Ascertaining the paternal lineage in crossbred bull calves

Abstract
Karyotyping is one among the parameters used for taking up culling decisions in bovine breeding. It has been recommended to perform cytogenetic screening of breeding bulls before using them for semen production for artificial insemination. In the present study, the chromosomal analysis of crossbred Jersey (n=12) and crossbred HF (n=13) bulls revealed that the modal chromosomal number (2n) was 60, with 29 pairs of autosomes and one largest sub-metacentric X chromosome and one smallest metacentric Y chromosome. Among 25 samples screened, one crossbred HF bull calf was possessing an acrocentric Y-chromosome, which was further confirmed with CBG-banding. It is unacceptable from the breeders point of view, that in bovine crossbreeding programme, the sire line should be maintained with the exotic breed, either Jersey or Holstein Friesian. In this case, mismating of crossbred cow would have occurred with the bull of indigenous origin (Bos indicus) when the animal sent for grazing and subsequent fertilization of ovum resulted with indigenous bull spermatozoa. Based on the results, decision on culling was taken up as the paternal line used for crossbreeding was from indigenous origin. Thus, cytogenetic analysis helps to identify such crossbred calves of undesirable parentage and these calves should be culled at an early stage of selection which could save time and amount spent towards genetic improvement programmes. In addition, the karyological screening study is able to identify the gross chromosomal variations among the indigenous, exotic and crossbred cattle, helpful in taking up early decision on culling. This analysis supports the recommendations laid down in the minimum standard protocol of Government of India, in the production of frozen semen.
Description
TNV_20thMVC_PP_Feb-2020_PA24
Keywords
Veterinary Science
Citation