Associations between bovine beta-lactoglobulin polymorphism within coding and regulatory sequences and milk performance traits
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The bovine beta-lactoglobulin (LGB) gene is considered a potential quantitative trait locus in dairy cattle breeding. In Black-and-White dairy cattle the LGB gene has two predominant alleles A and B. This can result in three possible genotypes AA, AB and BB. Moreover, within the promoter of the gene several point mutations were found. A herd of one hundred and twenty-four Black-and-White cows were genotyped for two loci: locus LGB (exon IV, alleles A and B) and locus LGB-R (SSCP polymorphism within a fragment of LGB promoter: SSCP patterns R2, R3, R1, R9). In our sample 13 AA, 58 AB and 53 BB LGB cows and 66 R2, 16 R3, 40 R1 and 2 R9 LGB-R cows were identified. A statistical analysis revealed significant associations between LGB, LGB-R genotypes as well as intragenic haplotypes LGB/LGB-R and milk protein content during the first complete lactation. Cows with AA LGB genotype, R3 LGB-R SSCP pattern and AA/R3 haplotypes had the highest protein content. These results support the hypothesis that sequence variation within the promoter of the LGB gene is probably one of the factors responsible for differences in milk protein content.
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S.Kaminski, University of Warmia and Mazury, Department of Animal Genetics, ul. M. Oczapowskiego 5, 10-718 Olsztyn, Poland