Natural Horse Care Resources

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1 SRP Bulletin #110 (6/27/2003) S R STAR RIDGE PUBLISHING P NATURAL HOOF CARE SERIES Natural Horse Care Resources The Supercorium Jaime Jackson Article Summary: Discussion of the dermal structures, collectively called the Supercorium, which produce the capsule and horse-to-hoof attachments. SRP is the Voice of the Natural Horse Care Movement I NTRODUCTION In the whole horse trim approach to natural hoof care [See Bulletin #109], the hoof is viewed as an extension of the integument (skin) above the hairline or coronary band. The dermis (inner skin or corium) above the coronet produces hair, below it produces the hoof, or capsule. Both are epidermal (outer skin) accretions of the dermis. The hoof dermis within the capsule is actually a complex, integrated mass of contiguous but differentiated and highly specialized coria. Each corium, on its outer face, produces a part of the capsule, including the periople (stratum externum), hoof wall proper (stratum medium), inner hoof wall (stratum internum), sole, frog and heelbulbs. On its inner face, it forms an attachment to the horse. The coria of the hoof dermis fill with blood during the support phase of the mechanism [See Bulletin #108]. During flight, the hoof contracts and blood is squeezed out. During support, a hydrodynamic equilibrium ensues which protects the dermis and other structures within the capsule from damage due to compressional (weight-bearing) forces. In effect, hydraulic pressure supports the horse, now held buoyantly within the capsule by the engorged, pressurized dermis. Collectively, the coria of the hoof dermis form a Supercorium, hence the title of this article. The Supercorium is not only a highly vascular structure, it is also innervated and thus capable of receiving and transmitting information. For example, when the capsule is not shod, as is the case with wild and naturally trimmed, barefoot domestic horses, the Supercorium senses and responds to the environment and other holistic forces. It builds a strong, thick capsule to enable balanced and efficient movement. The same capsule, shod, however, becomes thin, weak, and hypersensitive. The Supercorium is also subject to disease and breakdown. We see this in a range of hoof ailments, including Supercoriaitis [ laminitis, see Bulletin #102], thrush, abscesses, and wall splits. It is also capable of unique, adaptive responses to provide efficient support for the horse with serious injuries above the hairline [e.g., club foot, see Bulletin #112]. The purpose of this article is to identify the specific coria comprising the Supercorium, and to describe their function in capsule production as well as their attachment mechanisms to the Visit our web site at: ¹Founder: Prevention and Cure the Natural Way, available from Star Ridge Publishing ( com) or other retail book outlets nationwide Jaime 1 Jackson

2 J. Jackson C C L Figure 1 With contents of hoof removed, the groove (C) of the coronary band reveals countless small circular holes pocking its surface. Minute dermal papilla (Figure 2) emanating from the coronary corium insert into these sockets to produce hair like tubular horn. They are cemented together by interbular horn to form the hoof wall. Epidermal leaves (L) replace the tubularintertubular horn to form the inner hoof wall. horse. Also discussed is how natural hoof care practitioners communicate with and influence the Supercorium to build a sound, sturdy capsule. A NATOMY OF SUPERCORIUM The Supercorium comprises all the dermal structures underlying the capsule. It nourishes the hoof and provides the attachment mechanisms which connect the capsule to the horse. The Supercorium is conventionally known as the dermis or quick, which is subject to profuse bleeding, pain, and infection when, for example, it is penetrated, or quicked, near the white line by errant nails during horseshoeing, or by aggressive trimming of the solar dome. It is a complex maze of tough, reticulated connective tissue, interspersed with arteries, veins and capillaries, and specialized nerves.¹ The outside of the Supercorium is covered with a thin sheath or membrane called the basement membrane.² Germinal epidermal cells arise from this membrane, which produce the capsule. On the inside, the Supercorium attaches itself firmly to the horse by means of its connective tissue. The Supercorium is comprised of the coronary corium, lamellar (laminar) corium, perioplic corium, ¹See Christopher C. Pollit, Color Atlas of The Horse s Foot (Mosby- Wolfe: 1995), for a thorough description of the sub-coria of the Supercorium. Includes many fascinating photographs and invaluable line drawings. ²In addition to Pollit s Color Atlas, which contains fleeting discussions of the basement membrane, I recommend also his more sole corium, and frog corium. Coronary Corium The coronary corium circumscribes the hoof behind the coronary band, that is, the soft epidermal horn of the perioplic corium (discussed in a later section). It produces the hoof wall, including the bars. The coronary corium is visible in the color plate on page 4. If the coronary corium is detached from the capsule, a groove circumscribing the upper hoof wall is left in its wake (Figure 1). Close examination of the groove reveals thousands of tiny holes pocking its surface. Each hole forms a socket approximately 5 mm long, tapering to a point within the upper hoof wall. A layer of basal or germinal epithelial cells, produced and nutrified by the coronary corium, line all the holes and the interspace between them. As the cells undergo mitosis (proliferation of new cells from a single cell), keratinization occurs and the hoof wall (stratum medium) is produced at the approximate rate of 1 cm per month [See Bulletin #100]. This process is continuous during the horse s life. Thread-like tubular horn is produced by specialized recent research papers, Anatomy of the Inner Hoof Wall and, C.C. Pollitt and M. Daradka, Equine Laminitis Basement Membrane Pathology: Loss of Type V Collagen, Type VII Collagen and Laminin Immunostaining. These are available as free downloads at the Farrier and Hoofcare Resource Center website ( com) 2

