KARYOTYPING TO IDENTIFY INDIGENOUS MALE PARENTAGE IN CROSSBRED CALVES

Cytogenetics is the study of structure and properties of chromosomes and chromosomal behaviour during cell division. Chromosome analysis is done routinely to examine the animals for breeding soundness and selection. A karyotype is the arrangement of chromosomes in homologous pairs in a systematic manner. The diploid chromosome number in cattle is 60 (29 pairs of autosomes and one pair of allosomes). The unique chromosomal feature that differentiates cattle of exotic origin (Bos taurus) from that of indigenous cattle (Bos indicus) is the structure of the Y-chromosome. The Bos taurus bulls have meta- or submeta-centric Y-chromosome whereas the Bos indicus bulls bear an acrocentric Y-chromosome. Blood samples from the selected males which resembled Jersey crossbreds phenotypically were received at this department for karyotyping. Short-term leucocyte culturing was carried out with each sample. The karyotypes were made from good spreads by arranging the chromosomes in homologous pairs using Applied Spectral Imaging software. Analysis of karyotypes of 30 samples revealed that three karyotypes were found with acrocentric Y-chromosome. The acrocentric Y-chromosome should have been inherited from the indigenous sires only. Though it is not possible to identify the exact parentage by using this method, this is one of the best and cheapest methods to eliminate crossbred calves born to indigenous sires.