Laminitis is a very common and painful disease, especially of ponies. It may occur a single acute episode and commonly re-occurs due to inadequate dietary control. Obesity is a major risk factor in predisposing horses to laminitis. Obese horses have large fat deposits on the neck (resulting in a thick crest under the mane) over the ribs (which may be hard to feel) and over the rump. The size and hardness of the neck fat are sometimes taken as an indicator of susceptibility, but this is a myth.
Table Of Contents
- Laminitis Causes
- How does diet-induced laminitis occur?
- % Soluble Sugars In Grass
- Laminitis Symptoms: Clinical Signs of Laminitis
- Laminitis Treatment – Why does treatment of laminitis fail?
- What is the prognosis?
- How To Treat Laminitis
- Preventing laminitis
- Dealing with other causes
- Excess intake of lush grass high in soluble sugars (fructans) usually in spring and autumn. High starch diets (usually from cereal grains) in sport or show horses may have the same effect.
- A severe toxaemia, arising for example, from a severe infection in the uterus (womb) after foaling or from colic.
- Long-standing non-weight bearing lameness in one limb, which may cause laminitis in the opposite limb due to overloading.
- Excess concussion, for example in a horse being driven or ridden fast on asphalt roads.
- Equine Cushing’s disease. Rarely, as a side effect of corticosteroid (cortisone) medication.
- Metabolic syndrome, suffered by excessively obese horses, in which the large fat stores may produce corticosteroid-like hormones.
How does diet-induced laminitis occur?
There are two principal theories as to the mechanism whereby diet-induced laminitis occurs:
The vascular theory
The abnormal bacterial activity in the horse’s large intestine caused by the intake of high-sugar teed results in the uptake of large amounts of amines, which cause the blood vessels in the feet to constrict, thereby depriving the laminae of their blood supply and causing them to degenerate.
The enzyme theory
It is proposed that the abnormal activity in the intestine causes the absorption of an unknown substance that causes excessive activity of the enzymes (matrix metalloproteinases) that normally break down the bonds between the sensitive and insensitive laminae allowing the foot to grow. (Toxins absorbed from an infected uterus may have the same effect.)
The effect of these changes in the feet is that the bonds between the sensitive laminae on the surface of the pedal bone and the insensitive laminae in the inside of the hoof wall (a Velcro-like attachment) become weakened, resulting in some cases in rotation or sinking of the pedal bone. In severe cases the pedal bone may rotate until the tip penetrates the sole, or sinks to such a degree that the entire pedal bone is in danger of coming through the sole (a sinker).
% Soluble Sugars In Grass
|After overnight at 16C (61F)||14%||23%|
|After overnight frost||24%||28%|
If the night is warm, the sugar (fructan) made by the grass during the day is partially consumed by the plant during the night. But it the weather overnight is cold (for example in May or September), the sugar level does not fall. Further sugar is added each day, causing the level in the grass to rise steeply. This explains why laminitis is more common when the daytime weather is warm but the nights are cold and why the safest time for grazing is in the morning.
Laminitis Symptoms: Clinical Signs of Laminitis
Initially the horse shows a reluctance to walk quickly and may favour walking on softer ground when led. If asked to turn in hand there is obvious pain in the inside leg. There is an increased strength of the digital pulse in the affected feet. Foot temperature is variable and an unreliable guide to diagnosis.
The horse is otherwise bright and eats normally. If kept on the same field, after a few days it becomes reluctant to move, shifts its weight from foot to foot and adopts the classic laminitic stance, leaning backwards with the fore feet extended to reduce the weight they bear. If hoof testers are applied to the sole in front of the apex of the frog the horse will flinch.
Severe cases may spend a lot of time lying down, may sweat and be in great discomfort.
Recovered cases may show evidence of a previous bout. Rings in the hoof wall (which do not in themselves indicate that the horse has had laminitis before) will diverge at the heel, unlike in the normal horse where the rings are parallel. The sole may be flat or convex, and the white line at the toe is much wider than normal.
Laminitis Treatment – Why does treatment of laminitis fail?
It is not unusual for laminitis cases to be very difficult to treat and eventually the horse will have to be put down.
The reasons for treatment failure are:
- Failure to recognise the disease and take aggressive treatment action early enough
- Failure to fit frog supports
- Failure to confine the horse to a stable all of the time
- Failure to feed an appropriate diet once the diagnosis has been made inability to control the pain in severe cases
- Lack of skill and experience in the vet and farrier
What is the prognosis?
If detected early the horse may recover in less than a month, sometimes in not much more than a week. It is essential however that even rapidly recovering cases are box rested for six weeks for full mechanical strength to recover in the foot. Over time, with the aid of x-rays, may be able to trim the feet to restore the pedal bones to their correct position. More advanced cases may take 2-12 months to recover and some will remain ‘footy’ for life. Sinkers require specialised treatment by a remedial farrier over many months and many do not respond.
How To Treat Laminitis
Laminitis is an emergency. The way the horse is treated in the first 24 hours critically affects the outcome of the case and time taken to recover. If in doubt it is always best to proceed as though the horse has laminitis.
- Remove the horse from pasture immediately and put it in a stable with a deep bed of woodshavings or sand. Fit a plank across the doorway at floor level so that a deep bed can be provided right up to the door. The horse must remain in the stable until fully recovered. If sand is used, forage should not be fed from the stable floor as an excessive intake of sand may occur, resulting in colic.
- Summon veterinary help. If likely to be delayed, fit temporary frog supports.
- Contrary to traditional advice, do not walk the horse. This will further disrupt the Velcro-like attachment of the pedal bone to the inside of the hoof.
