To Graze or Not to Graze? Spring Pastures & Laminitis

Sure, that lush pasture looks great, but what about laminitis? Melanie O’Neill gives us the lowdown on whether or not you should worry.

Pete Markham/Flickr/CC

It’s spring! The birds are singing, the grass is greener, and horse people are worried about laminitis. Do you need to worry about your horse? There are some signs to look for that may help you decide if your horse is at risk.

First, let’s look at the causes of laminitis, which are broken down into three categories:

• Supporting Limb Laminitis (SLL.) This occurs when there is an injury in one leg and the other legs have to support more weight, most famously seen in the sad case of Barbaro, 2006 Triple Crown contender.
• Systemic Inflammatory Response Syndrome (SIRS.) The horse is systemically ill. Causes are things like systemic infections, retained placenta, poisoning from black walnut shavings, or grain overload, among others.
• Endocrine Dysfunction. This category represents at least 90% of laminitis cases. Endocrine glands produce hormones, such as insulin–meaning that this category includes horses with insulin resistance, now called Equine Metabolic Syndrome (EMS), as well as those with PPID (equine Cushing’s disease.)

PPID is a tumor on the pituitary gland which releases excess of a hormone known as ACTH. If your horse has been diagnosed with EMS or PPID you know to be careful with how much sugar and starch your horse eats. The amount of sugar plus starch in any feedstuff is called NSC (non-structural carbohydrate.) These horses’ diets should be kept below 12% NSC (with some sources suggesting below 10%.) Carefully read feed labels and test hay for horses with diagnosed EMS or PPID.

So the question remains: do you have to worry about your horse getting laminitis from spring grass? Some horses can get the second type of laminitis from spring grass, similar to a grain overload. This is why it’s important to introduce horses to new green pastures slowly, just like you’re introducing new grain and hay. Given the opportunity, most horses will gorge on fresh pasture, consuming three hours’ worth of grass in a single hour. Try grazing your horse on someone’s green lawn to see this in action: this is not how horses that are on pasture all day would normally eat. This is also why it is not a good idea to take a grazing muzzle off for a few hours.

There is some thought that pasture-associated laminitis still has an endocrine cause, because laminitis cannot be induced in most healthy young horses by experimentally simulating pasture overload. Horses that are on pasture as it’s growing generally have time to adapt to higher carbohydrate content. If you are still worried about letting your horse have pasture, or he seems gassy or has loose stools on pasture, there are products available to help his digestive system adapt to high-carbohydrate meals. They usually contain ingredients like pre- and probiotics, enzymes and buffers.

But what about the third type? While endocrine dysfunction accounts for 90% of laminitis, only about 10% of horses will develop it. Is your horse in the 10%?  Both of these conditions (PPID and EMS) are more likely to occur as horse age. While the two conditions often go together, each has its own set of symptoms. EMS is more likely to occur in certain breeds, with minis and ponies at higher risk.

The definitive way to know if your horse is developing EMS is through a blood test. The biggest indicator that you may need to test is regional adiposity, specifically a cresty neck. Researchers at Virginia Teach developed a Cresty Neck Scoring System (shown below.) A cresty neck score greater than or equal to 3 is an indicator of possible insulin resistance. It does take some experience and skill to accurately score a cresty neck, but it’s a valuable tool for visualizing changes in a horse’s condition. Any abnormal fat deposit can be sign of insulin resistance: other common areas are the hollow spots above the eyes and the tail head. An abnormally swollen, dirty sheath can also be a sign of IR. Generally, easy keepers are more like to develop EMS.

If your horse has some of these signs that might indicate insulin resistance, it would be best to get him tested. Most vets will recommend testing for PPID at the same time. Those horses may need grazing restrictions. Remember that even healthy horses need to be introduced to fresh pastures slowly–but if your horse is not at risk for laminitis please let him enjoy his spring grass. He deserves it after this past winter!

Pete Markham/Flickr/CC

Resources

Katy Watts, safergrass.org

Thelaminitissite.org

Getty, J. (2009). Feed Your Horse like a Horse. Dog Ear Publishing, USA
Feed Your Horse Like A Horse: Optimize your horse’s nutrition for a lifetime of vibrant health, Juliet M. Getty, PhD

Rebecca A. Carter, Raymond J. Geor, W. Burton Staniar, Tania A. Cubitt, Pat A. Harris
Apparent adiposity assessed by standardised scoring systems and morphometric measurements in horses and ponies
The Veterinary Journal, Volume 179, Issue 2, February 2009, Pages 204-210

About Melanie: I’m an event and dressage rider from Bucks County, PA.  I teach equine nutrition at Delaware Valley University in Doylestown.  I also organize dressage shows at Bucks County Horse Park and work at veterinary clinic. I have my own business for riding lessons and training as well as equine massage, fecal testing and nutrition consultations.  I am married and have 3 sons.