AVIAN HEMATOLOGY
Doç. Dr. Dr. Yasemin SALGIRLI DEMİRBAŞ
Resident ECAWBM (BM)
BLOOD
• Blood;
transports O2, nutrients and hormones to body cells/
carries CO2, water and other wastes away from cells
is composed of plasma (contains protein, salts, sugar) and blood cells
Avian blood plasma has a higher sugar and fat content – nitrogenous waste product
• Blood cells float in the plasma
• The blood of every bird contains erythrocytes or Red Blood
Cells (RBCs),leukocytes or White Blood Cells (WBCs) and
Thrombocytes, the avian equivalent to mammal platelets.
ERYTHROCYTES
The mature avian erythrocte is oval with a centrally positioned oval nucleus.
Ex-Theory: The anucleated erythrocyte, as it is seen in mammals, is considered more evolutionarily ‘‘advanced’’
Mammals have smaller end-blood-vessels (capillaries of about 3 lm in diameter) than birds - The presence of a nucleus may prevent big nucleated RBC to squeeze through small
capillaries.
During the evolutionary development, nature has found that it was better to extrude the nucleus and also other cell organelles, such as endoplasmic reticulum for protein synthesis, which were not needed for their actual function as oxygen carrier.
However, nucleus in the erythroblast is about 2 lm in diameter. And, if it was distributed at peripherally inflated region of the erythrocyte, it would neither hinder erythrocyte
deformation nor its entrance into end-blood-vessels.
ERYTHROCYTES
New Theory: Enucleation may facilitate erythrocyte deformation into the biconcave
shape and becoming soft and elastic.
Nuclear and mitochondrial extrusion may help mammal erythrocytes to better adapt to high-sugar and high-heme conditions, where they live.
Avian erythrocytes are much larger than most mammalian erythrocytes.
The size varies among species (7,5 µm- 13,5 µm).
A small degree of anisocytosis* is usually seen in clinically healthy birds
Besides typical mature RBCs, lesser numbers of other cells representing different stages of RBC development can be found on the blood of healthy birds - The presence of small numbers (between 1 to 5% of total circulating RBCs) of these immature cells in peripheral blood is normal
elevated counts are described as polychromasia or polychromatophylia and indicative of increased erythropoiesis as seen in regenerative anemias
• *Anisocytosis: RBCs are of unequal size
ERYTHROCYTES
Total RBC count in birds is usually estimated by manual methods but more recent flow cytometric analysers properly adjusted can also be employed.
Total RBC count is lower in birds (1,5 to 4,5 x 106 cells/µL) than in mammals.
Avian RBCs have a shorter half-life (25 to. 45 days) than mammal cells
ERYTHROCYTES
Rbcs number depends upon : 1. Age: is higher in young animals 2. Sex: Male is higher than females 3. Hormones:
Anabolic hormones as thyroid hormones increase number of Rbcs.
Estrogen interfere iron absorption so decrease Rbcs count.
4. Seasons: Winter stimulate thyroid activity so increase Rbcs count . 5. Altitude: High altitude increase Rbcs due to increase
6. Erythropoitin hormones.
ERYTHROPOESIS: process of RBC formation
Normal erythropoiesis takes place in the bone marrow although ectopic erythropoiesis can be occasionally found on the spleen and liver
This process comprises eight sequential stages of cell development:
1. Rubryblasts (or erythroblasts) are the first stage of RBC development.
2. Prorubrycites are the second stage of RBC development-the lack of nucleoli and mitochondrial spaces in the cytoplasm
3. Basophilic rubrycites are the third stage of RBC development and have homogenous basophilic cytoplasm and round nuclei
4. Initial polychromatic rubrycites - beginning of hemoglobin synthesis.
5. Polychromatic RBCs (Rubricyst) - There is a spectrum of blue color due to synthesis of hemoglobin
6. Metarubrucyte - This is the last nucleated erythrocyte stage 7. Reticulocyte - The reticulocyte is slightly larger than the mature
erythrocyte 8. RBC
ERYTHROPOESIS
• Erythropoietin (EPO):
• kidney hormone that controls erythropoiesis - Glycoprotein hormone
• In case of low O2 levels –– EPO is secreted - stimulates red blood cell
formation – (Humans - Anemia Treatment) – EPO
ERYTHROCYTES
Avian RBCs have a shorter half-life (25 to 45 days) than mammal cells
- this may be associated with a higher body temperature in birds and rapid metabolic rate of avian rbcs, which consume higher rates of oxygen and nutrients than their mammal counterpartsBlood volume in birds is estimated between 4,4 and 8,3 % of body weight
(converting grams to mililiters) with younger birds having a higher blood volume than adults.
Compared to mammals, avian blood is more viscous
because RBCs are larger and less deformable.Blood density is mostly influenced by the concentration of plasma proteins
Birds have lower blood albumin concentration and lower oncotic pressure than
mammals
HEMOGLOBIN
Normal values of Hb
Chicken: 9.3 gm%
Ducks: 10.3 gm%
Turkey: 10.3 gm%
8-12 g/dl in chicken blood
In most vertebrates, hemoglobin is made up of four subunits, each one of which has its own binding site for oxygen.
There are some significant differences between avian hemoglobin and hemoglobin found in other vertebrates:
In adult birds there are two different types of hemoglobin, hemoglobin A and D, both of which vary from each other in their affinity for oxygen.
Hemoglobin A is often the more prevalent form and has a lower affinity for oxygen compared to hemoglobin D.
A lower affinity means that oxygen is more readily dissociated from hemoglobin as arterial blood
Hb
In general, avian hemoglobin shows more
cooperativity with oxygen than does hemoglobin in other vertebrates.
Cooperativity is the phenomenon whereby the binding of one molecule of oxygen with
hemoglobin facilitates the binding of the next molecule of oxygen and so on up to the binding of four oxygen molecules by a molecule of
hemoglobin.
This cooperativity accounts for the sigmoidal shape of the oxygen-hemoglobin binding curve.
The advantage of this high cooperativity is that
it increases the delivery of oxygen to tissues.
Hb
Another feature of avian hemoglobin is its interaction with inositol pentaphosphate and inositol tetraphosphate which shifts the oxygen-hemoglobin dissociation curve to the right and decreases the affinity of oxygen for hemoglobin, enhancing the delivery of oxygen to tissues.
In mammals the principal organic phosphate is 2,3- biphosphoglycerate (2,3-BPG), formerly known as 2,3-diphosphoglycerate (2,3-DPG),
The presence of two hemoglobins with different oxygen affinities, means that the
erythrocytes have a greater range of oxygen partial pressures over which oxygen can be bound and released, favoring the uptake of oxygen where there is little oxygen available in the environment
Carbon dioxide also affects the binding of oxygen to hemoglobin. In mammals, the binding
of carbon dioxide with hemoglobin is more. It appears that in birds the strong binding of
the organic phosphates to hemoglobin prevents this carbon dioxide effect.
LEUKOCYTES
As in mammals there are Granular and Agranular leukocytes.
Number of leukocytes:
oChicken: 19-30 thousands/mm3 oDuck: 32 thousands/mm3
Leukocytes are either granular or Agranular.
Granular leukocytes 1-Heterophils
2-Eosinophiles 3-Basophils
Agranular leukocytes 1-Lymphocytes
2-Monocytes
