Testing insulin levels in ponies could predict risk of laminitis

  • Knowing a pony’s insulin levels makes it possible to determine how at risk of laminitis it is – with the highest indicating a 70% chance of developing the condition, research has shown.

    A study led by Edd Knowles of Bell Equine and the Royal Veterinary College (RVC), funded by the RVC and Mars Petcare, has provided further evidence on indicators that a pony is at risk of laminitis.

    The project involved 374 ponies, with no history of laminitis, from 24 premises. Over four years, they had six-monthly examinations, during which sugar syrup was administered and blood samples taken to monitor levels of insulin and ACTH, the hormone measured in PPID (pituitary pars intermedia dysfunction, often called Cushing’s disease) diagnosis. The ponies were also weighed and measured. Of the 374 ponies, 43 cases of laminitis were reported over four years.

    Dr Knowles told H&H the aim of the study was to assess which factors were most useful when considering whether a pony was at risk of developing laminitis.

    “We have known for a long time there are different things that can cause laminitis, whether it’s being overweight, grass, hormones, and we wanted to look at things that are practical for vets to measure and owners to determine fairly easily,” he said.

    “In those who developed laminitis, when we looked at all the information collected in the visits beforehand, we found the levels of insulin in the blood were the most important factor. We expected insulin to be important, but what was interesting was how important it was compared to other things, like measuring a cresty neck for example. Blood testing tells you something you can’t see from the outside.”

    “By knowing the different levels of insulin we can put a number on how high the risk is for that pony. For ponies where insulin stayed normal for four years, they were at a very low risk of laminitis. But for animals with the highest insulin dysregulation, we could say about 70% of them would develop laminitis in that time.”

    Dr Knowles said it is important owners consider which ponies are at risk of developing laminitis and how they are kept. He added “logically” it could be assumed the study’s results would apply to horses as well as ponies, but more work is needed.

    “We need to get better at identifying the animals at risk, and consider how we want to keep them.”

    David Rendle, chair of the British Equestrian Veterinary Association’s health and medicines committee, told H&H the study backs up previous research and makes it “really clear” there is a strong link between insulin concentrations and the risk of laminitis.

    “It’s helpful for owners to see that their horse has a high insulin level. We’ve spent years trying to persuade owners that their horses are overweight and need a diet, and it’s really difficult to change owner behaviour. So if we can show a horse has a very high level, that’s black and white evidence the horse has a metabolic abnormality,” he said.

    “If you’ve got a pony with insulin above 45, they have a 70% chance of developing laminitis. Those numbers are powerful and the question is what do you do about it? The central theme has to be the same drum we keep banging that horses need to be leaner and fitter. Owners often have an optimism bias that even if they appreciate their horse is slightly larger than it should be, they always think they won’t be the one that gets laminitis.”

    Mr Rendle added that it would be helpful for owners to test insulin levels more regularly, but warned that low insulin is not a get-out-of-jail-free card.

    “If you get a low result you can’t be completely complacent about the risk of laminitis. With changes in diet and body condition insulin can quickly go up,” he said.

    Read the study here.

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