Page 731 - The Veterinary Care of the Horse

• A measurement of the number of red blood cells per litre of blood.

• The haematocrit or Packed Cell Volume (PCV). This is the percentage volume of red
VetBooks.ir • blood cells in a sample of whole blood.

Haemoglobin concentration. This is measured in g/dl.

The expected ‘normal’ values vary according to the type of horse and its level of fitness. A fit

Thoroughbred in training would be expected to have more red cells and a higher
haemoglobin concentration than a child’s pony or a cob. These can be measured from a blood

sample.

CAUSES

The red blood cells have a lifespan of approximately 120 days. They are produced in the

bone marrow and released into the circulation. When they reach the end of their life, they are
removed and destroyed by the liver and spleen. Anything that upsets the balance between red
cell production and their removal from the blood is likely to lead to problems.

Anaemia occurs if:

• fewer red blood cells are produced than normal

• blood cells are lost from the circulation due to injury or disease.

Reduced red cell production

This occurs if there is a problem with the bone marrow. Examples include lymphoma and

leukaemia. These types of cancer are uncommon in the horse.

Increased red cell loss

Examples include:

• severe haemorrhage, e.g. from trauma, uterine haemorrhage post foaling and guttural

pouch mycosis
• intestinal parasites, e.g. redworm

• external parasites, e.g. Haematopinus asini, the sucking louse

• any other condition where there is chronic blood loss such as a tumour that is bleeding
internally, e.g. certain tumours affecting the spleen will do this.

Clotting disorders and haemophilia are rare in the horse.