3 C. Pollit Figure 2 Supercorium Minute papilla ( P ), here teased from the upper (proximal) hoof wall, are protrusions of the coronary corium (Supercorium). They fit into the tapering holes sockets of the proximal hoof wall seen in Figure 1. germinal cells lining the inside of the tubes. These arise from minute hair-like papillae, which are actually protrusions of the coronary corium. These are seen in Figure 2 and in the color plate on page 6. Each papillae produces a single horn tubule. A tubule is non-pigmented and is composed of relatively brittle, concentrically arranged keritinized horn, called keratinocytes. The tubule has a hollow core or medulla (Figure 3). Keratinocytes produced by the coronary corium between the papilla form a relatively strong, pigmented, cement-like matrix in which the tubular horn is embedded. As such, the intertubular horn endows the hoof wall with form, color, and structural integrity. The tubular horn is analogous to hair growing above the coronary band. If macerated from the hoof wall, as seen in the color plate on page 6, the hair-like quality of the tubular horn is evident. Tubular horn is produced in greatest concentration near the outer stratum medium (i.e., the outer wall). Near the inner hoof wall (stratum internum discussed in next section), there are fewer tubules and they have larger diameters than those near the outer wall. The reason for this gradient is taken up in the next section. The coronary corium attaches to the horse where it meets the extensor tendon, collateral cartilages, and the subcutaneous tissues of the digital cushion.¹ It has no direct attachments to the coffin bone (distal phalanx). On its outside, the coronary corium is covered by the perioplic corium, which is discussed in a separate section. Moving towards the inside of the hoof, the coronary corium differentitates and undergoes structural and functional changes. Besides producing fewer tubules of a larger diameter, further examination of the coronary groove reveals that the papillar sockets here give way to long, leaf-like structures. These are called the primary lamina, which are part of the inner hoof wall or stratum internum. There are 550 to 600 of these epidermal leaves produced in an average hoof. Each epidermal laminar leaf is shaped like a long, thin rectangle, which can be seen in Figure 1 ( L ). A single leaf is approximately 7 mm wide and stretches from the coronary groove down to the ground. Like the horn tubule, it grows downward constantly from its (Continued on page 12) ¹See Pollit s Color Atlas (fn. 1, page 2) for vivid images of these and other structures of the hoof s interior gross anatomy. C. Pollit I T M 3 Figure 3 Medulla (M) of tubular horn (T) surrounded by intertubular horn (I).

4 J. Jackson CC DL Peering into the face of the Supercorium. (above) Soaking in its own vascular fluids after having been macerated from the hoof capsule, the Supercorium is a living, breathing and intelligent entity dwelling beneath the capsule, which it creates, nutrifies, and shape-shifts in the 4th-Dimension mechanism [See Bulletin #110]. It is a modified extension of the same dermis (skin) extending above the hairline, producing instead a matrix of keratinized leaves (lamina) and hair (horn tubules) glued together with other specialized horn (intertubular horn) in its own image. The Supercorium is formed by the coronary, lamellar, solar, perioplic and frog coria. Visible above are the coronary corium (CC) and dermal leaves (DL) of the laminar corium. (facing page, top) I have teased open the folds of the dermal leaves of the Supercorium with a screw driver to show their depth and vascular nature. (facing page, bottom) Epidermal leaves (EL) are part of the capsule; they intermesh with the lamellar dermal leaves (above) forming a strong, but clearly flaccid, connection to the horse. The connection is not rigid. The avascular epidermal leaves do not attach directly to P3 (pedal bone or distal phalanx) either, contrary to popular belief, but are indirectly attached by means of connective tissue of the Supercorium. I believe the leaves suspend the horse passively in the capsule; they also function as guy lines during the hoof s non-support phase, orienting the capsule around P3 in preparation for support. True digital support, in my opinion, appears to be provided by powerful hydrostatic (vascular) forces that arise in the composite dermal-epidermal interface the Supercorium during the weightbearing phase of the hoof mechanism. In effect, the Supercorium is an hydraulic system that buoyantly supports P3 and the entire horse in the capsule. 4

