Newly identified mutations at the CSN1S1 gene in Ethiopian goats affect casein content and coagulation properties of their milk

Relation between αS1-casein, genotype, and quality traits of milk from Swedish dairy goats

Locally produced food is becoming popular among Swedish consumers. One product that has increased in popularity is artisan-manufactured goat cheese, and although the dairy goat industry in Sweden is small-scale, production is gradually increasing. In goats, the CSN1S1 gene regulates expression of the protein α_S1-casein (α_S1-CN), which has been found to be important for cheese yield. Over the years, breeding animals have been imported to Sweden from Norway. Historically, a high frequency of the Norwegian goat population carried a polymorphism at the CSN1S1 gene. This polymorphism, called the Norwegian null allele (D), leads to zero or significantly reduced expression of α_S1-CN. Using milk samples from 75 goats, this study investigated associations between expression of α_S1-CN and genotype at the CSN1S1 gene on milk quality traits from Swedish Landrace goats. Milk samples were grouped according to relative level of α_S1-CN (low: 0-6.9% of total protein; medium-high: 7-25% of total protein) and genotype (DD, DG, DA/AG/AA). While the D allele leads to extremely low expression of α_S1-CN, the G allele is low expressing and the A allele is highly expressing for this protein. Principal component analysis was used to explore the total variation in milk quality traits. To evaluate the effect of different allele groups on milk quality attributes, 1-way ANOVA and Tukey pairwise comparison tests were used. The majority (72%) of all goat milk samples investigated showed relative α_S1-CN content of 0% to 6.82% of total protein. The frequency of individuals homozygous for the Norwegian null allele (DD) was 59% in the population of sampled goats, and only 15% carried at least one A allele. A low relative concentration of α_S1-CN was associated with lower total protein, higher pH, and higher relative concentration of β-casein and levels of free fatty acids. Milk from goats homozygous for the null allele (DD) showed a similar pattern as milk with low relative concentration of α_S1-CN, but total protein was only numerically lower, and somatic cell count and α_S2-CN were higher than for the other genotypes. The associations between levels of α_S1-CN and the investigated genotype at the CSN1S1 gene indicate a need for a national breeding program for Swedish dairy goats.

A New AS-PCR Method to Detect CSN201 Allele, Genotyping at Ca-Sensitive Caseins Loci and Milk Traits Association Studies in Autochthonous Lazio Goats

Calcium-sensitive caseins are the main protein component of milk. In the goat, they are encoded by three genes (CSN1S1, CSN2, and CSN1S2) located on chromosome 6. A high number of alleles has been discovered for these genes in the goat species, responsible for changes in the milk’s qualitative and quantitative characteristics. This study aimed to develop an Allele-Specific PCR (AS-PCR), which allowed us to unequivocally detect goat carriers of the CSN201 allele. Subsequently, the calcium-sensitive casein loci genotype was investigated in three native goat breeds of the Lazio Region (Bianca Monticellana, Capestrina, and Ciociara Grigia). No individuals were carriers of the CSN1S101, CSN1S1E, CSN201, CSN1S2D, and CSN1S20 alleles, while a high frequency of the alleles CSN1S1F and CSN1S1A*,B* was observed. Association analyses between the different genotypes at the CSN1S1 locus and some milk traits, namely the fat and protein yielded and the fat, protein, solids-not-fat, and casein percentages without an effect on the milk yield, were observed.

Review: Genetic and protein variants of milk caseins in goats

The milk casein genes in goats, are highly polymorphic genes with numerous synonymous and non-synonymous mutations. So far, 20 protein variants have been reported in goats for alpha-S1-casein, eight for beta-casein, 14 for alpha-S2-casein, and 24 for kappa-casein. This review provides a comprehensive overview on identified milk casein protein variants in goat and non-coding DNA sequence variants with some affecting the expression of the casein genes. The high frequency of some casein protein variants in different goat breeds and geographical regions might reflect specific breeding goals with respect to milk processing characteristics, properties for human nutrition and health, or adaptation to the environment. Because protein names, alongside the discovery of protein variants, go through a historical process, we linked old protein names with new ones that reveal more genetic variability. The haplotypes across the cluster of the four genetically linked casein genes are recommended as a valuable genetic tool for discrimination between breeds, managing genetic diversity within and between goat populations, and breeding strategies. The enormous variation in the casein proteins and genes is crucial for producing milk and dairy products with different properties for human health and nutrition, and for genetic improvement depending on local breeding goals.

