Laminitis is not a modern condition--it has been recognized for well over 2,000 years. The Greek philosopher Aristotle even referred to it around 350 B.C. as 'Barley Disease,' presumably because it was associated even then with excessive grain consumption. However, according to Patricia Harris, MA, PhD, Dipl. ECVCN, VetMB, MRCVS, there has recently been an increased interest in pasture-associated laminitis and researchers have devised management strategies to minimize at-risk horses' chances of being affected by it.
The results of a survey conducted in the United Kingdom relay that 61% of the horses and ponies that suffered from laminitis attacks were out on grass prior to the attack; 30% lived both on grass and in a stall; and only 9% were stabled. The results of a similar study in the United States revealed that about 45% of laminitis cases were linked to pasture turnout.
"It has recently been shown that giving relatively large amounts of a particular fructan (a carbohydrate found in plant cells) can induce laminitis in the horse," Harris said. "It is thought that as for other mammals the horse does not have the necessary enzymes to digest grass fructans directly within the small intestine. Grass fructans, therefore, pass relatively unchanged into the hindgut where they are readily fermented, in a similar manner to starch or other sugars that escape digestion in the small intestine." This process contributes to the development of laminitis.
Harris suggests a few guidelines to ensure that at-risk horses can still have access to turnout while decreasing the probability of a pasture-associated laminitis attack:
- Consider a zero grazing environment, such as a dry lot (while providing the horse with suitable forage alternatives) if it is essential that the horse ingests minimal levels of sugar, starch, and fructans or if the horse is on a strict weight management program;
- Turn horses out to pasture when fructan levels are likely to be at their lowest, such as from late night to early morning, removing them from the pasture by mid-morning;
- Do not graze these horses on pastures that have not been properly managed by regular grazing or mowing. Try to maintain an expanse of grass, as mature stemmy grasses contain higher levels of stored fructans;
- Avoid or restrict turnout in spring (before flower development) and autumn. Always consider restricted turnout to pastures during flowering and early seeding;
- Do not allow horses to graze on drought-stressed pastures or those that have been exposed to low temperatures (e.g., frosts) followed by warm, sunny days;
- Consider maintaining turnout by using grazing muzzles that still allow horses easy access to water; strip grazing behind other horses; mowing and removing clippings; spreading a deep layer of wood chips over a small paddock; or using drylots or arenas for turnout; and
- Rotate pastures regularly, preferably with other species such as sheep or cattle, to keep the grass levels at an appropriate height and to avoid the paddocks becoming "stressed" through either under- or overgrazing.
Harris cautions that all horses should be observed for signs of laminitis, even those that do not outwardly display the major risk factors (such as Equine metabolic syndrome, obesity, or insulin resistance) associated with the disease.
"Pasture turnout can be a trigger factor for laminitis even in the lean, non-obese animal," she explained. "Obesity may increase the risk, as does a pasture with a high nonstructural carbohydrate content, such as simple sugars, fructans, and starch."
Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.