Laminitis, and the grass that causes it
4 min read · Updated
Horses
Laminitis is the reason a great many horses are put down, and the version most people picture — a fat pony turned out on spring grass — is only part of it. The majority of cases have an underlying hormonal cause that was there long before the grass came through, which means laminitis is largely a disease you can see coming.
What laminitis actually is
The hoof wall is attached to the pedal bone inside it by interleaved layers of tissue called the laminae. That attachment carries the entire weight of the horse.
In laminitis those laminae become inflamed and weakened. It is exquisitely painful — the swelling is inside a rigid hoof capsule with nowhere to expand — and if the attachment fails the pedal bone rotates downwards or sinks within the hoof, driven by the pull of the deep digital flexor tendon and the weight above it. That is the point at which the word founder is used, and the change is permanent.
It usually affects the front feet, because they carry more of the horse's weight, and it is usually both of them at once. A horse lame on one foot has something else going on.
The damage happens early. By the time a horse is visibly lame, the process has been underway for a while, which is why laminitis is treated as an emergency even in a horse that seems only slightly footsore.
And it recurs. A horse that has had one episode has damaged feet and a raised risk for life, so management afterwards is not optional.
Why it happens, and the part people miss
Most cases — the figure usually quoted is around nine in ten — are endocrine. The horse has equine metabolic syndrome, or PPID, and the resulting high insulin is what damages the laminae. Grass with a high sugar content is the trigger, but the loaded gun was there already.
Equine metabolic syndrome means insulin dysregulation, and it comes with a recognisable shape: regional fat pads on the crest of the neck, over the tailhead, behind the shoulders and in the sheath or udder. A cresty neck on a native pony is not just a look. It is a finding.
PPID — Cushing's — is a pituitary problem in older horses, and the coat is the giveaway: a long curly coat that does not shed properly, along with muscle loss over the topline, drinking more, and recurrent infections. Both can be blood tested, and both can be treated.
The other routes matter but are rarer. Grain overload from a horse getting into the feed store. Severe systemic illness or toxaemia, including retained placenta after foaling. And supporting-limb laminitis, where a horse non-weight-bearing on one leg overloads the opposite foot for weeks.
Grass itself peaks in sugar in spring and autumn, on bright cold mornings, and in the afternoon after a day of sunshine. A frosty sunny morning in October is a higher-risk turnout than a warm wet night in July.
The signs, in order of subtlety
The stance is the classic: weight rocked back onto the heels, front feet pushed out in front, hind legs tucked underneath to take the load. A horse standing like that is in a lot of pain.
Reluctance to walk, and a pottery, short, tender gait that is markedly worse turning in a tight circle or on hard stony ground.
Lying down more than usual, and being reluctant to get up — which in a horse is significant on its own.
Heat in the hoof wall, and a bounding digital pulse. Learning to feel that pulse at the back of the fetlock when your horse is well is one of the more useful things an owner can do, because the change is obvious once you know the normal.
Shifting weight from one front foot to the other while standing.
Earlier and subtler: a slight shortening of stride, a horse that has become footy on gravel, or growth rings on the hoof wall that are wider at the heel than the toe — evidence of previous low-grade episodes nobody noticed. A widening white line and a flattening sole point the same way.
Any of the above is a vet call the same day. This is one of the genuine emergencies in horse keeping, and the outcome depends heavily on how early it is treated.
What to do first, and what to do afterwards
Get the horse off grass immediately, and do not walk it any further than necessary. Movement on damaged laminae causes more damage, so bring the stable to the horse if the horse is in a field and cannot easily reach a stable.
Deep bedding, right to the door, shavings or sand — something that supports the whole foot and lets the horse find a position that hurts less.
Call the vet. Pain relief, usually an anti-inflammatory, and radiographs to see where the pedal bone is: that image is what the farrier's plan is built on, and taking it early gives a baseline to compare against.
Do not starve the horse. It is a common instinct and it causes hyperlipaemia, which is its own emergency, particularly in ponies and donkeys. Soaked hay at around one and a half per cent of bodyweight, weighed, is the usual starting point.
No hard feed, no treats, no carrots and no apples.
Then the farrier, working with the radiographs, for support and a plan to reduce the pull on the bone.
Afterwards, the long game: blood test for EMS and PPID, because treating the cause is what prevents the next episode. A grazing muzzle or a track system rather than a bare paddock. Hay soaked or analysed for sugar content. Weight off, slowly. Exercise once the feet are sound, which is the most effective treatment there is for insulin dysregulation. And a weight tape and a photograph every month, because a horse creeping up two kilos a week is invisible day to day and obvious in pictures taken eight weeks apart.