Ask The Vet Series – should I worry about laminitis?

On the back of our new ‘Ask The Vet’ series, we had a question in from Colin in Co. Meath. A question that is particularly relevant for this time of year, with the grass FINALLY starting to grow!

I recently bought a pony for my young daughter, he is an absolute gent and a great school master but he is a little on the “rotund” side. We have a paddock out the back but a friend told me that he could end up getting laminitis. What do you think the risks of this are?

Grass founder/ summer laminitis can be explained with a quick look back on basic biology. Photosynthesis involves the use of light to convert carbon dioxide and water to oxygen and glucose. Therefore, in these spring/summer months when daylight increases, so too does the production of glucose in the grass. If you have a horse who is prone to laminitis or in the high risk category (see table below) you must be very vigilant about your horse’s grazing routine.

So let’s go through a few simple steps that make a big difference in the prevention of laminitis.

  1. Establish the risk:

If your horse has ever had laminitis before, unfortunately they are already in the high risk category. Talk with your vet and establish whether your horse/pony is at risk of laminitis. Below are some of the indications that your pony could be predisposed to laminitis.

  1. Night grazing
  • Going back to our equation, sunlight is needed to make sugars; however, sugars are used throughout the day and night to grow the plant. As a result, the most at risk time for horses is late evening, after a full day of sunlight. And conversely, the lowest risk is before dawn when sugar levels are at their lowest. So we would recommend that ideal grazing would be between 10pm and 3am (well, we’re not suggesting you get up at 3 to bring your pony in, but we do recommend bringing at risk horses and ponies in as early in the morning as is possible!).

Exception – When grass is unable to grow due to stress, e.g. drought, frost, then again the sugars are high. Therefore, at risk horses should not be put out to graze during frosty nights or during particularly dry periods in a season (not a major concern in Ireland 🙂 )

  1. Gradual changes
    • The hindgut of the horse is a very sensitive balance of gut flora that can become a melting pot of toxins if exposed to high levels of soluble sugars. If horses are allowed to graze lush grass for extended periods of time without gradually been exposed, it can lead to colitis/colic and or laminitis. So after a long winter indoors, gradually return your horse to grazing to avoid such complications.
  1. Rotational grazing
    • Avoid overgrazing a pasture. As grass plants grow, it’s the root that stores the most sugar, the last 8cm of grass are therefore the most dangerous to horses. So often we think a big bare field is the answer to our at risk horses and ponies, but it might in fact be the worst thing for them. Rest paddocks until 15-20cm of grass re-grows.

A help – A grazing muzzle that is adapted to prevent grazing so low down can be an aid for those who don’t have the room for rotational grazing.

  1. No grazing
    • Unfortunately in some horses and ponies, the “cruel to be kind” method is the only way to prevent laminitis. We would like to believe that to be out on grass all day is the natural state for horses and at one point it was. However, overtime we have modified our grazing to ensure high uptake of carbohydrates and sugar to ensure weight gain and milk production in the agricultural industry. In nature, the grasses horses would have eaten would have been much higher in fibre and not as readily available. So restriction to a sanded area, a dirt area or a shed might be the kindest option as laminitis is an incredibly painful disease.
    • If it is the case that you keep your pony inside, get your hay tested as they vary greatly in sugar content and if you have any worries soak the hay for at least 3 hours before giving it. An extremely good alternative to hay is oat straw or oat straw chaff. It has a digestible energy content of around 6MJ/Kg, a starch content of 1% and is only 5% sugar, so more can be fed to satisfy the fibre need of your pony, without increasing the energy level of the diet.

So what is the take home message, find out if your horse is predisposed to laminitis and if necessary put in simple changes to his routine to decrease the risk of disease. And don’t forget exercise either – keeping an at-risk horse or pony well exercised will help to burn off those excess calories….


Please note that our veterinary articles are written to give you insights and understanding of common equine veterinary problems and are not intended to take the place of a veterinary examination by your own vet. If in doubt, always call your own vet should your horse require attention. 


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