Normally, foals get their antibody from their dam's colostrum (the first milk). This antibody is vital to the newborn's immune system. Without it, they will not survive. Unlike humans, foals do not receive any immunity through the placenta prior to birth.

When plasma is given to foals, it is primarily intended to increase antibody levels.

Newborn foals less than 20 hours old have an "open gut" meaning that they have relatively large microscopic channels between the inside of the intestine and the bloodstream that allow the absorption of large antibody molecules (antibodies are relatively very large proteins) from the intestine.

After 24 hours, the gut is said to have "closed" - the channels no longer permit the passage of these vital large molecules. Foals that fail to absorb sufficient antibody are said to have failure of passive transfer (FPT).

Foals less than 12 hours with FPT old can be given colostrum or concentrated oral IgG to boost their antibody levels. After 24 hours, the only reliable way to boost antibody levels is through the use of plasma containing the needed antibody.

Hyperimmune plasma has concentrated IgG antibody and may have increases in specific antibody to particular disease agents. In most cases, 1 liter of hyperimmune plasma is sufficient to boost a foal's antibody levels into the normal range. In foals with very low levels, more may be needed.

Plasma also provides a variety of other important protein factors that contribute in various ways to health and immunity. These include fibronectin, albumin, protein C, protein S and antithrombin III. These are especially important in treating septic foals, and may increase survival.

In some cases, fresh frozen plasma is given prophylactically to provide specific antibody against particular diseases. The most common disease for which plasma is given this way is Rhodococcus equi Pneumonia. On farms in which this disease is endemic (meaning that the organism is present and infection is possible) newborn foals may be routinely administered plasma hyperimmune to Rhodococcus.

Plasma is supplied to your veterinarian as a frozen product, usually in liter bags. Blood cells have been separated from the whole blood, leaving the liquid component, the plasma. The plasma is slowly thawed in lukewarm water immediately prior to use.

To administer plasma, your vet places an intravenous catheter into the jugular vein of the foal's neck. A special filtered administration blood administration set transfers the plasma from the bag to the catheter. The bag is held or hung above the foal. In many cases, the foal is allowed to walk around the stall, with the bag carrier following along.

In many cases, plasma can be run as a rapid stream, with all administered within 5-10 minutes. However, for some foals, administration must be slowed to prevent reaction. The foal is monitored by your vet for any untoward effects, until the entire liter has been administered. The catheter is then removed and pressure placed on the site to prevent bleeding.