SCIENCE SUPPLEMENTS – Laminitis: Part 3

This week we continue to look at laminitis and discuss treatment and prevention. To read what laminitis is and what it looks like please click here.

First Aid Treatment

Immediate treatment on the first day that signs of laminitis are noted is vital in improving the overall outcome; your vet should be contacted straight away if signs of laminitis are noticed. Whilst waiting for the vet to arrive the horse should be moved into a stable with a deep bed of shavings right up to the door. The horse may be reluctant to walk if laminitis is severe and it is best not to walk the horse far. If they are out in the middle of the field, the use of the trailer to bring them back to the stable is advised if possible.

First aid treatment consists of intravenous anti-inflammatory medication (e.g. ‘bute’) to reduce the inflammation within the feet and to provide much needed pain relief for the horse. Some very painful horses require additional painkillers such as morphine. Additionally, a long acting sedative called acepromazine is often also given which encourages the horse to lie down and reduce weightbearing on the laminitic feet.

Icing, or ice-cold water bathing, of the lower limbs can be useful in the initial stages of laminitis to reduce inflammation (Fig. 1).

Icing for at least 20 minutes is recommended; basically, the longer, the better. Sole supports can also be applied to the bottom of the foot to provide additional comfort. There are various different sole supports available and using materials such as putty, silicone and styrofoam.

Fig. 1: Icing of the feet can be useful first aid treatment for laminitis.

Ongoing Treatment

Box rest and anti-inflammatory medication (often ‘bute’) need to be continued and the horse’s progress monitored closely. When the laminae are inflamed, they are very fragile. Any movement during this inflamed phase results in tearing of more laminae making box rest absolutely essential.

Once the horse is stabilised, radiographs (x-rays) of the affected feet should be taken to determine if there has been movement of the pedal bone. Any rotation or sinking of the pedal bone is irreversible and reduces the prognosis for return to work. The radiographs can also be used by the farrier to guide corrective trimming of the hoof and for placement of specialist shoes if required.

 

Treatment for laminitis can take a long time often requiring months of box rest and a slow rehabilitation process. Treatment of severe cases is not always possible if the degree of movement of the pedal bone is too severe and therefore preventing laminitis is of paramount importance.

Prevention

Underlying metabolic disorders (equine metabolic syndrome and Cushing’s disease) are associated with 90% of laminitis cases (click here to read more). Controlling these conditions is therefore crucial in preventing laminitis in the majority of horses. Often laminitis does not respond well to treatment until the underlying metabolic disorder is corrected.

Cushing’s disease can be very successfully treated with daily oral medication (pergolide) whilst treatment of equine metabolic syndrome (EMS) involves improving insulin sensitivity by diet and exercise. Resistant cases may require drugs such as metformin or thyroxine to initiate weight loss but most cases can be adequately managed by strict diet and exercise alone.

Obviously, exercising a laminitic horse is not possible which again emphasises the importance of prevention rather than treatment being at the heart of laminitis management.

It is critical to understand that horses with a history of laminitis, EMS or Cushing’s disease need life-long modification of both their diet and daily management because of differences in the way that their bodies respond to the food they eat.

Diet and Management

Pasture turnout

Grazing is risky for many horses with EMS/ Cushing’s disease or a history of laminitis as grass can contain high levels of non-structural carbohydrates (NSC), the sugars and soluble starches. For horses which need to lose weight, pasture turnout should be avoided completely for the initial 6-12 weeks of a weight loss program. Incredibly, horses are capable of eating 60% of their daily food allowance in just three hours if unrestricted and gorging like this will result in severe insulin spikes.

The long-term management of horses at risk of laminitis will always involve restricted grazing. Grazing muzzles can allow some horses and ponies more freedom and permit re-integration into a herd of horses. Grazing muzzles must be used carefully and should not be worn for more than twelve hours. Grass length must not be excessively short or long if using a muzzle as this will prevent the horse from being able to eat anything at all. For advice of how to use a grazing muzzle, follow this link to the National Equine Welfare Council 

High risk grazing periods for laminitics are when the grass is growing quickly (spring and autumn), when the grass is stressed (after frosts, droughts, or when over-grazed), or when grazed on rich pasture. Many horses and ponies are kept on old dairy farms with predominantly ryegrass pasture. Ryegrass is an excellent choice of grass for a dairy cow as it is naturally fast growing and high in energy and protein. Unfortunately, these properties make it highly unsuitable for horses, particularly native ponies predisposed to EMS.

Hay

The only way to truly understand the nutritional value, and therefore safety, of your hay is to send a sample of it for nutritional analysis, or to buy from a supplier who has already done this. The nutritional value of hay will vary dependent on the species of grass used, when it was cut, and the weather conditions when it was cut. It is incorrect to assume meadow grass hay will be low in sugars or that ryegrass hay will be high in sugars. For horses and ponies at risk of laminitis, hay should contain less than 10% NSC.

Hay which is low in NSC is preferable to haylage for laminitics because haylage evokes a greater insulin response when fed, even when it has the same NSC as hay. However, a low sugar haylage (<6% NSC) would still be more suitable for a horse or pony prone to laminitis than a high sugar hay.

