Practical Understanding of Claw Lesions Sarel Van Amstel, BVSc, College of Veterinary Medicine University of Tennessee, Knoxville, TN

Introduction Successful control and and swelling resulting in more pain and management of lameness in commercial inflammation. Progression from partial to swine operations should include the full thickness horn lesions develops over following: Early detection of lameness time but is also dependant on other problems on an individual and herd factors such as flooring and housing. basis. This can be achieved by: 1) Close Hard floors increase concussion on observation of individual animals for individual claws and dissipation of signs of lameness and/or lesions (See tension forces through the claw created flow chart); 2) Lesion identification and by weight bearing becomes less record keeping; 3) Knowledge of the efficient. This may not only lead to causes and corrective actions progression of existing lesions but can necessary for each of the different lead to mechanical trauma of the soft lesions. tissues within the claw which will result in further pain and inflammation. This Visible lesions of the foot without applies particularly to the outer claw of swelling or lameness do not penetrate the back leg which carries more weight through the full thickness of the horn compared to the inner claw. Overgrowth (wall, sole, heel or white line) and as a of the outer claw may further predispose result cause no pain and require no the claw to mechanical trauma. In immediate action. However, it is unpigmented claws inflammatory important that lesions are identified and changes can be seen as red the prevalence recorded. High discoloration below the horn surface. prevalence rates warrant investigation Swelling at and above the coronary as to the possible cause in order to band, particularly in the presence of a institute corrective actions. For example, discharging tract, are signs of deep vertical wall cracks may indicate poor sepsis of the foot often accompanied by horn quality and keratinization and may osteomyelitis. Such lesions are serious point to nutritional imbalances or and usually unresponsive to treatment. deficiencies. Lesions that penetrate though the full thickness of the horn Lameness in the absence of visible cause pain due to penetration into the lesions may indicate problems in the corium (the underlying soft tissue layer) upper leg such as osteochondrosis or which is highly innervated with pain osteoarthritis. Osteoarthritis may follow receptors. Trauma and infection of the osteochondrosis and is commonly seen exposed corium lead to inflammation in the elbow joint of older pigs.

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Structure of the foot

The foot includes the limb below the distal interphalangeal (DIP). P3 is fetlock joint. It is comprised of two digits completely enclosed within the claw each of which has a horn-covered claw. horn capsule.The deep flexor tendon is The term “claw” is preferable to hoof. attached to the flexor tuberosity at the

When referring to an area nearest the back P3.The navicular bone is attached longitudinal axis (i.e. toward the center) to P3 and also to P2. The navicular bursa it is designated as axial, whereas is situated between the navicular bone structures away from the center are and the deep flexor tendon and permits designated as abaxial. movement of the deep flexor tendon over the surface of the navicular bone Each digit of the foot consists of: during extension and flexion of the claw. phalanx 1 (P1), phalanx 2 (P2), phalanx P3, the DIP joint, navicular bone and 3 (P3), and navicular bone; and 2 joints: navicular bursa are within the claw horn proximal interphalangeal (PIP) and capsule. The claws

The purpose of the claw horn parallel to each other. Toward the heel capsule is to protect the underlying these ridges diverge reflecting a more sensitive tissues of the corium and rapid rate of growth in the heel region dissipate the concussion forces that due to faster rates of wear. In mature occur when the digits impact the ground. sows the normal toe length is 45 to It consists of the wall, which can be 50mm. divided into the abaxial (outside) and the axial (inside). The abaxial wall is further The sole is connected to the wall subdivided into the dorsal (or front/toe) by means of the white line. The white and lateral (abaxial) aspects. The wall line courses forward from the area of the is demarcated from the heel on the heel on the abaxial side of the claw, abaxial side of the claw by the abaxial around the tip of the toe and about 1/3 groove. Perioplic horn is the softer horn of the way back on the axial side of the lying just below the skin-horn junction. claw’s weight bearing surface. The white At the back of the foot the periople line is a unique and important structure. gradually widens and eventually It is the softest horn within the claw becomes the horn of the heel. Coronary capsule. This permits it to provide a horn, the hardest horn within the claw flexible junction between the harder capsule makes up the bulk of the horn horn of the wall and the softer horn of of the wall. The wall has faint ridges or the sole. On the other hand, because of rugae, which run horizontally and its softer nature it also represents a

