Carol Nelson
06-04-2010, 03:43 AM
This was recently sent to all of us members of Southwest Region. I thought it was very good, and very relevant and probably should be posted here:
The Difference Between Shod and Bare
Although it appears now that the shoe does not actually protect what we thought it did, and may not be necessary, is there any harm in it?
Here are some of the effects of shoes that have been discovered so far:
Decreased shock absorption. Studies which have measured the impact vibrations on the inside of the hooves of shod and unshod horses have found significantly less ability to dampen vibrations in the shod foot. This is thought to be due to the more limited motion of internal and external structures of the foot while shod (Dyhre-Poulsen, Smedegaard, Roed, and Korsgaard, 1994). Although the heels still do expand in the shod hoof on impact as much as in the unshod hoof, it appears that the rest of the hoof capsule is not as capable of natural flexion (Colles, 1989). This is especially pertinent to horses working on hard terrain (Simons-Lancaster, 2004). There are also anatomical differences in the structures in the rear of the foot responsible for shock absorption (see below).
Faster breakover (less flexing of foot).
The shod hoof breaks over faster than the unshod hoof. This means the foot has a snapping lever action as it leaves the ground, instead of having the flexibility to leave the ground in gradual stages (somewhat like the human foot rolls off the ground from the heel to the ball to the toe). This is a drastically different movement pattern than the horse is designed to exhibit. The result is that the foot has less time before it leaves the ground to dissipate energy, and may result in ossification of the lateral cartilages (Simons-Lancaster, 2004).
Decreased circulation.
Whenever the hoof is peripherally loaded (i.e. the weight bearing is only around the outer rim) doppler radar studies have shown that the perfusion of blood in the hoof is only between 50 and 65 %. This is in comparison to a horse with even loading over the sole (such as barefoot standing on pea gravel), that has approximately 90% perfusion. Even glue on or rubber shoes by their very design peripherally load the foot, thereby reducing the perfusion of the tissues while the horse is at rest (Bowker, 2007c).
The differences in circulation during movement are difficult to study for obvious reasons. However, it has been shown that the negative pressure phase as the hoof becomes weight bearing (responsible for creating the vacuum to draw blood into the hoof) is shorter in shod horses than barefoot (Simons-Lancaster, 2004).
Mechanical damage to hoofwall.
This has not been studied, but can be observed whenever a shoe is pulled. Nail holes (opening tissue to fungal infection), chunks of hoof wall torn away, and in bad cases nails going through sensitive internal structures (quicking) are all examples of this.
Thinning of sole (lowered P3 position).
This is best observed in radiographic studies, although there are less precise ways to gauge sole thickness without these measures. In order for a shoe to be nailed onto the hoof, the hoof must be flattened to make an adequate interface. Rasping the foot flat necessitates the thinning of the sole. The more the sole is thinned the less a healthy sole callous can develop. Less material is under the coffin bone to support, and it can begin to sink in the hoof capsule. This repositioning of the coffin bone is what makes it so dangerous to try and overly shorten a long hoof capsule in one session, when signs show the sole is thin. The solution for this problem is to leave the sole alone to callous, regain concavity, and gradually reposition the coffin bone higher in the hoof capsule (Ramey, 2002).
Unnatural distribution of weight (peripheral loading).
In the discussion of what the shoe actually protects, we discovered that the weight bearing responsibility is shared by the hoof wall and sole. When a shoe is nailed on, the effect is to hang the weight of the horse from the hoof wall, placing undue stress on the wall and the lamina. As the wall grows longer and is unable to wear away, this unbalance becomes worse (Simons-Lancaster, 2004; Ramey, 2002).
