Characteristics of kappa-casein gene polymorphism in cows of Swiss breed and their productive qualities at a large dairy

Kappa-casein is a fraction of the main milk protein, which determines the technological properties of milk and the quality of dairy products, especially cheese and fermented milk products. The study tested the distribution of kappa-casein gene genotype polymorphism (CSN3) in mothers and daughters of the Swiss breed cows, taking into account their milk productivity qualities. The study was performed on 111 cows of the Swiss breed on a large dairy. The observation group I included 51 cow-mothers of the Swiss breed; group II – 60 cow-daughters of the Swiss breed. In a study of the polymorphism of the kappa-casein gene in cow-mothers and cow-daughters of the Swiss breed, the dominance of allele B (0.73 and 0.70) was found, which was registered more than two times more often than allele A. The incidence of genotypes AA – AB – BB in cow-mothers of the Swiss breed was as follows: 5.9% – 43.1% – 51.0% with indicators of observed heterozygosity 0.43 and expected heterozygosity 0.40. In cow-daughters of the Swiss breed the frequency of the BB genotype was the same, but, genotype АА was registered almost twice as often, with lower indicators of observed heterozygosity and smaller increases of indicators of expected heterozygosity than in cow-mothers. Cow-mothers of the Swiss breed with the AA genotype, in comparison with the AB genotypes, had higher milk yields during lactation (by 43%), fat production (by 86.9%), ratio of fat to protein (by 40.5%). Also note, the cow-mothers of the Swiss breed with the AA genotype, in comparison with the BB genotypes, had reliably high rates of fat to protein (by 35.8%) and only a trend to higher fat production; fat and protein. The production of fat in dairy cows-daughters with the BB genotype was higher than with the AA genotype, but only at the level of tendency. The correlation analysis showed that the AA genotype of the kappa-casein gene in cow-mothers of the Swiss breed was associated with the duration of lactation, indicators of milk yield during lactation, fat production, fat content and protein in milk with registration of reliable and positive coefficients of correlation. The genotypes in cow-daughters did not have a reliable correlation with the duration of lactation and fat or protein content in milk. The results of the kappa-casein gene polymorphism study indicated that the AA genotype of cow-mothers of the Swiss breed was associated with higher productive milk qualities which should be taken into account when forming a highly productive herd of cattle of the Swiss breed under intensiveoperative technology at a large-scale dairy unit.

Meta-analysis of SNP in growth hormone gene associated with milk traits in dairy cows

Previous studies reported varied findings regarding growth hormone polymorphisms and their association with milk traits in dairy cattle. The objective of the present study was to combine the information of Alu1-derived gene polymorphisms of growth hormone in 6571 dairy cows using 51 published studies for obtaining pooled estimate of gene frequency of L allele in dairy cows and for deriving common effect size of association of gene variants with various milk traits (lactation milk yield, fat yield, fat%, protein yield, and protein%) using meta-analysis. The pooled estimate of gene frequency was obtained using proportion as effect size with 95% confidence interval under random effects model. For association analysis, standardized mean difference was employed as effect size under four genetic models comprising additive (LL vs. VV), dominant (LL + LV vs. VV), completely over dominant (LL + VV vs. LV), and recessive (LL vs. LV + VV). The heterogeneity between studies was estimated using Q test and I² statistic. The results showed that pooled estimate of gene frequency of L allele was 0.81 (95% CI: 0.77, 0.85; I² = 96.86%). Subgroup analysis revealed that it was significantly higher in Bos indicus cows (0.97, 95% CI 0.89, 1.00; I² = 95.15%) than Bos taurus/cross cows (0.78, 95% CI 0.73, 0.82; I² = 96.84%). An association analysis showed that the effects of GH variants on milk-related traits were not significant (P > 0.1) under all genetic models. Substantial range of heterogeneity indicated modest effects of SNP genotypes with milk traits. It was concluded that although allele L is predominant than V allele of GH in dairy cows over large geographical populations, they may not be particularly useful for selection programs for improving milk traits in dairy cows.

Polymorphisms of kappa-casein gene and their effects on milk production traits in Holstein, Jersey and Brown Swiss cattle

The objectives of this study were to detect kappa-casein (κ-CN, CSN3, CASK) gene polymorphisms and to investigate the association between the κ-CN gene polymorphisms and milk yield and composition in cattle. For this purpose, a total of 365 blood and milk samples were collected from Holstein, Jersey and Brown Swiss cows. Polymorphisms of κ-CN gene were detected by the PCR and restriction fragment length polymorphism. A 776-bp fragment of exon IV was amplified by PCR and digested with HindIII and HaeIII restriction endonuclease to distinguish allele A, B and E. The analysis of associations between κ-CN genotypes and milk yield and composition were conducted with the use of the general linear model procedure. As a result, allele frequencies were detected as 0.736, 0.357, 0.308 for A allele, 0.186, 0.643, 0.692 for B allele in Holstein, Brown Swiss and Jersey breeds, respectively, and 0.079 for E allele in Holstein. This study also demonstrated the presence of E allele in Turkish Holstein. Although κ-CN genotypes were associated with protein and solids-not-fat content of milk in Hostein and Brown Swiss, they were associated with milk fat content in Jerseys (P < 0.05).