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Blood groups in cattle

With kind permission of Dr A.P.Usha.
Extract from PhD Thesis, University of Edinburgh, 1996.

Cattle red cells consists of a bilipid plasma membrane associated with protein and carbohydrate. There are slight differences in the structure of these proteins or their associated carbohydrate between individual cows which form the red cell antigens. These protein variants are detected by immunological tests. Blood from one individual is injected into another so that the recipient produces antibodies reacting with red cell antigens of the donor which are different from its own. After separation into different types/specificities, these antibodies can then be used to detect the antigens on the erythrocytes of other individuals and are termed blood typing reagents. Cattle erythrocytes do not agglutinate easily, so the reactions are detected in a haemolytic test in which a suspension of red cells is mixed with antibody and complement (fresh serum from rabbit or guinea pig). Binding of the antibody to the red cell antigen in the presence of complement results in lysis of the cell and the release of haemoglobin.

Serum from immunised animals may contain haemolytic antibodies directed against a few or more red cell antigens. Such a serum is known as polyvalent antiserum. Serum having antibody against a specific red cell antigen or monovalent antiserum is obtained by absorption of polyvalent antiserum with cells which have the antigen recognised by antibody. The resulting antiserum is tested using haemolytic test on known antigens and then used as a blood typing reagent. Thirty to forty monovalent sera are used in cattle for undertaking parentage confirmation and identification of individual animals.

The accuracy of conventional blood typing for parentage verification is limited due to the finite number of blood group systems. In addition, developing a complete set of reagents for the red cell antigens and the standardisation of the technique is difficult and time consuming. Although a large number of serum proteins are available, many of them are present at low concentration and are difficult to detect, or have limited polymorphism, while the presence an quantity of protein at a few loci are affected by age and disease. For example, in babesiosis the amount of total haemoglobin is reduced affecting the concentration of erythrocytes. Moreover, the presence of null alleles often complicates interpretation of the results as they are recessive to all other alleles, therefore the phenotype needn't correspond to the genotype.