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The Truth About Laminitis: Dispelling the Myths

A laminitic foot showing the rotation of the pedal bone.

Laminitis is a subject that is on the mind of many horse owners, and especially as we head into spring. A debilitating disease with severe welfare and economic impacts, it is not yet fully understood and is often difficult to treat and manage. Recent research has helped elucidate the causes, and a relatively new proposal of the different types has been given. Throughout this confusion, there remains a constant element – that prevention is much better than cure and that the identification of horses and ponies at risk is a key factor.

Anatomy and physiology

The horse’s foot is enclosed in a hard, protective keratinised structure called the hoof capsule, which is made up of the hoof wall, the sole and the frog. The foot has a very complex and intricate blood supply. The bone of the foot – the pedal bone – is encased in the hoof capsule and held by an interface of insensitive (epidermal, horny) laminae on the hoof wall, and sensitive (dermal, vascular) laminae on the pedal bone, which interleave with each other. A basement membrane holds them both together. The basement membrane forms an adhesion at the laminar interface, giving the foot structural integrity, and also is involved in its thermoregulatory control and the exchange of nutrients. This attachment of laminae – or lamellae as they are probably more accurately called – is incredibly strong in a healthy hoof, but is compromised in a case of laminitis.

Laminitis

Laminitis means ‘inflammation of the laminae’ but recently, this term has been challenged because it may not be particularly accurate in many cases. The disease involves a failure of the laminar interface between the pedal bone and the hoof capsule. Hoof horn production is affected and it may take many months after a bout for healthy hoof horn to grow back.

Recently three different types of laminitis have been proposed:

  1. Inflammatory laminitis, e.g. from overeating starchy grain, induced via starch or fructan overload or black walnut poisoning, or via colitis, retained placenta or septicaemia. Involves a ‘sick’ horse, release of inflammatory toxins from the hindgut, vascular dysfunction, leucocyte (white blood cell) infiltration and a breakdown of the lamellar basement membrane via MMPs (enzymes).
  2. Endocrinopathic laminitis e.g. from insulin resistance, EMS (Equine metabolic syndrome) or PPID (Cushing’s syndrome). Most cases of laminitis and probably all cases of grass-induced laminitis. Potentially should be termed ‘endocrinopathic laminopathy’ due to a lack of inflammation being involved. There is abnormal cellular activity in the laminae, the basement membrane in the foot becomes stretched and the hoof distorted.
  3. Contralateral limb laminitis e.g. from too much weight bearing on the opposite limb from a fractured limb. May not involve inflammation as a primary cause, and more likely to be caused by poor blood flow.

It’s possible that all three have some overlap, and the common theme is the separation of the laminae along the basement membrane.

EMS is a term used to describe a condition that includes obesity, laminitis and insulin resistance. Obesity tends to cause insulin resistance, and both are associated with an increased risk of laminitis. Insulin resistance is a failure of body tissues to take up glucose as a result of circulating insulin, resulting in higher insulin levels. EMS may still exist in animals who appear slim externally, perhaps because they have previously been obese or due to some other anomaly. Note that being slim doesn’t rule out endocrinopathic laminitis.

Grass-induced laminitis is unlikely to be simply due to an acute overload of fructan (inflammatory laminitis) and more likely to be due to an endocrinopathy with some level of obesity and insulin resistance. The energy content of pasture and the high palatability means that free access will result in excessive weight gain in many horses and ponies, especially if they are sedentary. Both the free sugar and the fructan content of pasture grass can contribute to or cause insulin resistance.

PPID-associated laminitis probably occurs due to insulin resistance, which might explain why some affected horses get laminitis and yet others do not. Veterinary diagnosis of PPID cases is essential because medication can make a big difference to their health and their risk of laminitis.

The symptoms of laminitis have been described elsewhere. The disease is much easier to recognise in the acute stages, and long-term subclinical laminitis might be missed. Any foot abnormalities should be taken seriously.

Management

Effective treatment both urgently during an acute bout and on an ongoing basis is absolutely key and the vet should be called without delay if a bout is suspected. Medication may be required, the environment will probably have to be adapted and the hooves will need to be supported and realigned via trimming, ideally with radiographs (x-rays).

Prevention is most definitely better than cure. At risk animals must be identified, which is not easy. Acute inflammatory cases are easier to identify due to the initiating factor, and action to treat the gut disturbance and ice the feet should be taken as early as possible. Icing the feet seems to help, probably by limiting inflammation and reducing oxidative damage.

Overfatness and high circulating insulin levels are both high risk factors for endocrinopathic laminitis, and action should be taken whenever either is recognised. Weight loss, an appropriate diet and exercise (if the horse is sound) are key treatments.

PPID is a risk factor, with around 65% of affected horses suffering from laminitis, and medication is necessary for control of the PPID and associated laminitis. In these cases, medication is even more important than the diet in controlling laminitis symptoms.

Feeding

Correct feeding of laminitics is absolutely key for recovery, to reduce future risk and to help avoid the disease in the first place. First and foremost, the importance of a well-balanced diet cannot be overemphasised. Adequate levels of all the essential nutrients are key for optimal health and function of every body system. Vitamin and mineral intake can easily be forgotten in the focus on weight loss but is more important in a restricted diet, and absolutely essential for good healing after foot damage.

