It is not possible to sterilise whole blood products and therefore they must be harvested aseptically. Horse and Sheep Blood are the most widely used animal blood products in clinical culture media. The choice of which type of blood to use is largely traditional, with much of continental Europe & the USA preferring Sheep Blood, whilst the UK and certain parts of the Commonwealth prefer Horse Blood. The fresh aseptically harvested Sheep/Horse Blood goes through a controlled defibrination process before being pooled via a filter to remove any residual fibrin and is then allocated a unique lot number prior to being dispensed into sterile containers for ease of use to add as a supplement to various culture media. No additives or preservatives are added to E&O’s whole blood products. Vacuum assisted defibrination is the accepted best method of preventing freshly harvested blood from forming clots. It must be carried out during the blood harvest and the gentle agitation must be sufficient to clump the fibrinogen but not to cause any rupture of the erythrocytes which encourages haemolysis. The haemolytic reactions of Sheep Blood are different to those of Horse Blood.