Thursday, March 20, 2008

Standard Pasture Trim vs. Physiological Barefoot Trim

I am frequently asked what sets the physiological barefoot trim apart from the barefoot trim practiced by most traditional farriers. Because many unshod horses suffer from the same sort of ailments the physiological trim successfully corrects or avoids, it is important to understand that there are a number of differences. It is a fact that farrier schools and texts seldom address the different needs of the bare hoof (although they ALL advocate leaving the hoof unshod whenever possible) and instead focus on shoeing techniques. As a result, many farriers simply trim the unshod horse exactly as they would trim the horse to shoe. Keep in mind that I have simplified these comparisons in that I have not gone into detail concerning any possible exceptions to the general idea in the interest of hitting the main points.

1. Farrier Trim (FT) trims toe from the BOTTOM of the foot, often taking a considerable amount of live sole with it. This is done to prepare a flat surface for shoeing. The Physiological Trim (PT) manages the toe by rolling the wall, mainly from the top. This dramatically improves breakover without creating thinned sole at the toe. Trimming toe from the bottom routinely can tip the coffin bone within the hoof capsule, create flared toe, and contribute to joint problems in the lower leg.

2. FT pares out sole material, carving concavity. This is done to raise the sole off of the ground and prevent bruising. Clearly, on some level, it is recognized that the sole of the horse's foot should be concave, but the erroneous assumption is that the concavity's purpose was to keep the sole clear of the ground. PT allows the sole to fill in, striving to develop an even sole thickness across the bottom of the foot. Healthy, adequate sole quickly takes on natural concavity, mirroring the shape of the underside of P3 (impossible to achieve with a hoof knife!). Recent research has shown that the sole is intended to be the primary loading surface on the bottom of the foot; the concavity is not there to lift the sole off of the ground. Carving sole weakens sole (support to the structures within the hoof is greatly compromised), makes sole tender, and disturbs the natural medial/lateral, anterior/posterior internal arch of the foot.

3. FT trims the bars level with the carved sole. PT lets the hoof decide the height of the bars. The bars generate much of the sole material that is then pushed forward under P3. In addition, the bars provide support to the back of the foot, particularly in young horses with immature hooves, and in horses with poorly developed digital cushion and lateral cartilages. Removing bar hinders sole growth, weakens the back of the foot, disturbs integrity of the internal arch.

4. FT trims a uniform flat surface around the wall upon which to fit the shoe. Farrier texts instruct the shoer to be especially careful not to trim the quarters even with the sole plane, or there will be a low spot which will not meet the shoe. PT trims the wall to the level of the healthy sole, where it is intended to be. The wall at the quarters will naturally be shorter, creating a curve up through the quarters. Leaving the wall at the quarters long produces pressure points at the quarters, disturbs even growth of wall, and leaves the quarters prone to flaring, chipping, and quarter cracks.

5. FT places high importance on toe angle, as well as dorsal wall height, and this is largely what shoers will base their trim upon. It is high time that we recognized the fact that trimming for toe angle is obsolete. It was probably invented as a "best guess" to match the angle of P3 within the hoof. PT uses the uniform thickness of adequate sole coverage and the depth of the collateral grooves at heel and frog apex to determine what to trim from the bottom. The wall is then rolled to prevent flaring, and the resulting tight, healthy connection of wall to P3 quickly becomes evident growing down from the coronet. This will hold P3 up within the hoof capsule, creating a short dorsal wall height and the optimum toe angle for the individual horse. Trimming for toe angle can quickly go awry and create runaway flare, coffin bone "rotation" (the hoof capsule is what has actually rotated - not the bone!), late breakover, and high, contracted heels.

6. As noted in #4 above, FT trims the wall (and edge of the sole) flat. PT creates a bevel, rolling the wall. Leaving wall flat creates a separation force, contributes to flaring, stretched laminae, laminitis; retards natural breakover; and makes wall prone to chipping and cracking.

7. FT frequently leaves the heels extremely long in an attempt to "fix" an unacceptable toe angle. PT trims the heels by gauging sole depth at the back of the foot, and puts the frog in contact with the ground. Leaving the heels long, or "growing heel" to change the toe angle, lifts the back of the foot (frog, digital cushion, lateral cartilages) out of engagement, contributing to heel contraction and atrophy of support structures at back of foot. It can also lead to underrun heels, where the point of heel purchase moves forward, away from its healthy position of support for the bony column.

8. FT routinely shaves much of the surface of the frog. PT only removes flaps and diseased frog material. Carving the frog exposes tender, untoughened tissue prone to infection; this can quickly lead to chronic thrush, which may be the leading cause of heel pain in domestic horses.

9. FT will often trim the foot in an attempt to "fix" angular limb deformities. For example, it is not unusual to see FT trim one side of the hoof shorter, changing the sole plane completely, to prevent a pigeon-toed horse from toeing in. PT respects that the angular deformity impacts the entire limb. The foot is trimmed for the optimum health of the foot. "Fixing" limb angles puts incredible stress on joints that are not aligned for a straight limb, and creates an imbalanced foot that will be prone to numerous problems.

10. FT rarely maintains the trim more frequently than every 6 weeks. PT trims as needed: at the outside, 4 weeks elapse between trims, and often trimming is on an even more frequent schedule. PT attempts to mimic natural wear. Extended intervals between trimming force the hoof and leg to adjust to the radically longer or shorter hoof.

That's a mighty long list, and I hope it makes the distinction between simply pulling your horse's shoes, and enlisting competent barefoot hoof care clearer!

1 comment:

Katie No-Pockets said...

Thank you for the great article. I've recently switched from having a Farrier trim my horses to giving them a natural trim myself. Your comparison of the differences really enlightened me as to why my horses have certain problems which I am dealing with such as high, very contracted heels (the farrier said she left them to correct toe angle ...).