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weak area on the weight-bearing tubules per mm2 in the wall and 20/mm2 surface that is vulnerable to damage. in the sole and heel. Intertubular horn The epidermal layer overlying the interconnects the tubular horn. corium produces horn cells in the form Intertubular horn consists of sheets of of tubules (tubular horn). Cells within the elongated horn cells arranged parallel tubules are arranged in a steep spiral with the bearing surface. Since tubular around the center axis. Tubules differ in horn is what imparts structural strength size, number and shape in various parts to the horn capsule, it follows that the of the claw and are round near the horn of the wall is structurally the inside of the wall and oval near the strongest followed by the sole and the surface. There are approximately 80 heel. Horn quality and physical properties Horn quality is dependent on a of protein, energy, lipids, vitamins A, D number of internal as well as external and E, calcium and phosphorous. factors. Internal factors would include Micronutrients such as the sulfur blood and nutrient supply whereas containing amino acids like cysteine and external factors relate to environmental methionine are essential for cross- influences. Horn production requires linking of keratin filaments. Trace good vascular supply. Any compromise minerals particularly zinc, copper and in blood flow will have a negative effect the vitamin biotin have very important on horn production. Horn production is roles in the keratinization of horn cells also dependent on the supply of and integrity of the intercellular nutrients which include adequate levels cementing substance of claw horn. Biomechanics of weight bearing

Observation of slaughter house heel of the outer claw overgrows and as specimens and claw measurements such is more predisposed to mechanical have shown that weight bearing injury particularly on hard walking between front claws is relatively evenly surfaces. In some instances it appears distributed while there is a significant as if the inner claw of the back leg is difference in claw size between the almost non-weight bearing and under- outer and inner claws of the back leg. goes disuse atrophy. A genetic base for The outer claw has a larger surface area this difference in claw size needs to be and carries more weight. As a result the investigated.

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Pathogenesis of lameness

Lameness is an indication of the steroid (cortisol) release results in presence of pain. The corium is highly gluconeogenesis (break down of body innervated with pain nerve endings. protein to glucose), and activates Inflammatory changes cause the hormone sensitive lipase, an enzyme release of cytokines and which converts body fat (triglycerides) to neurotransmitters which activates pain fatty acids for transport to the liver fibers resulting in transmission of pain where it is used for energy. Cortisol also signals to the brain. Pain is highly causes insulin resistance which makes it catabolic and results in significant more difficult for blood glucose to enter weight loss despite maintenance of cells which in turn will induce further normal food intake. The basal cellular breakdown of body reserves. metabolic rate is elevated. Endogenous

Horn lesions

The claw consists of structurally Sole: Fissures/cracks and sole crack different types of horn which on at the heel/sole junction biometric strength (hardness) ranks as Heel: Erosion and cracks follows (hard to most soft): wall; sole; Coronary band: Hemorrhage; heel; coronary band and white line. discharging tract and swelling Lesions in the different areas are the White line: Hemorrhage; separation following: which is often continuous with Wall: Horizontal and vertical wall separation at the wall/heel junction fissures; Wall crack at the wall/heel and/or heel/sole junction. junction; wall hemorrhages; overgrowth

Vertical wall fissures

Vertical wall fissures occur mainly on Intercellular cementing substance the abaxial wall in one or multiple claws. consists of long chain fatty acids. Biotin The fissure may start at the coronary is important in the production and band or the bearing surface and may elongation of these fatty acids and involve part or full length of the wall. supplementation of biotin can reduce Cracks start in the intertubular horn and the prevalence of vertical cracks in progress along the intercellular cement problem herds. Other causes of vertical substance which connect horn cells wall cracks include trauma. Some pigs together (like the cement in a brick wall). will constantly rub the abaxial wall of the

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outer claw of the back foot in contact origin has to be carried out. This can be with flooring surface when they are lying recognized as red discoloration on the down. This will result in thinning and inside of the wall on multiple feet. weakening of the wall with subsequent Another common location for development of a vertical wall crack. vertical wall crack is the wall/heel Full thickness cracks will cause junction, also referred to as the abaxial severe irritation of the corium with groove. The cause of this lesion is lameness. This is exacerbated by associated with weight bearing on hard secondary infection and inflammation. floor surfaces. The pathogenesis Cracks starting at the coronary band appears to be as follows: During weight can lead to deeper infection of the foot bearing there is expansion of the heel with severe swelling. Infection may towards the outside. This will cause the spread to the bone (usually P2 ). creation of tension forces which pass Not all vertical wall cracks will cause upwards through the heel/wall junction. lameness and careful examination for Dissipation of such forces is less the presence of other problems such as effective on a hard surface and may inflammation of the corium of systemic eventually lead to fracture.