Capture Sequencing to Explore and Map Rare Casein Variants in Goats

Genetic variations in the four casein genes CSN1S1, CSN2, CSN1S2, and CSN3 have obtained substantial attention since they affect the milk protein yield, milk composition, cheese processing properties, and digestibility as well as tolerance in human nutrition. Furthermore, milk protein variants are used for breed characterization, biodiversity, and phylogenetic studies. The current study aimed at the identification of casein protein variants in five domestic goat breeds from Sudan (Nubian, Desert, Nilotic, Taggar, and Saanen) and three wild goat species [Capra aegagrus aegagrus (Bezoar ibex), Capra nubiana (Nubian ibex), and Capra ibex (Alpine ibex)]. High-density capture sequencing of 33 goats identified in total 22 non-synonymous and 13 synonymous single nucleotide polymorphisms (SNPs), of which nine non-synonymous and seven synonymous SNPs are new. In the CSN1S1 gene, the new non-synonymous SNP ss7213522403 segregated in Alpine ibex. In the CSN2 gene, the new non-synonymous SNPs ss7213522526, ss7213522558, and ss7213522487 were found exclusively in Nubian and Alpine ibex. In the CSN1S2 gene, the new non-synonymous SNPs ss7213522477, ss7213522549, and ss7213522575 were found in Nubian ibex only. In the CSN3 gene, the non-synonymous SNPs ss7213522604 and ss7213522610 were found in Alpine ibex. The identified DNA sequence variants led to the detection of nine new casein protein variants. New variants were detected for alpha S1 casein in Saanen goats (CSN1S1^∗C1), Bezoar ibex (CSN1S1^∗J), and Alpine ibex (CSN1S1^∗K), for beta and kappa caseins in Alpine ibex (CSN2^∗F and CSN3^∗X), and for alpha S2 casein in all domesticated and wild goats (CSN1S2^∗H), in Nubian and Desert goats (CSN1S2^∗I), or in Nubian ibex only (CSN1S2^∗J and CSN1S2^∗K). The results show that most novel SNPs and protein variants occur in the critically endangered Nubian ibex. This highlights the importance of the preservation of this endangered breed. Furthermore, we suggest validating and further characterizing the new casein protein variants.

Goat cheese yield and recovery of fat, protein, and total solids in curd are affected by milk coagulation properties

The aims of the present research were to quantify the effects of each coagulation trait, traditional milk coagulation properties [MCP: rennet coagulation time (RCT), curd-firming time (k₂₀), and curd firmness at 30 min (a₃₀)], and modeled curd-firming over time (CF_t) parameters [estimated rennet coagulation time (RCT_eq), curd-firming instant rate constant (k_CF), and potential curd firmness (CF_P)] directly on the following: (1) recovery of 3 milk components in the curd (%REC), (2) 3 measures of cheese yield (%CY), and (3) 3 daily cheese yield traits (dCY) from goat milk. Cheese-making traits were analyzed using 2 mixed different models, the first to test MCP and the second to test CF_t parameters. Pearson correlations were also calculated. Significant and favorable relationships (negative for time intervals and positive for CF measures) were found between the traditional MCP and the CF_t parameters and %REC and %CY traits. The effects of milk fat and protein contents were particularly important on all cheese-making traits, with the only exception being the effect of fat content on water retention in cheese (%CY_WATER). We found an optimum value of milk k₂₀, associated with the highest recovery of components and cheese yield in solids (%CY_SOLIDS). In addition, a lower level of curd water retention and an increased fresh curd yield (%CY_CURD) were associated with greater recovery of fat. The collection of all available information during the process of milk coagulation and curd-firming allowed us to discover the effect of RCT_eq on %REC traits and %CY_SOLIDS, which had not previously been revealed for traditional RCT. Moreover, higher k_CF values were associated with increased %CY_CURD and %CY_SOLIDS. Given that CF_t parameters showed a high level of independence from one another, these can also be easily used and characterized in future applications at the industry level. Information provided by traditional and modeled coagulation properties could efficiently support the goat dairy industry and lay the foundations for a quality payment scheme for goat milk.