5 J. Jackson EL 5

6 J. Jackson CP CC DL TP (Above, left) Scruffy hair-like fibers on surface of toe wall are actually horn tubules visibly separated from the cement-like intertubular horn of the stratum medium. These threads of tubular horn arise from minute papilla produced by the coronary corium. (Above, right) A clump of coronary papilla (CP) can be seen here just above the dermal leaves (DL) of the laminar corium near the heel. Most of the papilla have fallen away from the coronary corium during the maceration process. A few tufts of terminal papilla (TP) are visible too at the distal edge of the dermal leaves. (Facing page) Quadraplex of images contrasts the coronary and laminar coria with capsule. The Supercorium builds in its own image. Even the angle-of-growth of the capsule, shown in the lateral view (bottom), follows from the disposition of the baleen-like dermal leaves of the Supercorium. 6

7 J. Jackson 7

8 J. Jackson (Above) The Supercorium takes a turn where the solar corium and laminar corium intersect and intermesh. With a screwdriver I ve depressed a bundle of dermal lamina and terminal papilla, and behind them, a section of the solar corium, to emphasize the depth and rubber-like flexibility of the Supercorium at this juncture. This is an area of significant vascular activity that underlies powerful hydrostatic forces during the support phase of the hoof mechanism. (Facing page, top) This interesting profile of the Supercorium shows the dermal leaves (DL) of the laminar corium, responsible for the bars; the frog corium (FC), which produces the frog and heel-bulbs (page 10); and the sole corium (SC), which produces the sole. The sole corium is adjoined at its outer perimeter by the laminar corium, and by the frog corium forward of the dermal leaves that form the bars. (Facing page, bottom) Close-up of hoof capsule barely reveals tiny pock holes (sockets) inhabited by the sole papilla (SP, blue arrow), which have separated from the sole corium following maceration of the Supercorium from the capsule. The frog corium (FC) in the top image fits snugly into the epidermal body of the frog (F) seen here as a recession in the capsule. Red arrow marks a few sockets housing frog papilla. The cleft-like recession (C) of the frog corium in the upper photo fits over the frog stay (FS) in the capsule (also see color plates, page 11). The frog stay corresponds to the frog cleft on the bottom of the hoof. Epidermal leaves (EL) of the bars are at left. 8

9 J. Jackson SC DL FC C SP F EL FS 9

10 J. Jackson FC SC (Above) The frog corium (FC) has tremendous flexibility, reflecting its contiguous relationship with the largely fibro-fatty digital cushion above it. The solar corium (SC) is less so, since it is largely backed by the relatively inelastic coffin bone. The blue arrow points to a band of sole papilla that remained with the sole corium following maceration. By now, one can appreciate not only the vascular and elastic character of the Supercorium, but also its hairy appearance above and below the dermal leaves of the laminar corium. (Facing page) Little imagination is required to see how the Supercorium fits snugly into the capsule it has produced. The heel bulbs (HB) and periople (P) are very elastic and, like a cushion, yield readily to the tremendous compressional forces associated with the early support phase of the hoof mechanism. At the same time, the Supercorium is engorged with blood and an hydraulic system arises which helps support the weight of the horse. 10