Soaking hay is an excellent way of reducing its nutritional value, which will aid weight loss, and reducing the glycaemic response (the rise in blood sugar following feeding). The sugar lost from hay by soaking is very variable and will depend on the species of grass used to make the hay, along with how long it is soaked for, and the temperature of the water. For optimal sugar reduction from hay, it is recommended to soak for nine hours at 16°C; this can often be difficult to ensure when it is done outside! The downside of soaking hay is that it can cause a drastic increase in bacterial populations found in the hay, which can cause respiratory disease. Steaming hay after soaking is an effective way of reducing this bacterial burden. Steaming alone will not result in the same reduction in calorie content.

Equally as important as the calorie content of hay, is the amount of hay which is fed. When discussing feed requirements we tend to refer to dry matter. Dry matter (often seen abbreviated to DM) is the weight of the feed or forage once the water has been extracted from it. Most hays are around 85-90% dry matter. A normal healthy horse will tend to eat around 2-2.5% of its body weight per day in dry matter. For a 500kg horse this would be about 10-12kg dry matter, equivalent to 11.5-14kg of hay ‘as fed’. To encourage a horse to lose weight the calorific content of the food and the amount fed must be reduced. The typical advice for a horse at risk of laminitis which needs to lose weight would be to restrict all grazing, and feed 1.5% body weight dry matter.

Some horses and ponies are very resistant to losing weight. In these cases, the dry matter content may need to be reduced further. Before reducing dry matter below 1.5% bodyweight it is advisable to talk to a vet or a qualified equine nutritionist. Steps to try before doing this would include:

  • Soaking hay for 9 hours
  • Not rugging (to increase energy expenditure keeping warm)
  • Clipping out the belly hair (in winter) to encourage using more energy to keep warm
  • Increasing exercise (if safe to do so; this should only be done if the horse is sound)

Other feed

Additional feed may be needed in order to provide additional quality protein (especially for ponies with Cushing’s disease) or for high risk laminitics which have poor dentition or are skinny. When choosing a feed ensure that total NSC are less than 12%.
Vitamins

A healthy, mature, horse or pony not in work which has unlimited access to good quality pasture would fulfil its requirements for vitamins E, C and beta-carotene (vitamin A precursor) without needing further supplementation. These vitamins however are poorly preserved in forage (hay or haylage), therefore they should be supplemented when pasture access is limited.

Inflammatory conditions such as laminitis, EMS and Cushing’s disease increase requirements for natural antioxidants. Vitamin E and Vitamin C are two of the most important antioxidants for the horse. A healthy horse can make vitamin C in the liver and does not rely heavily on absorption of vitamin C from the diet. However, inflammatory diseases increase requirements and the liver cannot always keep up with demand. Ascorbic acid, the natural form of vitamin C is poorly absorbed by the horse. When additional vitamin C is needed, it should be supplemented as ascorbyl monophosphate which is much better absorbed (bioavailable). The horse cannot make vitamin E, and relies entirely on dietary sources for supply. Natural Vitamin E, as opposed to synthetic forms, is absorbed more efficiently by the digestive tract and would always be the preferred source.
B vitamins are produced by microbes in the horse’s hindgut. However, dietary restriction can influence the microbiome balance, which in turn could reduce the production of B vitamins. B vitamins are essential for energy and metabolism, and therefore it is sensible to supplement them for horses on restricted diets. Another useful way of supporting B vitamin production would be to feed a pre- and probiotic.

Vitamin D is made by the horse when its skin is exposed to sunlight. Vitamin D is essential for calcium absorption, but also for immune function. Given horses and ponies at risk of laminitis tend to spend more time stabled, supplementation is sensible, especially in the winter. It is worth remembering that ponies with Cushing’s disease tend to have very thick long coats, which will further reduce UV exposure of the skin.

Minerals

For a horse which has low levels of exercise, hay fed at 1.5% body weight dry matter will usually provide sufficient calcium, phosphorus, magnesium, potassium and sulphur. Sodium is only found in forage at very low levels, so supplementation is advised for all horses. This can be done by either providing a salt lick (if the horse is not in work, or very light work, and he uses it), or by adding table salt to a meal.

Trace minerals are essential to the diet, but are only required in very small amounts and over supply of trace minerals can be dangerous. With the exception of iron, the amounts of trace minerals found in forage tend to be below what the horse requires, so supplementation is important.

Of particular importance for laminitis-prone horses and ponies are copper and zinc, which have important roles in tissue strength and integrity, especially for the skin and hoof, and selenium, another anti-oxidant. Trace elements should be supplemented in their organic forms where possible as this will increase their absorption, as well as being safer.

Improving hoof growth

After a bout of laminitis, the quality and rate of hoof growth is poor. Providing adequate amounts of trace minerals is a good starting point for improving the quality of hoof growth. Other important ingredients to consider are biotin and methionine. Supplementing biotin at ranges between 20-75mg will support good quality hoof growth. Methionine is an amino acid which contains sulphur, large amounts of which are contained within the hoof wall and needed for hoof growth.

Exercise

Maintaining a consistent exercise regimen is an essential part of a laminitis prevention plan. Keeping horses moving uses stored energy supplies in the muscle and liver cells. Where ridden exercise is not possible lungeing, long reining or hand walking (especially for smaller ponies) is incredibly valuable for both physical and mental stimulation. Swimming provides high intensity, low impact exercise which can encourage fast, safe weight loss.

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