An 11-bp Indel Polymorphism within the CSN1S1 Gene Is Associated with Milk Performance and Body Measurement Traits in Chinese Goats

The casein alpha s1 (CSN1S1) gene encodes α-s1 casein, one of the proteins constituting milk, which affects milk performance, as well as improving the absorption of calcium and bone development in mammals. A previous study found that an 11-bp insertion/deletion (indel) of this gene strongly affected litter size in goats. However, to our knowledge, the relationships between this polymorphism and the milk performance and body measurement traits of goats have not been reported. In this paper, the previously identified indel has been recognized in three Chinese goat breeds, namely the Guanzhong dairy goat (GZDG; n = 235), Shaanbei white cashmere goat (SBWC; n = 1092), and Hainan black goat (HNBG; n = 278), and the following three genotypes have been studied for all of the breeds: insertion/insertion (II), deletion/deletion (DD), and insertion/deletion (ID). The allele frequencies analyzed signified that the frequencies of the "D" allele were higher (47.8%-65.5%), similar to the previous report, which indicates that this polymorphism is genetically stable in different goat breeds. Further analysis showed that this indel was markedly associated with milk fat content, total solids content, solids-not-fat content, freezing point depression, and acidity in GZDG (p < 0.05), and also affected different body measurement traits in all three breeds (p < 0.05). The goats with II genotypes had superior milk performance, compared with the others; however, goats with DD genotypes had better body measurement sizes. Hence, it may be necessary to select goats with an II or DD genotype, based on the desired traits, while breeding. Our study provides information on the potential impact of the 11-bp indel polymorphism of the CSN1S1 gene for improving the milk performance and body measurement traits in goats.

A 100-Year Review: Advances in goat milk research

In the century of research chronicled between 1917 and 2017, dairy goats have gone from simply serving as surrogates to cows to serving as transgenic carriers of human enzymes. Goat milk has been an important part of human nutrition for millennia, in part because of the greater similarity of goat milk to human milk, softer curd formation, higher proportion of small milk fat globules, and different allergenic properties compared with cow milk; however, key nutritional deficiencies limit its suitability for infants. Great attention has been given not only to protein differences between goat and cow milk, but also to fat and enzyme differences, and their effect on the physical and sensory properties of goat milk and milk products. Physiological differences between the species necessitate different techniques for analysis of somatic cell counts, which are naturally higher in goat milk. The high value of goat milk throughout the world has generated a need for a variety of techniques to detect adulteration of goat milk products with cow milk. Advances in all of these areas have been largely documented in the Journal of Dairy Science (JDS), and this review summarizes such advances.

A novel indel within goat casein alpha S1 gene is significantly associated with litter size

The ruminant casein gene family (CSNs, link as CSN1S1-CSN2-CSN1S2-CSN3) is characterized by diverse variations and has been extensively studied for ruminant milk traits, however, studies on insertion/deletion (indel) mutations within this gene family and their effects on prolificacy are extremely limited. This study aimed to detect possible novel indels within CSNs in an indigenous Chinese goat breed-Shaanbei White Cashmere goat (SBWC, n = 3047) and four other Chinese goat breeds (n = 1136) with varied litter size rates (105%-283%) and different estrus types (seasonal vs. perennial), as well as exploring the association between these potential indels and litter size. Only one novel 11-bp indel within the CSN1S1 gene was found. The association analyses uncovered that this novel indel was related to the first-birth litter size of SBWC population (n = 2690) (P < 1.0 E-8). Individuals with the II genotype (n = 676) had the best litter size when compared with those ID genotype (n = 1098) and DD genotype (n = 916) individuals. Animals with the II genotype were found to have higher relative expression level of CSN1S1 gene in the ovary (P < 0.01). Besides, Chi-square tests for different litter size and estrous cycle breeds showed that perennial-estrus breeds and multi-kids breeds had higher "I" allelic frequencies and "II" genotypic frequencies. These findings suggest the 11-bp indel within the CSN1S1 gene is significantly associated with reproduction traits and can be an effective molecular marker for litter size of goat breeding.

Milk yield, quality, and coagulation properties of 6 breeds of goats: Environmental and individual variability