11 J. Jackson DL FC SC P HB 11

12 (Continued from page 3) matrix in the coronary corium at the rate of 1 cm per month [See Bulletin #100]. The top narrow edge of each leaf is curved and forms the lower shoulder of the coronary groove seen in Figure 1. The lower narrow edge fuses with the sole and forms the white line visible at the bottom of the hoof. The long outer edge is, like the body of the horn tubule, embedded in the intertubular horn matrix of the stratum medium proper. The inner long edge faces the coffin bone (or the cartilages or digital cushion, as the case may be) but is separated from it by the laminar corium, which indirectly secures the leaf to the face of the bone (cartilage, etc.) by means of connective tissue. Blood supply to the coronary corium is discussed in a separate section of this article (CIRCULATION AND THE SUPERCORIUM). C. Pollit Supercorium Supercorium Laminar Corium The laminar corium intermeshes with the coronary corium at the shoulder of the coronary groove and continues down to the bottom of the hoof where it intermeshes with the sole corium. The laminar corium forms the face of the Supercorium behind the entire hoof wall, including the bars. The relationship between the two is evident in the quadra-plex of color plates on page 7. On its outside (i.e., the hoof wall side), the laminar corium fills the space between each of the primary epidermal laminae created by the coronary corium. In other words, it forms complementary dermal leaves that reach from the coronary groove down to the ground. On the inside, it forms a strong attachment via connective tissue to the face of the coffin bone, the collateral cartilages, and the subcutaneous tissues of the digital cushion. At the bottom of the hoof, as stated, it intermeshes with the solar corium. Under powerful microsopic inspection, it will be seen that each dermal leaf described above is, like the tubule socket of the coronary corium, covered by an extracellular dermal layer called the basement membrane. This membrane resembles the laminar corium, in that it is vascular, innervated, and comprised of strong connective tissue. The outside of the basement membrane is covered with germinal epidermal (parabasal) cells. These cells proliferate keritinizing daughter cells, which sustain a secondary set of epidermal folds ( secondary lamina ) along the length of each primary epidermal laminae.¹ These are seen in Figure 4 Primary and Secondary Lamina (Top) Tapered primary lamina extend towards P3. (Bottom) Magnification of primary lamina reveal secondary folds ( secondary lamina ) along tapered lengths. Figure 4. There are approximately 150 to 200 secondary folds (leaves) per primary epidermal laminae. As can be seen in Figure 4, the spaces between the secondary folds are filled with dermis from the laminar corium. The leaves and folds of the epidermal lamina project towards P3, but they are separated from it by the dermis. The dermal and epidermal leaves together comprise the inner hoof wall or stratum internum (also called the stratum lamellatum). During normal wall growth, it is assumed that the epidermal lamina and stratum medium descend past the stationary basement membrane (and its parabasal cells) and laminar corium. It is thought that remodeling enzymes break down the interfacing cell-tocell bonds during cornification (the formation of keritinized horn by the basement membrane along the leaves of the laminar corium) which allows growth from the coronary corium to move past. Specialized rivet cells called desmosomes create new bonds to replace the old, ostensibly in a staggered manner. ¹Veterinary researchers studying wild horse hooves claim that there are tertirary folds. I will update here as evidence is documented. 12

13 J. Jackson SE SM SI (Lamellar Wedge) S Figure 5 Lamellar Wedge In this interesting cross-section of a chronic Supercoriatic (laminitic) hoof, the forward streaming toe wall reveals its aberrant stratifications. The thin layer at top is the periople or stratum externum (SE); next the true wall or stratum medium (SM); then the inner hoof wall or stratum internum (SI); and at bottom, supporting everything above, the sole. The highly disorganized inner hoof wall is known as the lamellar wedge in this state. It is produced by surviving epidermal germinal cells still attached to the basement membrane following acute Supercoriaitis. Normal interdigitation with the primary epidermal lamina is obstructed by the presence of certain enzymes which erode the dermal-epidermal attachment mechanism. Natural trimming and horsekeeping practices help to reverse this condition. During laminitis [See Bulletin #102], cornification is disrupted by the massive proliferation of these enzymes which overwhelm normal desmosome capacity.¹ The epidermal lamina then elongate and separate from their dermal counterparts. The void between them fills with gas and disorganized epidermis (produced by surviving kerotinocytes still attached to the basement membrane), called the lamellar wedge (Figure 5). A stretched white line, visible at or near ground level, is the result. Near the sole, the bottom (distal) edge of each dermal leaf projects hair-like terminal papilla that resemble the coronary and perioplic papilla (See color plate, page 6). These papilla also insert into epidermal sockets where they produce and nurture horn tubules surrounded by intertubular horn. This horn intermeshes with tubular-interbular horn produced by the solar corium. The descending primary lamina are embedded in this confluence of epidermis and are thence directed by it to the ground, where, notwithstanding neglect, the entire mass, which forms the white line, is worn (or trimmed) away. I think it is worth describing a much overlooked part of the inner hoof wall and outer hoof wall junction. This concerns the water line (Figure 6, page 14).¹ I believe its significance is completely overlooked by the general hoof care community, where it is normally abraded flat into the bearing surface of the hoof, and subsequently shod. The water line has its origin in the highly vascular dermal leaves of the Supercorium. This moisture apparently permeates the adjacent stratum medium (outer wall) to a certain ¹C.C. Pollit, Equine Laminitis: A Revised Pathophysiology. Farrier and Hoofcare Resource Center ( ¹So named by L. Emery, J. Miller, N. Van Hoosen, Horseshoeing Theory and Hoof Care, p ,