High body fat levels seem to increase the risk of laminitis so ensure a healthy body condition. This risk could be via insulin resistance and/or endocrine effects of fat tissue. Gradual fat loss is the healthiest strategy, and the horse or pony should never be starved. Ideally drop to a minimum of 1.5% of bodyweight intake in dry matter daily, and if this does not cause fat loss, then source a lower energy (calorie) forage. The body fat levels must be monitored and more carefully so after the ideal weight is reached, to ensure longer term health. Weigh tapes can be used to monitor changes in body fat level, despite not being particularly accurate for actual weight. Condition scoring can also be used, although it can be difficult to score accurately.

Simply feeling the body fat under the skin can be helpful in determining whether or not the horse is too fat. If the ribs cannot be felt easily, then the horse is too fat. The ribs should be easily felt, the neck crest should be soft (unless a stallion) and the bony structure of both the shoulders and the pelvis should be relatively easily felt.

Equine metabolic syndrome cases will benefit from body fat loss, and also from exercise, where possible. Excess weight reduction in horses is associated with improved insulin sensitivity, which in turn will help reduce the risk of laminitis. There is no evidence to show that being very thin compared to slim has any added benefit and care should be taken not to be over zealous with weight loss to the point of starvation and muscle wastage.

Since high insulin levels can be involved in laminitis, the diet should contain controlled water soluble carbohydrate (sugar and fructan) and starch levels. Ideally the entire diet including the forage should have a non-structural carbohydrate (NSC) content of less than 10%. If in doubt the forage should be analysed because it is not possible to tell from looking at it.

Hay can be soaked to reduce WSC (sugar and fructan), but the result depends entirely on the original content so it is best to have the hay analysed to begin with. A 10 –hour soaked high WSC hay might still have more WSC than an unsoaked very low WSC hay.

Soaking hay leaches out energy as well as WSC, so can help with body fat loss as well as helping to avoid high WSC intake. The hay should be soaked for around 10 hours to decrease WSC and energy significantly.

Grass intake can contribute significantly to insulin levels and to body fat levels, and it is a major risk factor in many horses and ponies. All horses and ponies at risk of laminitis or over-fatness should have their grass intake restricted. Restriction should ideally be done by using bare fields, grazing muzzles or strip grazing since simply turning out for a restricted amount of time causes horses to compensate by ingesting much more grass in that time.

Supplementation

First and foremost the diet should be balanced, and most cases should be fed a vitamin and mineral supplement since most will not be given much if any hard feed. ReadySupp Essential Vitamins and Minerals is an ideal product to balance a restricted diet. Once the diet is balanced, certain nutrients, nutraceuticals and herbs can be given to support metabolic health, maximize hoof strength and resilience, and provide antioxidant therapy. ReadySupp LamiCare is a blend of powerful ingredients that help support metabolic and vascular health, and promote healthy hoof horn.

Biotin, a B-complex vitamin with an important role as a component of major metabolic enzymes, is involved in the synthesis of intercellular glue and this may be why supra-optimal dietary levels can increase hoof quality. Several research studies have shown improvements in hoof horn quality and/or growth rates in supplemented horses. 30 mg of biotin is included in a daily serving of LamiCare

Sulphur is an important component of hoof and hair, because it’s essential for the disulfide bonds in keratin. In this way it helps maintain strength in the hoof horn. The essential amino-acid methionine is included in LamiCare as a biologically available source of sulphur, along with the sulphur-rich compound methyl sulphonyl methane (MSM).

The two most important essential amino acids lysine and methionine have been added to LamiCare to upgrade the quality of protein, which is key to tissue repair and regeneration.

The essential microminerals zinc and copper are involved in keratinized tissue, and amino acid chelates of these minerals are included in LamiCare, due to their higher bioavailability. Zinc is a constituent in many enzymes, including those involved in keratinization, and low body zinc has been associated with reduced hoof horn hardness and strength.

Essential fatty acids including omega-3 fatty acids are involved in maintaining cell membrane fluidity and function, and are a key component of the integrity of keratinized tissues including hoof and skin. Docosahexaenoic acid (DHA) from algae is used in LamiCare, which provides essential omega-3 fatty acids in the form used in the body, rather than the intermediary, alpha linolenic acid. DHA has been shown to have an effect on the endothelium, modulating flexibility and balancing inflammation, and is involved in both the epidermal water barrier and the intercellular glue that connects the hoof tubules.

Live yeast balances digestive disturbance and helps ameliorate the gut disturbances that can be involved with laminitis. Researchers in France have demonstrated that live yeast is viable in the equine digestive tract and the beneficial immunomodulatory effects of probiotics are proven.

Cinnamon and fenugreek are included for their metabolism-balancing effects. Because vets have proposed that most cases of laminitis are endocrinopathic, supporting a healthy metabolism with diet is key in management. Cinnamon is under investigation as a therapy for diabetes in humans due to its action of improving insulin sensitivity and reducing postprandial glucose levels, and there is good scientific evidence that fenugreek reduces blood glucose levels in diabetic patients. Hypoglycaemic effects of fenugreek have been confirmed in animal and human trials.

Hawthorn tips and nettle are included for their vascular supporting effects. Hawthorn has a wide range of effects on the cardiovascular system including vasodilating, endothelial-protective and inotropic (cardiac-muscle function) effects. It has activity on factors that affect vascular function such as nitric oxide, and affects endothelial permeability function at the cellular level. Nettle has powerful antioxidant effects. Citrus extracts, which include the bioflavonoids hesperidin and naringin, also have powerful antioxidant effects, which promote healing and improve capillary function.

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Posted in Equine Health, Equine Nutrition, Supplements
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