Genetic polymorphism of beta-casein gene and its associations with milk traits in Holstein-Friesian cows

In animal breeding finding and using effective genetic markers for improving important traits it is a continuous challenge. In this respect, several genetic markers were associated in cattle with increased milk production or a better milk quality. This proved to be a useful tool for improving certain traits by selecting individuals carriers of allelic variants that have an effect on a desirable trait. In particular, positive associations between certain alleles found at the milk protein loci with some milk production traits convincingly demonstrated in several cattle breeds. Although, in some cases the results obtained in various studies were not in agreement and varied between breeds or populations. Therefore the objective of this study was to establish associations (if any) between alleles found at the beta-casein (CSN2) locus and some milk production traits (milk yield and fat, protein, casein and lactose content) in a Holstein-Friesian population reared in Romania. Genetic variants at CSN2 locus were identified by isoelectric focusing (IEF) of milk samples. In order to determine milk composition the samples were analysed with MilkoScan FT 6000. For the statistical analysis of data SPSS v.19 for Windows was used. At the CSN2 locus four alleles and seven genotypes were identified in the analyzed cattle population. The cows carriers of CSN2 A2 allele produced the highest milk yield and the highest milk protein content, this result being in agreement with other previous studies