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The most common types of beta-casein in cow’s milk are A1 and A2, which differ in one amino acid. During the gastrointestinal proteolysis of A1 beta-casein in humans this difference results in the release of beta-casomorphin-7, an opioid which may lead to severe effects on human health, causing various ailments (type-1 diabetes mellitus, ischemic h...
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... not in those of A2A2 (P>0.05, Figure 2B). When the fi rst and second lactations were considered together (Table 2) and the genotypes compared for milk quantity in both of them (Table 3), A1A1 (7727.92 L on average) and A1A2 (8174.02 ...Context 2
... in milk protein concentrations were signifi cant only within the second lactation between A1A2 vs A2A2 genotype (P<0.01, Figure 3A). However, when the total milk production was assessed in both lactations (Table 3), signifi cant differences were detected between A1A2 (3.13% on average, Table 2) vs A2A2 (3.19%, Table 2) genotypes (P<0.01) only, while the differences A1A1 (3.16%, Table 2) vs A1A2, and A1A1 vs A2A2 were proved insignifi cant (P>0.05). ...Context 3
... in milk protein concentrations were signifi cant only within the second lactation between A1A2 vs A2A2 genotype (P<0.01, Figure 3A). However, when the total milk production was assessed in both lactations (Table 3), signifi cant differences were detected between A1A2 (3.13% on average, Table 2) vs A2A2 (3.19%, Table 2) genotypes (P<0.01) only, while the differences A1A1 (3.16%, Table 2) vs A1A2, and A1A1 vs A2A2 were proved insignifi cant (P>0.05). ...Context 4
... when the total milk production was assessed in both lactations (Table 3), signifi cant differences were detected between A1A2 (3.13% on average, Table 2) vs A2A2 (3.19%, Table 2) genotypes (P<0.01) only, while the differences A1A1 (3.16%, Table 2) vs A1A2, and A1A1 vs A2A2 were proved insignifi cant (P>0.05). The average milk protein concentrations were signifi cantly higher in the second lactation (P<0.01, Figure 3B), regardless of the genotype detected. ...Context 5
... both the fi rst and the second lactation milk fat concentrations were highest if produced by A2A2 cows and differed signifi cantly in comparison with A1A1 and A1A2 genotypes (P<0.01), and A1A2 vs A2A2 in the fi rst and second lactation, while there was no signifi cance (P>0.05) of differences between other pairs of genotypes ( Figure 4A). The results were identical (Table 3) when the data from both lactations were considered together (in A1A1 3.36% on average, in A1A2 3.37% and 3.44% in A2A2, Table 2). In cows of all of the three genotypes signifi cantly higher milk fat concentrations were in the second lactation (P<0.01, Figure 4B). ...Citations
... However, the average values in this study correspond to those reported in [26]. The higher percentages of the main components of cheese (protein and fat content) are shown in [27]. ...
One of the ways to increase the profitability of the cheese industry is the genetic selection of dairy cows to obtain milk with excellent cheese-capacity characteristics. The object of this study is the technology of fresh soft cheeses made by the acid-rennet and thermo-acid method from the milk of cows with different β-casein genotypes (A1A1, A1A2, A2A2). The subjects of research are the physicochemical indicators of raw milk from cows with different genotypes for β-casein (A1A1, A1A2, A2A2); as well as the yield of soft cheeses. The study has established that the physicochemical parameters of milk from cows with different β-casein genotypes are typical for fresh cow's milk. The study showed that with the acid-rennet method, the composition of cheeses from A1A1 milk was 51.60 %, 21.63 %, and 23.62 % of moisture, protein, and fat, respectively. A1A2 milk cheeses contained 50.70 % moisture, 20.96 % protein, and 25.12 % fat. A2A2 milk cheeses consisted of 52.50 % moisture, 20.70 % protein, and 23.71 % fat. With the thermo-acid method, cheeses from A1A1 milk were characterized by the moisture content of 55.13 %, proteins – 23.31 %, and fat – 20.21 %. A1A2 milk cheeses contained 58.13 %, 22.62 %, and 17.98 % of moisture, protein, and fat, respectively. A2A2 milk cheeses consisted of 54.03 % moisture, 22.33 % protein, and 22.25 % fat. The calculation of the production efficiency of soft cheeses from the milk of cows with different genotypes according to β-casein with the acid-rennet method of production is 119.3 % on average, which is more compared to milk A1A2 (by 4 %) and A2A2 (by 7 %). With the thermo-acidic method, the efficiency of cheese production from A2A2 milk is 107.5 %, which is higher compared to A1A2 milk (by 9 %) and A1A1 (by 5 %). The conclusions show that changes in the β-casein genotype in raw milk can affect the yield and quality of cheese, and therefore, the profitability of production
... Cows with the β-casein A2A2 genotype produce the popular "A2 milk" (3). Additionally, A2A2 genotyped cows have a higher milk fat % than their A1A1 and A1A2 counterparts (6). Furthermore, during digestion and metabolism, A1 β-casein produces β-casein-7, which has been linked with Gastrointestinal (GI) issues and lactose intolerance disorders in humans (7,8). ...
