Laminitis is the inflammation of the sensitive laminae, which support the pedal bone or foot of the horse. The foot is suspended within the laminae, which are a web like structure made up of membrane. Inflammation is swelling that is accompanied by heat and pain.
There is an interruption of the flow of blood to the laminae, with the blood flow being directed into the veins and back up the leg instead of to the laminar corium of the foot.
Blood is trapped within the foot and the laminae are deprived of oxygen and nutrients and this causes pain. Pain also results when blood flow is resumed. The greater the reduction in the supply of blood and the longer that this occurs, the greater the damage to the foot.
Laminitis is defined according to the degree of the laminitis:
FOUNDER The laminae first stretch and then separate. This causes the separation between the bone and the hoof. The pedal bone rotates downwards and descends towards the sole, with the sole becoming flattened or convex. The (circumflex) artery and associated blood vessels become trapped between the pedal bone and the sole resulting in haemorrhage. In worst case scenarios; the pedal bone pierces the sole and this is a solar prolapse.
SINKERS If the blood flow is interrupted to the entire laminar corium, the pedal bone becomes detached from the hoof and is loose within the foot and the pedal bone rests on the sole.
- A change in normal behavior indicates that the animal is unwell.
- Be familiar with the digital pulse of the individual.
- Be familiar with the contours of the coronary band, which will aid an appreciation of the characteristic depression of founder.
- The severity of laminitis varies: slight lameness at walk or trot, but can affect a single limb, though more often a forelimb. All limbs may be affected.
- The horse may be down, sweating and blowing.
- Laminitis and founder cases tend to walk on their heels, sinker cases slap their feet down in a flat-footed way.
- There is a characteristic stance of acute laminitic animals: That is they stand with their hindquarters underneath them and their front legs extended in front of them resting on their heels. They may rock from foot to foot.
- Growth rings are wider at the heal converging towards the toe.
- X-rays of the feet will show rotation of the pedal bone.
- In white footed animals that have foundered, blood from the coronary corium can be seen in the wall as a red ring and bruising on the sole about 6 weeks after foundering.
- Call a horse vet.
- Stable the horse on a deep bed. If the animal is unable to walk, or if the stable is some distance, a trailer should be used to transport the horse.
- Fit frog supports; A pad can be made from carpet, plastic, rubber, leather or use a tail/leg bandage, within the margin of the frog.
- If unable to walk, wait for the vet and do not allow it to eat.
- The vet will give anti inflammatories and painkillers (phenylbutazone).
- A laxative feed may be recommended in order to clear the digestive system as quickly as possible of the offending nutrients.
- Movement aids circulation, but care must be exercised because under the effect of painkillers the horse may be induced to move more than it should, thereby aggravating the laminitis.
- Removal of the entire wall of the hoof from the coronary band downwards may be advised.
- Heartbar shoes fitted to chronic laminitic cases may be useful.
- It may take a year or more after the onset, diagnosis and treatment of laminitis (depending upon severity) before the animal can resume work.
The animals most likely to be disposed to laminitis are small native ponies, however all horses may suffer from the disease.
The latest research suggests that it is specifically the imbalance of fructans (a polysaccharide) and argenine (essential amino acid) in grass that is the cause in grass kept ponies or horses.
Stressed grass, e.g. starvation paddocks, lush spring and autumn grass and frosty grass on winter mornings tends to have high levels of fructans.
It is therefor suggested that horses or ponies predisposed to laminitis should not be turned out in these conditions.
Obesity, overeating and insufficient work are the most common cause of the disease.
The horse/pony should be maintained at the correct weight:
- Regular use of a weight tape to monitor weight.
- Restrict access to pasture
- Ponies can be muzzled
- Grow a sward (mixture of grasses) that are relatively low in nutrients.
- If stabled then a balanced diet of hay, alfalfa and a supplement to provide protein and micronutrients is required. (No cereals!).
- Fat animals should be dieted and not starved. A too rapid reduction of weight can cause hypolipaemia
Other causes are:
* Bad/irregular trimming
* Drug related
* Pituitary tumour
The contributory factors that may cause laminitis should be understood and measures to prevent the disease should be undertaken: refer to the Discussion.
Some animals are more susceptible than others and there are a number of nutraceuticals and herbal remedies that can be useful in the treatment and the prevention of laminitis. Dependent upon the cause of the laminitis these include MSM, garlic, ginseng, licorice, cats claw, valerian and cloves.