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Pasture and Laminitis

Pasture plants contain varying levels of simple sugars, fructans, and starch. The vegetative tissues of temperate (cool season or C3) pasture grasses, such as perennial ryegrass or fescue, accumulate fructan as the primary storage carbohydrate, with most fructan stored in the stem until required by the plant as an energy source. In contrast, starch is the storage carbohydrate of the seed of temperate grasses and the seed and vegetative tissues of legumes (eg, clover) and warm season (C4) grasses, such as Bermuda. The type of fructan varies among grass species. A large number of environmental factors influence the accumulation of starches and fructans in pasture plants; these include the intensity and duration of sunlight, temperature (ambient and soil), soil fertility, water availability, and nitrogen status. Pasture
NSCs are highest in spring, lowest in midsummer, and intermediate in the fall. Thus, pasture NSCs tends to increase during the morning, reaching maximal values in the afternoon and then declining overnight. Therefore, horses grazing in the afternoon, when compared with nighttime or the morning, may ingest between two and four times as much NSCs. Stress conditions that restrict plant growth (and therefore energy demands) result in accumulation of NSCs. These stress conditions include low temperatures, killing frosts, applications of nonlethal herbicides, and low soil fertility. One of the proved causes to cause laminitis is starch or fructan contained in pastures. The induction of the disease depends on the amount of starch or fructan present.
It is possible that the dosage of NSCs (eg, as fructan) required to trigger digestive and metabolic disturbances in susceptible animals (ie, a horse or pony with an insulin resistant phenotype) is considerably lower than that needed to induce disease reliably in healthy experimental animals. Another possibility is that susceptible horses and ponies have differences in their gut flora compared with animals less prone to laminitis, with heightened hindgut fermentative responses to a given load of NSCs and increased production of laminitis trigger factors.

What you can do to prevent laminitis induced pasture in high risk animals?

1) You have to work with your veterinarian to reduce overweight in high-risk horses and ponies
2) Develop strategies to limit the access of NSCs from pasture and other feedstuffs.
Horses and ponies with a history of laminitis or metabolic problems should be evaluated and treated accordingly (See insulin resistance article in client education tab).
3) Prevent access to pasture that is known to trigger the disease. Is not necessary to remove the horse completely from the pasture many horses or ponies that have had one or more episodes of pasture laminitis can return to grazing activity if the metabolic underlying disease has been addressed.
4) The horse or pony should be held off pasture until there has been complete resolution of the acute laminitis episode and gradual reintroduction to pasture may be considered. Follow your Dr. recommendations but you can start with 1 to 2 hours of grazing once or twice per day. Be careful during spring, when pasture is green and growing rapidly.

5) Horses with metabolic disease such as obese insulin-resistant horses should be held off pasture for a longer period (eg, 2–3 months), while you restrict the diet, increased physical activity).

6) Turn susceptible animals out late at night or early in the morning with removal from pasture by mid-morning.

In summary

_ Animals predisposed to laminitis should be denied access to grass pastures during the growing season.
_ At other times of the year, limit the amount of turnout time each day (eg, 1–3hours) and turn animals out late at night or early in the morning, removing them during the day.


So… what to feed!?

What not to feed:

  • Grain and sweet feeds.
  • ‘Treats’ such as carrots and apples.


What to feed:

  • Forage (hay or hay substitute, such as chop, chaff,  or  haylage) as the Mature grass hay (ie, with visible seed heads and a high stem-to-leaf ratio) has higher fiber and lower NSCs when compared with immature hay and is suitable forage for the obese horse or pony.              
  •  Alfalfa, clover hay or other legumes are less preferred.


The author which this article is based recommends supplementing the forage diet with a low-calorie commercial ration balancer product that contains sources of high-quality protein and a mixture of vitamins and minerals to balance the low vitamin E, copper, zinc, selenium, and other minerals typically found in mature grass hays.

Reference:

Veterinary Clinics of North America equine practice: Clinical Nutrition:Vol:25 N1, April 2009