Ascertaining the paternal lineage in crossbred bull calves
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Date
2020-02
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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