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Short Communication: Carora Cattle Show High Variability in _s1-Casein

A. Caroli^*,1, S. Chessa, F. Chiatti, D. Rignanese, B. Meléndez, R. Rizzi and G. Ceriotti

^* Dipartimento di Scienze Biomediche e Biotecnologie, Universitá degli Studi di Brescia, Viale Europa 11, 25123 Brescia, Italy
Dipartimento di Scienze e Tecnologie Veterinarie per la Sicurezza Alimentare, Universitá degli Studi di Milano, Via Trentacoste 2, 20134 Milano, Italy
Facultad de Ciencias Veterinarias, Universidad Central de Venezuela, Maracay, Edo. Aragua, Venezuela

¹ Corresponding author: caroli{at}med.unibs.it

The objective of this study was to analyze the genetic variability of milk proteins of the Carora, a shorthorned Bos taurus cattle breed in Venezuela and in other Southern American countries that is primarily used for milk production. A total of 184 individual milk samples were collected from Carora cattle in 5 herds in Venezuela. The milk protein genes _s1-casein (CN) (CSN1S1), β-CN (CSN2), -CN (CSN3), and β-lactoglobulin (LGB) were typed at the protein level by isoelectrofocusing. It was necessary to further analyze CSN1S1 at the DNA level by a PCR-based method to distinguish CSN1S1*G from B. Increased variation was found in particular at the CSN1S1 gene, where 4 variants were identified. The predominant variant was CSN1S1*B (frequency = 0.8). The second most common CSN1S1 variant was CSN1S1*G (0.101), followed by CSN1S1*C (0.082). Moreover, a new isoelectrofocusing pattern was identified, which may result from a novel CSN1S1 variant, named CSN1S1*I, migrating at an intermediate position between CSN1S1*B and CSN1S1*C. Six cows carried the variant at the heterozygous condition. For the other loci, predominance of CSN2*A² (0.764), CSN3*B (0.609), and LGB*B (0.592) was observed. Haplotype frequencies (AF) at the CSN1S1-CSN2-CSN3 complex were also estimated by taking association into account. Only 7 haplotypes showed AF values >0.05, accounting for a cumulative frequency of 0.944. The predominant haplotype was B-A²-B (frequency = 0.418), followed by B-A²-A (0.213). The occurrence of the G variant is at a rather high frequency, which is of interest for selection within the Carora breed because of the negative association of this variant with the synthesis of the specific protein. From a cheese-making point of view, this variant is associated with improved milk-clotting parameters but is negatively associated with cheese ripening. Thus, milk protein typing should be routinely carried out in the breed, with particular emphasis on using a DNA test to detect the CSN1S*G variant. The CSN1S*G allele is likely to have descended from the Brown Swiss, which contributed to the Carora breed and also carries this allele.

Key Words: milk protein • Carora cattle • Venezuela • _s1-casein