Laminitis – Causes and Prevention

Principal Causes
Cushing’s Disease – a malfunction of the pituitary gland, leading to excess production of cortisol, which is a natural steroid. It reaches the hooves via the bloodstream, where it causes separation of the laminae that bind the various tissues of the hoof. This is a typical problem of the older horse or pony.

EMS – Equine Metabolic Syndrome caused by obesity, especially in ponies. It causes imbalances in blood sugar/fat/insulin ratios, which result in insulin resistance which can trigger laminitis.

Insulating the lower limbs & hooves with suitable wrappings or leg protectors can help plus the usual dietary considerations – feeding meadow rather than ryegrass haylage or hay, & soaking it. Choosing feeds with the lowest possible starch & sugar content is essential for example unmolassed plain oat chaff + mineral/vitamin supplement or balancer (be careful – the latter may contain some starch & sugar). Live yeast will help maintain a healthy hind-gut microbial population, further reducing the risk of laminitis (& loose droppings).
 Molasses-free blends based on alfalfa & oat straw could be used, with a little soaked low-sugar beet pulp for palatability. If poor condition is a problem, add some cooked linseed meal. Starch + sugar content is about 7.5%; copra’s is 11% & full fat soya’s is 18%. In cold weather adding a cupful or 2 of vegetable oil to the daily diet can help prevent weight loss.
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Other Causes
● Undigested sugars and starches passing into the hind-gut of the horse.
● Percussion – the effect of riding/jumping on hard ground.
● Use of steroids – thought to make the gut wall more permeable to the toxins which trigger laminitis.
●Infection – e.g. post-parturition.
● Antibiotics can upset the balance of the hind-gut microflora.
● Stress.
● Sensitivity or allergic reaction; the author knows of a horse, and an owner, who are both sensitive to rapeseed oil. The horse developed severe laminitis. The person developed blotchy skin, which eventually returned to normal after stopping taking a supplement containing the oil. This particular problem is fortunately rare. Some other feed ingredients can also cause similar problems, in particular, skin irritation.

Laminitis is frequently caused by undigested sugars and starches passing into the hind-gut of the horse, where they are broken down by bacteria to lactic acid. This increases the acidity in the hind-gut, suppressing the fibre-digesting microbes. Other species (Streptococcus, Salmonella, E. Coli etc) proliferate. It is thought that they produce toxins which pass into the bloodstream. When they reach the hooves, these toxins trigger laminitis.
Fast-growing lush grass produces large amounts of sugars, especially on bright sunny days, including frosty ones. Unused sugars are stored as fructans, especially if the grass is stressed because of cold or drought. Fructans are very sweet, and make grass extremely palatable. They cannot be digested in the horse’s small intestine and so pass into the hind-gut where they are readily broken down to lactic acid by the resident microbes, with consequent problems, which may include scour as well as laminitis.

Control & Prevention
●Susceptible horses & ponies should be on restricted grazing, preferably at night the grass is not making sugar.
●Hay should be soaked long enough to remove as much sugar as possible.
●Feed should be high in digestible fibre, with as little starch & sugar as possible.
●Live yeast should be included, to maintain a healthy gut microbe population.
●Cushinoid horses & ponies will require treatment. Some will respond to Agnus Castux, from which Vitex is prepared, or drugs such as Pergolide or Prascend, for which a prescription is required.

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