Research has shown that pasture-induced laminitis occurs at times of rapid grass growth. The accumulation of certain carbohydrates in pasture forage – including fructans, starches, and sugars (non-structural carbohydrates or NSCs) – during autumn, spring and early summer, particularly after rainfall, precipitate this laminitis. Therefore, we must carefully manage pasture turnout and forage intake in horses and ponies who are at risk of developing laminitis, and those who are currently affected.
Horses suffering from insulin resistance (IR) and or Cushings (also known as PPID) as well as easy-keeping types who are often overweight, and may be persistently hyperinsulinemic, should also be managed carefully with regard to their carbohydrate intake.
Decisions regarding whether, and to what extent, affected animals can be allowed access to pasture must be made on a case-by-case basis; however, in general:
- The affected horse or pony should be held off pasture until there has been complete resolution of the acute laminitis episode and, when indicated, diagnostic testing for IR and PPID. If there is no evidence of IR or PPID, a gradual reintroduction to pasture may be considered. Start with one to two hours of grazing once or twice per day, or turn out for longer periods with a grazing muzzle. More caution may be required when pasture is green and growing rapidly (eg. in spring).
- Obese, insulin-resistant horses should be held off pasture for a longer period (e.g. two to three months), while their management is changed including increasing physical activity, which will result in improved insulin sensitivity. Even then, it is advisable to restrict severely, or avoid, any grazing during periods in which the pasture forage NSC content is likely to be high ( spring and early summer, and after summer and autumn rains that cause the grass to turn green, as well as pastures that have been frosted or drought-stressed).
- Some insulin-resistant horses and ponies with history of repeated episodes of laminitis need to be permanently kept in a dry lot, because they seem to be susceptible to further episodes of laminitis even with small variations in the nutrient content and availability of pasture.
The following points summarize current advice regarding strategies for avoiding high NSC intakes by horses and ponies at risk for pasture laminitis:
- Animals predisposed to laminitis should be denied access to grass pastures, particularly during the autumn/spring.
- At other times of the year, limit the amount of turnout time each day (eg one to three hours) and turn animals out after 8pm or early in the morning, removing them from pasture before 10am at the latest, because NSC levels are likely to be at their lowest at night through early morning.
- Alternatively, limit the size of the available pasture using temporary fencing to create small paddocks, or a grazing muzzle.
- Avoid pastures that have not been properly managed by regular grazing or cutting, because mature stemmy grasses may contain more fructan (it is stored in the stem).
- Do not turn horses out onto pasture that has been exposed to low temperatures in conjunction with bright sunlight, such as occurs in the autumn after a flush of growth, or on bright, cool winter days, because cold temperatures reduce grass growth, resulting in the accumulation of fructan.
- Do not allow horses to graze on recently-cut stubble, because fructan is stored predominantly in the stem.
If horses are denied access to pasture for most or all of the day, you must provide alternative feedstuffs. Horses at maintenance need approximately 2% of their bodyweight as forage, or forage plus supplement, to meet daily nutrient requirements. Grain and sweetfeeds should not be fed, and the feeding of treats, such as carrots and apples, should be discouraged.
Forage (as hay or hay substitute, such as forage pellets or cubes, chop, chaff, or haylage) should be the primary, if not sole, energy-providing component of the ration. Lucerne hay or other legumes, such as clover, on average, have lower NSC content when compared with grass hay, but have considerably higher calorie/energy content. Generalities regarding carbohydrate value of forages should in most cases, however, be avoided.
Ideally, hay should be analysed for water-soluble carbohydrates (WSC), ethanol-soluble carbohydrates (ESC) and starch before selection. The addition of WSC and starch is the closest to what we call NSC, and for the at-risk or laminitic horse, this value should be less than 10% in hay. Caution should be taken when feeding significant amounts of poorly-digestible hay and forages; anecdotally, this practice increases the risk for impaction colic in some animals.
Forage-only diets do not provide enough minerals or vitamins. Therefore, you should supplement the diet with a low-calorie commercial ration balancer product (such as Hygain Balanced) 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 lacking in mature grass hays. These products are often designed to be fed in small quantities (eg, 500g/d); and they can be mixed chopped forage to increase the size of the meal and extend feeding time, which may help alleviate boredom in animals provided a restricted diet.
HYGAIN® offers some ideal feed choices for horses and ponies at risk of contracting metabolic disorders such as laminitis, cushings, chronic obesity, insulin resistance and tying up. For ponies suffering from these conditions, HYGAIN ZERO® is ideal as it is a scientifically-formulated high fibre, low-starch, low-GI fortified pellet with less than 1.5% starch and no cereal grains.
HYGAIN® ICE® is designed for ponies in work, prone to metabolic-related disorders, maximising performance while keeping them calm and cool.
Get a free personalised diet analysis for your horse: Fill out the five easy step Hygain Nutrikey form at the link below, and have a nutrition consultant assess your horse’s diet.