A bone in the horse's forearm, closely associated with the other forearm bone, the radius. In the horse, the ulna is partially fused with the radius and only extends a short distance toward the carpal joint. It therefore has no weight-bearing function; its most important structure is the olecranon tuberosity, a point of attachment for muscles.

Sound waves with frequencies greater than 20 kHz (20,000 cycles per second), therefore, above the range of human hearing. Ultrasound waves are used in diagnostic imaging and medical therapy.

Deformation of the heels in which the horn tubules grow at an angle that is much less steep than the angle at the toe, in some cases the heels may grow almost horizontally. This total collapse of the heels as a supporting structure in the rear part of the hoof can lead to serious lamenesses (palmar/plantarhoof pain).

A hoof without a horseshoe. Barefoot.

A forging technique in which the width or thickness of a piece of metal (e.g., the branch of a horseshoe) is increased by compression. When forging, the dimensions of a piece will change, but the volume remains the same. Decreasing the length always results in an increase in the cross-sectional area.

As a part of the passive stay apparatus, the horse is able to 'lock' its patella by hooking it over the medial trochlear ridge of the femur. For movement, the patella must be unlocked - a process that normally takes no longer than a fraction of a second. If the time taken for a horse to unlock its patella is increased, or it remains permanently fixed, this is a pathological condition known as a habitual or permanent upward fixation of the patella.

Liquid excretory product of all mammals. Urine is produced by the kidneys and excreted through the urinary tract. The excretion of urine is responsible for the regulation of body water content, for the elimination of excess nutrients, vitamins and minerals and for the removal of metabolic waste products such as urea and ammonia.