March 30, 2017 
Spring is the peak time for grass-associated laminitis in most parts of the world. You can effectively treat, or better yet, prevent it, but only if you understand the mechanism.
First, what it’s not…
There is zero evidence to support the idea that naturally occurring spring pasture laminitis is related to fructan and hind gut fermentation. In fact, all research points to it being caused by high sugar/starch and insulin resistance (IR). Therefore, products like the antibiotic Founderguard or hind gut buffering agents will not be effective.
Animals most at risk include ponies, minis, donkeys, full-size horses of breeds prone to insulin resistance, and pregnant mares. There may be a history of prior episodes of spring grass laminitis in the individual or their relatives.
A fat pony is the ‘pasture child’ for grass-associated laminitis. Photo: Rebecca Scott
An additional factor, besides sugar/starch levels in rapidly growing grasses, is magnesium content. (Although there is a desperate need for well designed studies to further examine this.) In all species studied, low magnesium status worsens insulin resistance, while replacing it results in improvement.
Grasses with magnesium less than 0.2% and potassium 3% or higher can cause magnesium-related problems in ruminants. This is most likely to occur in rapidly growing grasses and made worse by fertilizers containing potassium. If animals cannot be removed from pasture, supplement with 8–10 grams of magnesium per day for an average sized horse. However, there is no guarantee this will actually be protective.
Limiting grazing time is not always an effective preventative, at least in part because horses given restricted grazing time have been shown to consume grass at 3 times the normal grazing rate. As owners of affected animals can tell you it does not take a long grazing time for susceptible equines to eat enough to cause laminitis.
The best prevention is to avoid access to spring grass completely. You can still turn out for 2–4 hour intervals, but with a completely sealed muzzle. Feed only hays known to have a combined sugar (ESC) and starch level of less than 10%. Have minerals analyzed and properly balanced.
©Tomi Tapio K/Flickr
If you are dealing with an active case, the above measures still need to be implemented immediately. The key to stopping the process is eliminating the cause. If unsure whether your hay is safe, soak it for 1/2 hour before feeding. A supplement that specifically targets only magnesium, phosphorus, copper, zinc, selenium and iodine will cover the most frequently found mineral deficiencies until a hay analysis can be obtained. Chromium is useful for hays grown on alkaline soils.
Radiographs and a trim to make sure the hoof wall is tightly aligned to the internal structures is very important in both comfort and preventing any further damage. Pain control is understandably a major concern, but it’s important to realize you can’t control pain without removing the cause (above). NSAIDs like flunixin, phenylbutazone or firocoxib are reasonable for a few days but are not very effective for pain relief. That’s because features of other types of laminitis, such as inflammation, enzyme activation and endotoxemia, do not apply to grass induced laminitis. Once the correct diet and trim are in place consider a supplement to support circulation to the feet.
Preventing spring grass laminitis is certainly preferable to treating it, but effective measures are available if you are faced with this challenge.
All content is for informational purposes only. Contact your local veterinarian if you have any questions regarding the health of your animals.
About the Author
Eleanor Kellon is the Staff Veterinary Specialist for Uckele Health and Nutrition. Dr. Kellon also offers private nutritional consultations and online courses through Equine Nutritional Solutions. Find out more at www.drkellon.com.
