The grass is certainly growing with the mixture of sunshine and showers we have had the last few weeks. For those of us with horses this means being vigilant for the signs of over indulgence and in particular, a well known and feared condition called laminitis. This week and next we look at the contributory causes of laminitis alongside how to recognise, diagnose and treat the condition.
Although the name laminitis may suggest an inflammatory condition, it is actually a vascular (blood vessel) disorder of the extremities, usually caused by a generalised problem. The bone at the bottom of the foot, the pedal bone, is suspended in the hoof by a sensitive tissue known as laminae. When the blood supply to the foot and therefore the laminae becomes compromised (redirected away from the hoof,) painful destruction which sometimes includes tearing of the laminae can occur. As a result of this loss of support tissue the pedal bone potentially may rotate or sink/drop in the hoof capsule.
The vascular changes responsible for this damage are brought about by the action of chemicals that act on the blood vessels called catecholamines. These chemicals are released in response to a number of different situations including; grain overload, drinking large amounts of cold water, high dose or long term steroid treatment, stress, generalised infections, Cushing’s disease and obesity and also the most frequent cause, the consumption of lush grass. When large amounts of lush grass are eaten, the sugars in the grass cause the release of these catecholamines resulting in the vascular changes responsible for the damage. Obesity itself especially in pony breeds, can lead to a condition called insulin resistance which will also increase the blood vessel sensitivity to these chemicals. All equines, but in particular native ponies, have evolved to store a lot of fat internally during the summer so that they can survive on very little food during the winter. Unfortunately the way many of us keep our horses means they are stabled in during the winter, fed high carbohydrate diets whilst often barely being exercised or turned out. This means that there is less opportunity to use up the fat stores before the following summer making them prone to obesity and laminitis.
In a pony affected with laminitis you would typically expect to see them rocked back onto the heels of their feet, reluctant to move with some even laying down and refusing to get up. If they will move at all it is often with a characteristic “heel before toe” gait. Commonly it is either the front feet only or all four feet that are affected and the pain in the feet maybe severe enough to cause them to sweat. By the time these signs are being seen the condition may have been going on for as long as 36-48hrs. Irreversible, life threatening damage can occur to the structures of the foot in as little as 72hrs from the onset of the vascular changes, so if you suspect your horse or pony has laminitis it is important that appropriate treatment is started as soon as possible so ring your vet immediately.
Next week we will look at how laminitis is diagnosed and treated, alongside what you can do to try and help prevent it.