Help Prevent Grass Founder 

While most of us herald the arrival of spring, horse owners are usually more cautious.  The possibility of grass founder is real, but more likely in high-risk horses.


table of contents: 

Founder basics

How does spring pasture cause founder

Reduce the risks

Signs of laminitis and first aid


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The basics of laminitis and founder


  • Laminitis and founder are closely related. Laminitis is the swelling of the laminae inside the horse hoof, and founder is the rotation of the coffin bone resulting from laminitis. These terms are used interchangeably. 


  • Inside the hoof, a network of folded tissue, the laminae, is rich in blood supply and connects the hoof wall to the interior structures of the hoof – namely the coffin bone. During laminitis, the blood flow is compromised, and the laminae inflame. The inflammation has nowhere to go – the hoof is a solid structure, creating pain and destruction of the laminae. The coffin bone may be rotated, as the laminae fails to provide structure for the bones inside the hoof.  


hoof x ray on a screen

Diagnostic imaging can help determine the cause of any hoof problem.


There are several causes of laminitis:


Supporting leg laminitis 


  • An injured leg sometimes causes a weight shift to the other leg of the pair. Over time, the uninjured, supporting leg develops laminitis from the strain caused by the extra weight. 

Systemic disease process


  • The risk of laminitis increases if a horse becomes ill, especially with a fever. Colic, virus, and systemic infections, including retained placenta in a mare.  

Concussive forces


  • Road founder describes laminitis as a result of working or playing on hard surfaces. This may pop up quickly, or the concussive forces build over time, creating laminitis.

Insulin dysregulation



  • When insulin is on the rise, as with IR, the blood vessels within the hoof are damaged, thus increasing founder risk. 

Exposure to toxic trees and plants


  • Black walnut is an instant trigger for laminitis, and horses that spend even 20 minutes on shavings can develop laminitis and swollen lower legs. Other toxic plants may trigger a whole-body response, including laminitis in the hooves. 

Gorging on grains and new foods


  • There’s always that houdini horse that can escape their pen and head straight for the feed room. When a large quantity of food hits the horse’s hindgut, colic and laminitis can happen from the shock to the system. 


gray horse in far corner of green grass pasture

Fetlock deep pasture


How does spring pasture create grass founder?


  • Spring pasture starts growing when temps and daylight hours tell the grass it’s time to ramp up photosynthesis. As a result, the leaves of grass fill with tasty sugars to fuel the growing cycle. It’s a quick process, often changing from dry, crusty grass to lush green in a week or two.  


  • When a horse eats this high-sugar deliciousness, those sugars act like grain after a horse has busted into the feed room – there’s a large influx of tasty sugars zipping through the digestive system.


  • Some of the hindgut microbes have a feast and then a hangover. The feasting changes the pH of the hindgut, which can destroy other microbes that eat things like fiber, not sugar. Dead microbes, hungover microbes, and a pH change create a toxic gut, which can leak across the intestinal wall. Those endotoxins hitch a ride in the bloodstream and land in the hooves, triggering laminitis.  


For high-risk horses, the volume of grass is one factor; the speed at which sugars hit the hindgut is the other.  


  • Take the parallel situation of feeding your horse grain, concentrated feed, or ration balancer. Let’s say the daily amount is about 7 pounds. When eaten all at once, there’s a high volume and speed for the ingredients to enter the hindgut. Smaller, more frequent meals – the recommended way to feed by vets and nutritionists alike – prevent hindgut overload. 


lush green pasture with barn in the background

Salad for days


Spring grass is a diet change


  • It’s helpful to view spring grass as a diet change. Those same vets and equine nutritionists reminding us to split concentrated meals also know that changes to any part of the diet – forage, feeds, or pasture should happen over two weeks.  


  • Horses that have been on dry lots and then turned free on spring grass without being acclimated are like that kid who eats all of their Halloween candy in one sitting.  


  • Make gradual transitions to lush spring grass to reduce the risk of colic and grass founder. 


More high-sugar times for grass


It’s worth noting that the sugar content will spike any time grass is growing or stressed. This happens:


  • After a mow. You just gave that pasture an unwanted haircut, and it needs to hoard sugars to grow out again. Before introducing your horse to a freshly mowed field, you could wait a day to be safe. 


  • Short grass, eaten down. When pasture resources are slim, the shorter grass needs to grow again and will stock up on fuel. Horses also perpetuate this cycle by eating the shorter grass – those sugars are tasty! 


  • Chilly mornings – When temps fall below about 40º F, spring grass wakes up confused and in self-preservation mode. You guessed it, more sugars. 


  • Hot afternoons – Sun-baked grass when the afternoons’ cook will also stress the grass. Many farms let horses out overnight to eat, and back in during the day. Bugs and hot, stressed grass are avoided. 


  • Going to seed – Grass that has gone to seed has one thing on its mind – hoard sugars in the seeds for the new grass to thrive.


  • The fall bloom of grass. Often, fall grasses experience the same “pow” of growth in the fall. There may be late, warm weather, lots of chilly mornings, and rain that gives fall grass a boost to grow. Also, a horse’s hormonal changes in the fall put some horses more at risk.  


gray horse in deep spring grass with grazing muzzle

Grazing muzzles can slow down eating and limit the volume of food consumed. 


Reduce the risk of spring founder


Now is the time to make a plan for spring – and fall, really.  

