Latest Research into Laminitis & Equine Cushing's Syndrome

Laminitis Developments

C.C.Pollitt (BSVc, PhD)

Laminitis is not a condition that solely affects the horse's feet. During the developmental phase of the disease, it is possible that the horse may suffer problems with respiration and the kidneys, the reproductive, endocrine and musculoskeletal systems.

Enzyme Theory Etiology

Horse's produce enzymes (MMP) to maintain their growth & shape of various body parts. It has been suggested that these enzymes may have a function in the development of Laminitis. If the horse produces too much MMP, this may inhibit the growth of new lamellae and cause a detrioration in foot structure and capillaries, reminiscent of "classic Laminitis". It is suggested that due to the destruction in these capillaries, blood instead is sent to larger veins & arteries. It is supposed that this is the theory behind a strong digital pulse often found in laminitic horses. It has been suggested that certain bacteria are to blame for the proliferation in MMP enzymes.

(J ournal of the American College of Nutrition 16(5): 404-10, 1997)

Insulin Resistance as a causative factor

It is supposed that most laminitics suffer from insulin resistance, caused by peripheral cushings or glucose toxicity etc. It is suggested that there are certain types of equine who are genetically predisposed to a insulin and have in their make up, a "thrifty gene". Furthermore there are suggestions that up to 90% of laminitic horses are in the early stages of Cushing's Syndrome.

Daytime/Night-time effects

Research eg. from M Fredericks (c/o WWW.horseshoes.com) has suggested that serotonin and melatonin may also play a part in triggering laminitic attacks, due to their association with day length.

Dietary Deficiencies

There are suggestions that Magnesium (Mg) and Chromium (Cr) play a role in causing Laminitis and that Mg in particular is connected with insulin resistance. There has been evidence to suggest that supplementation with Mg can improve insulin resistance. However it is unclear as to whether Mg causes insulin resistance or whether insulin resistance causes levels of Mg to be low. In studies, laminitic horses had Mg & Cr supplementation withdrawn & were started on Pergolide. There were rapid improvements, leading the researchers to conclude that the latter was responsible. Some researchers have also found that Cr supplementation can be effective in cases of insulin resistance although this has not been widely substantiated.

www.rockies.co.uk has useful information regarding this issue & relevant products.

Latest Management Advice

• A water soluble carbohydrate called fructan has been linked to laminitis. These accumulate in bare frosty paddocks with slow growing grass. It is sensible therefore to strip graze, or to use a muzzle with a small hole cut out of the bottom to limit grass intake. You must also cut down on the number of hours the horse has grazing.
• Never let a laminitic pony's fibre intake fall below 1% of his bodyweight and never starve a laminitic. Feed a stemmy hay.
• Do not feed starchy cereal mixes. Feed a high fibre diet. Soya oil can be fed to recovered laminitics who need a higher energy requirement.
• Always feed a broad spectrum supplement.
• Consider using a supplement containing antioxidants (vitamins A, C, E) to absorb the "free radicals" which are molecules that increase in instances of tissue damage and illness. You can also feed bioflavanoids to improve circulation.
• The safest time to turn a laminitic horse out is overnight between dusk and dawn when fructan levels are low.
• A new product called "Founderguard" is now available from some vets. This is the only product of its kind that has been proven to prevent an attack of non-Cushing's related laminitis

Cushing's Syndrome Developments

New Drug for Cushing's

Research carried out at the Royal Veterinary College in the UK has suggested that "Trilostane" (a drug which blocks adrenal production of specific hormones) could be useful in treating the symptoms of Equine Cushing's Disease. The stress unfortunately is still on "symptoms" as regrettably there are still no products that are thought to be able to cure the condition completely. Cushingoid horses were given the drug orally for 30 days, after which, their initial Dex. test was repeated. Cortisol levels had reduced and clinical symptoms such as lethargy, polydipsia & poluuria all improved. Laminitis that was described as "chronic" in some of the animals, improved or did not worsen during the trial. These results mean that an alternative to Pergolide and Periactin is now available in future. "Laminitis & Cushings Support (UK)" has contacts who are using this drug. If you are interested, please contact us.

Peripheral Vs Pituitary Cushing's

This is a contraversial debate in the USA which is coming to light over here in the UK. Vets in the USA have drawn a distinction between true "Pituitary" Cushing's, ie. that which is actually caused by a tumour on the Pituitary gland, and "Peripheral" Cushing's. The latter has been suggested by vets in the USA (Johnson and Messer) in horses who have normal cortisol levels but elevated insulin levels. It is thought that in some horses there is an increase in a certain enzyme (HSD) which causes an excess of cortisol to from in the peripheral tisues as opposed to the blood stream. As a consequence, such horses produce Cushing's - LIKE symptoms but DO NOT have the Pituitary tumour. At present though there is no way to determine clearly between the two and the distinction is not highly regarded by some experts.