Goat milk and cheese production is continuously increasing and milk composition and coagulation properties (MCP) are useful tools to predict cheesemaking aptitude. The present study was planned to investigate the extension of lactodynamographic analysis up to 60 min in goat milk, to measure the farm and individual factors, and to investigate differences among 6 goat breeds. Daily milk yield (dMY) was recorded and milk samples collected from 1,272 goats reared in 35 farms. Goats were of 6 different breeds: Saanen and Camosciata delle Alpi for the Alpine type, and Murciano-Granadina, Maltese, Sarda, and Sarda Primitiva for the Mediterranean type. Milk composition (fat, protein, lactose, pH; somatic cell score; logarithmic bacterial count) and MCP [rennet coagulation time (RCT, min), curd-firming time (k₂₀, min), curd firmness at 30, 45, and 60 min after rennet addition (a₃₀, a₄₅, and a₆₀, mm)] were recorded, and daily fat and protein yield (dFPY g/d) was calculated as the sum of fat and protein concentration multiplied by the dMY. Data were analyzed using different statistical models to measure the effects of farm, parity_, stage of lactation and breed; lastly, the direct and the indirect effect of breed were quantified by comparing the variance of breed from models with or without the inclusion of linear regression of fat, protein, lactose, pH, bacterial, somatic cell counts, and dMY. Orthogonal contrasts were performed to compare least squares means. Almost all traits exhibited high variability, with coefficients of variation between 32 (for RCT) and 63% (for a₃₀). The proportion of variance regarding dMY, dFPY, and milk composition due to the farm was moderate, whereas for MCP it was low, except for a₆₀, at 69%. Parity affected both yield and quality traits of milk, with least squares means of dMY and dFPY showing an increase and RCT and curd firmness traits a decrease from the first to the last parity class. All milk quality traits, excluding fat, were affected by the stage of lactation; RCT and k₂₀ decreased rapidly and a₃₀ was higher from the first to the last part of lactation. Alpine breeds showed the highest dMY and dFPY but Mediterranean the best percentage of protein, fat, and lactose and a shorter k₂₀ and a greater a₃₀. Among the Mediterranean goats, Murciano-Granadina goats had the highest milk yield, fat, and protein contents, whereas Maltese, Sarda, and Sarda Primitiva were characterized by much more favorable technological properties in terms of k₂₀, a₃₀, and a₄₅. In conclusion, as both the farm and individual factors highly influenced milk composition and MCP traits, improvements of these traits should be based both on modifying management and individual goat factors. As expected, several differences were attributable to the breed effect, with the best milk production for the Alpines and milk quality and coagulation for the Mediterranean goats.

Variability of the caprine whey protein genes and their association with milk yield, composition and renneting properties in the Sarda breed. 1. The LALBA gene

The 5' flanking region and 3' UTR of the caprine LALBA gene were analysed by SSCP and sequencing. A total of nine SNPs were detected: three in the promoter region, two were synonymous coding SNPs at exon-1, and four SNPs were in exon-4, within the 3'UTR. The nucleotide changes located in the promoter region (c.-358T>C, c.-163G>A, c.-121T>G) were genotyped by SSCP in 263 Sarda goats to evaluate their possible effect on milk yield, composition and renneting properties. We observed an effect of the three SNPs on milk yield and lactose content. Genotypes TT and CT at c.-358T>C (P A (P C and c.-121T>G were part of transcription factors binding sites, potentially involved in modulating the LALBA gene expression. The LALBA genotype affected renneting properties (P < 0.001), as heterozygotes c.-358CT and c.-163GA were characterised by delayed rennet coagulation time and curd firming time and the lowest value of curd firmness. The present investigation increases the panel of SNPs and adds new information about the effects of the caprine LALBA gene polymorphism.

Principal milk components in buffalo, holstein cross, indigenous cattle and red chittagong cattle from bangladesh

The aim of the present study was to get a total physical and chemical characterization and comparison of the principal components in Bangladeshi buffalo (B), Holstein cross (HX), Indigenous cattle (IC) and Red Chittagong Cattle (RCC) milk. Protein and casein (CN) composition and type, casein micellar size (CMS), naturally occurring peptides, free amino acids, fat, milk fat globule size (MFGS), fatty acid composition, carbohydrates, total and individual minerals were analyzed. These components are related to technological and nutritional properties of milk. Consequently, they are important for the dairy industry and in the animal feeding and breeding strategies. Considerable variation in most of the principal components of milk were observed among the animals. The milk of RCC and IC contained higher protein, CN, β-CN, whey protein, lactose, total mineral and P. They were more or less similar in most of the all other components. The B milk was found higher in CN number, in the content of αs2-, κ-CN and α-lactalbumin, free amino acids, unsaturated fatty acids, Ca and Ca:P. The B milk was also lower in β-lactoglobulin content and had the largest CMS and MFGS. Proportion of CN to whey protein was lower in HX milk and this milk was found higher in β-lactoglobulin and naturally occuring peptides. Considering the results obtained including the ratio of αs1-, αs2-, β- and κ-CN, B and RCC milk showed best data both from nutritional and technological aspects.