Lecture 21 3/27/25 Flashcards
What is laminitis?
inflammation of the laminae of the hoof wall
What is the pathogenesis of laminitis?
-failure of the suspension system of the third phalanx (P3)
-mechanical injury to the sole corium and epidermis
What are the support structures for P3?
-laminar corium
-collagen fibers
-digital cushion
What are the characteristics of the laminar corium as a P3 support structure?
-interdigitations between the laminar corium and horn leaflets
-well developed at toe and abaxially
-weaker axially; axial wall is smaller
What are the characteristics of the collagen fibers/sling apparatus as a P3 support structure?
-originate in horny corrugations on the inner surface of the hoof wall
-insert into areas of the distal phalanx that have no periosteum
-pedal bone is “suspended” from wall of the hoof
-strong collagen fiber attachment between P3 and claw wall abaxially and distal cruciate axially
What are the characteristics of the digital cushion as a P3 support structure?
-found between back of P3 and sole of horn
-provides shock absorption
-composed of fat and connective tissue
What are the issues that can occur with the digital cushion?
-digital cushion is thinnest around peak lactation
-thin cows can have increased lameness
-increased lameness can cause thin cows
-small digital cushions can lead to increased mechanical injury to the corium
What happens if the caudal support of P3 breaks down?
sinking of P3 further into the hoof occurs
Which mechanical injuries can lead to laminitis?
-overgrowth of toe
-overgrowth of heel
-increased body weight/increased force on limbs
What are the characteristics of matrix metalloproteinases?
-allow for normal enzymatic remodeling of epidermal laminae
-accidentally recruited during laminitis; cause increased breakdown
Why is it important that laminitis does not occur in a state of vasoconstriction?
cooling the limbs can lead to decreased development of clinical signs
What are the non-inflammatory causes of laminitits?
-break down of collagen attachment of suspensory apparatus
-laxity of collagen attachment
-epidermal growth
What are the inflammatory causes of laminitis?
changes in circulation; especially associated with endotoxin
What is the pathogenesis of laminitis?
-vascular changes affect differentiation and proliferation of keratinocytes within germinal layer of epithelium
-horn cells are not properly keratinized
-reduced rigidity leads to poor quality horn
-horn is more susceptible to damage, excessive wear, and other claw diseases
What are the characteristics of acute laminitis?
-rare in cattle
-more common in feedlot cattle and first lactation dairy cows
-associated with grain overload and acidosis
What are the clinical signs of acute laminitis?
-increased RR
-increased HR
-runny stools
-decreased ruminal contractions
-may go down in the front
What is the treatment for acute laminitis?
recognize it as an emergency
-rumen lavage
-NSAIDs
-transfaunation
-supportive care
-soft surface for standing/increased bedding
What are the characteristics of subclinical laminitis?
-no clinical signs in early phase
-seen in dairy cows, feedlot cattle, and young bulls
-claw horn is weakened; leads to flaky soles
-P3 suspensory apparatus is weakened and can cause sole bruising
-may see subsolar hemorrhage
-increases the incidence of other foot disorders (white line dz, false sole)
What is the physical appearance of sole hemorrhage?
white line appears red
What are the other terms for chronic laminitis?
-founder
-slipper foot
What are the characteristics of chronic laminitis?
-mostly seen in older cows
-coronary band is darker and may have fragmenting horn
-rotation and sinking of P3
-concave dorsal wall
-sole and white line get wider
-poor prognosis
What is the physical appearance of chronic laminitis?
-claws widen, flatten, and have horizontal ridges
-toe tends to grow longer
-weight is displaced to the heel; toe lifts
What causes ulcer formation?
prolapsed corium and increased pressure at the area
Which ulcer is NOT associated with laminitis?
sole ulcers in the “typical place”
Which ulcers ARE associated with laminitis?
-heel ulcer
-toe ulcer
What are the characteristics of pre-ulcers?
-sole hemorrhage without pain OR
-sole hemorrhage with pain on pressure/mild lameness
What are the characteristics of clinical ulcers?
-full thickness horn defect with protruding corium
-can be normal; flat, non-prolapsed corium that the body can heal over
-can be granulating; must cut off tissue so body can heal
What are the characteristics of complicated sole ulcers?
-develop after several months
-deep digital sepsis
What are the characteristics of grooves?
-wall grooves are known as hardship grooves
-wall fissures are cracks that penetrate the entire wall
-the more distinct the groove, the more likely the dorsal wall will bend
What is the treatment for a pre-ulcer in which there is sole hemorrhage with no pain?
lower and slope affected heel to transfer weight to healthy claw
What is the treatment for a pre-ulcer in which there is sole hemorrhage with pain?
slope sole and apply claw block to the sound claw
What are the steps to treatment for an ulcer with exposed normal corium?
