Bandalero Ranch Blog

Veterinarian Blast - Vasculature of the Hoof/Laminitis

By Bandalero Ranch
Sep 10, 2012

 
On August 31, 2012 I posted a image of the vasculature of the hoof on our facebook page; consquently, I have received a great deal of interest. This is an excellent way to introduce the condition of laminitis which is commonly called ‘founder’. 

The introduction to laminitis as written by Dr. Stashak himself describes inflammation of the lamina as a gross oversimplification of a

Vasculature of Hoof

complicated, interrelated sequence of events that result in varying degrees of breakdown of the interdigitation of the primary and secondary epidermal and dermal lamellae in the foot.   If you understood that and want a further more detailed description, then this article is not for you.  This is laminitis made understandable.

As you may have now surmised, the blood flow to the foot is very delicate.  When a horse has circulating digestive toxins from eating a large amount of grain, eating extremely lush pasture, eating an overly rich cutting of alfalfa, or possibly being switched from a low energy diet to a high energy diet, the horse can create swelling in and around those fragile vessels.  This is similar to the feeling of water retention or bloat that we feel whenever we eat at an all-you-can-eat Chinese buffet, or spend too much time grazing at a wedding reception or an office party.  The next morning you have a difficult time getting your rings on or off your fingers.  Your shoes may feel too tight.

Chronic founder, years of poor blood flow have allowed the bone of the foot to atrophy.

Another common cause of laminitis is illness.  Peritonitis, retained placenta, pregnancy, bacterial or viral infections can all cause founderalso.  Circulation can be compromised during illness and may pool in the extremities as the body is out of balance.  This is further complicated in the horse, because all of the extremities are as low as you can get.  Gravity does not help to reduce the ‘pooling’ effect. A horse can also have traumatic laminitis.  This may be referred to as ‘road founder’.  It occurs after a horse had been ridden long, fast, or carried a heavy load on hard or rocky ground.  Human marathon runners probably have a similar feeling, but even just standing on the cement in our laboratory for a prolonged period of time can make my feet ache.

Finally, there is yet another way that we can create founder.  A horse was not designed to bear weight on only one opposing limb.  There are no three legged horses.  When a horse cannot stand on one hoof, the other hoof must do the work of two for prolonged periods of time.  The horse has a special tissue on the bottom of the foot that is part of the sole.  It is called the ‘frog’.  It is soft and pliable compared to the rest of the hard sole.  When the horse puts pressure on the frog, the frog pushes up against the vasculature on the coffin

Acute founder, a gas line can actually be seen between the bone and the hoof wall.

bone and catapults it out of the foot.  A standing horse that cannot walk, cannot utilize this mechanism.  This further increases the combination of increased weight load, inflammatory products in the body from an opposing limb fracture, and just plain gravity.  To the sorrow of millions, this is why Barbaro was put to sleep.  His fractured leg could not bear weight so the opposite rear foot finally foundered.

The problem with the horse is that the hoof wall acts as a complete cast around the entire foot.  As you can see from the blood supply, a very protective suit of armor was necessary.  But really good armor does not expand.  If the tissue inside the hard hoof begins to swell, it has nowhere to go.  This can cause microtrauma to the tiny linkages (lamellae) that hold the hoof wall to the bone and its blood supply.   These tiny connections hold the bone within the foot and literally the weight of the horse suspended above the sole of the hoof.  The tiny bonds break and the coffin bone actually rotates and sinks, just like the Titanic.

If you have ever lost a finger or toe nail you have experienced the same thing.  This is life threatening to the horse.  The horse cannot stand on the bone of his foot while he grows a new nail. 

Video of frog in movement [youtube=http://www.youtube.com/watch?v=VLmEzqSpqeo&feature=related]

Please feel free to direct any questions you may have here or email me directly at doc@bandaleroranch.com.

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