14 OW Figure 6 Water line (Top) W marks the water line, ironically a narrow band of tough, dry horn at ground level. It circumscribes the entire white line (WL) of the hoof wall from heel to heel. It is an area of little or no pigmentation and has a lower concentration of tubular horn than does the outer wall (OW). The water line is thought to be the outermost salient of the hoof wall proper (stratum medium) that receives abundant moisture from the dermal leaves above the terminal papilla, hence the derivative of its name. (Bottom) In the wild horse hoof, the water line is the most distal part of the hoof wall (and mustang roll) enduring active contact with the ground; thus, it is thought to be the toughest and most durable part of the hoof wall, if not the entire capsule. (Middle) Accordingly, natural hoof care practitioners trim the water line to endure active ground contact [See Bulletin #106]. Blue arrow points to rim of active water line. J. Jackson W OW Sole WL W J. Jackson Sole WL W 14

15 extent, evident when a hoof paring dessicates upon the ground and shrivels into a crescent. However, by the time the terminal papilla and associated interbular horn fuse the hoof wall to the sole, the water line dehydrates and becomes what may be the most durable and wear-resistant structure of the capsule. In the naturally worn hoof s ordering of relative concavity, it sits prominently at the base of the volar dome. As I ve written in the HOG, and Bulletins #106 and #107, natural hoof care practitioners target the water line specifically for its role in active wear when contouring the mustang roll. Perioplic Corium Periople is a layer of relatively soft horn that forms a thin skin over the coronary band and upper hoof wall (Figure 5). It is produced by the perioplic corium, which forms a cord-like ring around the upper front surface of the coronary groove. Like the stratum medium, periople is extruded by minute papillae embedded in intertubular horn. Perioplic papilla are smaller than the papilla of the coronary corium. Emery has speculated that perioplic horn serves as a varnish-like protective coating to prevent excessive evaporation of the upper stratum medium s inner moisture.¹ Pollit states that it connects the hoof to the skin.² Looking to the Supercorium for clues, I would suggest that it serves also as a sealant or band-aid of sorts for closing off coronet wounds and resolved infections (e.g., abscesses from hot nails ) in the laminar corium. Concerning the latter, purulent matter under growing exothermic pressure in the vertically oriented dermal leaves apparently follows the path of least resistance between the epidermal lamina to the coronary corium. A wound to the white line at the quarters, for example, will travel up at the wall s angle-of-growth to the coronet (Figure 7). The thin and supple periople yields readily to the hot abscess within; just as quickly it heals over as the abscess is passed. It would be the rare hoof care professional who has been spared these unctuous, fetid outbreaks at the coronet, which nearly always resolve in soundness of the hoof. Sole Corium The sole, or solar, corium intermeshes with the laminar corium where the sole and stratum medium are adjoined by the inner hoof wall. It also intermeshes with the wedge-shaped frog corium along the collateral Figure 7 wound abscess coronary band eruption of abscess through perioplic skin Abscess in sole/laminar corium expelled along path of least resistance. Eruption of abscess occurs through perioplic skin. sulci. Like the coronary and perioplic coria, the solar corium produces keritinized tubular and intertubular horn. The color plates on pages 8, 9 and 10 provide views with descriptions of the sole corium and its interface with the capsule. Frog Corium The frog corium is also distinguished by minute papilla which produce tubular horn embedded in interbular horn. The color plates on pages 9, 10, and 11 include views with descriptions of the frog corium. CIRCULATION AND THE SUPERCORIUM The Supercorium is stimulated into action by an optimal hoof mechanism and barefootedness, the two being synonymous. During the hoof s weight bearing phase, the Supercorium engorges with blood is under pressure, in other words and the horse is hydrodynamically supported within the capsule. With flight and loss of the weight bearing force, hydrostatic pressure diminishes as blood is evacuated from the hoof through the venous plexus. A fascinating description of this hydrodynamic system, taken from a century old British War Department Manual for hoof care, is worth remembering: The blood supply is so bountiful that in addition to giving nourishment to the foot, it acts like a water bed, helping to equalize the tremendous pressures to which the whole structure is (Continued on page 18) ¹Emery, et al., Horseshoeing Theory and Hoof Care, p. 27 ²Pollit, Color Atlas, p

