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Laminitis is a complicated and debilitating disease which is becoming all too common among equines. There seem to be many pre disposing factors including Equine Metabolic Syndome, an overload of high starch feeds, chronic obesity and the consumption of grass containing high levels of Water Soluble Carbohydrates (WSC) which include fructan.
Water Soluble Carbohydrates (simple sugars and fructan) are the building blocks of plant growth and build up in high concentrations during rapid photosynthesis with either low water availability or cold temeratures as the grass cannot use the sugars for growth. Horses do not have the enzymes needed to digest fructans in the small intestine, so they pass into the hindgut unchanged. There, they are rapidly fermented releasing large amounts of lactic acid, which makes the gut contents more acidic and disturbs the balance of bacteria and micro-organisms.
This change in the environment within the large intestine leads to the accumulation of various factors, which may be responsible for triggering laminitis. The overgrowth of organisms such as Streptococcus bovis leads to the release of MMP activators; while those bacteria that cannot survive the acidic conditions release endotoxins. The high lactic acid concentration damages the lining of the intestine, making it easier for these toxins to be absorbed.
The fructan content of the pasture is affected by a number of factors. Fructans are found in significantly greater amounts in the stem than in the leaves. They are present in highest concentration at times of restricted growth but continued photosynthesis, such as during a drought. The amount of fructan present in the grass also varies during the day. Generally there is less at night and early in the morning. Certain grasses, such as timothy have larger fructan molecules. These may be broken down more slowly in the hindgut and may therefore be safer than other grasses that contain smaller molecules. Levels of 14-20% fructan in fresh grass are not uncommon. Haylage is likely to contain less fructan than grass because it has already started to ferment. Hay is likely to have levels between those of grass and haylage.
So, to reduce the risk of fructan-induced laminitis, suggested measures that could be taken include:
- Choose pasture that is regularly grazed or cut (the grass stems tend to have high fructan content) and contains species such as timothy that produce low levels of fructans.
- Turn horses onto pasture late at night and bring them in before mid-morning, so they are grazing when the fructan content is lowest.
- Restrict grazing in spring and autumn when the fructan and water soluble carbohydrate levels are high.
- Don't use stubble grazing (i.e. after it has been cut for hay - because the stems will have a high fructan content.
- Don't turn horses onto pasture that has been exposed to frost and bright sunlight. (The sunlight produces energy within the grass, which the grass cannot use for growth because of the cold temperature, and so it is stored as fructan).
The WSC fraction of forage should be below 10% in order to be safe for laminitics.
When we look at conserved forage (hay/haylage) as a suitable feed for laminitics, it is important to look at the WSC content without the fructan fraction as the levels of fructan in conserved forage have not been found to be high enough to cause a problem with laminitics.
We call this subset Ethanol Soluble Carbohydrate (ESC) and these simple sugars are digested in the foregut and raise insulin levels. Too much can lead to laminitis due to raised blood insulin. When grass is cut and dried to make hay, the sugars will continue to metabolise and therefore decrease in concentration until the moisture levels are below 40%. When hay is dried quickly and is made from high sugar grasses such as Ryegrass, the ESC content may not be below 10%. Soaking can reduce it but due to the varying quality of hay and the range in time spent soaking this is not a reliable method to use. Additionally, much of the calories and vitamins can be leached out leaving a very nutritionally poor forage, not to mention heavy! However, when grass in baled slightly damp and wrapped in an air tight environment, bacteria naturally present in the grass will utilise the majority of WSC present (using it as an energy source during replication), producing Volatile Fatty Acids (VFA). It is these VFA's that gives haylage it's wonderful smell! Well made haylage that has undergone efficient fermentation should have an ESC content of below 10%, meaning it is a much safer option to feed to laminitics.
Forageplus, who carry out our forage analysis, takes things one step further when analysing forage and it's suitability for laminitics by combining the ESC content with the starch figure. The starch content of hay cannot be reduced by soaking and more often than not, an in depth analysis of hay is not available, so by feeding haylage with known values, you can be sure that the forage is safe. Please see our analysis page for the combined sugar and starch values of our haylage.
Below you can see 2 articles, one written by Clare MacLeod MSc RNutr the other by Dr Peter M Bedding, both of which illustrate a very in depth knowledge of Laminitis.
Clare MacLeod MSc RNutr is an independent Registered Equine Nutritionist with expertise in equine health and fitness. She holds a first class BSc honours degree in equine science and has also achieved a distinction in her Masters degree (MSc) in human and equine sports science.
Laminitis and low sugar diets
Clare Macleod Msc RNtr.
