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The horse hoof is the distal phalanx of the III digit of the four limbs of Equus species, and it is covered by complex horny structures. The well known sentence "No hoof, no horse" underlines how much the health and the strenght of the hoof is crucial for the horse soundness and usability. Look up phalanx in Wiktionary, the free dictionary Phalanx (Greek word from phalangos, meaning Finger) can refer to: phalanx formation in ancient warfare. ...
Equus is Latin for horse; it may refer to: Equus, the genus of horses and their close relatives. ...
Both wild and feral equid hooves have a unbelievable strength, and they allow any gait on any ground. It is very interesting to underline that the Mustang is not at all a breed, but a set of many horse breeds. Therefore, the well known Mustang hooves strenght is probably a potential, commom trait of many domesticated horse breeds, and perhaps of all from them. Mustang can refer to: The word mustang, from Spanish animalia mixta, mesteño or mestengo, an ownerless beast: Mustang, a feral horse living on the western or southwestern plains of the US. P-51 Mustang, a World War II military aircraft. ...
Mustang can refer to: The word mustang, from Spanish animalia mixta, mesteño or mestengo, an ownerless beast: Mustang, a feral horse living on the western or southwestern plains of the US. P-51 Mustang, a World War II military aircraft. ...
The recent Barefoot movement claims that such a strength can be almost completely restored into the domesticated horses too when appropriate trimming and boarding is applied, to an extend that horseshoes are no more necessary in almost any horse, so undermining the well known sentence "The horseshoes are a necessary evil". The Barefoot horse movement is a growing, world-wide set of horse owners, practicians, teachers and vets advocating the use of barefoot horse, a wild-horse trim and the naturalization of horse diet and boarding settings. ...
Modern horseshoes are most commonly made of iron and nailed onto the hoof. ...
Outline of horse hoof anatomy
 Barefoot hoof, lateral view. Coronal band (1), walls (2), toe (3), quarter (4), heel (5), bulb (6), P2 (small pastern) (7) The hoof is made up by an outer part, the hoof capsule, made up by various horny specialized structures, and an inner, living part, containing soft tissues and bone. The corneous material of the hoof capsule is different in structure and properties in different parts; it covers and supports P3 (the coffin bone) anteriorly, and specialyzed soft tissues (tendons, legaments, fibro-fatty and/or fibrocartilaginous tissuen, cartilages) posteriorly. The upper, circular limit of the hoof capsule is the coronet (coronary band), obliquous in its plane with an angle of approx 30° to the ground. The walls originate from the coronary band; they are modified nails. Walls are longer in the anterior portion of the hoof (toe), intermediate in lenght in the lateral portion (quarter) and very short in posterior portion (heel). Heels are separated by an elastic, gummous structure named frog. In the posterior part of the foot, above the heels and the frog, there are two oval buldges named bulbs. Image File history File links Hoof_lat. ...
Image File history File links Hoof_lat. ...
 Transitioning barefoot hoof, from below. Details: heel perioplium (1), bulb (2), frog (3), central groove (4), collateral groove (5), heel (6), bar (7), seat of the corn (8), pigmented walls (external layer) (9), water line (inner layer) (10), white line (11), punta del fettone (12), sole (13), toe (14), how to measure width (15), quarter (16), how to measure lenght (17) When you pick up the hoof and you look at its lower surface, you can see the walls free margin, encircling most of the hoof. In the central area, you can see a triangular gummy structure; lateral to the frog, you can see two grooves, deeper in their posterior portion, named collateral grooves. At the heels, the walls bent suddenly, following the external surface of collateral grooves; here they are named bars. The lower surface of the hoof, from the outer walls and the inner frog and bars, is covered by an exfoliating horny material, named sole. Image File history File links Download high resolution version (738x981, 156 KB) Summary Author: User:Alex brollo Horse hoof, bottom view, quoted. ...
Image File history File links Download high resolution version (738x981, 156 KB) Summary Author: User:Alex brollo Horse hoof, bottom view, quoted. ...
Just below the coronet, walls are covered for about an inch by a horny, opaque material named perioplium. In the posterior part of the hoof, the perioplium is thicker and gummous over the heels, and it merges with frog matherial.
Characters and functions of the external hoof structures
The walls The walls are to be considered both as a protective shield, covering sensible internal hoof tissues, just like esoskeleton of arthropodes, and as a structure devoted to concussion energy dissipation and to grip into different terrains. They are elastic and very tought, similar to a teflon layer; its thikness is approx mm 6 to mm 12. The walls are built up by three different layers, the pigmented layer, the water line, and the white line.