16 C. Pollit CCA DA CC 1 TA 8 2 CAS Figure 7 Circulation and the Supercorium Two main arteries, the lateral and medial digital arteries (DA), come down each side of the lower leg to the hoof. Eventually they enter the back of the coffin bone where, inside, they merge together. This juncture is called the terminal arch (TA). The digital arteries have several main branches and countless sub-branches which form and nutrify the Supercorium. All of them anastomose (i.e., interconnect). Just above the coronary band, the coronary circumflex artery (CCA) winds around the pastern. It has many smaller downward directed branches (1) which divide further to become a part of the coronary corium (CC). Above the coronary circumflex artery, posterior branches (2) of the main digital arteries descend to become part of the frog corium, posterior laminar corium, and posterior coronary corium (4). Behind the coffin bone on either side, branches of the digital arteries pass through notches in the palmer processes (3). New sub-branches lead out from there. One branch leads downward to become part of the circumflex artery of the sole (CAS), which circumscribes the periphery of the sole; subbranches off this arterial loop project under the coffin bone to become part of the solar corium (not seen in photo). Other branches lead to the back of the hoof to become part of the frog corium, posterior laminar corium, and posterior coronary corium (4) ; and forward, to form the laminar corium at the quarters above the circumflex artery (5), and also to re-enter the coffin bone wherein they anastomose once more with the digital arteries just behind the terminal arch (6). Inside the coffin bone, branches off the terminal arch pass through foramen in the face of the bone to form part of the laminar corium (7). These laminar arteries also form upward directed branches (8) that anastomose with branches of the coronary circumflex artery at the coronary corium (CC). They also direct branches (9) to the sole where they become part of the circumflex artery of the sole (CAS). All the above major arteries continue to branch into countless smaller and smaller units (facing page). This insures that blood can flow freely in virtually all directions throughout the hoof and the Supercorium, in short, wherever it is needed to nourish new growth and sustain vital hydrostatic forces. Blood exits the hoof through the venous system (not shown in photo) with equal freedom. Besides capillaries and veins, there are unique valves called arteriovenous anastomosis which enable blood to flow directly from artery to vein, thus bypassing the capillary beds altogether. These help to equalize hydrostatic forces throughout the body of the Supercorium. 16

17 (Right) Countless blood vessels circulating through the hoof were filled with latex and the capsule dissolved in acid. The dark colored medial and lateral digital arteries (DA) are visible at back of hoof. The light colored venous plexus (VP) that drains the lower veins of the hoof is also visible nearby. These major arterial and venous pathways eventually downsize to form the complex vascular system of the Supercorium. J.A.W. Dollar, A Handbook of Horseshoeing, 1898 VP DA (Below) I ve contrasted the corrosion above with a similar profile of the Supercorium. J. Jackson 17

18 (Continued from page 15) constantly subjected, and keeping the bones and sensitive parts contained in the hoof buoyantly supported, like a big ship in a little dock.¹ The Supercorium, which we might envision now as a complex vascular sponge, engorges with blood via a unique network of interconnecting anastomosing arteries. Once they reach the Supercorium, these arteries then branch ever downward in size until they terminate in a microscopic capillary network, at which point they are evacuated by a parallel system of veins. These arteries (and capillaries and veins) penetrate the entire Supercorium, including each minute papillae. The color plates on pages 16 and 17 provide images and descriptions of the Supercorium s vascular network which both nutrifies and comprises a significant portion of its mass.² Hydrodynamic and mechanistic stimulation also causes the Supercorium to accrete extraordinary dermal and epidermal mass as an adaptive or survival mechanism [See Bulletin #108]. This is seen in the hooves of wild, free-roaming horses and in high performance barefoot domestic horses. The capsule becomes sturdier and proportionately larger in mass relative to P3. P3 SUPPORT AND THE SUPERCORIUM Much has been written in the veterinary and farriery literature about the support function of the inner hoof wall in the hoof-to-horse connection. Convention states that the interdigitated dermal and epidermal leaves suspend the coffin bone (P3) and, thus, the weight of the horse, within the capsule. Such support, it is argued, is made possible by the many secondary folds (secondary lamina) of the primary epidermal lamina. These bond tightly with the connective tissue of the basement membrane of the dermis (Supercorium), which, in turn, is fused to the face of the coffin bone through its own maze of reticulated connective fibers. This interpretation once seemed plausible to me, but now seems deficient in view of the highly vascular interface the Supercorium between P3 and the capsule. I believe that hydrostatic forces arise in the interface to cushion the dermis as the weight-bearing force is transmitted from P3 to the capsule. In other words, it is principally hydraulic pressure, rather than a simple suspensory bridge of reticulated epidermal leaves and connective tissue, that provides P3 support during weight bearing. During flight, when the hoof is in its naturally contracted, non-weight bearing phase, the Supercorium is relatively flaccid and emptied of blood since it is lightly compressed between the capsule wall and P3. This compression squeezes blood out of the Supercorium and into the hoof s major venous plexus (actually, there are two, one on either side of the collateral cartilages), where it remains pooled until support. As the hoof enters support, the Supercorium engorges with blood as mechanistic forces increase the volume of the space between the capsule and the coffin bone it certainly isn t getting smaller, since the capsule is expanding under the weight of the horse and P3 is not. Blood in the venous plexus is now driven up the leg as pressure is exerted upon it by the bulging coronary corium, upper interior hoof wall, collateral cartilages, extensor tendon, and outer integument.¹ Expansion of the capsule commences at the frog and heel bulbs, and moves forwards from there [See Bulletin #108]. We ve seen in the color plates (pages 10 and 11) that this posterior region of the Supercorium is very elastic and able to spread apart into the buttresses of the capsule. This is due to the presence of the spongy digital cushion above the frog corium. The entire weight of the horse is not concentrated here, however, since the propulsory action of the deep digital flexor tendon (driven by the expanding semiflexor joints of the upper leg, see my book The Natural Horse, page 55) is proactively pulling the weight bearing digit forward towards the toe; the hoof would fall over backwards, if this weren t the case. At this time the arched sole of the capsule also gives slightly under the weight of the horse. The sole corium fills with blood as the space between the capsule and P3 increases. As the weight bearing force moves forward (off of the digital cushion and buttresses), the solar interface comes under hydraulic pressure. At the same time, the flaccid inner hoof wall ¹Animal Management, Prepared in Veterinary Department of the War Office. London: His Majesty s Stationery Office, p ²Please refer to Pollit s Color Atlas, which has excellent images of the hoof s circulatory system described here. ¹Pollit s 1990 video study (available at com) of circulation in the hoof shows blood pumping out of the hoof during support, which argues against my hoof hydraulic theory. But Pollit uses a cadaver with the venous plexus severed open, which precludes hydrostatic venous back pressure from building in. Redden s wild horse hoof venogram study (The Wild Horse Hoof, 2001 Laminitis Symposium) demonstrates the extraordinary back pressure in the closed system I am postulating. 18

