Spring is upon us and hopefully warmer weather has arrived where you are! Many of our horses will soon begin to receive a substantial amount of their daily nutrients from new growth pasture.

While it can be a relief to turn horses out on green pasture after a long winter (for both the horse and the owner), these horses can be faced with a challenge that strikes terror in the hearts of horse owners everywhere: Laminitis.

Laminitis is a specific disease of the foot, which is characterized by damage or inflammation at the junction between the sensitive and insensitive laminae. This important area allows for the attachment of the hoof wall to the coffin bone within the hoof. Laminae become inflamed when an accumulation of toxins and lack of blood flow is found in the hoof. Although laminitis can be caused by a myriad of different things, we classify it in two ways:

1. Metabolic laminitis
2. Mechanical laminitis

Metabolic laminitis is more common of the two types and often coincides with some sort of toxemia in the body. It has been reported that approximately 45% of laminitis cases were triggered by lush, green growing pasture. While lush grass is one known cause, laminitis can also be caused by grain-overload (think feeding meals that are way too large, or your horse breaking into the feed room) or even by a retained placenta in a broodmare.

It can be hard to make the connection between something that the horse eats to a hoof disease, so let’s walk through an example: Your horse has been turned out on lush spring pasture that he hasn’t had access to all winter. He over consumes the rich grass which in turn overwhelms the upper digestive tract, and leaks into the hind-gut (cecum/large colon). Certain microorganisms in this part of the GI tract rapidly ferment the starches and sugars that leaked into the hind-gut resulting in an alteration in the pH. This change in the pH level kills off critical populations of cecal and colonic bacteria (good bugs) that help in the digestion process. Not only is the digestion process inhibited, but these dead bacteria release endotoxins which get into the horses blood. The endotoxins in the blood restrict blood flow to the hoof, damage those delicate laminae tissues and result in laminitis.

The second type, mechanical laminitis, is usually trauma induced. Overload on a horse’s foot from excessive body weight, riding on a hard-surface, or where the horse is trying to lessen the pain from a separate injury by shifting more weight to the good leg can all be causes of mechanical laminitis. A well known example of mechanical laminitis is Barbaro, the 2006 Kentucky Derby Winner.

In either metabolic or mechanical situations laminitis can happen in any foot, but most commonly it will occur in the front feet of horses on pasture. They will have a tender footed stance and act like they are “walking on egg shells”. A close inspection may show that the horse is shifting their weight—maybe backwards or even from side to side in an effort to compensate for the pain that they are experiencing in their affected leg or legs. If you find your horse in this situation, or suspect laminitis for any reason, contact your veterinarian immediately!