A1 and A2 Polymorphism in β-casein gene and lactoferrin gene fragment in indigenous cattle breeds
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Date
2017
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Rajasthan University of Veterinary and Animal Sciences, Bikaner
Abstract
The main aim of this study was to determine the polymorphism of A1 and A2 variants of β-casein and fragment of lactoferrin gene of Rathi, Tharparkar, Kankrej, Sahiwal
and cross bred of Rathi (Rathi×Holstein Fresian) cattle from Rajasthan. The screening result of β-casein showed 100% A2A2 type of genotype in Rathi,
Tharparkar and Kankrej cattle but in Sahiwal cattle showed two type of genotype of β-casein viz: A1A2 and A2A2. The number of A2A2 and A1A2 animals was 26 and 4
respectively. Allele A2 was found predominantly in high frequency (0.933) than A1
allele (0.06). It might be due to presence of A1 allele in recessive form in their
pedigree and now after some time it co-dominant in these cattle. Cross bred shows only A2A2 genotype of β-casein which was an exception, it may be a consequence
of non random mating, and depletion of A1 allele among the herd. The average
observed heterozygosity values (0.06) showed substantial number of heterozygotes
in the population.
For lactoferrin protein, 301bp fragment of oligonucleotide primer used in favour of
amplification of lactoferrin gene. The amplified products were subjected to PCR
RFLP technique using EcoR1 restriction enzymes. The frequency of genotype AA
was higher in all the indigenous breeds, while the frequency of AB genotype was
lower. The allelic frequency of A and B were 0.9833 and 0.0167 respectively in
Tharparkar cattle. The allelic frequency of A and B were 0.8333 and 0.1667
respectively in Kankrej cattle. But in the Rathi and Sahiwal cattle there was presence
of 100% AA genotype. The studied cattle population was under hardy-weinberg
equilibrium for milk proteins.
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The study revealed the existence of A2 allele of the β-casein in indigenous cattle and
cross bred of Rathi, shows that this type of milk is good for human consumption and
these cattle give better milk performance. The lactoferrin gene confirmed that the
presence of AA genotype with higher frequency in all indigenous cattle. The work
supported the future breeding policies at the farms for maintaining the gene pool and
producing cattle with higher milk production as well as better resistance to mastitis.
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