In Holstein cows, β-casein, one of the most critical proteins in milk, exists in two main genotypes, A1 and A2. Herein, 45 Holstein cows [categorized into three groups based on β-casein A1A1, A1A2, and A2A2 genotypes (N = 15)] with the same feeding management and litter size were enrolled to explore differences in rumen microflora and metabolites across various β-casein genotypes. Rumen fluids were collected for metagenomics and metabolomics analyses. Metabolomics and weighted gene co-expression network analysis (WGCNA) revealed that arachidonic acid (AA), adrenic acid (AdA), glycocholic acid (GCA), and taurocholic acid (TCA) were significantly and positively correlated with milk fat % in dairy cows (p < 0.05). Furthermore, macro-genomics and Spearman’s correlation analysis revealed significant positive correlations (p < 0.05) between the characteristic flora (g_Acetobacter, g_Pseudoxanthomonas, g_Streptococcus, and g_Pediococcus) and the five characteristic metabolites in the rumen of A2A2 dairy cows. Moreover, functional enrichment analysis revealed more genes enriched to the TRP channel’s inflammatory mediator-regulated pathway and the mTOR signaling pathway in A2A2 genotyped cows. Additionally, the regulatory effects of AA on bovine mammary epithelial cells (BMECs) were examined using CCK-8, EdU, and qRT-PCR assays, revealing that AA promoted triglyceride (TG) synthesis and upregulated the milk fat marker genes including SREBF1, ACSS2, AGPAT6, and FASN. Overall, we identified characteristic microorganisms and metabolites in A2A2 Holstein cows and established that AA could be a biomarker for higher milk fat %.
... This occurred in Brazil (Mendes et al., 2019). Approximately 12 beta-casein gene (CSN2) variants are available, the most common of which are A1 and A2 (Marko et al., 2020). Regarding the frequency, there were differences among breeds and herds. ...
... In total, 112 blood samples were collected from randomly selected Holstein-Zebu (HZ) cows, descendant of diverse bulls from four dairy herds. Antisepsis was conducted using 70% alcohol, and a sterile needle was used for each animal (Marko et al., 2020). Five milliliters of blood was collected in Vacutainer tubes containing ethylenediaminetetraacetic acid (EDTA), and it was placed in a thermal box with ice and sent to the Laboratório de Sanidade Animal of Universidade Federal de Minas Gerais to be stored at -20°C. ...
This study aimed to investigate A1 and A2 polymorphisms of the beta-casein gene in crossbred Holstein-Zebu (HZ) cows from four herds in Northern Minas Gerais, Brazil. Blood samples were collected from 112 randomly selected cows, of wich 66 were at ½ HZ, and 46 were at ¾ HZ. DNA extraction was conducted using the phenol-chloroform method, and polymorphisms were evaluated using the amplification refractory mutation system - polymerase chain reaction technique. The results demonstrated that 72/112 (64.3%) cows were heterozygous (A1A2), 33/112 (29.5%) were homozygous for A2A2, and 7/112 (6.2%) were A1A1 homozygous. The percentage of A2A2 cows ranged from 10.7 to 41.4% among the evaluated herds. The frequencies of the A1 and A2 alleles were 38.4 and 61.6%, respectively. The A2 allele was the most frequent in both breeds. The ½ HZ cows were 1.8 times more likely (Odds Ratio) to belong to the A1A1 genotype. The distribution of genotypes was in Hardy-Weinberg equilibrium in three of the herds; however, the total of samples and the stratified samples according to breeds were not in equilibrium considering α = 0.05.
... This difference results from the single nucleotide polymorphism (SNP) at codon 67, which is CCT (A2, proline) or CAT (A1, histidine). Therefore, cows with the A2A2 genotype produce milk containing A2 beta-casein, unlike cows with A1A1 and A1A2 genotypes, which synthesize A1 beta-casein (Ristanić et al., 2020). The polymorphism that caused the replacement of proline with histidine leads to critical changes in the secondary conformation of the expressed beta-casein gene (Elliott et al., 1999, McLachlan, 2001. ...
... The results of allelic and genotype frequencies could be useful as a starting point for selecting cows with the desirable A2 allele, in order to encourage small and large dairy farmers to form herds that would produce A2 milk exclusively (Ristanić et al., 2022). The results of the β-casein polymorphism research performed by Ristanić et al. (2020) showed a higher frequency of the A2 (0.604) allele in regards to the A1 (0.396) allele, with the frequencies of the genotypes A2A2 (33.02%), A1A2 (54.72%), and A1A1 (12.26%). ...
... Just a few studies are dedicated to the problem of the frequency of the A1 alleles within the cattle breeds in Serbia and the Balkans. The most important research was published by Ristanić et al. (2020Ristanić et al. ( , 2022, in Serbia. From research done by Ristanić, we can conclude that the A1 allele is present to a lesser extent within the milk cattle compared to A2 alleles, which is similar to the results of our research. ...
One of the most important milk proteins, β-casein, has several genetic variations, of which A1 and A2 are the most important. The goal of the research was to determine the frequency of A1 and A2 alleles, and the different types of genotypes inside the population of Holstein cows from the territory of Vojvodina. A1 type of this protein during digestion in the gastrointestinal system, decomposes into certain opioid peptides, such as 7-casomorphine (BCM7), which causes damage to various systems and leads to the development of many diseases. Many studies claim that this opioid peptide is to some extent involved in the development of autism, schizophrenia, several allergic reactions and disorders of the digestive system. After the concern about the A1 variant on human health, a selection favoring the A2 allele was carried out in different countries, which has not been proven to harm human health. This study included 30 samples of Holstein cows which are tested for β-casein polymorphism. DNA isolation was performed from the follicle of the tail hair. The methods included in the study are based on DNA isolation, the PCR gene amplification and the use of the RFLP method to detect polymorphism of β-casein gene. Out of 30 samples, the A2A2 genotype had frequency 0.967, and A1A2 genotype had a frequency 0.033. Alleles frequency of the A1 and A2 was 0.017 and 0.983, respectively. Research on this topic is important for raising the awareness of breeders, in order to pay attention to β-casein and its consequences on human health, that is, to enable breeders to select those cattle that carry the allele for the A2 form of β-casein.
... The existence of a probable difference between the indices of standard milk for cows with different genotypes for the beta-casein locus is confirmed by the works of a number of authors that were conducted on commercial and local cattle breeds (Kumar et al., 2019;Ivanković et al., 2021). Data on increased milk yield values that are typical for individuals of the Holstein breed with the A 2 A 2 genotype are confirmed by the results obtained by Olenski et al. in Poland as well as by Ristanic et al. in Serbia (Olenski et al., 2010;Ristanic et al., 2020). ...
Peculiarities of the genetic structure of the population of Holstein cattle bred in Ukraine were studied by beta-casein and tumor necrosis factor alpha loci. Using the methods of allele-specific PCR (AS-PCR) and PCR with restriction fragment length polymorphism (PCR-RFLP) analysis, polymorphism of the beta-casein gene (CSN2) by allelic variants A1 and A2 and of the tumor necrosis factor-alpha (TNF-α) by SacI-polymorphism in the promoter region of the gene (–824 A>G marker mutation) and RsaI-polymorphism in the fourth exon were analyzed. It was proven that both loci are polymorphic in the studied cattle population. For each of the polymorphic loci, the main genetic and population parameters of the Holstein cow population were established. For the CSN2 locus, a significant predominance of the frequency of the A2 allele over A1 was established (0.78 vs. 0.22). For the SacI- and RsaI-polymorphisms of TNF-α, maximal (1.980 and 1.988) values of the locus polymorphism level (the number of effective alleles) were detected. For both mutations in the TNF-α gene, actual parity in the frequency values of the corresponding alleles was established (0.55 and 0.45 for the SacI-polymorphism; 0.54 and 0.46 for the RsaI-polymorphism). For the RsaI-polymorphism in the TNF-α fourth exon, a deviation from the state of genetic equilibrium according to Hardy–Weinberg was recorded in the studied population of animals, and a significant excess of heterozygous individuals was detected (25%). Based on the results of the analysis of milk productivity parameters of individuals with different CSN2 locus genotypes, it was established that individuals with the A2A2 genotype are characterized by higher values of standard milk production as compared with individuals with the A1A1 genotype (p = 0.042). For the SacI- and RsaI-polymorphism of the TNF-α gene, there were no significant differences in the parameters of standard milk productivity for two lactations between individuals with different genotypes.
... The Holstein-Friesian (HF) is the leading dairy breed in the world; its genetic potential for high milk yields is being exploited in virtually all developed countries. Milk production and milk composition are the most carefully selected traits in dairy cattle breeding programs [1,2]. The discovery of molecular markers associated with the aforementioned traits and the application of marker-assisted selection (MAS) made a huge impact on dairy cattle breeding in recent decades. ...
Simple Summary
This study focuses on identifying the genetic factors associated with milk-related traits in dairy cows. This research employed various genomic techniques to discover a significant association between a specific gene marker and milk protein concentration. The study also assessed inbreeding levels and revealed insights into the genetic mapping of dairy cows. We identified a marker that is significantly associated with milk protein concentration in first lactation (adjusted to 305 days) and, in addition to this marker, we also revealed genomic regions under selection pressure for other economically important traits. Moreover, we revealed low inbreeding levels among the tested animals. These findings contribute to enhancing breeding programs for Holstein-Friesian cattle and improving milk production.
Abstract
To improve the genomic evaluation of milk-related traits in Holstein-Friesian (HF) cattle it is essential to identify the associated candidate genes. Novel SNP-based analyses, such as the genetic mapping of inherited diseases, GWAS, and genomic selection, have led to a new era of research. The aim of this study was to analyze the association of each individual SNP in Serbian HF cattle with milk production traits and inbreeding levels. The SNP 60 K chip Axiom Bovine BovMDv3 was deployed for the genotyping of 334 HF cows. The obtained genomic results, together with the collected phenotypic data, were used for a GWAS. Moreover, the identification of ROH segments was performed and served for inbreeding coefficient evaluation and ROH island detection. Using a GWAS, a polymorphism, rs110619097 (located in the intron of the CTNNA3 gene), was detected to be significantly (p < 0.01) associated with the milk protein concentration in the first lactation (adjusted to 305 days). The average genomic inbreeding value (FROH) was 0.079. ROH islands were discovered in proximity to genes associated with milk production traits and genomic regions under selection pressure for other economically important traits of dairy cattle. The findings of this pilot study provide useful information for a better understanding of the genetic architecture of milk production traits in Serbian HF dairy cows and can be used to improve lactation performances in Serbian HF cattle breeding programs.
... The genotype β-CN A 2 A 2 produces higher fat yields than genotypes β-CN A 1 A 1 and β-CN A 1 A 2 (Ristanic et al., 2021), while there was a higher coagulation time and lower curd firmness of those with the allele A 2 in comparison to alleles β-CN A 1 A 1 and BA 1 (Hallén et al., 2007;Bisutti et al., 2022). These results point to the importance of the allele β-CN A 1 in cows that produce milk appealable for cheesemaking. ...
... In contrast, another study says that CSN1S1 C has a considerable influence on milk protein content (Boettcher et al., 2004). One study reports higher fat yield for β-CN A 2 A 2 over other polymorphisms evaluated (Ristanic et al., 2021), while another study found no significant influence of β-CN genetic variants on milk traits (Braunschweig, 2008). This can be explained by the possible association of breeds and sire families (Bonfatti et al., 2010), which are different between both studies, that is, Serbian Holstein Frisian and Swiss Fleckvieh cattle (Ristanic et al., 2021;Braunschweig, 2008). ...
... One study reports higher fat yield for β-CN A 2 A 2 over other polymorphisms evaluated (Ristanic et al., 2021), while another study found no significant influence of β-CN genetic variants on milk traits (Braunschweig, 2008). This can be explained by the possible association of breeds and sire families (Bonfatti et al., 2010), which are different between both studies, that is, Serbian Holstein Frisian and Swiss Fleckvieh cattle (Ristanic et al., 2021;Braunschweig, 2008). ...
... β-CNs A1 and A2 are the two major proteoforms in milk (Farrell et al., 2004), and it is hypothesized that the A2 proteoform of β-CN brings the original amino acid sequence; however, a point mutation on exon VII of bovine β-CN gene on sixth chromosome led to a conversion from cytosine to adenine base leading to the replacement of proline (A2 allele) by histidine (A1 allele) amino acid at position 67 and caused the appearance of the β-CN A1 proteoform in modern Western cattle breeds, exhibiting mixed A1 and A2 β-CN proteoforms (Sebastiani et al., 2022). Cows with genotype A2A2 produce milk containing β-CN A2 proteoform (A2 milk), unlike cows with genotypes A1A1 and A1A2, synthesize β-CN A1 proteoform (Ristanic et al., 2020). ...
... β-CN was found to be related with fat percentage and protein yields (Ng-Kwai-Hang et al., 1984;Bovenhuis et al., 1992). The A2 β-CN allele was associated with higher milk and protein yields (Ikonen et al., 1999;Comin et al., 2008;Heck et al., 2009;Ristanic et al., 2020) compared with A1 allele in Finnish Ayrshire, Italian Holstein, Dutch Holstein-Friesian, and Serbian Holstein-Friesian cows. Cendron et al. (2021) described that A2A2 cows produce milk with slightly, albeit significant, greater milk protein content (10.6%), ...
... With regard to milk fat, β-CN genotype (A1A1, A1A2, and A2A2) has no relationship with milk fat percentage or milk fat yield in dairy cows (Heck et al., 2009;Vallas et al., 2012;Cendron et al., 2021). However, Ristanic et al. (2020) observed higher milk fat content in A2A2 milk compared with A1A1 and A1A2 genotypes in Serbian Holstein-Friesian cows, and in Finnish Ayrshire cows, the high fat content was associated with β-CN A1 allele (Ikonen et al., 1999(Ikonen et al., , 2001. Morris et al. (2005) reported that β-CN A2A2 tends to correlate with a lower content of medium-chain-length fatty acids and higher-long-chain fatty acids. ...
... Results from Cieślińska et al. (2012) suggest that most BCM7 is released from hydrolysed and processed milk in association with the A1 allele of beta-casein, regardless of the lactation period. The genotype distributions presented in Table 1 are shown in (Çardak, 2005): A, (Ristanic et al., 2020): B; (Hanusová et al., 2010): C, and (Kamiński et al., 2006): D, and it can be concluded that based on the data presented, that the A1A2 heterozygous genotype is typically the most prevalent in the Holstein-Friesian breed. In one of the four studies (study A), the proportion of the A2A2 genotype was very low. ...
... In terms of genotype frequencies, it can be observed that compared to the 38.83 % A2A2 genotype prevalence of the A site, the B site lags behind by almost 10 %. The lowest proportion of cows with genotype A1A1 was observed, 14.02 % in site A and 9.26 % in site B. These results are similar to those reported by Ristanic et al. (2020) for Serbian and Kamiński et al. (2006) for Polish conditions, who found a similar genotype distribution in the herds they studied. The A2 allele is present in more than 60 % of individuals. ...
... The A2 allele is present in more than 60 % of individuals. A similar finding was also reported by Ristanic et al. (2020) and OleńskI et al. (2010), while Antonopoulos et al. (2021) reported an allele frequency of 74 %. Table 3 shows the results of a genotyped heifer population of 150 heifers from colony A. We observed homozygous genotype A2 in 138 individuals, 92 % of the total number of heifers. ...
The main objective of this study was to determine the beta-casein A1/A2 polymorphism status of animals in two Holstein Friesian dairy cow herds in Győr-Moson-Sopron County, Hungary. The A1/A2 status of cattle is determined by the beta-casein gene on the sixth chromosome. The analysed single nucleotide polymorphism is non-synonymous; A1 and A2 variants of bovine beta-casein differ at position 67 of the amino acid chain: A1 variant codes for histidine and A2 codes for proline, which may affect the milk protein degradation process. The analysed polymorphism leads to key conformational changes in the secondary protein structure of beta-casein. Beta-casomorphin (known as BCM7) is released only from A1-type milk and cannot be completely degraded by enzymes during digestion. DNA isolation was performed from whole blood, and a polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method with agarose gel electrophoresis was applied in order to determine individual genotypes. The results from the two dairy farms demonstrate that a high proportion of cows (86.08 and 90.74 %) carry the A2 gene variant without targeted selection. At farm "A", beta-casein polymorphisms were determined in 599 cows and 148 heifers. The genotype distribution of the cows was 47.25 % heterozygous, 38.83 % homozygous A2, whereas 14.02 % of the cows carried the A1A1 genotype. In heifers, A2A2 was already present in a remarkably high frequency (91.89 %), whereas the prevalence of heterozygotes was 7.43 %, and A1A1 animals made up only 0.67 % of the analysed heifer population. In Hungary, a growing number of dairy farms are using verified A2 homozygous breeding bull semen. The introduction of homozygous A2 sperm on the farm "A" remarkably increased A2 frequency in the heifer population. In total, 324 cows were genotyped on farm "B", where the A2A2 genotype was observed in 30.55 % of the animals. The second most common genotype was A1A2, with a genotype frequency of 60.19 %, whereas A1A1 homozygotes occurred with a 9.26 % frequency. The growing popularity of A2 milk due to potential health benefits is driving Hungarian stakeholders towards the targeted selection of dairy populations; animal genotyping is an evident approach to facilitate this transition.
... However, the average values in this study correspond to those reported in the works of scientists [1,28]. Higher percentages of the main components of cheese (content of protein and fat, dry matter) are shown in the work of scientists [29]. ...
Cheese production is a complex process that is influenced by many factors: protein:fat ratio, acidity, and type of rennet. An option for improving the profitability of the cheese industry is the genetic selection of dairy cows to produce milk with good rennet protein coagulation. The object of the study is the technology of cheeses made from milk from cows with different β-casein genotypes (А1А1, А1А2, А2А2). The subject of the study is the physical-chemical parameters of milk from cows with different genotypes for β-casein; yield of cheese from this milk and its quality indicators. Samples of Gouda cheese were produced according to traditional technology. The research established that the quality indicators of milk samples are typical for fresh cow's milk. The content of fat, protein, and dry matter in the milk of cows with the β-casein genotype A2A2 were slightly higher compared to A1A1 and A1A2. The study of the quality indicators of the cheese samples showed that the type of β-casein did not affect the organoleptic properties of the cheese. However, according to the content of the main chemical components, cheeses made from A1A2 milk had a higher content of dry matter and protein (61,6 % and 19,2 % on average, respectively) and a lower fat content (37.2 %). The amino acid profile of cheese from milk of cows with β-casein A1A2 and A2A2 genotypes showed a higher total content of amino acids – 14.89 mg/g and 13.84 mg/g, respectively. Calculations of cheese yield showed that cheese yield from milk of cows with β-casein genotype A1A2 was higher (mean value 13.1 %) than with A1A1 and A2A2. The obtained results are of practical importance, as it is possible to take into account how changes in the β-casein genotype in milk can affect the yield of cheese, and therefore, the profitability of production
