Laminitis and other endocrine disorders
As we enter spring everyone is starting to watch the grass come through and concerns start being raised, especially amongst those of us with small native ponies. As the sun starts (slowly) showing itself, and we are still getting periods of rainfall the grass is growing quite quickly and therefore has a higher sugar content than has been ingested over winter. This is a common reason for a peak in laminitis cases at this time of year.
Laminitis is defined as inflammation of the laminae which are the cobweb like structures on the inside of the hoof capsule that suspends and supports the pedal bone within the hoof. Therefore when these become inflamed they become weakened and painful.
Laminae is a highly vascular structure and, due to its complexity, any disruption to the blood flow or the content of the blood will have an effect on its health.
The most common cause of a problem with the laminae blood supply is ACTH (the stress hormone released in excess in Cushing’s disease patients) and Insulin resistance (which occurs in Equine Metabolic Syndrome patients). In Cushing’s cases the chronic high levels of ACTH hormone leads to insulin resistance, which in turn, results in the same problem of too much glucose in the blood stream as with Equine Metabolic Syndrome.
This lack of glucose delivery to the hoof keratinocytes (the cells in the hoof) decreases the cells’ ability to regenerate/recover. The other outlook on insulin resistance is that insulin is considered a slow vasodilator, therefore if the animal is insulin resistant then this will decrease the ability of the circulatory system to dilate to increase blood flow, and therefore the perfusion of the hoof capsule (and resultantly the laminae) is decreased.
So how does a seemingly “healthy” horse/pony develop laminitis from being out on lush grass when no endocrinological problem is currently considered a problem? When a large quantity of what is called Non structural carbohydrates are ingested, formed by simple sugars, starches and fructans, they exacerbate an insulin resistance type response in the individual. These high sugar and starch levels in the gut also lead to disruption in the gut flora which subsequently leads to release of endotoxins, exotoxins and vasoactive amines into the circulatory system
Pedal bone rotation and/or sinking occurs when the damaged/weakened laminae cannot support and hold the pedal bone in place within the hoof capsule.
The severity of the pain demonstrated by individual horses/ponies varies depending on the individual’s pain threshold, but once an equid has had laminitis it means they are predisposed to having other episodes later in life.
Although Cushing’s is thought to be an older horse/pony disease it has been diagnosed in equids as young as 7yo, and Equine Metabolic Syndrome is not a disease of solely obese native types (although they are more prevalent). Any concerns you may have with regards to the above should be discussed with your vet.
It is vital, especially in at risk horses and ponies, that good quality farriery is undertaken on a regular basis (normally every 6 weeks depending on hoof growth) to ensure the best opportunity to maintain a good hoof pastern axis, which should result in a good pedal bone, short and long pastern axis inside the limb, thereby reducing any abnormal pressure on the laminae.
If you wish to improve your knowledge or understanding on the above, please ring the office on 01270 766455 or email firstname.lastname@example.org to book a place on our Laminitis and Cushing’s Talks
Ref: Frank N, Insulin Resistance In Horses. AAEP Proceedings 2006;52:51-54Follow us Share this