Association of polymorphism κ-casein gene with longevity and lifetime production of Holstein-Friesian cows in Vojvodina

The aim of this study was to identify frequencies of alleles and genotypes, to evaluate their frequency in population of Holstein-Friesian cows, and to investigate association of kappa-casein genotypes with longevity and lifetime production of cows. Blood samples were collected from 192 Holstein cows which have finished their production. Cows were reared at one farm in Vojvodina in Serbia. In the current study the following ratios of kappa-casein genotypes were found: 0.50 were AA, 0.40 were AB and 0.10 were BB. Frequencies of alleles A and B were 0.70 and 0.30, respectively. Based on these results, it can be concluded that cows with heterozygous genotype AB had the longest life (2809 days) with the highest number of productive days (2062), while the cows which were homozygous recessive of genotype BB had the shortest life expectancy (2627 days) and the lowest number productive days (1878). The same trend was observed with regard to the production results of cows of these genotypes, where statistically significant differences have been observed (P<0.05) in the most traits between cows of heterozygous and homozygous genotypes, while between cows of dominant and recessive homozygous genotype statistically significant differences were not observed (P>0.05). The effect of dominant genes in observed traits was greater than the additive effect of genes. From the ratio of the additive and dominant gene effects, it can be seen that the average degree of dominance in observed traits was positive.