I like many people this year for the first time have been caught out with laminitis. I have a horse that is now in her twenties and has never had a problem, and we got caught out. In fact, the reason that I have not blogged for the last couple of weeks is that I have been managing her routine and this has taken up a lot of time.
A big factor has been that the weather this late winter/early spring has been as you know snow and rain, followed by hot humid weather and this has brought the grass on in leaps and bounds. Also, in my case, my horse has got older and she is more susceptible to the disease. Everywhere I have spoken to different people have been touched by the condition and are having to make adjustments to their routines and help their horses.
In a recent review of research one of the authors, Cathy MacGowan spoke to British Horse about the different findings and discussed the different findings. The paper – ‘Paradigm shifts in understanding equine laminitis’ is a review of many studies and a summary of where that research has changed the practical position on laminitis.
A clinical Sign.
One of the first things that came out of the paper is that laminitis is a clinical sign of a systemic disease. This means that it is a sign of something going wrong in the systems of the horse. In 2007 a group of scientists led by Cathy MacGowan realised that insulin directly caused laminitis. I know that in the past laminitis has always been thought of a disease in the own right.
Their findings showed that it was the grouping of different diseases – a symptom of a disease or clinical syndrome caused by a number of diseases.
There was finally an understanding of the link between insulin and laminitis and that laminitis was a clinical syndrome associated with systemic diseases such as endocrine disease, sepsis or systemic inflammatory response syndrome (SIRS).
It was also found that people were confused by the most common form of laminitis, which is a pasture-associated form of laminitis, which is fat ponies out on the lush grass. There had been a lot of research on the link with tummy upsets Endocrine Laminitis is now recognised as the most common form of naturally occurring laminitis in horse and ponies.
An earlier misconception was that laminitis was predominantly associated with sepsis or SIRS. This misconception was highlighted in a study in the US that showed that grain overload, retained placenta, colic or diarrhea accounted for only 12 percent of cases of laminitis. The remained where associated with dietary problems or obesity, or where of an unknown cause. Also, more convincing studies identified the endocrine disease in 90 percent of cases of laminitis in horse and ponies presenting with lameness.
The main equine endocrine disorders resulting in laminitis are Equine Metabolic Syndrome and/or pituitary pars intermedia dysfunction (PPHD – also known as Cushings Disease) the former characterised by obesity, insulin resistance dysregulation, and laminitis.
Check Insulin Levels.
Another key finding was that we can induce laminitis simply by infusing insulin into a horse. It is insulin that causes laminitis not the fructans in the grass. Fructans are less likely to cause metabolic disturbances than glucose and all the other non-structural carbohydrates or carbohydrates in the grass. It is to do with the sugar content in the grass.
It is important that not all ponies and horses are prone to laminitis and it is the abnormal metabolism or insulin dysregulation that makes them prone to it. It’s a bit like saying that any child under the age of 10 can’t eat sweats otherwise they will get diabetes. That just isn’t true, every child has a different metabolism so you would need to check that first. The only way to really determine which child would have a problem would be to do a test to see how each child reacted to sugar in their body.
It’s the same with ponies, you shouldn’t remove them from pasture because it is frosty until you have done a test. If you would like to know if it is the sugars in the grass that are going to cause a problem, first you need to know if the animal is metabolically normal – has it got normal insulin sensitivity? If you want to know if it is the grass that is affecting your horse, put the horse on the grass and then test their insulin levels to see how they react to the grass.
We call it insulin regulation or dysregulation because some animals have tissue insulin resistance which means the insulin isn’t working properly and the body responds by producing more insulin to make sure the blood glucose is maintained at normal. Therefore, high insulin is causing laminitis.
There is also a subgroup of horses who, when they eat, carbohydrates or any sugars or amino acids, get a higher spike of insulin directly from a gut-derived insulin exerting agent and the effect are much more severe.
It’s the same with diabetic people – it is not a problem until you feed them sweets, and it’s the same with insulin resistant horses – there’s not a problem until you give them the sugars.
Ways to test.
There are two ways of testing for insulin dysregulation in your horse. The first is where you get your vet to perform a baseline insulin test, usually before breakfast, (but not fasted too long – this is another mistake people make, staving their horses for hours before the vet came and then wondered why the insulin was really low, and it wouldn’t have been an accurate test of whether they are going to be laminitic or not). It is a single blood test and the easiest to perform.
The second test is where we give a ‘carbohydrate challenge’ which is like an endocrine system stress test. It picks up subtle insulin resistance that can be missed with fasting glucose and insulin. A high carbohydrate meal is given and blood samples are taken at certain intervals to measure glucose and insulin levels. Any abnormality in any of these parameters points to the underlying cause of the dysfunction in carbohydrate metabolism.
The third option is more of a management tool than a diagnosis and it tests what the horse is going to be eating in the future. It checks how they react to the food you are giving them, so if they are having a response to it, you can change their diet to suit them better and not have such an insulin response.
Tests were done on haylage versus hay, and although the sugar content in haylage is lower than hay because it has all be fermented away, it produces a bigger insulin response to hay.
Elongation of Lamellar Cells.
Something else they found was that insulin directly damages the cells in the hoof. In the past, the picture of laminitis that had been taken were of severe inflammatory cases and the horses’ pedal bone dropped out of the hoof very quickly. Thos picture didn’t really expain what was going on inside the hoof from endocrine laminitis.
By looking at the naturally occurring (endocrine) laminitis, we realised that what insulin was doing was causing damage to the cells that hold the pedal bone and the hoof wall together. The key here is that they lose their cellular skeleton and instead of being nice round balls, they stretch. So if you have stretched cells and you walk around on them a lot, they can break. Think about an elastic band – they are either nice, firm, tight little things, or they’ve stretched and lost strength. It explains why the pedal bond drops in the foot because the cells have stretched and moved down.
The other finding is that these cells can be damaged and stretched but get better again, and when that happens, you get a laminitic or divergent in the hoof. We have countless horses that have rings down their hooves but have never been lame. What that shows us it that is that these rings are a pre-clinical, pre-laminitic phase that opens up a huge window of opportunity to tread these animals before it becomes painful.
The ring grows out from the coronary band and the pedal bone can be retracted with the right farriery and as long as the structures haven’t come too far out of alignment. The key is to get there before the horse goes lame.
By understanding more about how laminitis works, we can make better judgments on how to treat and manage our horses and ponies. If we can get our owners to realise and accept these changes in understanding, we will save a lot of horse and ponies from a lot of pain.
Owners should ask themselves, has my horse recently been very unwell, did he suddenly have non-weight bearing lameness or does he have an endocrine disease? If yes, get the vet to check insulin levels.
Let’s understand what causes laminitis, understand the role of insulin and make sure we monitor that so that we can efficiently manage the condition.
All of the above information has come from an article in British Horse’s April 2018 addition and the work of Cathey McGowen and her colleagues. I wanted to make sure that our readers have chance to see the information and be able to understand what has been found.
If you have enjoyed this article and would like to know more about what we are looking at please feel free to sign up at our website or Sam Goss Coaching’s Facebook page.