When peripheral loading occurs, it can actually change the anatomy of the foot. In areas of increased stress the lamina begin to bifurcate (divide into multiple, thinner weaker lamina). Horses who are shod tend to have a greater amount of lamina, which are thinner than barefoot horses. When the load is borne on the periphery of the foot, changes can also happen to the coffin bone. Similar to osteoporosis in humans the bottom of the coffin bone does not receive enough load, and begins to demineralize. The load from the shoe is reflected up the hoof wall and places unnatural pressure against the higher portions of the coffin bone and lateral cartilages and can cause bone to be laid down where it should not be (Bowker, 2007a, Bowker, 2007b).
IMPAIRED DEVELOPMENT OF Digital Cushion and Lateral Cartilages!! !!
This fact is perhaps the most damning against the use of shoes, especially on young horses. The digital cushions (DC) and Lateral cartilages (LC) are soft tissue structures in the back of the foot which are responsible for cushioning the landing of the horse and allowing the back of the hoof capsule to flex for shock absorption and circulation (the front of the capsule is held rigid by the coffin bone). The DC when it fully develops is a tough fibrocartilagenous mass, and the LC is an inch thick highly vascularized tissue. When a shoe is placed on a horse, the development of these structures stops. The DC remains a jello-like fat deposit, only capable of supporting a foals weight, and the LC remains thin and nearly devoid of blood vessels, impairing the hydraulic shock absorption system of the foot. The underdevelopment of these structures changes movement patterns, subjecting the horse to massive tendon and ligament damage, and greatly increasing the risk of disorders such as navicular syndrome and contracted hooves. (Bowker, Atkinson, Atkinson, and Haut, 2001; Bowker, Van Wulfen, Springer, and Linder, 1998; Bowker, 2007). This is, in my opinion, one of the most important considerations in not shoeing horses, especially young ones.
Even if, in your heart of hearts, you do not believe that horses are capable of carrying a human barefooted, technology now exists (i.e. hoof boots) that protects the horses foot without the negative side effects of shoes. This technology grows better every year.
In conclusion, the choice to go barefoot was easy for me to make, when I was presented with the best current knowledge. In the years I have tried it, I have not been disappointed, and I have learned to overcome the obstacles that kept me shoeing my horses before. I hope that the information that helped me to come to my decision, helps you in some way to think about the decision you have to make about the care of your horses feet. In the end, we are all responsible for doing our own research about what is the healthiest for our own animals. I wish you the best of luck in this endeavor.
Works Cited
Bowker, R.M., Atkinson,P.J. , Atkinson, T.S., and Haut, R.C. 2001. Effect of contact stress in bones of distal interphalangeal joint on microscopic changes in articular cartilages and ligaments. American Journal of Veterinary Research 62, no.3: 414-424.
Bowker, R.M., Van Wulfen, K.K., Springer, S.E., and Linder, K.E. 1998. Functional anatomy of the cartilage of distal phalanx and digital cushion in the equine foot and a hemodynamic flow hypothesis of energy dissipation. American Journal of Veterinary Research 59, no.8: 961-968.
Bowker, R.M. Contrasting structures of good and bad feet. University of Colorado, hoof care seminar. Ft. Collins, CO. 5 August, 2007a.
Bowker, R.M. Growth and Adaptive Capabilities of Hoof Wall and Sole: Functional Changes in Response to Stress. University of Colorado, hoof care seminar. Ft. Collins, CO. 5 August, 2007b.
Bowker, R.M. Doppler Ultrasound on the Equine Foot and determining the normal physiological functioning of vascular flow during health and disease. University of Colorado, hoof care seminar. Ft. Collins, CO. 5 August, 2007c.
Colles, CM. 1989. The relationship of frog pressure to heel expansion. Equine Veterinary Journal 21, no.1:13-16.
Dhyre-Poulsen, P., Smedegaard, H.H., Roed, J., and Korsgaard, E. 1994. Equine hoof function investigated by pressure transducers inside the hoof and accelerometers on the first phalanx. Equine Veterinary Journal 26, no. 5:362-366.
Ramey, P. 2002. Making Natural Hoofcare Work for You. Star Ridge Publishing; Harrison.
