Knowledge
Nutrition Focus
Lorna Edgar – specialist equine nutritionist
Laminitis Nutrition Looking at feeding management
After reading the October article on a method of treatment for laminitis, I was inspired to continue the subject and talk about feeding management for the laminitic; an area I don’t think I have covered before, but something I have come across in polo ponies. Generally, we would not associate polo ponies with laminitis – it is a disease found in ‘fat natives’ after all – how wrong we are! With the high cereal/starch rations that polo ponies receive, rapid changes in diet, possible steroid injections and exercising or playing on hard ground they could still be at risk, but how do we manage and avoid it?
What is Laminitis?
The Cause
Laminitis manifests itself in one or more of the horse’s hooves but nearly always arises as the result of a metabolic upset. Severe illness, mainly from gut disorders, like colic, colitis or salmonella poisoning, result in the release of endotoxins (harmful substances), from the cell walls of dead gut bacteria, which get into the bloodstream and have potent effects on circulation. Retention of the 68
Polo Times, November 2020
commonly in the spring and autumn is the volume of the grass available as the warm damp conditions mean there is simply plenty of grass for the horse to eat. Levels of fructans tend to rise during the day, peaking in the afternoon to early evening, but decline in the early hours of the morning.
Nutritional Causes
Fructan Overload – Too Much Grass The component in grass thought to be responsible for laminitis is fructan which is a water-soluble carbohydrate; the fibre element of grass is insoluble carbohydrate and it is this which is fermented slowly in the hind gut to produce energy. The horse is unable to digest fructan in the stomach and small intestine so it passes into the hind gut which can cope with small amounts of it also being fermented by bacteria. Fermentation results in the production of lactic acid but, if levels of fructan are excessive, the gut becomes more acidic resulting in the death of some of the beneficial gut bacteria. As these bacteria die, they produce the endotoxins, as previously mentioned and are able to pass into the bloodstream more easily, as a result of damage to the gut wall caused by the excessively acidic conditions. Grass needs light to make sugars, which it uses as an energy source to grow, and needs a temperature of 5°C or above to grow. If it’s not warm enough to grow but bright enough to make sugars, the grass stores the extra sugar that it makes as fructan. Cold bright conditions therefore see an increase in the fructan content of the grass which is why laminitis can occur in December and is now not just considered a spring problem. The reason laminitis occurs
Photograph by Polo Times
Laminitis is an acute vascular disease of the hoof causing disruption to the blood supply to the laminae within the hoof, resulting in decreased oxygen delivery to the laminae and reduced removal of metabolic waste. Laminae are the ‘scaffold’ that hold the pedal bone to the hoof wall and work to transfer the load onto the hoof walls so that the sole does not bear weight. This process is hard work for the laminae so they require a large blood supply to bring oxygen and nutrients and to remove waste. Decreased blood supply to the laminae results in their death, which can occur within hours and causes considerable pain. Laminae death decreases the strength of the attachment of the pedal bone to the wall of the hoof which can result in movement of the bone because of the weight on it and the pull of the deep digital flexor tendon. Limited laminae death will cause rotation, but extensive death causes the bone to sink.
placenta after foaling or the long-term use of drugs, like corticosteroids, can lead to similar results. Excessive trauma to the hoof can however also lead to an onset of laminitis, as a result of over working on hard surfaces, poor hoof balance or severe lameness which overloads an unaffected hoof or hooves. By far the most common causes of laminitis seems to be nutrition related and include fructan overload from pasture, which causes the release of amines that disrupt the circulation in the hoof, or starch overload from cereals which reaches the hind gut, upsetting the bacterial population and resulting in the release of endotoxins.
Autumnal & spring grass has a higher fructan content
Starch Overload – Too Much Cereal Just as grass stores sugar as fructans so the grains of cereal plants store it as another soluble carbohydrate, starch. This concentrated source of energy is ideally absorbed in the small intestine but if too much is consumed at one time, it passes on to the hind gut where it can disrupt the bacterial population in a similar way to excess fructan. Undesirable bacteria start to digest the excess starch producing stronger acids than would normally exist in the hind gut. The more acidic environment kills off the beneficial, fibre-digesting bacteria resulting in the release of endotoxins, that enter the circulation through the acid damaged gut wall, and these trigger other chemicals in the www.polotimes.co.uk
