Caroli A, Chessa S, Chiatti F, Rignanese D, Meléndez B, Rizzi R, Ceriotti G
Dipartimento di Scienze Biomediche e Biotecnologie, Universitá degli Studi di Brescia, Viale Europa 11, 25123 Brescia, Italy.
J Dairy Sci. 2008 Jan;91(1):354-9. doi: 10.3168/jds.2007-0420.
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 alpha(s1)-casein (CN) (CSN1S1), beta-CN (CSN2), kappa-CN (CSN3), and beta-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 CSN1S1G from B. Increased variation was found in particular at the CSN1S1 gene, where 4 variants were identified. The predominant variant was CSN1S1B (frequency = 0.8). The second most common CSN1S1 variant was CSN1S1G (0.101), followed by CSN1S1C (0.082). Moreover, a new isoelectrofocusing pattern was identified, which may result from a novel CSN1S1 variant, named CSN1S1I, migrating at an intermediate position between CSN1S1B and CSN1S1C. Six cows carried the variant at the heterozygous condition. For the other loci, predominance of CSN2A2 (0.764), CSN3B (0.609), and LGBB (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 CSN1SG variant. The CSN1SG allele is likely to have descended from the Brown Swiss, which contributed to the Carora breed and also carries this allele.
本研究的目的是分析卡罗拉牛（委内瑞拉和其他南美国家的一种短角黄牛品种，主要用于产奶）乳蛋白的遗传变异性。从委内瑞拉5个牛群的卡罗拉牛中总共采集了184份个体乳样。通过等电聚焦在蛋白质水平对乳蛋白基因α(s1)-酪蛋白（CN）（CSN1S1）、β-酪蛋白（CSN2）、κ-酪蛋白（CSN3）和β-乳球蛋白（LGB）进行分型。有必要通过基于PCR的方法在DNA水平进一步分析CSN1S1，以区分CSN1S1G和B。尤其在CSN1S1基因处发现了增加的变异，在该基因处鉴定出4种变体。主要变体是CSN1S1B（频率=0.8）。第二常见的CSN1S1变体是CSN1S1G（0.101），其次是CSN1S1C（0.082）。此外，还鉴定出一种新的等电聚焦模式，这可能是由一种新的CSN1S1变体引起的，命名为CSN1S1I，它在CSN1S1B和CSN1S1C之间的中间位置迁移。6头奶牛处于杂合状态携带该变体。对于其他基因座，观察到CSN2A2（0.764）、CSN3B（0.609）和LGBB（0.592）占优势。还通过考虑关联性估计了CSN1S1-CSN2-CSN3复合体的单倍型频率（AF）。只有7种单倍型的AF值>0.05，累积频率为0.944。主要单倍型是B-A2-B（频率=0.418），其次是B-A2-A（0.213）。G变体的出现频率相当高，由于该变体与特定蛋白质的合成呈负相关，因此在卡罗拉品种内的选择中很有意义。从奶酪制作的角度来看，该变体与改善凝乳参数相关，但与奶酪成熟呈负相关。因此，应该在该品种中常规进行乳蛋白分型，特别强调使用DNA检测来检测CSN1SG变体。CSN1SG等位基因可能源自布朗瑞士牛，布朗瑞士牛对卡罗拉品种有贡献，并且也携带这个等位基因。