Simons-Lancaster, L. 2004. The Sound Hoof: Horse Health from the Ground Up. Tallgrass Publishers, LLC; Larkspur.
The Difference Between Shod and Bare
Although it appears now that the shoe does not actually protect what we thought it did, and may not be necessary, is there any harm in it?
Here are some of the effects of shoes that have been discovered so far:
Decreased shock absorption. Studies which have measured the impact vibrations on the inside of the hooves of shod and unshod horses have found significantly less ability to dampen vibrations in the shod foot. This is thought to be due to the more limited motion of internal and external structures of the foot while shod (Dyhre-Poulsen, Smedegaard, Roed, and Korsgaard, 1994). Although the heels still do expand in the shod hoof on impact as much as in the unshod hoof, it appears that the rest of the hoof capsule is not as capable of natural flexion (Colles, 1989). This is especially pertinent to horses working on hard terrain (Simons-Lancaster, 2004). There are also anatomical differences in the structures in the rear of the foot responsible for shock absorption (see below).
Faster breakover (less flexing of foot).
The shod hoof breaks over faster than the unshod hoof. This means the foot has a snapping lever action as it leaves the ground, instead of having the flexibility to leave the ground in gradual stages (somewhat like the human foot rolls off the ground from the heel to the ball to the toe). This is a drastically different movement pattern than the horse is designed to exhibit. The result is that the foot has less time before it leaves the ground to dissipate energy, and may result in ossification of the lateral cartilages (Simons-Lancaster, 2004).
Decreased circulation.
Whenever the hoof is peripherally loaded (i.e. the weight bearing is only around the outer rim) doppler radar studies have shown that the perfusion of blood in the hoof is only between 50 and 65 %. This is in comparison to a horse with even loading over the sole (such as barefoot standing on pea gravel), that has approximately 90% perfusion. Even glue on or rubber shoes by their very design peripherally load the foot, thereby reducing the perfusion of the tissues while the horse is at rest (Bowker, 2007c).
The differences in circulation during movement are difficult to study for obvious reasons. However, it has been shown that the negative pressure phase as the hoof becomes weight bearing (responsible for creating the vacuum to draw blood into the hoof) is shorter in shod horses than barefoot (Simons-Lancaster, 2004).
Mechanical damage to hoofwall.
This has not been studied, but can be observed whenever a shoe is pulled. Nail holes (opening tissue to fungal infection), chunks of hoof wall torn away, and in bad cases nails going through sensitive internal structures (quicking) are all examples of this.
Thinning of sole (lowered P3 position).
This is best observed in radiographic studies, although there are less precise ways to gauge sole thickness without these measures. In order for a shoe to be nailed onto the hoof, the hoof must be flattened to make an adequate interface. Rasping the foot flat necessitates the thinning of the sole. The more the sole is thinned the less a healthy sole callous can develop. Less material is under the coffin bone to support, and it can begin to sink in the hoof capsule. This repositioning of the coffin bone is what makes it so dangerous to try and overly shorten a long hoof capsule in one session, when signs show the sole is thin. The solution for this problem is to leave the sole alone to callous, regain concavity, and gradually reposition the coffin bone higher in the hoof capsule (Ramey, 2002).
Unnatural distribution of weight (peripheral loading).
In the discussion of what the shoe actually protects, we discovered that the weight bearing responsibility is shared by the hoof wall and sole. When a shoe is nailed on, the effect is to hang the weight of the horse from the hoof wall, placing undue stress on the wall and the lamina. As the wall grows longer and is unable to wear away, this unbalance becomes worse (Simons-Lancaster, 2004; Ramey, 2002).
When peripheral loading occurs, it can actually change the anatomy of the foot. In areas of increased stress the lamina begin to bifurcate (divide into multiple, thinner weaker lamina). Horses who are shod tend to have a greater amount of lamina, which are thinner than barefoot horses. When the load is borne on the periphery of the foot, changes can also happen to the coffin bone. Similar to osteoporosis in humans the bottom of the coffin bone does not receive enough load, and begins to demineralize. The load from the shoe is reflected up the hoof wall and places unnatural pressure against the higher portions of the coffin bone and lateral cartilages and can cause bone to be laid down where it should not be (Bowker, 2007a, Bowker, 2007b).
