Causes of Laminitis(Grass Founder)

 For many horse owners, watching their horse grazing in a lush, green pasture can be an ideal image, but any horse with equine metabolic syndrome(EMS) or Cushing's disease(pituitary pars intermedia dysfunction, aka PPID) are at risk for laminitis, also known as grass founder.

 If a horse or pony with EMS will often show telltale symptoms, including being slightly obese, insulin resistant, or having recurrent laminitis. Even if they are not fat they may have fat deposits along the crest of the neck, dock and eyes. This condition most often occurs in horses and ponies that developed under harsh climates and are usually easy keepers.

 Horses with PPID, a condition that occurs mostly in horses over fifteen, have patchy deposits and insulin resistance, just like EMS horses, but also have additional symptons. These include loss of topline muscle and a thick coat that sheds later than usual, or even never at all.

 If your horse has any of these conditions, keep a careful eye on them to make sure they don't develop laminitis.

Carbohydrates
Carbohydrates play a major role in causing laminitis. Grazing in a pasture that is high in non-structural carbohydrates(NSCs), meaning fructan, sugar, and starch, is dangerous and can cause laminitis. On the other hand, structural carbohydrates, the fibrous part of the cell wall that gives a plant rigidity, are digested differently NSCs.

 Most pople believe that fructan is the sole cause for laminitis, but that is simply not true. Fructan is not found in springtime grass, when many horses are known to founder, and further study can prove that conditions that create high fructan concentrations in forage also raise sugar and starch level. This means that NSCs in general can be attributed to grass founder.

Conditions to Watch Out For

Even if you don't have any high-risk horses, it is best to watch out for founder-causing conditions.

Temperature: Kathryn Watts, a researcher specializing in pasture grass and laminitis-prone horse once said that if it is below 40 degrees Fahrenheit( approximately 4.4 Celsius) the enzymes that help plants grow simply won't function. As a result, sugar, caused by photosynthesis, continues to build up. NSCs can double or even triple if those conditions(sunny and below 40 degrees) last for several weeks. Since that happens in the fall and spring in many parts of the country, those seasons are associated with grass founder.

Lack of Fertilizer: Lack of fertilizer(nitrogen) can also cause laminitis. Even though the plant may have plenty of sugar stored up in it, without nitrogen it cannot use the excess sugar, which continues to pile up. Watts said, "I use the analogy of an assembly line: If the plant does not have all of the elements it needs to grow, the line shuts down and the other raw materials pile."
 Because lack of nitrogen can be potentially dangerous, make sure that the pasture is properly fertilized. Watts suggests using a fertilizer with moderate fertility, not maximum.

This may be your dream pasture for your horse, but you should
always watch out for signs of founder. (credit)

Drought: Right now, in the middle of summer, drought can be the biggest cause of founder, especially because of the heatwave that has been striking most of the country. Drought also causes sugar to build up in grass. In Texas, summer is founder season. Fructan in cool-season grasses turns to sugar during a drought, "increasing the chances of metabolically driven laminitis."(Watts)

Mature Grass: You should always mow the pasture before the sugary, starchy seed head appears. Horses will often pick around other grass to eat the heads off the mature grass, which can cause founder.

Weeds: Most pastures are filled with weeds, which often contain more sugar than grass. The weeds containing the most NSCs are dandelion, thistle, and plantain. Often, killing off the broadleaf weeds, such as dandelions, with herbicide is enough to reduce the risk of founder.
 While having thick, healthy grass may be enough to reduce weeds and the amount of sugar per mouth full of grass, there may still be more grass per acre, which also means more sugar per acre. When a pasture has been previously overgrazed and now has an abundance of grass, you may want to limit grazing time.
 Weeds can also grow in dry lots, where horses and ponies are housed to keep them out of the pasture. Since horses can still founder of the small amount of weeds, your best bet is to through there with a weed-wacker, knocking down every single weed.

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Next week I will continue to write about grass founder, next time featuring how to prevent it and how to treat its early stages.

This post has been linked to: The Home Acre Hop