- Withhold all concentrate feeds and instead feed a chaff product recommended for laminitics, along with a limited amount of high fibre coarse hay or haylage. Hay or haylage should be soaked by immersion for 8 hours before feeding, to leach out the soluble sugars.
- Do not starve the horse. Starvation will have little or no effect on its weight in the short term, is inhumane and will deprive it of essential nutrients to repair the damaged feet. Conversely, because the horse will be stabled for along time before it recovers, it will readily gain weight due to its inactivity and become over-fat. For these reasons, it should only be fed just enough. Inevitably there will be times in the day when the horse has nothing to eat.
- Feed a dedicated hoof supplement unless the essential nutrients are already present in the chaff product.
- The vet may administer an anti-inflammatory injection (usually phenylbutazone) and possibly other drugs to improve the blood supply to the feet. If the laminitis has been caused by toxaemia, this will also be treated aggressively.
- Frog supports will be fitted to support the pedal bone and prevent rotation or sinking. These may be temporary supports, for example rolled crepe bandages taped to the feet. Later on more permanent support is provided in the form of rubber polymer infill or plastic or steel heart-bar (heart-shaped) shoes.
- The vet may obtain x-rays of the feet to establish the position of the pedal bone. These are best taken 3-4 weeks after the onset when the pedal bone has settled in its final position and can used as a guide to prognosis for long-term use, and as a guide for the farrier when trimming or remedially shoeing the feet.
- The feet must be trimmed every four weeks.
Restrict grass intake
Because it is very difficult to establish how much grass horses are eating, a ‘boom and bust’ approach is best. Allow the horse to graze a normal paddock (non-fertilised, and not pure ryegrass) for a maximum of four hours per day (two hours if the horse has suffered from laminitis before). Fructan levels in grass are lowest from late at night to early in the morning. Turnout should be as early as possible with the horse removed from grass by mid-morning.
The ‘down time’ can be spent in a loose box or wandering in a pen, with access to some hay and low-sugar high-fibre feed. The aim is to ensure that the periods of disruption of the gut bacteria by grass intake are short, and are ‘settled’ by an extended period of hay feeding. The frequent practice of allowing animals to graze, say, only at night or only during the day, that is for 12-18 hours, is just too long a period for safety. Alternatively the area of grass available can be restricted using an electric fence.
The area of the pen must be so small that the grass is tightly grazed. Remember grass grows surprisingly quickly and an apparently bare patch may still generate sufficient grass to trigger laminitis. If necessary, supplementary feed, such as hay and or straw can be provided daily. If the horse isn’t eating the hay, then the pen may be too large.
Where a pony is kept as a companion for a bigger horse, a pen can be made in the field for the pony, while the horse has unrestricted access to the whole field.
Use an electric fence tester regularly to check the output of the fence battery or whether the charge is present in the entire fence (wires commonly fail). Hungry horses will soon discover if the fence is ‘live’ or not. Consider fitting a small mains fencer unit, which may be more reliable and cheaper in the long-term.
Use of a grazing muzzle is an attractive option in that the available grazing area or grazing time can be greater. Muzzles are a far from perfect solution. Apart from the fact that some ponies seem to be able to remove them in spite of exhaustive efforts to keep them in place, they can cause rubs and skin irritation from prolonged wear. They should therefore only be used intermittently.
Tethering the pony on a long lead can be extremely effective if done with care by ensuring gradual introduction, close supervision, a quick-release system, careful selection of the site to avoid hazards and the provision of water and shade. Unfortunately and unjustifiably this method has largely fallen out of use.
Laminitis is rare in fit animals (unless they are rested due to injury and the feeding rate is not reduced). Provide as much exercise as possible to keep the bodyweight down. if a child rider is not available, ponies can be lunged or led from a horse (or bicycle) while exercising. it can be almost impossible to reduce the weight of a fat native pony without exercising it.
Feed with care
If supplementary feed must be provided then use high-fibre low-starch feeds for example coarse hay or haylage (avoid soft haylage), straw, high-fibre cubes, unmolassed sugar beet and high-fibre chaff products (such as Dengie ‘HiFi’, Dodson & Horrell ‘Safe and Sound’ and Spillers ‘Happy Hoof’). Do not feed conventional horse and pony nuts, coarse mixes and other starchy feeds or nuts.
Founderguard, an antibiotic feed supplement from Australia, claims to prevent laminitis by controlling the abnormal chemical activity in the large intestine. it is only available on veterinary prescription. Experience suggests that it is of very limited value in grass laminitis control and is more appropriate for concentrate (starch)induced laminitis.
Look for the early signs The onset of the disease is slow and often missed. If your pony normally trots to the gate for a titbit and all of a sudden merely walks, but seems othenwise ‘normal’, it may well be in the early stages. When led or ridden a tendency to favour grass verges rather over hard tarmac, or walking with a stilted ‘straight-legged’ gait may be warning signs. If in any doubt, get the pony off the pasture immediately and don’t wait for the full-blown signs to appear.
Dealing with other causes
Laminitis due to toxaemia is usually very severe and difficult to treat. Mares with severe womb infections will be treated with frog supports, intensive antibiotics, and drugs that minimise the effects of the toxins. The uterus will be flushed to remove bacteria and toxins, and intravenous fluids will, be given in large quantities. Severe colic cases will receive surgery to correct the surgical problem.
Concussive laminitis in addition is treated with rest on soft bedding and remedial foot care as already outlined. Cushing’s Disease cases require drug treatment in addition to dietary control.