Effect of CSN1S1 G allele on some characteristics of milk produced by Cinisara cows

In bovine milk about 37-40% of total casein is represented by s1-casein. The CSN1S1 G allele is characterised by a less efficient protein synthesis (about 40%) compared with the other known alleles because of the insertion, in the 19th exon, of a Long Interspersed Nuclear Element relict. This allele is responsible for a reduced mRNA stability. The lower proportion of s1-casein in milk is associated with faster formation, higher firmness and greater resistance to compression of the curd. The purpose of this study was to analyse the G allele distribution at the CSN1S1 locus in Cinisara breed and its influence on some milk traits. The Cinisara is a small Sicilian breed for which, recently, recovery and safeguard actions were accomplished. Milk obtained from this breed is mainly used to produce the Caciocavallo Palermitano, a typical stretched-curd (pasta filata) cheese. This product represents an example of link between breed, breeding environment, and traditional dairy technology, factors highly appreciated by consumers today. We typed 192 lactating cows, by means of PCR-RFLP analyses, in order to identify CSN1S1 G carriers. Individual milk samples of 14 cows (low as1-casein) and 23 control cows (normal s1-casein) were analysed for total nitrogen (TN) and non-casein nitrogen (NCN) according to FIL-IDF standard procedures, and for fat by an infrared method (Combi-foss 6000, Foss Electric, Hillerød, Denmark). Coagulation properties were measured using the Formagraph. Control cows were chosen in the same herds of G carrier cows and had comparable lactation stage and number. Data were analysed using ANOVA procedure in which the fixed factor of CSN1S1 was evaluated. The frequency of the CSN1S1 G allele in the 192 analyzed cows was 0.039 (1 homozygous and 13 heterozygous cows). The analyses of milk traits and clotting parameters show that also in Cinisara the CSN1S1 G allele is associated with significantly lower protein (p<.049), casein (p<.046), and casein index (p<.039). Moreover the milk of cows with CSN1S1 G allele show a tendency to a lower percentage of fat (p<.072). As a consequence, the CSN1S1 G allele is associated with significantly lower coagulation time (r) (p<.019), and tendentially lower curd firming time (k20) (p<.057), and higher curd firmness (a30) (p<.063). These results confirm that CSN1S1 G allele considerably affects milk traits. Further analyses are necessary to evaluate the influence of this allele on yield and composition of Caciocavallo Palermitano cheese.