Complete Blood Count (CBC)

Description: Blood is collected from an animal and placed into a tube which contains material that stops clots from forming. The blood cells themselves are then analyzed according to their shape, size, color, and relative numbers present in the bloodstream (hence the term "count").

Diagnostic Value: Certain diseases can be detected and even initially diagnosed with a simple CBC. Problems such as anemia, severe infections, and some types of cancers can be detected.

Risks to Patient: There are very few risks to the sheep or goat, providing that the blood is collected under sterile conditions by a trained professional.

Relative Cost: The cost of performing this test is low to moderate.

Normal Ranges: The following chart lists the normal ranges for many of the common items found on a CBC. Realize that these numbers can vary greatly between different locations and different laboratories.

Test    Sheep    Goats    Units
Packed Cell Volume (PCV)    27 - 45    22 - 38    %
Red Blood Cell (RBC)    9 - 15    8 - 18    x 106/uL
Reticulocytes    <0.5%    0    #/uL
Platelets    240 - 700    340 - 600    x 103/uL
Segmented Neutrophils    0.7 - 6.0    1.2 - 7.2    x 103/uL
Band Cells    Rare    Rare    x 103/uL
Lymphocytes    2 - 10    2 - 9    x 103/uL
Eosinophils    0 - 1    0.05 - 0.065    x 103/uL

Many of these reference numbers were taken from Duncan JR, Prasse KW: Veterinary laboratory medicine - clinical pathology, ed 2, Ames, IA, 1986, Iowa State University Press; and Kramer JW: Normal hematology of cattle, sheep and goats. In Schlamís veterinary hematology, ed 5, Philadelphia, 2000, Williams & Wilkins.

Interpretation of Results:

  1. Packed Cell Volume (PCV) - This is the total percentage of the blood that is composed of red blood cells.
    1. A high PCV occurs most commonly with dehydration and certain heart defects.
    2. A low PCV can be the result of not enough red blood cells (anemia) or the occasional state of over-hydration.

  2. Red Blood Cell (RBC) - This is the total number of red blood cells in one microliter of blood.
    1. Low numbers of RBCs (anemia) can be the result of blood loss, inadequate RBC production in the bone marrow, or actual destruction of the RBCs within the body.

  3. Reticulocyte - Reticulocytes are immature red blood cells.
    1. High numbers of reticulocytes indicate a regenerative response (i.e. the bone marrow is producing more red blood cells).
    2. Low numbers of reticulocytes when anemia is present may indicate a bone marrow malfunction.

  4. Platelets - Platelets are circulating compounds that help blood to clot.
    1. If low platelet numbers occur, the animal may be prone to bleeding disorders.

  5. Neutrophils - These are white blood cells (WBC) that are important in fighting infection.
    1. High numbers of neutrophils (neutrophilia) occur when the animal is under stress (shipping), has an infection, or when steroids have been administered.
    2. Low neutrophil numbers (neutropenia) can occur with very severe infections, some viral infections, and when there has been long term bone marrow damage.

  6. Band Cells - Band cells are the early stages of a neutrophil.
    1. The presence of band cells usually indicates that an infection is occurring in the body. When high numbers of band cells are observed, it is called a "left shift."

  7. Lymphocytes - These are WBCs that are part of the immune system.
    1. High levels of lymphocytes (lymphocytosis) can occur when the animal has a chronic infection or lymphocyte leukemia.
    2. Low lymphocyte numbers (lymphopenia) indicate administration or release of steroids, viral infections, or stress.

  8. Eosinophils - These are white blood cells that are common in situations where irritation or inflammation of tissue is found.
    1. High numbers of eosinophils indicate a possible parasite problem or an allergic reaction.

This section lists only a few of the most common possibilities for cell changes in a CBC. A physical examination, additional history, and other tests may be required before a specific diagnosis can be determined.