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This complex disease is still not fully understood and a cure has yet to be found but whatever the original cause of the disease, nutrition plays an important part in its management and the horse’s ultimate recovery; more importantly, it is fundamental to the successful prevention of an attack.
What is Laminitis?
Laminitis is an acute vascular disease of the hoof causing disruption to the blood supply to the laminae within the hoof resulting in decreased oxygen delivery to the laminae and reduced removal of metabolic waste. Laminae are the scaffold holding the pedal bone to the hoof wall and work to transfer the load onto the hoof walls so that the sole does not bear weight. This process is hard work for the laminae so they require a large blood supply to bring oxygen and nutrients and to remove waste.
Decreased blood supply to the laminae results in their death which can occur within hours and causes considerable pain. Laminae death decreases the strength of the attachment of the pedal bone to the wall of the hoof which can result in movement of the bone because of the weight on it and the pull of the deep digital flexor tendon. Limited laminae death will cause rotation but extensive death causes the bone to sink.
Laminitis manifests itself in one or more of the horse’s hooves but nearly always arises as the result of a metabolic upset. Severe illness, mainly from gut disorders, like colic, colitis or salmonella poisoning, result in the release of endotoxins (harmful substances), from the cell walls of dead gut bacteria, which get into the bloodstream and have potent effects on circulation. Retention of the placenta after foaling or the long term use of drugs, like corticosteroids, can lead to similar results.
Excessive trauma to the hoof can however also lead to an onset of laminitis, as a result of over working on hard surfaces, poor hoof balance or severe lameness which overloads an unaffected hoof or hooves. By far the most common causes of laminitis though, seem to be nutrition related and include fructan overload from pasture, which causes the release of amines that disrupt the circulation in the hoof, or starch overload from cereals which reaches the hind gut, upsetting the bacterial population and resulting in the release of endotoxins.
Fructan Overload - Too Much Grass
The component in grass thought to be responsible for laminitis is fructan which is a soluble carbohydrate; the fibre element of grass is insoluble carbohydrate and it is this which is fermented slowly in the hind gut to produce energy. The horse is unable to digest fructan in the stomach and small intestine so it passes into the hind gut which can cope with small amounts of it, also being fermented by bacteria.
This fermentation results in the production of lactic acid but, if levels of fructan are excessive, the gut becomes more acidic resulting in the death of some of the beneficial gut bacteria. As these bacteria die they produce the endotoxins we have already mentioned and these are able to pass into the bloodstream more easily as a result of damage to the gut wall caused by the excessively acidic conditions.
Grass needs light to make sugars, which it uses as an energy source to grow, and needs a temperature of 5°C or above to grow. If it’s not warm enough to grow but bright enough to make sugars, the grass stores the extra sugar that it makes as fructan. Cold bright conditions therefore see an increase in the fructan content of the grass which is why laminitis can occur in December and is now not just considered a spring problem. The reason laminitis occurs commonly in the spring and autumn is the volume of the grass available as the warm damp conditions mean there is simply plenty of grass for the horse to eat. Levels of fructans tend to rise during the day, peaking in the afternoon to early evening, but decline in the early hours of the morning.
Starch Overload - Too Much Cereal
Just as grass stores sugar as fructan so the grains of cereal plants store it as another soluble carbohydrate, starch. This concentrated source of energy is ideally absorbed in the small intestine but if too much is consumed at one time, it passes on to the hind gut where it can disrupt the bacterial population in a similar way to excess fructan. Undesirable bacteria start to digest the excess starch producing stronger acids than would normally exist in the hind gut. The more acidic environment kills off the beneficial, fibre-digesting bacteria resulting in the release of endotoxins, that enter the circulation through the acid-damaged gut wall, and these trigger other chemicals in the body, including hormones, that disrupt blood flow to the hoof.
Overweight horse and ponies are more susceptible to laminitis due possibly to the increased load placed on the hooves (trauma) but also, as recent research is suggesting, due to a resistance by their bodies to the effects of insulin, the hormone responsible for regulating the level of glucose in the blood. There is a link between the level of certain types of fat deposits and this resistance which results in the hoof laminae not receiving enough glucose (food) resulting in their death. Diseases such as Cushing’s, which affects the pituitary gland of, generally, older horses, also cause a reduction in the uptake of glucose by the laminae making sufferers more prone to laminitic attacks.
In Case of an Attack
If you suspect your horse has even a hint of laminitis you should call your vet immediately; all the serious changes associated with the disease occur within 72 hours. Although the condition results in a disruption (reduction) of the blood supply to the feet, it is thought to be followed by a rush of blood returning (reperfusion) which is why the hooves feel warm to the touch and we may feel a pounding digital pulse. Any potential cause should be removed from the diet eg. grass and cereals/compound feed, and only clean forage with a low nutritional value provided in the early stages. Your vet will recommend how best to proceed but a source of vitamins and minerals, like a balancer, should be reintroduced as soon as possible and it is worth making use of feed company Helplines for both short and longer term advice on management and prevention.
