Anyone who has cared for a horse or pony with laminitis knows it can be an uphill struggle to keep the condition at bay.
Yet obesity and overfeeding of energy remain the most common causes of laminitis in the UK and the developed world. The brutal fact is that laminitis can strike down any horse, regardless of breed or type, and horses must be managed in accordance with their breed, age, size and workload. There are two issues to consider:
- Feeding to avoid laminitis
- Feeding a horse with laminitis
Depending on the cause of laminitis, the two approaches to handling the condition may differ significantly.
1. Feeding to avoid laminitis
Feeding excess energy will result in weight gain, putting unnecessary strain on the heart, lungs and joints. Juvenile obesity in young horses contributes to the development of arthritis in many joints in all limbs (known as multicentric degenerative joint disease).
Sources of energy
Energy-rich feeds include cereals (for example, wheat, barley, oats and maize), legumes (such as peas and beans) and grass.
Cereals and legumes contain high concentrations of energy-rich starch, a polysaccharide, which is made up of long chains of glucose molecules. Starch is digested in the small intestine. However, if excess starch is fed, it ‘overflows’ into the hind gut, where it disturbs the normal bacterial population. This can result in acidic droppings, scouring and laminitis.
Grass contains different types of energy source: fructans and simple sugars. The horse cannot digest the fructan chains in the small intestine, so they enter the hind gut for digestion by bacteria. Excessive fructan in one meal causes the same devastating changes in the hind gut bacterial population as an excess of starch, and results in bloat (tympanic colic), scouring and laminitis.
Therefore, to avoid laminitis of dietary origin, you are advised not to feed cereals or feeds containing cereals in other words, straights and coarse mixes. If you use feed balancers, check the list of ingredients. If you do wish to use feeds containing cereals, you should introduce them gradually to the horse over a period of at least one week, and offer them in small quantities.
Similarly, it is vital that the horse is not allowed to gain access to excessive amounts of grass, particularly after rain or when it is growing in the spring or autumn. Researchers have induced laminitis in horses weighing 400kg by administering just 2.5kg of fructan or 5kg of wheat starch by mouth. As grass can contain 50 per cent fructan on a dry matter basis, and ponies can eat up to 15kg of grass a day, it is easy to see how a pony can ingest a dose of fructan sufficient to cause laminitis.
Introduction to a new pasture should initially be for a limited time about half an hour. The time at pasture should only be increased when there has been a reduction in all other feed sources and the growing season is ending.
So, what can you feed your horse? The answer is a low-calorie, high-fibre diet. The molecular structure of the polysaccharide determines whether it can be hydrolysed (reacting with water), in the small intestine or fermented (reacting with enzymes) in the large intestine. Polysaccharides constructed with linkages tend to be hydrolysable, whereas those without linkages are fermentable. (The type of linkage refers to the shape of the joined molecules; linkages do not allow attachment of the horse’s digestive enzymes). Some fibre molecules are more rapidly fermented in the large intestine than others.
Excess of either hydrolysable fibre (such as the starch found in cereals), or rapidly fermentable fibre, (for example, some fructans in grass), can result in laminitis. So we need to watch the type of fibre we are feeding, as well as the amount. When it comes to fibre in the form of grass, we need to consider the stage in the growing season. As the plant matures. the amount of lignin increases. Lignin is indigestible, so a relatively larger amount of lignified (and therefore later) grass can be eaten without an increased risk of laminitis.
2. Feeding a horse with laminitis
Laminitis is an emergency condition that requires box rest and prompt attention from a vet. He or she should fit frog supports and recommend appropriate medication.
It is essential that the animal is not starved to attain a weight reduction. A sudden reduction in calorie intake can induce another metabolic disaster, that of hyperlipaemia. In this case, the horse tries to mobilise its own fat reserves as an energy source without ingesting sufficient glucose sources.
For underweight animals, the goal is to slowly increase the animal’s bodyweight without upsetting the hind gut. Laminitis in a thin horse is unlikely to be of dietary origin. it is more likely that the horse is suffering from chronic liver or kidney disease or Cushing’s disease. ln such cases, restricting the calorie supply will lead to greater weight loss, possibly with the horse having to break down its own muscle to provide its daily energy, putting strain on the liver and kidneys.
It is essential to provide the animal with all the essential micronutrients it needs to build and repair tissue, principally horn.
All laminitis cases tend to have toxins circulating in their bloodstream from the gut, uterus or another infected area. A supplement that provides choline, inositol, methionine and cobalt is recommended to help the liver. if the horse’s kidneys are diseased, he may not be able to eliminate the toxins.
Don’t fatten up
An overweight horse is predisposed to other undesirable conditions, apart from laminitis.
Insulin resistance is when the horse does not respond normally to the insulin hormone produced by his pancreas gland. insulin lowers blood glucose and allows glucose to enter body cells. Insulin resistance results in an abnormally high blood glucose concentration and the appearance of glucose in the urine.
Peripheral Bushing’s disease is a common condition in which the horse produces cortisol, a steroid hormone, not only from the adrenal gland, but also from peripheral tissues. Cortisol exacerbates insulin resistance, starving vital cells of glucose. Cortisol also potentiates the action of the hormones adrenaline and serotonin – this reduces the blood flow to vital tissues. Cortisol may also increase the ‘leakiness’ of the gut lining, allowing toxins into the bloodstream.
Diabetes mellitus, which is also seen in humans, is a shortage in insulin secretion.
The big variable in the horse’s diet during the grazing season is grass itself. it is almost impossible to estimate how much carbohydrate your grazing contains, but there is a general rule you can follow:
- ln plants, the energy from sunlight converts carbon dioxide and water to sugars this process is known as photosynthesis. When the rate of sugar production by photosynthesis exceeds the rate of growth and seed production, grass accumulates sugars in the form of fructan. Therefore, on a sunny but cold day, which allows the plant to photosynthesise but prevents it growing, there is likely to be a higher level of fructan in the plant than on a sunny, warm day. This is one of the reasons why people have become wary of unrestricted turnout of horses onto frosted paddocks.
- The peak fructan content of ryegrass is from May to September and from midday to early afternoon, During these times, it is essential to ration the horse by measures such as strip grazing, limited turnout, use of grazing muzzles or a ‘dieting paddock’.
It is also vital to keep a check on the year-round condition of your horse. Keep the following pointers in mind:
- You should not be able to see the horse’s ribs, but you should feel them easily when you run your hand along his side.
- The horse should not carry fat deposits on the crest, over the ribs and loins, at the tail head or around the udder or sheath.