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White Line Disease
White line disease is a non-infectious condition that occurs when the sole separates from the side wall of the hoof, allowing foreign material to penetrate and infect the white line region.
The white line is easily damaged and is often an entry point for infection; tracks of infection may cause a localised abscess, or may penetrate to form a deeper abscess, and solid foreign bodies may lodge in the softened, widened area and may push through to the sensitive corium beneath. Exposure to moisture softens the region still further and any rupture of the structure is worsened by the impact of movement, particularly among animals housed on concrete.
White line disease is a major cause of lameness with the incidence in older cows being as high as 35%. The outer claw of the hindfoot is usually involved; where both claws are affected the problem may escape notice until lameness is more obvious in one limb than the other.
The degree of pain and lameness depends on the rate of development and the extent of the abscess; a discharge of pus from where the skin and horn meet is always reason to suspect a white line lesion and the white line should always be examined very carefully in cases of lameness with these symptoms.
The region of the wall of the hindlimb most often affected is the area of the claw that absorbs the concussion from walking first and in which horn growth and wear occur the most. Exposure to moisture from wet conditions underfoot softens the tissues still further.
As it is important that cows are not forced to change direction and pivot rapidly - which can place excessive force on the hoof and result in a rupture of the white line - this means that reducing the incidence of dominant cows bullying should be a prime focus area and cows should be handled quietly and competently, as white line problems tend to be exacerbated by the impact of movement, particularly among cattle housed on hard surfaces. Passageways and collecting and loafing areas need to be kept as free as possible of stones.
A separation of the white line without other complications is often seen when feet are inspected and trimmed. A routine inspection of the sole should include the complete examination of the white line area; black marks should be examined as potential sites for the formation of track of infection, but care should be taken not to over-trim the weaker white line area.
As with sole ulcer lesions, white line lesions need to be trimmed carefully by a competent trimmer and can benefit from the relief of pressure on the affected claw by the application of a block to the healthy claw. Local abscesses can be allowed to drain by removing a segment of the wall adjacent to the lesion. Swelling of the heel bulb can represent the most advanced form of this condition and could be misdiagnosed as foul-in-the-foot. Severe cases are likely to benefit from the attention of a vet.