19 (collectively, the interdigitated lamina) stretches slightly to accommodate this expansion. It also keeps P3 aligned and balanced in the capsule. The dermal leaves rapidly fill with blood and the Supercorium here too comes under hydraulic pressure. In short, wherever there is extreme weight bearing (i.e., compressional) pressure, hydraulic forces arise to offset it and augment the laminar suspensory mechanism. The vast interconnecting network of anastomosing vessels enables blood to move freely within the Supercorium in order to build, relieve and equalize pressure in the dermal interface. Without this hydrostatic force field, the full weight of the horse must be borne entirely by the soles and dermal-epidermal leaves of the inner hoof wall. S UPERCORIUM AND NATURAL HOOF CARE In the horse s natural world, the Supercorium produces the capsule with no other attention but to the animal s survival. Nothing else matters. Through its complex network of nerves and blood vessels, it is able to sense the environment that the horse must negotiate, and then build the most efficient and durable capsule possible for the stated purpose. In this interpretation, the hoof is not simply shaped by the environment, it is built by the Supercorium to withstand the environment. Natural, holistic forces pose the right challenge to bring out the best in the Supercorium to do its job. It must be challenged worked and nutrified properly or it becomes dysfunctional and produces weak, dysfunctional hooves. Precisely the plight of most domestic horses today. This is why horseshoeing came about: to cover up the problem. Unfortunately, shoeing does not strengthen the hoof, but further weakens it, and holds it perpetually in its dysfunctional state. Natural hoof care and holistic horsekeeping practices have arisen in recent years to take up the slack of a lax and alien domestic environment, and help the Supercorium build the hoof the horse requires to be sound and efficient. Natural hoof care practitioners do this by learning to communicate with the Supercorium. Practically speaking, this is done by studying the cause and effect of their work on the capsule s growth patterns. The wild hoof model, which represents the epitome of soundness and efficiency, provides the road map. The Supercorium lets us know if we are on track or astray. Let s consider several examples of how this works in the natural trimming of domestic horses. The Supercorium, according to whole horse 19 trimming principles, conceives the hoof s natural angle-of-growth, N, in response to holistic forces [See Bulletin #109]. Typically, unnatural environmental forces (e.g., unnatural diet, mechanically obstructive shoeing, biomechanically incorrect saddling systems, and close confinement) undermine N and transform it into H, the hoof s healing angle when under duress [See Bulletin #101]. Through natural hoof care methods and natural horsekeeping practices, practitioners stimulate the Supercorium to reorganize the hoof s dermal-epidermal mass such that H and N are harmonized, that is, so that H can modulate to N. The technical process of harmonizing H with N involves many potential influences. For example, wall flare is removed by following the Rules of Rasping [See Bulletin #106]. Run-under heels are restored to normal by lowering the heel-buttresses relative to H [See Bulletins #101 and #106]. Wall splits are closed and healed by balancing the capsule relative to the median plane [See Bulletins #101, #105, and #106]. And hoof separation from the horse (Supercoriaitis) is reversed by implementing changes in diet while adapting the natural trim methodically to the disfigured capsule [See Bulletins #103 and #104]. The repertoire of natural trimming techniques with which to stimulate and help the Supercorium to produce a healthy hoof is as extensive as it is precise. Among natural hoof care practitioners, it is a language that must be learned and administered judiciously and with respect for the living dermis behind the capsule. The Supercorium demands this of us, or it will surely revolt with dire consequences (e.g., Supercoriaitis, wall splits, and hypersensitive soles). In contrast, there is a propensity among many farriers, horse owners, and veterinarians to see the capsule and not the Supercorium as the only expression of the hoof. Consequently, there is no communication with the whole hoof and there is no perceived need to do so. Much effort thus goes into manipulating, often brutally so, the visible epidermis, while ignoring the subtle concomittant effects upon the dermal superstructure within. The Supercorium, only concerned with the horse s survival, must somehow make itself heard. Ignored, it provides not so subtle clues formation of a club foot, separation of the hoof wall from the sole, recurrent wall splits, hypersensitivity, and so on. These are not just symptoms of hoof dysfunction, they are signals to the practitioner (and horse owner) that he or she has failed to read the Supercorium s more subtle protests earlier on in the hoof care process. Lameness is the culmination of the communication breakdown. (Continued on back page)