Management and Prevention
In many instances this is simply a case of applying the “Rules of Feeding” to the letter to avoid overloading the horse’s system with either starch or fructan. The finger is often turned point blank on cereals and compound feeds but they are not a cause per se, it is more their misuse which is to blame. “Feeding little and often” means ensuring that where compounds are fed, meals are kept small; as a guide, ponies up to 14.2hh should have no more than 3 – 3½ lb (1 – 1½ “Stubbs” scoops) per meal and horses no more than 3½ - 4lb (1 -2 “Stubbs scoops) per meal. Most modern manufacturers also cook the cereal content of their feeds to increase the digestibility of the starch content and maximise the chances of it being digested where it should be, in the small intestine.
One of the most frequently forgotten or misinterpreted Rules of Feeding is the one about “feeding according to work done”. Many owners overestimate the amount of work their horse is doing and consequently over feed, resulting in weight gain which can lead to obesity and the risk of laminitis. A horse needs food for the maintenance of body functions and condition and to fuel his work – any that is consumed but not used will be laid down as fat. Good doers can be notoriously difficult to maintain in an acceptable condition but there is no excuse for allowing a horse to become dangerously overweight. Remember, forage contains calories too; it may be essential for healthy gut function, fermented slowly in the hind gut and highly unlikely to be a cause of laminitis on its own but too much can still make a horse fat!
Overweight horses and ponies and good doers must be maintained on a forage-based “calorie controlled diet”. Forage should be clean and dust free but of low nutritional value, so choose a stalkier hay, which will contain a higher proportion of indigestible fibre, or consider soaking it for about 2 hours to “wash out” a proportion of the nutrients. Limiting forage intake may be necessary to encourage weight loss (or prevent weight gain) but it should never be allowed to fall below 1% of the horse or pony’s bodyweight. If necessary, feed hay in small holed haynets and even put a net within a net to make a small amount of hay last as long as possible.
A Balanced Diet
Feeding a token gesture of hard feed may make us feel better but it will still be providing some calories that good doers are unlikely to need whilst leaving them short of other essential nutrients. Feeding a balancer, like Lo-Cal Balancer, which was originally formulated for natives and good doers, provides all nutrients a horse needs for health and well-being but without the calories. Quality protein is essential for muscle and tissue development and repair and it, along with vitamins and minerals, is not only vital for the healthy horse but also for helping any sick or injured horse, including the laminitic, recover successfully. Lo-Cal Balancer also contains good levels of nutrients, like biotin, zinc and methionine, which are all important for healthy hoof growth so is useful for the longer term maintenance of good, strong hooves as well as to help support recovery from a bout of laminitis.
Balancers are particularly useful where compound feed intake is unnecessary or limited since they help ensure the horse receives a fully balanced diet whilst keeping starch intake to a minimum. Increased workload, injury or illness, like laminitis, results in an increased requirement by the horse’s body for anti-oxidants to help eliminate harmful free radicals. A balancer will often supply these anti-oxidants as will the increasing number of specially developed supplements marketed to the owner of the laminitis prone. None should be seen as a cure however and strict weight control and meticulous general management remain the best way to avoid an attack.
Not only should starch intake and weight control be part of your preventative regime but steps will also be necessary to limit the susceptible horse’s exposure to grass and fructan. Strip grazing will help to limit the horse’s total grass intake, as will periods of turnout with a specially designed grazing muzzle. It may be that he is simply only allowed very limited time at grass, whilst turning out when the fructan content of the grass is low will also help avoid an overload. Since fructan levels are more likely to be high at certain times of the day, it is recommended that horses are turned out either very late at night or very early in the morning and are brought in by mid morning. Restricting access to grazing should not compromise the horse’s fibre intake which must be maintained to ensure healthy gut function.
Promoting “Safe” Weight Gain
Occasionally we are presented with the dilemma of a horse or pony who is susceptible to laminitis but who could do with carrying more condition. Even the most effective compound conditioning feeds must generally be avoided in this instance since their starch content is likely to be sufficient to trigger an attack. Oil offers the best alternative as it contains 2 ¼ times as many calories as carbohydrate from cereals and presents no risk to the gut’s bacterial population.
Although horses wouldn’t naturally consume much oil, their bodies can adapt well to use it. It must be introduced slowly however to allow this adaptation to take place and should be supported by the inclusion of additional antioxidants, such as vitamin E and selenium, to ensure its efficient utilisation. Specially formulated high oil supplements, such as Outshine, offer a mess free and palatable alternative to straight oil, whilst Outshine also contains the necessary supporting vitamins and minerals.
Since most attacks of laminitis involve a disruption of the microbial population in the horse’s gut, it can be beneficial to feed a digestive enhancer to help restore the balance. Probiotics contain live bacteria and can be useful to enhance the beneficial species in the gut, whilst prebiotics, like Digest Plus, encourage the proliferation of existing useful bacteria. Digest Plus acts as a food source for beneficial bacteria, helping their numbers to grow whilst other prebiotics “mop up” pathogenic species to allow the good ones the chance to proliferate. Digestive enhancers may of particular benefit to the underweight laminitic since they help to promote gut efficiency to help ensure they make the most of every mouthful.
Prevention the Only Answer
Research continues into the exact causes and mechanisms of this debilitating disease and it would be nice to think that someday we will be able to call the vet to administer a swift cure. Until then, and even if that were one day to happen, prevention is by far the best, and kindest, approach. Laminitis is rare in the fit, working horse and it’s vital to match calorie intake to workload; will power is as important in the horse owner as it is in the human “weight watcher” and a little bit of “cruel to be kind” may sometimes be necessary in order to keep a crippling bout at bay.