A placenta (afterbirth) that is not expelled within (maximally) 4 hours of the birth of a foal. This condition requires immediate veterinary attention as it can lead to a rapid and serious infection of the uterus, which in turn can cause laminitis.

A term refering to the movement of a limb: the limb is retracted when it is pulled backwards. The opposite of protraction.

Rhabdomyolysis, also known as tying-up, azoturia or monday morning disease is a serious disorder of muscular tissue. It results from a breakdown of muscle fibers and release of their contents into the bloodstream. This can lead to complications such as kidney failure.

It is caused by muscle cells working without oxygen (anaerobically) and building up excessive amounts of 'waste' products such as lactic acid, that can damage the cells and lead to their disintegration. The lack of oxygen supply to the muscles is either due to an inadequate blood supply or to great exertion. Many other predisposing and trigger factors are thought to be involved in this complex disorder, including genetic factors, nutritional factors (excessive carbohydrates, electrolyte imbalance), hormonal imbalances, lack of fitness, environmental conditions (cold, wet weather), etc.

A genus of the family of odd toed ungulates (perissodactyla), there are 5 species of rhinoceros all living in Asia or Africa.

Long, thin curved bones which form the rib cage around the chest cavity. A horse has 18 pairs of ribs, the first 8 of which articulate both with the thoracic vertebrae and the sternum and are called vertebrosternal or true ribs. The following 10 pairs are not attached to the sternum, these are known as vertebral or floating ribs. Due to their increased mobility, the floating ribs permit the chest cavity to expand during respiration.

The ridges or branches of the frog are the prominent parts of the frog between the central sulcus and the lateral grooves of the frog. In a healthy hoof, these are in contact with the ground when the hoof is loaded.

A horse that is bred and trained to be ridden (in any discipline).

A hoof that has a pattern of rings on its hoof wall. Their formation is due to changes in speed and sometimes direction of horn growth. The rings may be parallel to the coronary band, in which case they are generally due to changes in diet. Rings that diverge towards the quarters and heels are generally due to the changes in horn growth rate seen in horses with chronic laminitis.

A commonly used term refering to joint disease (osteoarthritis) in the distal interphalangeal joint (coffin joint). As there is often a considerable degree of bony proliferation, it can appear as a bony 'ring' around the pastern just above the coronet, hence the name.

An articular or periarticular proliferation of bone around the proximal interphalangeal joint. The articularringbone is due to osteoarthrosis of the joint and is a progressive degenerative disease that can lead to severe lameness. Periarticular ringbone is due to a periostal reaction of the bone in the immediate vicinity of the joint due to pulling of the joint capsule or the collateral ligaments, in these cases lameness may be less severe or absent.