20 (Continued from page 19) CONCLUSION The Supercorium is the voice of the whole hoof. Learning to speak its language is the vital key to effective natural hoof care. The language is learned by first identifying the sub-coria of the Supercorium, and then studying the cause and effect of natural trimming and horsekeeping practices on future capsule growth. Questions & Answers About The Supercorium If the Supercorium dwells behind the capsule, how can we communicate with it? Indirectly. The manner in which we contour the capsule (e.g., the Rules of Rasping, Bulletin #106), for example, influences how the Supercorium will respond with new growth. The way it s fed (e.g., a laminitic diet) also influences its ability to produce new growth. What effect do wall resections have on the Supercorium? It doesn t like them at all. During the 1990 s (and even into the present) wall resections, tantamount to surgery, became popular among veterinary (and farrier) practitioners desperate to bring seemingly uncontrollable laminitic growth under control. This trend, not surprisingly, resulted in countless cases of infection nationwide. Equally of concern, removing the hoof wall (usually around the toe) weakens the peripheral stability of the capsule, which obstructs the hoof mechanism. This, of course, affects circulation and the ability of the hoof to repair itself. What is Supercoriaitis? It s a term I coined to replace laminitis with. The latter leads us to believe that the hoof-to-horse attachment failure is limited to the laminar corium and P3. It s not, witness hoof slough. My hope is that horse owners and others will view the attachment failure far beyond the visible boundary of stretched lamina. It is truly a whole horse disease caused by unnatural diet, including veterinary drugs. Supercoriaitis is epidemic in the U.S. and elsewhere. We don t know what constitutes a natural diet for the horse, and therein lies the problem. I believe the answer lies in wild horse country, not in a laboratory. Veterinary researchers, funded by the feed and pharmaceutical industry, should mount an coordinated investigation of the founder-free wild horse diet. I noticed from the color plate in Figure 7 that the circumflex artery of the sole lies at the bottom of the laminar corium. Isn t barefootedness going to put pressure on this artery and cause damage to it? During support, the arched sole bends under the weight of the horse. Dermis in the region of the circumflex artery then engorges with blood and hydraulic pressure builds in. This pressure protects all the sensitive structures of the Supercorium, including the aforementioned artery and its counterpart the circumflex vein. Horseshoes, however, can actively obstruct mechanistic expansion of the solar dome and cause pressure necrosis of the sole corium, thus damaging the artery. JAIME JACKSON is a 27 year veteran hoof care professional specializing in natural trimming and booting of horses. He is the author of The Natural Horse: Lessons From The Wild For Domestic Horse Care; Horse Owners Guide To Natural Hoof Care; Founder: Prevention and Cure The Natural Way; Guide To Booting Horses For Hoof Care Professionals; and numerous articles. He conducts a private consultation service ( and is current Orientation Clinician and Director of the American Association of Natural Hoof Care Practitioners ( 20 This publication is issued solely by Star Ridge Publishing. All rights reserved. Copies may be purchased by contacting the publisher: P.O. Box 2181, Harrison, AR Order on-line at: