Potential influence of κ-casein and β-lactoglobulin genes in genetic association studies of milk quality traits

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.

Transcriptome study underling difference of milk yield during peak lactation of Kazakh horse

This study was designed to provide a basis for further understanding of the mechanism of lactation based on mRNA expression differences in milk fat between different milk yields in Kazakh horses. Total RNA was extracted from the milk fat during the peak of lactation period. A total of 310 differentially expressed genes (DEGs) were identified by comparative transcriptome analysis of the high-yield and low-yield group. These DEGs regulate lactation by participated in AMPK signaling pathway, FoxO signaling pathway, ErbB signaling pathway, VEGF signaling pathway. In addition, we performed quantitative PCR to validated 5 selected DEGs and the results were in agreement with RNA-seq analysis. A new profile has been established for revealing the mechanism of equid's mammalian lactation.

Genes encoding equine β-lactoglobulin (LGB1 and LGB2): Polymorphism, expression, and impact on milk composition

β-lactoglobulin is one of the most abundant milk whey proteins in many mammal species, including the domestic horse. The aim of this study was to screen for polymorphism in the equine LGB1 and LGB2 gene sequences (all exons, introns, and 5’-flanking region) and to assess potential relationship of particular genotypes with gene expression levels (measured in milk somatic cells) and milk composition traits (protein, fat, lactose, and total β-lactoglobulin content). Direct DNA sequencing analysis was performed for twelve horse breeds: Polish Primitive Horse (PPH), Polish Coldblood Horse (PCH), Polish Warmblood Horse (PWH), Silesian, Hucul, Fjording, Haflinger, Shetland Pony, Welsh Pony, Arabian, Thoroughbred, and Percheron—and revealed the presence of 83 polymorphic sites (47 and 36 for LGB1 and LGB2 genes, respectively), including eight that were previously unknown. Association analysis of the selected polymorphisms, gene expression, and milk composition traits (conducted for the PPH, PCH, and PWH breeds) showed several statistically significant relationships; for example, the two linked LGB1 SNPs (rs1143515669 and rs1144647991) were associated with total milk protein content (p < 0.01). Our study also confirmed that horse breed had significant impact on both gene transcript levels (p < 0.01) and on milk LGB content (p < 0.05), whereas an influence of lactation period was seen only for gene relative mRNA abundances (p < 0.01).