Horizontal wall fissures

A horizontal wall fissure usually with infections caused by gram negative extends across both the abaxial and organisms such as with mastitis or axial walls. They occur on multiple feet metritis. Endotoxin causes the release in the same animal and denote an of vasoactive agents capable of interruption in horn growth due to producing changes in the vascular compromise in the corium. microvasculature of the corium such as Several horizontal wall fissures may increased capillary pressure, edema, occur in the same claw indicating thrombosis and influx of cells associated repeated episodes of interrupted horn with inflammation. Nutritionally induced growth. The vascular compromise is laminitis has not been documented in usually due to substances such as swine. However microscopic changes of endotoxin which can be produced in the laminitis in the claw similar to those in gastrointestinal tract or be associated other species have been reported.

Wall hemorrhages

Red discoloration beneath the are usually traumatic in origin and may wall is an indication of hemorrhage be present in only one claw. Fracture of and/or inflammation. Wall hemorrhages the wall may be present at the same FeetFirst® Sow Lameness Symposium II, Minneapolis, Minnesota, USA, August 31-September 2, 2010 45

time. Severe inflammation on the other sign of a systemic problem or disease. hand may involve multiple feet and is a

Heel erosion and heel and heel/sole cracks

Heel erosion and heel cracks are overgrowth and opening of deep the most common lesions found in the fissures may be helpful to slow down the claw. The outer claw of the back leg is process. Thorough cleaning in addition often the most severely affected due to to antibiotics and anti-inflammatory the biomechanics of weight bearing. medication are indicated in the Heel horn is soft (has few horn tubules) treatment of such cases. Attention to the and makes up the largest part of the abrasiveness of flooring surfaces, foot weight bearing surface of the claw. This baths and social interaction in group is unlike other cloven hoofed animals housing may be useful in limiting the where the sole forms the largest part of incidence of lameness as a result of the weight bearing surface. The sole heel erosion and heel cracks. has more tubules and is harder than the heel. Lesions of the heel vary from Heel/sole crack is another entity shallow erosion to deep cracks which which may result in lameness. The heel often reach the underlying corium and becomes separated from the sole. This results in pain and lameness. Cracks separation may progress to include the become infected with anaerobic bacteria abaxial white line and sometimes the which produce keratolytic enzymes that axial white line. In such cases the heel will lead to further destruction of heel may almost become separated from the horn and cause inflammation. Removal rest of the claw. Such lesions often of some of the hyperkeratotic extend into the corium resulting in lameness.

White line separation (disease)

The white line consists of soft separation is also linked to the flexible horn. As such it is very biomechanics of weight bearing. The susceptible to the abrasive effect of abaxial white line is widest at its caudal concrete and the erosive effects of abaxial border where it connects with bacterial enzymes. Because of the soft the bottom of the heel/wall junction horn cell turn-over is faster than in other (abaxial groove). During weight bearing parts of the claw with the result that there is lateral expansion of the heel. more immature cells are in contact with The abaxial groove and white line is the bearing surface. White line pushed sideways. This results in FeetFirst® Sow Lameness Symposium II, Minneapolis, Minnesota, USA, August 31-September 2, 2010 46

widening of the white line and greater gets trapped into the separated area exposure of the soft flexible horn to the and may form an abscess which may bearing surface resulting in increased extend into the deeper tissues of the wear. Abaxial white line separation is foot. often continuous with heel/wall crack and/or heel sole crack. Dirt and bacteria

Dew claws

Overgrowth of the dew claws is swelling of the leg may follow. common. The dew claws may become Complications may include joint weight bearing and wear down to a infection or osteomyelitis. Such cases sharp tip which may cause trauma. are usually unresponsive to systemic Overgrown dew claws are prone to antibiotic therapy. Overgrown dew claws mechanical injury and may fracture at should be trimmed back to about 2 cm. the junction with the skin. Infection with

Long toes

Since the rate of growth usually commonly seen in the elbows of older exceeds the rate of wear, toes become Vietnamese potbellied pigs; The weight progressively overgrown. Overgrowth is bearing axis is moved further back usually not in a straight line but often which results in the flexor tendon deviates to the inside. Overgrown toes becoming over stretched. Overgrown may have the following effects: Normal claws should be trimmed. A trimming joint angles are disturbed which over method has been described. time may result in osteoarthritis. This is

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Lameness in pigs flow chart

Visible lesion

Yes No

Upper leg

Swelling Osteochondrosis Paralysis

No Yes Arthritis severe Spine

Lameness Joint Poor prognosis. Coronary band & tract Unresponsive to Fractured dew claw Antibiotics/anti - No Yes Anti-inflammatory/antibinflammatoryiotics

Horn lesion

Partial thickness Full thickness Wall fissures White line separation Wall/heel separation Heel erosion/cracks Heel/sole cracks

No treatment Corium involved/ Inflammation Record incidence/prevalence Anti-inflammatory/ Antibiotics

Determine cause: Trauma; Social interaction; Flooring; Genetic conformation; Nutrition; Horn quality

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