Grass Laminitis
What is laminitis?
Laminitis is the inflammation of the laminae, or the lining inside the hoof wall. The laminae is a complex structure, which plays an important role in the general health and circulation of the horse. It is rich in highly oxygenated blood, which helps it do its job, but makes it susceptible to infection and inflammation. It is this inflammation that causes the pain of laminitis, and which can lead to founder, which is an often irreversible and serious condition affecting the pedal bone in the hoof. For this reason, signs of laminitis need veterinary attention immediately.

What causes it?
Laminitis has many possible causes. Most can be prevented or at least easily recognized - overfeeding high energy grains, serious injury or illness, a genetic predisposition to the condition (usually insulin resistance), or some medications - even riding on hard ground can create conditions favorable for laminitis. Usually there are a combination of causes, or a build up of conditions that makes a horse prone to laminitis. However, one of the most common causes, and one which can be dangerously hard to predict, is laminitis caused by grass.

What makes grass dangerous?
Horses evolved to forage mainly on grasses, so it seems surprising that grass and grazing could be dangerous for your horse. However, there are some particular features of grass that can make it harmful. The nutrient content of grass does not remain stable throughout the year, or even over the course of a day. Grass growth responds to sunlight, and at certain times the leaves of grass produce high levels of a particular nutrient, fructans, that can cause problems for horses. Fructans are essentially a sugar, and are virtually indigestible by most mammals. In horses, as fructans enter the lower digestive tract, they create mineral and microbial imbalances that upset the natural activity of the gut, particularly the release of insulin and the balance of electrolytes. It is this that causes a metabolic response, an overreaction of the metabolism to the presence of an indigestible sugar - that can trigger laminitis.

Grass is higher in fructans at certain stages in its life cycle, at different parts of the grass leaf, and even at different times of the day. High fructan levels occur during the height of growth. This means that grasses are richer in dangerous fructans in spring, when the growing season starts, and autumn, when wet weather returns after the summer. Similarly, grass growth slows down overnight, so grasses contain lower fructan levels in the middle of the night and the early morning, peaking as the grass is exposed to sunlight during the day. Grass under stress can overproduce fructans, such as grass that is exposed to frost or which is heavily grazed and has adapted with more rapid growth. In fact, very long grass may actually be safer, because toward the end of a tall leaf growth is slowing and fructans are diminished. Some fertilizers, especially those designed for grazing for dairy cattle, can accelerate growth and consequently increase fructan levels in grass. Some types of grass, such as rye and clover, are naturally high in fructans as well. So, there are a lot of things to think about when determining if your grass is safe for your horse.

Are some horses more susceptible than others?
The short answer is yes. Some horses have a genetic predisposition to insulin sensitivity; these horses are unfortunately more likely to develop laminitis. Horses with chronic conditions such as ulcers or Cushing’s Disease are at risk, as are horses that are obese or prone to colic. Horses that have had laminitis in the past, have had a serious injury, or are obese are typically more likely to experience laminitis. Ponies have a reputation for being particularly laminitic; this is mainly due to their being more vulnerable to changes in the nutrient content of their food, simply because they are smaller, although some breeds - Shetlands in particular - do appear to have a genetic predisposition to laminitis as well. Some signs that your horse may be hiding insulin resistance, and so be more prone to laminitis, are fatty deposits on the crest, behind the shoulders, or at the dock, and routinely puffy eyes.

Symptoms
The symptoms of laminitis can be subtle, so it’s important to get to know how your horse looks and behaves when he is healthy, so you can spot any changes quickly. A horse with laminitis will likely be visibly uncomfortable, as the inflammation in the hoof can be very painful. However, since horses are often sore in both front feet, actual lameness may be difficult to spot. The Hooves of a laminitic horse will likely feel hot to the touch, and the horse usually will have a fever. Inflammation in the lower legs, especially the front, is common. A horse with severe laminitis will attempt to ease the pain in its front feet by leaning back, or standing with its front feet on higher ground than the back feet. If you see any of these symptoms, or are at all concerned that your horse may be developing laminitis, contact your vet immediately.

Treatment
Treatment for laminitis will be managed by your vet. It will probably involve a course of anti-inflammatories, and icing your horse's feet and lower leg. Your vet may prescribe probiotics or electrolytes to help restore the correct microbial balance in the gut. The horse will be assigned to stall rest. Over time, as your horse recovers, you should work with your farrier to minimize and potential damage to your horse’s feet. Your farrier may recommend heart bar shoes to support the pedal bone that is affected by laminitis. In some cases shoes with pour-in pads, regular pads, or hospital plates might be used.

These treatments address the symptoms of laminitis, but you will also need to identify and remove the cause, and your vet will talk you through the likely explanations so you can determine how to address them. You will need to remove any rye or alfalfa hay from your horse’s diet, and restrict him to simple meadow or timothy hay. You might need to soak the hay for several hours before feeding; this removes many of the carbohydrates from the hay - but it also removes much of the nutritional value as well. Your vet will help you manage your horse’s diet with appropriate supplements. Some commercial feed and forage is designed specifically for horses that have or have had laminitis; you might find you need to switch your horse to one of these alternative feeds - maybe for the rest of its life.

Prevention
Since laminitis has many possible causes, there are many preventive strategies to apply. Simple things like feeding a diet appropriate in carbohydrates for your horse’s specific needs, making changes to his diet gradually, avoiding riding on hard ground, and limiting or avoiding high energy legume hays like alfalfa are a start. To prevent grass laminitis, you need to look carefully at your pasture management and when, what, and how much grass your horse eats.

Even restricting your horse to just a few hours of grazing per day may not be enough. Horses can eat a remarkable amount in a short time - think about how quickly your horses finishes the hay that you thought would last him all night! Similarly, allowing your horse to graze for two hours in the afternoon will expose him to more risk than two hours of grazing at night or in the early morning. If your horse or pony is at risk of laminitis because of any compound conditions or other causes, you should consider keeping him in a dry (sand or gravel) paddock and offering plenty of timothy hay instead, so your horse does not have any access to grass.

Avoid treating your pastures with powerful fertilizers. You may dream of acres of lush green grass for your horse, but it isn't necessarily the best for him. Keep your pastures free of clover, no matter how pretty it is or how much your horse loves it, and don't over-mow long grass. Sharing pasture with sheep is an excellent preventative measure for laminitis- sheep generally pull the shorter, fructan-rich shoots of grass, leaving the longer, safer leaves for your horses - not to mention sharing with sheep can help to keep down parasites as well.

Be aware of the conditions your horse is grazing under. Avoid allowing your horse to graze soon after a frost, after a period of heavy rain (when grass growth is stimulated), and for long hours during the day. In many warm climates, horses graze overnight and are brought in during the day - this helps to minimize the risk of grass laminitis, and also protects the horses from heat, sunburn, and flies.

Feed low energy, low carb grains and dry hays - not alfalfa or other legumes. Some feeds are specifically designed for horses that need laminitis prevention or that have had laminitis before, and particularly avoid feeds with added molasses which is very high in sugars. Never starve a horse - there are plenty of high-fiber, low-carbohydrate options available, and starving a horse can also trigger dangerous imbalances in the gut. Do not allow your horse to become obese; manage all of the feed intake - including pasture - according to your horse’s size, breeding, natural tendency to gain or lose weight, and most of all the amount of work he does to keep him at a healthy weight. Most of all, when your horse spends all or even part of his day with access to grazing, keep a close eye on him and watch for any early signs of trouble. Immediate attention can mean the difference between a speedy recovery and a long term rehabilitation, or worse.

Back