-remove weight bearing by applying claw block
-slope and thin horn around protruding corium
-remove all loose horn
-do not cut or damage normal corium
What are the steps to treatment for an ulcer with protruding granulating corium?
-cut the granulating corium at the level of the sole
-bandage for hemostasis as necessary
-follow steps for normal corium ulcers
What is the recovery time needed for sole ulcers?
20 to 60 days
What is the pathogenesis of complicated ulcers?
-ascending infection through exposed and damaged corium and digital cushion
-osteitis of P3 flexor tuberosity and apex
-pathological fracture of flexor tuberosity and avulsion of DDF
-distal sesamoid bone bursitis and osteitis
-septic tenosynovitis
-retro-articular abscess
-septic distal interphalangeal joint
How does a foot abscess differ from a toe/sole ulcer?
foot abscesses do not have prolapsed corium
What are the characteristics of corkscrew claw?
-most commonly affects lateral claws of hind legs
-inward and upward spiral rotation of the toe
-highly correlated with laminitis
-heritable, but with low factor
-predisposes to secondary lesions
-usually bilateral
What are the clinical signs of corkscrew claw?
-axial rotation of lateral claw
-weight bearing with lateral wall caudally
-axial displacement of sole
-toe rotation
-overgrowth of affected lateral claw
-smaller medial claw with decreased weight bearing
What are the factors that can contribute to corkscrew claw?
-heritability
-abnormal horn growth rate/weight bearing
-laminitis
-management
What are the characteristics of heritable screw claw?
-heritability score is low; there are other predisposing factors
-usually seen before 3.5 years old
-absence of laminitis
-family history
-breed predisposition
What are the steps to corrective trimming for corkscrew claw?
-straighten the dorsal wall
-correct toe length
-balance weight bearing surface; sole and white line should become more visible
-trim every 3 to 4 months
How can screw claw be prevented?
-emphasis on genetic selection; wide, strong feet with good toe angle and heel height
-add a foot score system into bull selection
-look at younger female relatives of bulls for evidence of screw claw
-pay attention to nutritional impact on claw health
What is the pathophysiology of thin sole syndrome?
-mostly in dairy cattle
-excessive wear on soles
-slow horn growth/poor quality horn
-excessive trimming
What are the signs of thin sole syndrome?
-slow, painful gait
-soft or thin soles
-solar hemorrhage
What are the factors that play into thin sole syndrome?
-young
-early lactation
-concrete floors
-wet or slurry conditions
-long walking distances or standing periods
What are the potential complications of thin sole syndrome?
-ulcers
-white line disease
-subsolar abscesses
-sepsis
How can thin sole syndrome be prevented?
-minimize time on concrete
-facilities that focus on cow comfort
-proper flooring
-good nutrition
How is thin sole syndrome corrected?
-application of thin claw blocks
-placement of rubber mats
What are the characteristics of white line disease?
-very common in dairy cows and beef bulls
-no lameness unless advanced
-easy to treat if detected early
-most commonly affects rear lateral claw
-white line thickens and can pack things in it
What are the characteristics of the white line?
-connects sole with wall
-transmits weight bearing forces between wall and sole
-consists of matrix of horn cells which is flexible and soft
-softest part of claw capsule
What are the causes of white line disease?
-overgrowth
-metabolic and hormonal factors
-subclinical laminitis and breakdown of the suspensory system
-instability of P3 within claw
How does P3 instability in the claw cause white line disease?
-compression of corium ->
-hypoxia and hemorrhage ->
-weakening of white line
What are the characteristics of white line disease progression?
-white line is susceptible to shearing forces of abrasive concrete and erosion by bacterial keratolytic enzymes
-laminitis is predisposing factor
-begins with small crack or space that gets packed by stones and organic matter
-can result in ascending infection
What are the consequences of white line disease?
-white line hemorrhage
-white line separation
-white line abscess
-complications involving the heel structures and DIP joints
-septic inflammation and ascending infection
-abscesses at skin-horn junction
-joint/bone infection; requires amputation or cull
What is the treatment for white line disease?
-corrective trimming; remove ALL loose horn
-trim until there are no dirt lines remaining
-foot block and regional IV anesthesia as needed
How is white line disease prevented?
-feeding management
-regular hoof trimming
-comfortable stalls
-non-slip walking surfaces