Know your horse’s metabolic status


  • PPID horses are subject to a cascading effect of hormones, ultimately changing insulin levels. EMS is the other big one to worry about and includes overweight horses, horses with IR, and horses with a history of laminitis. 


  • Having your vet run some affordable diagnostic tests for metabolic problems is simple. If you find out that your horse falls into the “needs a low-sugar diet” category, you can make changes to keep them safe.

Make a slow transition to spring grass


  • Letting your horse acclimate to spring grass will help reduce the risk of spring grass founder. Take it slow and build up access over a few weeks when introducing pasture. Horses that have grazed all winter won’t take as long to acclimate. Look at the big picture of your horse’s lifestyle to set a pace for your horse. Your vet can help you assess risk factors and make a plan.


  • Food for thought – try not to change any parts of your horse’s diet during this time.  

Use grazing muzzles


  • Here’s the thing about grazing muzzles – they slow down the volume and speed of food entering the hindgut. This bodes well for high-risk horses and overweight horses. 


  • Horses moving from a no-grass situation into spring pasture can also benefit from a muzzle to help the process. This may be temporary use of a muzzle, but well worth it. 


  • If you notice that your horse hasn’t shed their winter pounds, or is an air fern that gains weight readily, use a muzzle. You can prevent so many problems with proper weight management.  


chestnut horse wearing a greenguard grazing muzzle

It’s a wearable hay net.


Use hay to slow down digestion.  


  • When your horse has some hay in their belly, this will physically slow down the digestion of grass. It’s the same logic as feeding hay before grains.  

Take your horse’s vital signs and memorize their digital pulses.  


  • There is usually an increase in the digital pulse from the beginning of any hoof problem. Daily pulse checks can alert you to trouble long before you see your horse hopping around uncomfortably. Early intervention gives your horse a great chance of overcoming laminitis. 


Add hindgut buffers to feed


  • Part of the chain reaction of spring founder is the change in pH of the hindgut. Buffering agents help minimize these changes, and luckily, our horses can eat them! Hindgut buffers are usually a stand-alone supplement, most without flavor, and easy to feed.   

Signs and first aid for spring grass founder


Know the signs of founder:

  • Shortened stride, maybe your horse appears to be walking on eggshells.


  • Turning is more like hopping around with short steps, like they’re sending weight back and pivoting around. 


  • The hooves feel hot. Fair warning – this is a subjective observation. Your horse may have been in the sun, and you feel the heat. Or, inflammation in the hoof is creating heat.


  • An increased digital pulse. Usually, the pulse of the artery going into the hoof is weak, if not absent. When the laminae swell, blood flow is impeded, and the artery starts to thump.  


  • Unwillingness to move from softer ground to harder ground. Those painful hooves make every step miserable. 


horse in buckets of ice

Ice boots and ice baths reduce pain and inflammation. 


Laminitis first aid 


  • Calling the vet is your top priority. The first instinct may be to call the farrier – but they can’t diagnose, prescribe pain medications, and create a treatment plan. Call your farrier when your vet has made a diagnosis. Your vet and farrier together can determine the best trimming or shoeing methods for maximum pain relief. 


  • Keep your horse on soft ground, preferably where they can easily reach food and water without moving too much. Stalls are ideal; you don’t want them to move around.  


  • Use ice. Icing hooves and lower legs continuously, often for days, relieves pain and reduces inflammation. 


  • Reduce sugars in your horse’s hay, feeds, and supplements. Aim to have every feed’s non-structural carbohydrate (NSC) value below 10%. You may be surprised that some feeds are upwards of 20% – even those marketed as “low sugar low starch.” 


  • If you have boots with major cushion, like the Soft Ride boots, use them. Even if your horse has shoes, these provide pain relief and comfort.  


  • Use anti-inflammatory medications from your vet. Don’t give more than prescribed. If your horse needs more pain relief, add ice, squishy boots, and extra shavings until you and your vet can talk.  


Prevention is always better for your horse, and your wallet. Hopefully, you will never have to deal with spring founder.


Video on taking the digital pulse of the horse.



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Safety break-away halter for grazing muzzles.



The best muzzle in the land – order one here! Also in raspberry and black colors.

Use code 15PROEQUINE for a lovely discount

EquiShure is a hindgut buffer that can help Cushing’s in horses as well as IR horses to balance their hindguts.

Equithrive Metabarol is also designed to support metabolic health


Quiessence is a supplement to reduce cresty necks, and may reduce the chance of founder. 


Heiro is designed to help horses with IR, which can happen with Cushing’s


These ice packs make for easy cooling of your horse’s legs and hooves. They last for hours.

This tall boot can be filled with ice or ice packs to help the horse with laminitis.


These affordable boots can be filled with ice to help your horse.


These Cloud boots are great for the horse that needs extra cushion, like the horse with laminitis


The best-known hoof supplement


Hoof and joint supplement

The gold standard in hoof dressings

AniMed hoof Supplement


Durasole – for hoof hardening



White Lightning for hoof infections in a soaking kit


White Lightning Gel

Hoof clay.

Another type of hoof clay.

SteriHoof Spray for thrush and white line

Magic Cushion takes the sting out of hooves

Ichthammol salve for wounds and hoof issues.


Bright green salt poultice for hooves.


Hoof Wraps Easy Soaker with pads



Hoof Wraps Brand Bandage – Affordable wrap for hoof protection


Good reading if the hoof is fascinating to you!


Thank you!




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