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Problem of eating excess grass over years...

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01 November 2010, at 12:00am

“MOST cases of laminitis occur when horses are eating grass, said Dr Teresa Hollands, a nutritionist with Dodson & Horrell, speaking at Laminitis Awareness 2010.

“Pasture-associated laminitis accounts for 66% of cases occurring in the UK. But what causes the laminitis?” she asked.

Experiments have shown that giving large meals of starch or fructans can cause laminitis, Dr Hollands said. Large amounts of these carbohydrates suddenly arriving in the horse’s large intestine disrupt the normal population of bacteria in the gut, leading to a cascade of inflammatory and toxic events, but fructans and starch are not responsible for most cases of laminitis.

She said it had been shown that laminitis could be induced by giving a large bolus of fructan (5g-12.5g fructan/kg body weight) – about 3.75kg fructan for a 500kg horse.

But if a 500kg horse ate an amount of grass equivalent to 2.5% of his body weight (12.5kg), his total intake of fructans would be about 1.9kg.

So the full daily intake falls short of the levels that have been shown to cause laminitis, she said.

“We need to move away from thinking about individual components of the diet,” Dr Hollands continued. “In the end it is the calories that are the main risk factor and grass provides more than enough calories for most horses in light work.”

She believed that the slow, insidious eating of excess grass over years was the problem.

Make sure horses do not get too much grass, she said. And make sure they receive adequate proteins, minerals and vitamins by feeding a low calorie commercial feed balancer. The solution is to reduce obesity: ensure nutrition is optimal, and increase exercise.

Other speakers at Laminitis Awareness 2010 were Professor Derek Knottenbelt, Dr John Keen, Dr Cathy McGowan and Dr Nicola Menzies- Gow.

The meetings were run by Dodson & Horrell in association with the London, Liverpool and Edinburgh veterinary schools.

  • Dodson & Horrell has produced a “fact sheet” with the following information:
  1. 66% of laminitis is pasture associated.
  2. Equine Metabolic Syndrome is on the increase and with it associated laminitis.
  3. Until recently researchers thought that fructans found in grass affected the hind gut in a similar manner to an overload of starch detrimentally changing the fermentation in the hind gut. However recent work has shown that the fructans do not reach the hind gut but are fermented in the small intestine of the horse.
  4. Laminitics have three times the levels of free radicals compared to non laminitics.
  5. Horses and ponies with a fat score >3.7 (0-5modified score) are at greater risk of laminitis and foot-related problems.
  6. It is likely that if amareisonadiet deficient in protein, vitamins and minerals (sub-optimum nutrition in utero) her foal will be born with insulin resistance.
  7. If fed in excess, high fat diets predispose a pony to insulin resistance more than high sugar diets.
  8. Ponies and horses with insulin resistance are at a higher risk of laminitis.
  9. Restricting a horse’s dry matter intake increases the risk of stereotypy, colics and gastric ulcers.
  10. Exercise is protective against insulin resistance.