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Haemoglobin (Hb) is a major protein component of blood and functions as the main oxygen transporter in erythrocytes (Nishi and others 2008). It is comprised of four globular subunits: two α and two β subunits (α2β2), bonding non-covalently. Each subunit possesses an iron protoporphyrin that enables Hb to transport oxygen and weighs approximately 17 kDa (for a total molecular weight of the tetramer of about 68 kDa) (Hardison 1996, Talarico and others 2000). With respect to age-related synthesis in human beings, different kinds of Hb, including adult (A1 and A2), fetal and embryonic (Gower I, Gower II and Portland), have been identified. Adult human Hb contains A1 and A2 with molecular structures of α2β2 and α2δ2, respectively. Synthesis of Gower I, Gower II and Portland types starts during the first three months of embryonic development, and subsequently fetal Hb (α2γ2) predominates over embryonic Hb during the fetal period (Telen and others 2009). It has also been demonstrated that the level of fetal Hb declines soon after birth, while its synthesis ability in response to anaemia persists (Kaneko 2000).
Like human beings, in most animal species, either embryonic or fetal Hb emerges depending on the stage of development. However, research into canine and feline Hb, especially in breed-associated variations, has thus …