There are several main causes of laminitis, however, the most common cause is metabolic or endocrine in nature. This includes insulin resistance (IR) and Cushing’s disease (PPID). These two causes of laminitis are referred to as being metabolic or endocrine induced and are often referred to as an equine metabolic syndrome, pasture laminitis, grass founder, equine syndrome X or endocrinopathic laminitis.
Because IR is such a common cause of laminitis, it is wise to assume and treat a laminitic horse as if it were IR. Unless there is another obvious cause – such as a feed room break-in, retained placenta or supporting limb laminitis – an immediate action plan and diet management must be implemented. This is always the safest initial action to be taken with any laminitic horse. This approach can always be modified down the track if the IR diagnosis proves otherwise.
METABOLIC/ENDOCRINE INDUCED LAMINITIS
Image: Pony showing classic long wiry coat and overgrown dished shaped hooves. Photo by GoBarefoot trimmer Sandi Chiswell
Cushing’s disease is a common cause of laminitis in horses and is caused by an enlargement or adenoma (benign tumour) in the portion of the pituitary gland called the pars intermedia. The more accurate term is pituitary pars intermedia dysfunction (PPID). It is estimated that over 20% of horses aged 15 or over have PPID. The symptoms of Cushing’s disease are due to an excess of the stress hormone, cortisol. A horse with Cushing’s disease will need to be medicated with Pergolide to control the disease. Please discuss this with your vet.
Missy’s Bucket – the best option to balance Minerals when testing the pasture and hay is not a practical option.
Insulin resistance (IR) is also a common cause of laminitis and founder in horses. IR in the horse is caused by elevated circulating levels of insulin which in turn is mainly the result of an inappropriate diet. However, it can be caused by pregnancy and other disease states. IR is characterised by a loss of insulin sensitivity at the cellular level. It is estimated that IR effects 10 to 15% of the equine population.
Image: Obese horse showing classic fat pads on crest, shoulders and tailhead
How is IR different to Cushing’s disease?
Cushing’s disease and IR are distinctly separate conditions. Diagnosis can be difficult, however. Often there are overlapping signs and symptoms and to confuse things further… many of Cushing’s horses can also have IR.
SYSTEMIC INFLAMMATORY DISEASE (SID)
Serious systemic disease with septic or toxic focus can cause laminitis. The horse will show signs of systemic (whole system) illness and have a raised temperature and often have diarrhoea. Causes might include post-colic surgery, colitis, peritonitis, poisoning or retained placenta in a mare.
Carbohydrate overload is also included under the category of SID. Acute laminitis can be induced very quickly if a horse’s hindgut is exposed to a large volume of carbohydrates. This is commonly seen when a horse breaks into the feed room – for example – and gorges itself on grain.
MECHANICAL or ROAD FOUNDER
Long, hard or prolonged work especially on the hard ground has been known to cause laminitis and is sometimes referred to as road founder. Damage and inflammation can occur in the hoof lamina from a repeated and ongoing concussion on hard surfaces. This occurs particularly where the hoof walls are too long, effectively putting pressure on the laminar connection. See pic below.
Image: Long toes cause lever forces on the hoof wall
Laminitis can also occur due to poor trimming or lack of trimming. When the hooves are allowed to grossly overgrow, the lever forces from the long hoof wall can pull, stressing the laminae and other tissues of the hoof.
For more info on Laminitis including treatment, rehab and prevention, have a look at the book ‘What is Laminitis? – A Practical, Step by Step Guide to Recovery’ written by Rebecca Scott and Zoe Messina. Available as an EBOOK
‘If your horse has laminitis, this is the FIRST book you should read!
A review by Linda Whitfield Cowles – Equine rehab specialist.