Abstract
The present study aims to define the distribution pattern of allelic variants in exon 4 and promoter region of β- lactoglobulin (BLG) gene in Indian native cattle (Bos indicus). PCR-RFLP analysis of exon 4 using HaeIII digestion in 968 animals of 23 Indian cattle breeds, revealed the predominance of BB genotype and B allele with an average frequency of 0.533 and 0.740, respectively. Further, comparative sequence analysis of BLG promoter region spanning 579 bp of proximal promoter region and 116 bp of exon1 revealed a total of 15 nucleotide variations with respect to Bos taurus sequence. Amongst these, variations at position -204 (C>G)/R5, widely considered to be an important site for milk protein binding factor was further screened by developing genotyping protocol using RsaI enzyme in 779 animals of Indian native cattle. Out of two alleles and three genotypes, G allele and GC genotype was found to be predominantly present with mean values of 0.639 and 0.444, respectively. Chi-square test indicated presence of genetic equilibrium in majority of the breeds with respect to studied variations and revealed no significant difference in distribution of variants across different cattle groups.
Highlights
Bovine milk contains 3-5% protein, of which 80% is casein and 20% is whey protein [1]
Β-lactoglobulin (BLG) forms the major portion in the milk of ruminants. This gene has been mapped to bovine chromosome 11 [2]
BLG protein variants A and B are associated with different amounts of BLG protein
Summary
Bovine milk contains 3-5% protein, of which 80% is casein and 20% is whey protein [1]. Β-lactoglobulin (BLG) forms the major portion in the milk of ruminants This gene has been mapped to bovine chromosome 11 [2]. Several groups have reported the significant effect of protein variants A and B on milk protein composition or milk production traits [8,9,10,11,12,13,14,15]. These studies revealed that BB genotype is associated with higher casein and lower BLG content. In a comprehensive study encompassing 8000 animals and three lactation records, Ng-Kwai-Hang et al [9] observed that with replacement of allele A by B, there was a significant increase in protein percentage in all the three lactations whereas protein yield increased significantly only in the second lactation [9]
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