ABSTRACT
The present study was carried out in four genetic groups of cattle, viz. Kangayam, Pulikulam, crossbred Jersey and crossbred Holstein Friesian, to compare the karyomorphological pattern between Bos indicus and Bos taurus x indicus bull calves. Metaphase chromosomal spreads obtained by short term lymphocyte culture technique revealed chromosomal complement (2n) of 60, with 29 pairs of autosomes and one pair of sex chromosomes in four groups. All the autosomes were acrocentric, X-chromosome was sub-metacentric and Y-chromosome was acrocentric in Bos indicus and metacentric in crossbred bulls. There was no significant difference in relative length, arm ratio, centromeric index and morphological index of autosomes and X-chromosome between indicine and taurine groups; but Y-chromosome differed significantly (P˂0.01) in relative length between Bos indicus and Bos taurus x indicus crosses. Y-chromosome polymorphism could help in the determination of breed origin and male lines used in the breeding programmes in order to prevent the possible interferences in the process of reproduction