefore did not pose a major risk. It is now evident that sugar levels in the diet need to be minimized in order to avoid a rise in insulin levels.
It is really important to remember that laminitis is a multi-factorial problem and that even if your horse or pony has laminitis caused by a non-nutritional factor, for example Cushing's disease or traumatic injury, it is very important to minimize adding to the factors that could trigger or worsen the laminitis. In other words, whatever the cause, it is important to feed a low sugar, low starch, high fiber diet, with calorie intake controlled when necessary.
Recognized risk factors for laminitis include:
- Excessive intake of sugar and starch (soluble carbohydrates), for example:
- Eating too much high-sugar/fructan grass, often in spring or autumn, but possible at other times of the year e.g. after frost. Research has indicated that stressed (e.g. closely grazed) or frosted grass is high in fructans, a type of storage sugar (oligosaccharide) that cannot be digested by the horse itself, so passes through the small intestine undigested to the hindgut where it triggers similar changes to a starch overload. This helps to explain the cases of laminitis seen in horses and ponies kept on 'starvation' paddocks or turned out in very cold or frosty weather. Further research has shown that sugar levels in grass buried under snow can be higher than previously thought at around 15% so this poses a further risk. One survey in the UK showed that 61% of laminitis cases occurred in animals kept at pasture.
- Eating too much cereal, either in one feed or in successive feeds.
- Eating too much cereal-based compound feed, especially if highly molasses.
All these situations also result in temporarily raised insulin levels in the blood, which may also trigger laminitis.
- Obesity is a risk factor for laminitis because internal fat, particularly in the abdominal region (omental fat), is hormonally active, excreting hormone releasing factors, hormones e.g. cortisol, and inflammatory factors that can all ultimately trigger changes in the foot that lead to laminitis. Obese horses also put more load on their feet. Obese horses that are also IR (Insulin Resistant) or suffering from EMS (Equine Metabolic Syndrome) are more likely to develop laminitis.
- Hormonal e.g. PPID (Cushing's disease) IR or EMS. It has been estimated that 28% of the native ponies in Australia are IR. It has also been estimated that 50-80% of horses with Cushing's disease in Australia suffer from clinical laminitis. More than 80% of laminitis cases reviewed in Australia and Finland had hormonal involvement. It has been demonstrated recently that simply administering insulin (to achieve approximately 3-4 times normal levels in the blood) precipitates laminitis in lean, healthy horses after 48 hours. Furthermore the very latest research has shown that MMP's (enzymes involved in normal modeling of lamellae) are not significantly involved in this process. Please ask for our separate article detailing these very significant risk factors which are now known to explain a great many cases where correct dietary management alone is insufficient to eliminate laminitis permanently. Certain drugs affecting the hormone system e.g. corticosteroids, are known to have the potential side effect of triggering a laminitic attack.
- Stress e.g. when traveling long distances or separated from field companions. This could be considered a hormonal risk factor
- Traumatic laminitis is caused by repeated physical trauma to the feet during e.g. endurance riding, driving, or jumping on hard ground; it can also be caused by overenthusiastic hoof trimming.
- Severe lameness in one limb will cause a horse or pony to carry excessive weight on his other limbs, which may cause laminitis. As with traumatic laminitis this is a physical trigger but one that is caused by pressure blocking the capillary blood supply to the weight-bearing foot. This appears to be a clear case of severe vasoconstriction causing laminitis.
- Toxins released by bacteria during certain illnesses e.g. following retained placenta, colic, diarrhea, liver or respiratory disease.
What action should be taken following a laminitis attack?
In those cases where excessive intake of sugars and/or starch is the final trigger for an attack nutritional advice should center on two aspects:
- Reducing sugar and starch intake to a minimum in case an insulin response is involved.
- Re-establishing the correct bacterial population, and hence the correct acidity, in the hindgut. This is one in which fibre-digesting bacteria dominate and bacteria which digest sugars and starch are not allowed to proliferate excessively.
Can laminitis be prevented?
Most cases of laminitis that are predominantly triggered by excessive intake of sugar and starch can be prevented by following sensible management strategies, including adopting high-fibre but nutritious diets. The following points may help susceptible horses and ponies, even if they are genetically insulin resistant or suffer from EMS:
- Find the most suitable grazing you can. Unproductive grassland such as hill land is ideal, where horses have to exercise a great deal to eat a moderate amount of average quality grass. Old meadow or parkland grazing is the next best. If you can arrange mixed grazing with sheep to keep the sward down that is hugely helpful and has the spin-off benefit of helping to control worms. Pasture sown with 'Improved' Italian Ryegrass may be ideal for high-yielding dairy cows but is the most likely to induce laminitis in susceptible horses and ponies as it is high in sugar. Limit access to lush pastures either by limiting turnout time or by fencing off small areas.
- Never make rapid changes in the diet e.g. do not suddenly turn out onto good pasture. Introduce it gradually; even if you are on a livery yard try to persuade the owner to let you move fields gradually rather than instantly. Similarly, make all changes to forage or hard feed gradually, over at least four days. The reason for this is that you are trying not to suddenly provide the microflora in your horse’ss hind gut with a large amount of a different type of feed because this often results in upsetting the balance of the microflora, with both colic and laminitis possible consequences.
- Avoid fertilized and frozen pasture. Trying to turn out when sugar levels in grass are at their lowest .A broad generalization is that sugar levels are at their lowest between midnight and dawn which is not hugely practical but some advantage may be gained by turning out after midnight or at first light providing you have brought your horse back in again by mid-morning at the latest. If the ambient temperature is below 5C then avoid turnout even if it is not actually freezing.
- Avoid letting horses and ponies become obese. For showing, a well-furnished look with good topline can be achieved by feeding and working to build muscle with zero use of cereal-grain- based feeds. If necessary to control his weight, increase the amount of exercise you do with your horse or pony to burn off more calories and reduce insulin levels by increasing insulin sensitivity. If he is not fit increase the amount of work he does gradually. Allow normal seasonality in weight i.e. allow horses to lose weight in winter in order to avoid problems with the anticipated weight gain in spring.
- Avoid feeds high in sugar e.g. molassed coarse mixes and straw chops.
- Avoid feeds high in starch i.e. cereals or cereal-grain based compound feeds.
- Where 'hard' feeds are needed provide them in small amounts i.e. little and often. Reduce the standard recommendations so that a 15hh horse for example never receives more than 1.5kg (dry weight) of 'hard' feed in any one meal. (The standard recommendation would be not to exceed 2kg/meal).
- Monitor the digital pulse daily to give you an early indication of imminent lameness. Feet that remain hot over 48 hours may also be a warning but short-term hot feet are not. Noting a loosening in droppings may also be helpful.
- Avoid unnecessary trauma to feet e.g. avoid stony, uneven ground and minimize trotting on roads. Do not jump on hard ground. Do not trim off excess hoof all at once.