Laminitis is a debilitating disease that is sadly all too common. Once a horse or pony has suffered from a bout, they will be prone to the disease in the future so they must be managed very carefully. Feed-induced laminitis is linked to either obesity, chronic intake of grass or short term excessive intake of starchy feeds or rich grass. The pathway of how body fat and dietary factors actually induce laminitis is not yet understood, and more research is necessary to elucidate the mechanisms.
Regardless of the cause of the laminitis, most affected horses or ponies will have their grass intake restricted as part of their management. Replacement forage should be chosen carefully because some hays contain high levels of the danger constituents: water soluble carbohydrates (sugar and fructan). Forage for laminitics should contain less than 10% water soluble carbohydrates and this should be checked by analysis before feeding. Soaking hay will reduce WSC, but even a 12 hour soak will not guarantee that the levels are reduced to less than 10%. Therefore just soaking hay is not a guarantee of a safe forage for laminitics.
Devon Haylage’s Timothy Haylage has very low sugar levels so is safe for laminitics, providing it is fed to maintain a healthy bodyweight. Along with haylage, laminitics should be fed a good quality multi-vitamin and mineral supplement to balance micronutrient intake and encourage healing in the hooves.
Laminitis, causes and effects
Dr Peter. M. Bedding. Nutritional Consultant.
The condition of laminitis has baffled veterinarians for many years and many theories have been put forward as to the cause of this serious disease. Protein, sugars and toxins have all been suggested as causative agents, although protein, as a cause, has now been laid to rest.
However we do know that a change in the hindgut pH towards acidity is without doubt a fundamental springboard to an imbalance of hindgut bacteria flora. This imbalance can be triggered by fructans in grasses and also by other water soluble carbohydrates (WSC’s) in hard feed. These, if undigested, reach the hindgut and sustain the proliferation of lactic acid producing bacteria, which changes the fermentation process and causes a drop in pH. This increase in acidity will negatively effect the permeability of the hindgut wall. Endotoxins, produced by the breakdown of dead bacteria, will then be able to penetrate the weakened gut wall and enter the bloodstream.
These Endotoxins, in a number of studies, have been shown to effect the increased production of enzymes in the hoof. The enzymes concerned are called matrix metalloproteinases (MMP’s). They influence the attachment of the laminae, giving rise to inflammatory processes in the hoof.
Another result of a disturbed fermentation process in the hindgut is the production of amines that are formed in the breakdown of proteins to amino acids. A number of these amines are actively vasoconstrictive and restrict the bloodflow through the blood vessels to the hoof. The overloading of the hindgut with an overflow of undigested WSC’s in the diet can cause serious effects of amine production and hemodynamic disturbances. It has been reported that, even during grazing, an increase of the amine content in blood plasma has been measured to such levels that are considered to be vasoconstrictive and could cause reduced bloodflow to the hoof, contributing to potential laminitic conditions.
Homocysteine, an amino acid, is also attributed to having a vasoconstrictive effect and has been researched in humans to be a possible cause of detrimental cardiac conditions. This is not proven in equines, but could potentially also have an adverse effect on bloodflow to hooves.
The production of B vitamins in the hindgut fermentation process are necessary for the synthesis of enzymes that break down homocysteine. A disturbance in the fermentation process could reduce B vitamin production resulting in a reduction of these important vitamins.
Inflammation in the hoof can furthermore be increased by pro-inflammatory enzymes or ingredients in the diet (technical metabolic description – Cyclooxygenase is released and catalyses the arachidonic acid released from the cell membrane into prostaglandins creating an inflammatory process). Nowadays it has become popular with feed manufacturers to add or recommend the addition of corn oil or other vegetable oils to increase the “slow energy” levels of feedstuffs. These oils are high in omega 6, which can be pro-inflammatory, so providing continuous large quantities or vegetable oil, on a daily basis, can cause muscle inflammation. The addition of anti-inflammatory omega 3 (the ratio of omega 6:omega 3 is suggested as 4.5:1) will help to prevent a chronic condition of inflammation. It is therefore not unreasonable to expect the similar situation in laminitic conditions. Inflammation could be triggered by excesses of Omega 6 oils in the diet.
Finally, because of the increased permeability of the gut wall, caused by the decrease in pH, it is possible that invasive antagonists will gain access to cell tissues. These antagonists could come from pathogens and mycotoxins found in feedstuffs and forage, thus a weakened gut membrane would make the horse or pony very vulnerable. The effects of poor feeding management and lack of specific nutritional support could increase the likelihood of toxins reaching bloodstream so leaving the animal prone to conditions like laminitis.