The pigmented layer is made up by the coronet, and its color is just like that of the coronet skin where it comes from. If the coronet skin has any dark patch, the walls show a parallel pigmented line, form the coronet to the ground, showing the walls growth direction. It has a prevalent protective role, and not so resistant to the contact to the ground, where it breacks and chips away.
The water line if built up by the coronet and by the walls corium, the living tissue deep to the walls; its thickness grows from the coronet to the ground, and in lower third of the walls is thicker than pigmented layer. It is very resistant to contact to the groung, and it has mainly a support function.
The white line is the inner layer of the walls; it is softer and fibrous in structure. Its color is yellowish. You can see it in the healty hoof as a thin line separating the sole and the walls. The white line comes out from the laminar connections; any visible derangement of the white line indicates some important derangement of laminar connections, that fix the walls to the underlying P3. Since white line is softer than both the walls and the sole, it wears fastly where it appears on the surface, and it looks like a subtle groove between the sole an the walls, with some debris or sand inside.
The three layers of the walls merge in a single mass, and they grow down together. If they don't wear from sufficient movement on abrasive terrains, then they stick out from the solar surface; then, in the best case, they self-trim breaking or chipping out.
Walls are used too to apply horseshoes; the nails are applied oblique to the walls; they enter the wall at white line and they come out to walls surface approx mm 15-20 from the hoof bottom.
Their anatomical analogue into the human finger are the nails.
The frog The frog is a triangular structure, about 2/3 of the sole in its lenght. Its thikness grows from the front to the back, and in the back it merges with heel perioplium. In the middle, it has a groove, the central groove, that extend up separating the bulbs.
It is dark gray-blackish in color, and a gummous consistence, suggesting its role as shock absorber and grip tool on hard, smooth ground. In the stabled horse, it doesn't wear, but it degrades for bacterial and fungal activity with an irregular, soft, slashed surface. In the free roaming horse, it hardens into a callous consistence with a rather smooth surface.
Its anatomical analogue in the human finger is the fingertip.
The sole The sole has a whitish-yellowish color, sometimes a grayish one; it fills the whole space from the walls edge to the bars and the frog into the bottom of the hoof. Its deep layer has a compact, waxy character and it is called "live sole". Its lower surface is variable in its character, as a result of ground contact. If there is no contact, as in shod hooves, or when the walls are too long or the movement poor, the lower surface of the sole has a crumbly consistence and it is easily removed scratching it with a hoofpick. On the contrary, it has a very hard consistence with a smooth, bright surface when there is a consistent, active contact with the ground; the resulting configuration is called "sole callus".
The bars They are inward folds of the walls originating from the heels with an abrupt angle; the strong structure built up by the extremity of the heel and of the bar is named "heel buttress". The sole between the heel walls and the bars is named "seat of the corn", and it is a very important landmark used by natural hoof trimmers to evaluate the correct heel height. The bars have a three layer structure, just like the walls. When overgrown, they bent outwards and cover the lower surface of the sole.
Internal structures
 Sagittal setion of a wild horsehoof. Pink: soft tissues; light gray: bones (P2, P3 and navicular bone); blue: tendons; red: corium; yellow: digital cushion; dark gray: frog; orange: sole; brown: walls) The third phalanx (coffin bone; pedal bone; P3) is completely, or almost completely, covered by the hoof capsule; it as a crescent shape, and a lower cup-like concavity. Its external surface mirrors the walls shape. The corium, a dermoepidemal, highly vascularized layer between the walls and the coffin bone, here has a parallel, laminar shape and is named "laminae". Laminar connection has a key role in the strenght and the health of the hoof. Into the back of the hoof, there is the digital cushion, that separates the frog and the bulb from underlyng tendons, joints and bones. In the foal and in the colt, the digital cushion is made by fibrofatty, soft tissue; in the adult horse if hardens into a fibrocartilagineous tissue, when sufficient, consistent concussion stimulates the back of the hoof. Normal transformation of the digital cushion into fibrocartilagineous tissue is now considered a key goal both to navicular syndrome prevention and rehabilitation [1]. The flexor tendon lays deeper, just along the posterior surface of small pastern bone and navicular bone, and it connects with posterior surface of P3, the navicular working as a pulley. Image File history File links Horse_hoof_wild_bare_sagittal. ...
Image File history File links Horse_hoof_wild_bare_sagittal. ...
Navicular Disease is a soundness problem in horses, and not an actual disease. ...
