Hematocrit in Veterinary Medicine: Ranges, Causes, and Measurement

What is hematocrit (HCT)?

A measure of the proportion of red blood cells in the total volume of blood, also referred to as packed cell volume (PCV).

What are the normal hematocrit ranges for sheep?

30% to 60%

What are the normal hematocrit ranges for goats?

24% to 45%

What are the normal hematocrit ranges for cattle?

24% to 50%

What factors can affect hematocrit values?

Age, health(diseases, nutritional deficiencies), reproductive status, environmental conditions, and sex.

How does age affect hematocrit values?

Older animals tend to have higher hematocrit values.

What is anemia?

Decrease in Red Blood cell concentration or production.

What effect does late pregnancy have on hematocrit values?

It typically results in lower hematocrit values.

What is the effect of altitude on hematocrit values?

Living at high altitudes can increase hematocrit values as a response to lower oxygen levels.

What nutritional deficiencies can indicate low hematocrit values? What else is iron needed for?

Deficiencies in iron, copper, or vitamin B12 (cobalamin) because they are needed for red blood cell production. Iron is needed to carry oxygen in the blood.

What internal and external parasites indicate low hematocrit values?

Haemonchus contortus (barber pole worm), stable flies (blood sucking flies), a lot of ticks, fleas, lice, and mosquitoes.

What disease indicates low hematocrit values?

Anaplasmosis

What is anaplasmosis?

Disease casued by bacteria Anaplasma marginale that infects RBCs so the body destroys infected RBCs leading to hemolytic anemia.

How is anaplasmosis transmitted?

Through ticks, flies, contaminated needles, or tool reuse causes blood from an infected animal can enter an uninfected animal’s body.

What can indicate low Hematocrit levels (injury related)?

Blood loss from severe injury or trauma, or from hemorrhaging

What is hemorrhaging?

blood loss from a broken/damaged blood vessel (internal bleeding)

What is hemolytic anemia?

Anemia caused by the destruction of red blood cells (RBCs).

What disease can cause hemolytic anemia in cattle and indicates low hematocrit levels?

Anaplasmosis, caused by the bacteria Anaplasma marginale, which infects RBCs.

What are common causes of low hematocrit values?

nutritional deficiencies, internal or external parasites, blood loss, and disease.

What can cause high hematocrit values?

Dehydration, high altitudes, polycythemia (erythrocytosis).

Increase in HCT can be caused by Dehydration:

Which is the reduced fluid intake or excessive fluid loss; causes less fluids in the blood so the concentration of RBC increase. can be from Diarrhea or excessive urination (polyuria) as well

Increase in HCT can be caused by high altitudes:

High altitudes increase RBC production to compensate for the lower oxygen levels

Increase in HCT can be caused by Polycythemia: (not normal and rare)

erythrocytosis; a blood disorder in which chronic hypoxia causes an increase in red blood cells

What is hypoxia?

Low oxygen levels in the blood.

Where does RBC production occur?

In the bone marrow.

How is hematocrit measured?

By collecting blood with anticoagulants in a capillary tube, sealing it, spinning it in a centrifuge, and using a percent RBC Hematocrit reader or a centrifuge with a built-in reader.

What anticoagulants are commonly used for hematocrit measurement?

EDTA and Heparin.

How to collect blood with a capillary tube?

by moving the tube back and forth at an angle until the desired amount enters and use clay to seal the end or use self sealing tubes.

What is the significance of establishing reference values for a herd's hematocrit?

The reference values define what is normal for a specific herd, and if a value falls outside those values, then something is wrong.