At present, there is a concern about the quality of milk and diseases related to its consumption, as it can generate discomfort and allergic reactions in some individuals due to its protein components. Thus, the present study was developed to identify the allele and genotype frequencies of genes for β casein, A1 and A2, in dairy herds in the region of Araguaína-TO, Brazil. Genetic material from 421 animals (crossbred dairy cattle in lactation) was used. All animals were numbered for identification, and DNA samples were extracted from hair bulbs. Samples for two markers from the polymorphic regions were characterized and confirmed by real time PCR using the ABI Prism® 7500 Sequence Detection System (Applied Biosystems). Allele and genotype frequencies were determined using the TaqMan™ detection system, where the primer and probe release different fluorescence signals for each allele of the polymorphism. The sampled herd showed frequencies of 28.27% for the A1 allele and 71.73% for the A2 allele. Genotype frequencies were 52.96% (223/421) for A2A2; 37.53% (158/421) for the A1A2 genotype; and 9.50% (40/421) for the A1A1 genotype. The frequency of the A1 allele for β-casein in dairy herds from the northern region of Tocantins was low and is per the results of previous studies. Although the A2A2 genotype of β-casein had a high relative frequency, the A1A2 genotype is still rather frequent, warranting greater selection pressure.

The expression of milk proteins in vitro is essential to exploit the mammary gland cells as a biological model. Enzymatic tissue disaggregation has been widely used to establish mammary cell culture, but its effect in long-term ovine mammary cell culture is not completely elucidated. This study aimed at comparing mechanical/enzymatic and mechanical dissociation methods to establish ovine mammary cell culture. We compared cellular differentiation induced by lactating ewe sérum or fetal bovine serum based on the gene expression levels of milk proteins (beta-lactoglobulin, alpha s1-casein, and betacasein). Mechanically dissociated cells were positive immunostaining for cytokeratin 8.13, such as mammary epithelial cells. These cells are responsible for milk protein expression and they are low immunostaining for vimentin, mesenchymal marker. Mechanical/enzymatic dissociation cells were positive for vimentin. The fastest cell growth (cell/hour) was observed in the mechanical dissociation group cultured with 10% fetal bovine serum medium. Mechanically and mechanically/enzymatically derived cells were able to express beta-casein and beta-lactoglobulin, but not alpha s1-casein. The relative expression of beta-lactoglobulin was not affected by the tissue dissociation method or culture media, beta-casein relative expression was down regulated in mechanically dissociated cells cultured in the presence of lactating ewe serum, (P = 0.019). Beta-casein relative expression was also down regulated in mechanically/enzymatically dissociated cells cultured with fetal bovine sérum (P = 0.021). In the present conditions, we conclude that mechanical dissociation followed by culture with 10% of fetal bovine serum was the most efficient method to induce milk proteins’ mRNA expression by ovine mammary epithelial cells in vitro.