F. Chiatti

Technical Note: Simultaneous Identification of CSN1S2 A, B, C, and E Alleles in Goats by Polymerase Chain Reaction-Single Strand Conformation Polymorphism

Most variability in goat caseins originates from the high number of genetic polymorphisms often affecting the specific protein expression, with strong effects on milk composition traits and technological properties. At least 7 alleles have been found in the goat alpha(S2)-CN gene (CSN1S2). Five of them (CSN1S2*A, CSN1S2*B, CSN1S2*C, CSN1S2*E, and CSN1S2*F) are widespread in most breeds, whereas the other 2 (CSN1S2*D and CSN1S2*0) are rarer alleles. Four different PCR-RFLP tests are needed to detect all of these variants at the DNA level. The objective of this study was to develop and validate a rapid method for typing 4 of the 5 most-common goat CSN1S2 alleles by means of PCR-single strand conformation polymorphism (SSCP). The method was validated by analyzing 37 goat samples at the protein and DNA level, respectively, by milk isoelectrofocusing and PCR-RFLP methods already described. The genotypes obtained using the PCR-SSCP approach were in full agreement with those obtained by the validation analyses. The newly developed PCR-SSCP approach provides an accurate and inexpensive assay highly suitable for genotyping goat CSN1S2.

Genetic variability of the ovine αs1-casein

Riassunto Variabilità genetica dell’αs1-caseina ovina. La variabilità genetica dell’ αs1-caseina ovina è stata valuta con particolare attenzione alla presenza delle varianti A, C, e D e del polimorfismo nell’esone 17 che determina una transizione T →C a cui corrisponde la sostituzione aminoacidica Ile186 →Thr186. La variante C è stata suddivisa in due tipi, C’ e C’’, in base all’aminoacido presente in posizione 186. L’aplotipo ancestrale è C’ (Pro13-Ser68-Thr186) mentre C’’ (Pro13-Ser68-Ile186) è risultato il più frequente in 5 razze ovine italiane.

The casein genes in goat breeds from different Continents: analysis by Polymerase Chain Reaction - Single Strand Conformation Polymorphism (PCR-SSCP)

Abstract A screening of casein gene variability was carried out by Polymerase Chain Reaction – Single Strand Conformation Polymorphism in 8 goat breeds from Sudan (Nubian goat), Turkey (Angora Goat Lalahan Tiftic, Angora Goat Yerkoy, Hair goat) and India (Jammu, Maharashtra, Rajasthan, South Goat). A total of 16 different alleles or groups of alleles were found, showing conspicuous differences among breeds. The allele frequencies were submitted to cluster analysis in order to highlight differences between breeds, also including data from Red Sokoto, West African Dwarf Nigeria, West African Dwarf Cameroon, and Borno Goat. The tree obtained from the cluster analysis showed two main lineages. The West African goat clustered together, the Indian and Turkish breeds were in the other group. Nubian goat was found in an intermediate position.

The influence of b-lactoglobulin genetic polymorphism on morphometric characteristics of milk fat globules and milk fatty acids composition in Italian Friesian cow

Abstract β-lactoglobulin (β-Lg) is the major whey protein in the milk of ruminants and some non-ruminants. It was first isolated 60 years ago and a wealth of physico-chemical and biological information has been accumulated. Results of studies on the effect of β-Lg genotypes on milk production traits (milk yield, protein and fat yield) and on milk coagulation parameters have been rather consistent. In this study we evaluated the relationship between genetic polymorphism of β-Lg morphometric characteristics of fat globules and fatty acids composition of cow milk. The trial was carried out on 89 unrelated pluriparous Friesian dairy cows reared in the same herd in a medium-temperate climatic zone in the province of Pisa. All animals were fed the same diet. Individual milk samples were collected and analyzed in a triplicate. One milk sample of milk was collected for each cow and no preservative was used. Genotypes were determined by isoelectric focusing analysis of single milk sample. Milk fatty acids composition and morphometric characteristics of fat globules were analysed on each milk sample in triplicate. The frequency distribution of total measured milk fat globules was evaluated according to their size. Fat globule diameters were divided into nine classes of 1.5 µm width: from class 1 (1.5-3 µm) to class 9 (>13.5 µm). Finally, fat globules were further classified into two groups: group S (1.5-6 µm), and group L (>6 µm). The analysis of variance was carried out to evaluate the effect of β-Lg genotype on all evaluated parameters with simultaneous adjustment for sampling season, parity, and days from calving as a covariate. As reported in literature, a higher gene frequency of the B variant of β-Lg was observed (0.59 vs 0.41). Significant effects of β-Lg genotype were observed for the percentage of the number of fat globules in the 8th (12-13.5 µm) and 9th class (>13.5 µm) which were higher in the AB genotype than in the other genotypes. The C20:4ω6 content was significantly higher in the AB genotype (P<0.05) and C15:1 content was significantly higher in the AA genotype (P<0.05) than in the other genotypes. Although β-Lg genotypes would seem to have limited relationships with the dimensions of fat globules of cows’ milk, the higher content of C20:4ω6 in AB genotype is of particular interest from the nutritional point of view.

Casein genetic polymorphisms in goat breeds of Lombardy

Riassunto Polimorfismo genetico delle caseine in razze caprine allevate in Lombardia. E’ stato condotto uno studio della variabilità genetica delle caseine in sei razze caprine allevate in Lombardia. La tipizzazione, condotta a livello proteico mediante isoelettrofocalizzazione, è preliminare ad un approccio molecolare dettagliato su un numero più limitato di soggetti, scelti in base a particolari fenotipi caseinici.