Acute laminitis in a Hereford bull on self‐feeder.
There are no outward lesions expressed or seen on the soles of the hoof, although inflammation may be observed in the coronary band and a digital pulse may be present. Subacute laminitis doesn't usually express itself until several weeks after the insult, and the symptoms observed are sole hemorrhage and discoloration of the white line and sole tissue.
Subclinical laminitis is due to periodic upsets in normal body function. A few scenarios that can predispose to chronic laminitis include:
Mismanagement of the young growing calf
Bulls on gain test
Cattle being prepped for sale
Cattle breeds involved with progressive genetic improvement
Cattle being fitted for show
Dairy cows being fed for maximum milk production
The general appearance of a hoof with subclinical laminitis is one that flares out at the wall with a flattened sole. Closer examination reveals white line separation with abscessation, vertical and horizontal wall fissures, heel erosion, and subsolar ulcers [2]. Horizontal lines (known as hardship lines) may be observed in a portion or the entire hoof wall. Over time, more than one hoof can be affected. Since hoof overgrowth is the number one initiator of lameness, cattle with chronic laminitis should have regular hoof trimming to maintain proper hoof health [3]. The vascular damage that occurs during episodes of subclinical laminitis can lead to a cascade of hoof problems, discussed in the following sections [4] (Figures 16.11 and 16.12).
Figure 16.11 Severe white line disease and hoof crack as a result of chronic subclinical laminitis.
Figure 16.12 Subclinical laminitis with hardship lines present as horizontal grooves in hoof wall.
Treatment of Solar Injuries
Many predisposing factors have been mentioned that lead to laminitis and play a part in subsolar injuries. The metabolic effects of subclinical acidosis and laminitis can affect normal hoof growth and lead to white line separation, toe ulcers, heel erosion or ulceration, and sole ulceration. Puncture wounds and traumatic concussive injury are other contributing factors to subsolar abscess formation. Without proper treatment, these conditions may lead to damage of deeper structures including pedal osteitis, infection of the navicular bursa, sepsis of the distal interphalangeal (DIP) joint, and septic tenosynovitis of the digital flexor tendon sheath.
Treatment of complicated subsolar abscesses and white line disease involves complete and total curettage of the overlying sole or hoof wall and removing all necrotic debris from the affected area. Exploration of all tracts is necessary to evaluate if deeper structures are involved. If sepsis of the pedal bone or coffin joint is suspected, radiographs should be performed at this time. Parenteral antibiotics and bandaging with astringent antiseptic compounds should be incorporated into a treatment plan when possible. While some practitioners elect to leave sole abscess lesions exposed, it is my opinion that these wounds heal better in beef cattle when protected. The application of a hoof block to the supporting claw prevents the affected claw from bearing weight and allows quicker healing due to the lack of contact with sole surface.
Vertical Hoof Cracks
The prevalence of hoof cracks appears to be increasing, most likely related to genetics and intensive management. Subclinical laminitis has been suspected as an underlying cause in many of these cases. These cracks can affect one or multiple claws (Figure 16.13).
Figure 16.13 Vertical fissure in hoof wall due to subclinical laminitis.
Lameness is caused by instability in the hoof wall as weight is shifted to the wall. Debris and soil may be packed into the crack, inducing abscessation with encroachment on the sensitive lamina. Remove all debris through careful curettage. If any debris is left before immobilization, it can lead to sepsis of the laminae. If debridement of the crack results in penetration of the laminae, antibiotic bandages should be applied until the wound completely heals and the crack is dry and hard.
To stabilize a hoof crack, drill horizontally across the crack and place stainless‐steel wire across the defect in a bootlace pattern. Application of an acrylic compound into the crack and around the wire will bond the hoof. Alternatively, the crack can be filled with fiberglass cloth and acrylic compound that bonds to the hoof wall. This will bridge the crack and stabilize it, allowing new normal hoof wall to be produced at the coronary band. Newer products are now available that come with an applicator that allows direct application to the affected area without the need for any other material to support the repair.
If there is radiographic evidence of abscessation or osteomyelitis, open and debride the area to allow for healing. Curettage of the coffin bone and removal of bony fragments may have to be performed. To alleviate pain during movement, apply a hoof block to the healthy claw or consider using a splint. Systemic antibiotics are always indicated in situations involving deep sepsis of the hoof, and localized vascular perfusion can aid in increasing antibiotic concentrations within the area. Potassium penicillin, ampicillin, and tulathromycin are commonly used for vascular perfusion. Common side effects of tulathromycin include vasculitis and localized tissue edema. Medicated bandages, analgesics, and support bandaging of the contralateral limb should also be considered.
Septic Arthritis of the Distal Interphalangeal Joint
Septic arthritis of the DIP joint is a common sequela to chronic infectious processes involving the hoof and/or interdigital space. Examination findings include a swollen coronary band with a draining tract occurring at the dorsal aspect of the extensor process, diffuse swelling of the pastern area, and partial or complete non‐weight‐bearing lameness. Radiographs will reveal osteomyelitis of the coffin joint and increased joint space, with osteolysis of the second and third phalanx (Figure 16.14).
Figure 16.14 Sepsis of the DIP joint with sequestrum formation.
To block the hoof and provide postsurgical analgesia, perform regional limb perfusion using a long‐acting local anesthetic, such as mepivacaine or bupivacaine. The following surgical approach to the DIP joint is preferred over the abaxial approach because it allows better exposure of the joint [5]. Closely trim the sole and heel area and disinfect with surgical scrub and alcohol. A full‐thickness incision is made through the heel and continuing through the deep flexor tendon to expose the intra‐articular area between the navicular bone and the proximal extent of the caudal portion of the coffin