The hoof mechanism
 Bare hooves imprints on the snow. Left, a front print, right, a hint print; note the different shape and the wide contact with the ground The horse hoof is not at all a rigid structure; it is elastic and flexible. Just pull and push the heels one to the other one, and you'll feel it. When loaded, the hoof phisiologically changes its shape. In part, it is a result of solar concavity; it has a variable depth, about cm 1 - 1.5. In part, it is a result of an arched shape of the lateral lower profile of the walls and sole, so that an unloaded hoof touches a concrete, regular ground only at toe and heels (active contact), where a loaded one has a wide area of ground contact (passive contact) covering lower walls edge, most of the sole, bars, frog. Active contact areas can be seen as slightly protruding spots in the walls or/and in the calloused sole. Image File history File linksMetadata Download high resolution version (1866x1353, 300 KB) Summary A front (left) and hind (right) footprint of a barefoot mare (1 year after de-shoeing). ...
Image File history File linksMetadata Download high resolution version (1866x1353, 300 KB) Summary A front (left) and hind (right) footprint of a barefoot mare (1 year after de-shoeing). ...
The shape change in a loaded hoof is a rather complex one. The plantar arch flattens, the solar concavity decreases in depth, and heels wander away one from the other. The hoof diameters increase to a "dilated" configuration; P3 slightly drops into the hoof capsule. There is some recent evidence that a depression takes place in this phase, with blood pooling ("diastolic phase") mainly into the walls corium. When unloaded, the hoof restores its "contracted" configuration, the pressure raises and the blood is squeezed off ("systolic phase"). This is just the opposite of what was believed (a "systolic" phase under load, with the frog acting as a blood pump).
The hoof mechanism ensures an effective blood circulation into the hoof, and it helps general circulation too.
Time-related changes of the hoof Hooves have to be considered a plastic structure, and their time-related, very complex changes can be considered in the short period (days/weeks), in the medium period (the horse's lifespan), and in the long period (the evolution of equids).
Hoof changes in the short period Just like the horny layer of epidermis and of any mammal nail, the hoof capsule is built up only by epidermis covering the skin. From a microscopic point of view, epidermis is a multi-layered, specialyzed cornifying epithelium. It lays on the dermis, and it it separated from it by a basal lamina; it has no blood vessel inside, and living cells get oxygen and nutrients by fluid exchanges and molecular diffusion from underlying dermis flowing into microscopical spaces among individual cells. Epidermis growth take place by mitotical activity in its deepest layer, mainly into the basal layer, and slow outward migration and maturation of cells; when approaching to the surface, peculiar proteins accumulate into their cytoplasm, then the cells die and "dry off" into microscopic, tightly connected individual laminae, made up mainly by cheratin; the resulting "dead" superficial layer has a protective function, saving underlying living tissues from injuries, from drying off and from fungal and bacterial attack. The constant thickness of the corneous layer results most commonly from regular superficial exfoliation; when a specialyzed corneous structure has a very peculiar toughness, as in nails and hair, little/no exfoliation occurs, and corneous structures have to slowly migrate away from their original position.
So, specialyzed horny structures of the hoof are the walls, the sole, the frog and perioplium. The first one doesn't exfoliate at all; it is constantly growing downward (about cm 1 a month) and self-trims by ground contact by wearing, sometimes by chipping, in wild and feral horses. Solar, frog and perioplium matherial grow outwards, and exfoliate at surface by ground contact and wearing. In the domesticated horses, movement and usual ground hardness are not sufficient to allow self-trimming, so humans have to care about them, trimming the walls and the frog and scratching the dead sole.
Hoof changes in the medium period Front and hint hooves are perfecly identical in the fool, but they have visible differencies in the adult horse: a good evidence of long term plasticity of the whole hoof shape, as a result of different, daily use. Slow changes of the hoof shape take place under any consistent change in the horse movement pattern and under a wide variety of pathological conditions. They could be seen now as a bright example of a complex adaptive system, a frequent feature of living beings and structures. A complex system is a system whose properties are not fully explained by an understanding of its component parts. ...
Self-adapting capabilities of the hooves show their maximal effectiveness in the wild equids, but is preserved in domesticated horses too, as proofed by the examples of perfect soundness of feral horses, like mustangs, in a wide variety of environmental settings. Mustang can refer to: The word mustang, from Spanish animalia mixta, mesteño or mestengo, an ownerless beast: Mustang, a feral horse living on the western or southwestern plains of the US. P-51 Mustang, a World War II military aircraft. ...
Hoof changes in the long period Equid hooves are the present, amazing end result of a 50-million-year long evolution of the horse. Wild and domesticated Equus species share a very similar hoof shape and function; they result from a slow loss of I,II,IV and V rays of the limbs, with deep changes in bones, joints and hoof capsules. The resulting setting allows a heavy, strong body to move with a high speed and resistance on any ground, and top effectiveness take place into open, hard and flat areas like prairies and deserts. Evolution of horse showing reconstruction of the fossil species obtained from successive rock strata. ...
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