IMPAIRED DEVELOPMENT OF Digital Cushion and Lateral Cartilages!! !!
This fact is perhaps the most damning against the use of shoes, especially on young horses. The digital cushions (DC) and Lateral cartilages (LC) are soft tissue structures in the back of the foot which are responsible for cushioning the landing of the horse and allowing the back of the hoof capsule to flex for shock absorption and circulation (the front of the capsule is held rigid by the coffin bone). The DC when it fully develops is a tough fibrocartilagenous mass, and the LC is an inch thick highly vascularized tissue. When a shoe is placed on a horse, the development of these structures stops. The DC remains a jello-like fat deposit, only capable of supporting a foals weight, and the LC remains thin and nearly devoid of blood vessels, impairing the hydraulic shock absorption system of the foot. The underdevelopment of these structures changes movement patterns, subjecting the horse to massive tendon and ligament damage, and greatly increasing the risk of disorders such as navicular syndrome and contracted hooves. (Bowker, Atkinson, Atkinson, and Haut, 2001; Bowker, Van Wulfen, Springer, and Linder, 1998; Bowker, 2007). This is, in my opinion, one of the most important considerations in not shoeing horses, especially young ones.
Even if, in your heart of hearts, you do not believe that horses are capable of carrying a human barefooted, technology now exists (i.e. hoof boots) that protects the horses foot without the negative side effects of shoes. This technology grows better every year.
In conclusion, the choice to go barefoot was easy for me to make, when I was presented with the best current knowledge. In the years I have tried it, I have not been disappointed, and I have learned to overcome the obstacles that kept me shoeing my horses before. I hope that the information that helped me to come to my decision, helps you in some way to think about the decision you have to make about the care of your horses feet. In the end, we are all responsible for doing our own research about what is the healthiest for our own animals. I wish you the best of luck in this endeavor.
Works Cited
Bowker, R.M., Atkinson,P.J. , Atkinson, T.S., and Haut, R.C. 2001. Effect of contact stress in bones of distal interphalangeal joint on microscopic changes in articular cartilages and ligaments. American Journal of Veterinary Research 62, no.3: 414-424.
Bowker, R.M., Van Wulfen, K.K., Springer, S.E., and Linder, K.E. 1998. Functional anatomy of the cartilage of distal phalanx and digital cushion in the equine foot and a hemodynamic flow hypothesis of energy dissipation. American Journal of Veterinary Research 59, no.8: 961-968.
Bowker, R.M. Contrasting structures of good and bad feet. University of Colorado, hoof care seminar. Ft. Collins, CO. 5 August, 2007a.
Bowker, R.M. Growth and Adaptive Capabilities of Hoof Wall and Sole: Functional Changes in Response to Stress. University of Colorado, hoof care seminar. Ft. Collins, CO. 5 August, 2007b.
Bowker, R.M. Doppler Ultrasound on the Equine Foot and determining the normal physiological functioning of vascular flow during health and disease. University of Colorado, hoof care seminar. Ft. Collins, CO. 5 August, 2007c.
Colles, CM. 1989. The relationship of frog pressure to heel expansion. Equine Veterinary Journal 21, no.1:13-16.
Dhyre-Poulsen, P., Smedegaard, H.H., Roed, J., and Korsgaard, E. 1994. Equine hoof function investigated by pressure transducers inside the hoof and accelerometers on the first phalanx. Equine Veterinary Journal 26, no. 5:362-366.
Ramey, P. 2002. Making Natural Hoofcare Work for You. Star Ridge Publishing; Harrison.
Simons-Lancaster, L. 2004. The Sound Hoof: Horse Health from the Ground Up. Tallgrass Publishers, LLC; Larkspur.