The horses hoof is attached to the underlying pedal bone by interconnecting laminae (leaves). The insensitive laminae line the inside of the hoof wall and abut the soft tissue sensitive laminae which attach to the pedal bone. Laminitis is an inflammation of the sensitive laminae and is an acutely painful condition with potentially disastrous consequences for the horse. It is often a recurrent condition and can disrupt the normal architecture of the foot. In the severest cases the pedal bone may separate from its laminar attachments to the hoof wall and rotate, sinking downwards and ultimately penetrating through the sole of the foot.
Causes.
Inflammation of the laminae subsequent to an inflammatory response related to colic, diarrhoea, retained placenta after foaling or severe pneumonia. The precise mechanism is unclear.
Hormonal. The hormone insulin seems to be involved and laminitis is more common in horses with insulin dysregulation such as those suffering Cushings (PPID) and Equine Metabolic Syndrome.
Supporting leg laminitis. Where weight is borne principally in one leg for example in cases of leg bone fracture, the circulation to the supporting hoof may be affected giving rise to laminitis.
Symptoms include lameness usually in more than one foot and most likely the front feet. The horse adopts a leaning backwards stance to relieve pressure on the front feet. Lameness is worse when walked over hard ground or on turning. Weight is shifted when standing and the feet may feel warm to the touch with an increased digital pulse. Pressure at the point of the frog causes pain. In severe cases the horse may lie down.
Treatment. Laminitis requires emergency veterinary attention. The horse should not be walked and provided with box rest. Along with pain relief, radiography may be performed to assess damage and possible rotation of the pedal bone. The disease can range from very mild with minimal lameness, to very severe requiring euthanasia.
Ongoing management requires veterinary advice and revolves around reducing dietary starch and sugar (NSC) content. The ration should avoid high starch components like grains and cereal based concentrate feeds and rely on forage feeds, principally hay which has been soaked to reduce soluble sugar content. Fibre sources such as non-molassed sugar beet and soy hulls may be useful. Grazing pasture can be problematic due to pasture fructan content at certain times and may need to be restricted. Any underlying triggers such as pneumonia or diarrhoea will need to be addressed initially and hormonal disorders like PPID managed also. Corrective farriery is often required. Management strategies need to be in place permanently to reduce the risk of recurrence.