Laminitis is quite unlike any other equine disease. Laminitis is a complex cascade of events that causes the soft tissues (laminae) within the hoof to swell, weaken and die. This can all occur before any symptoms are apparent and once the process has started it is extremely difficult to stop. In severe cases it is likely to leave behind a permanent reminder founder: which is an internal deformity of the hoof occurring when the supporting laminae loosens it grip and allows the coffin bone to rotate downwards (Barakat 2004).
Laminitis can occur due to many reasons such as chronic obesity, Cushings disease, gorging on high starch feeds (grains and pasture), weight bearing, concussion, hormonal, cold weather, stress, drug inducement and toxaemia. Laminitis can be a multifactorial problem that in most cases is very hard to predict. The main cause of laminitis in horses in Australia and in most parts of the developed world is Obesity Dependant Laminitis (ODL). The media has made a significant push on the unfortunate rate of human obesity but companion animals such as horses, dogs and cats are also suffering from alarming rates of obesity. In fact we are often, loving our four legged friends to death.
Obese or overweight animals are putting unnecessary strain on their heart, lung and joints. Incidences of ODL, diabetes mellitis and insulin resistance are greatly increased when animals are chronically overweight (Eustace 2003).
Horses suffering from ODL generally produce more cortisol, a steroid hormone, which like adrenaline suppresses insulin activity so much that it tends to starve vital cells of glucose. Cortisol also accentuates the action of adrenaline and serotonin. Both hormones cause blood vessels to constrict and reduce blood flow to vital organs and to the extremities of the body such as the hoof, resulting in a greatly increased risk of laminitis.
Insulin is a hormone that is produced and secreted by the pancreas. Insulin is released in response to an increase in glucose levels in the blood following a meal containing sugars or starches. Insulin then stimulates cells in the body to take up this circulating glucose from the blood. Once in the cells, glucose is used for energy or it is converted for storage as glycogen or fat. Horses suffering from insulin resistance show an eventual breakdown of this system. As the body becomes less sensitive to insulin the body simply produces more insulin until the insulin producing cells are exhausted. This is then commonly termed as diabeties. These horses would generally be considered “good doers” and are at a greater risk of suffering from ODL.
Too much sugar is bad for horses too!
Feeds rich in carbohydrate are quite energy dense that means a horse can easily consume more carbohydrates than its body can handle. Carbohydrates or excess of have been found to play an important role in the severity and risk of a case of laminitis. The type of sugar also has a lot to do with the risk of laminitis. Predominately cereal grains such as oats, barley, maize and wheat as well as short “lush” pasture are high starch (carbohydrates). Starches are basically a group of long chains of glucose molecules, which are called polysaccharides. Starch can be digested in the small intestine by the bodies own enzymes. If too much starch is fed it overflows into the large intestine where it overloads the bacteria population causing a change which can have a detrimental affect on the horse such as acidic faeces, scouring, laminitis and behavioural problems (Eustace 2003).
The other type of carbohydrate that has received a lot of attention lately is fructan. Fructans are fructose and glucose joined together into various lengths. Fructans of short length are called oligosaccharides. Horses do not have the enzymes to break fructans down so need hindgut bacteria population to do it. Fructans are extremely fermentable and if large meals of fructans are consumed it could quickly cause bloat, colic, scouring and laminitis.
Fructan levels can change throughout the day and are at there highest in the late afternoon especially in mild climates and also in mornings after a frost. As a result monitor conditions or reduce turnout time on pasture during spring, autumn and after rain during mild conditions as fructan levels can fluctuate dramatically (Meszoly 2005).
Feeding the Laminitic Horse
We must carefully manage pasture turnout and forage and grain intake in horses and ponies that are at risk for developing laminitis or are currently affected. We also understand that horses suffering from insulin resistance (IR) and/or Cushings as well as horses and ponies with the ‘‘easy keeper,’’ phenotype that are often overweight or obese, and may be persistently hyperinsulinemic should also be managed carefully with regard to their carbohydrate intake.
The following points summarize current advice regarding strategies for avoiding high NSC intakes by horses and ponies at risk for pasture laminitis:
- Animals predisposed to laminitis should be denied access to grass pastures, particularly during the spring. At other times of the year, limit the amount of turnout time each day (e.g., 1–3 hours) and turn animals out late at night (after 8:00pm) or early in the morning, removing them from pasture by midmorning at the latest (before 10:00am, because NSC levels are likely to be at their lowest late at night through early morning).
- Alternatively, limit the size of the available pasture by use of temporary fencing to create small paddocks or use a grazing muzzle.
- Do not turn horses out onto pasture that has been exposed to low temperatures in conjunction with bright sunlight, such as occurs in the autumn after a flush of growth or on bright cool winter days, because cold temperatures reduce grass growth, resulting in the accumulation of NSC.
- Many people simply put the horse on a “starvation ration” and severely limit the horses’ diet of all nutrients. This is one of the worst things you could do as horses still require maintenance energy to function as well as essential amino acids, vitamins and minerals to assist in repairing damage caused by laminitis.
- Horses at maintenance require approximately 2.0% of their body weight as forage or forage plus supplement to meet daily nutrient requirements. Sweet feeds should not be fed and the feeding of other ‘‘treats,’’ such as carrots and apples, should be discouraged. Lucerne hay or other legumes, such as clover, on average, have lower NSC content when compared with grass hay but have considerably higher calorie/energy content.
HYGAIN® Feeds also offers a forage-based low energy feed complete with vitamins and minerals: HYGAIN® ZERO®. HYGAIN® ZERO® is a unique Low Carb – Low GI formula for all horses, with less than 1.5% starch, less than 5.5% non structural carbohydrates (NSC) and absolutely no grain or grain by-products. HYGAIN® ZERO® was developed to support the specialised dietary requirements of horses and ponies with conditions such as Obesity, Insulin Resistance, Laminitis, Cushings, Tying-Up or Grain Intolerance. The unique Low Carb – Low GI profile however is suitable for any equine requiring a low sugar and starch diet.