Horizontal fissures run parallel to the coronary band and result from the disruption of horn production beneath the coronary band, resulting in a defect in the integrity of the wall, which can vary in its severity from a shallow groove to a complete break in the wall. The defect could be as a result of a period of nutritional deprivation or psychological stress. As the claw grows, a fracture can occur at the weakened point resulting in a 'broken toe', and a series of grooves can undermine the vertical strength hoof wall causing it to bend , producing a 'buckled toe'.
Vertical fissures (or 'sandcracks') account for a very small proportion of mobility problems in dairy cattle, and unlike other foot problems they tend to develop more in the foreclaws. Sandcracks vary in their severity depending upon size and where they are located, but rarely cause significant mobility problems. They are associated with cows kept in hot, dry and sandy conditions - as their name suggests - and are unlikely to be a problem in UK herds.
Fissures are believed to be caused by a wide variety of nutritional or psychological stressors, which could include a sudden, short-term but significant change in nutrition or by stress experienced at weaning, for instance. They can also be caused by an illness significant enough to affect the production of hoof horn. Minimising any such instance of stress is obviously desirable from any perspective of livestock husbandry.
Most fissures are not painful and require no treatment unless they are definitely identified as the origin of a mobility problem. Infected fissures should be lightly trimmed to remove loose or damaged horn and dressed with an antibiotic powder and a bandage. Larger vertical fissures may only require treatment - for cosmetic reasons - in the case of show animals.
Very deep horizontal fissures may eventually result in the formation of a 'thimble', which can be extremely painful. In these cases, the loose horn can be removed with pincers, under local anaesthetic if necessary, and may require veterinary attention.