MILK COMPOSITION AND IDENTIFICATION OF PROTEIN POLYMORPHISM IN MONTBÉLIARDE COWS TO SELECT THE BEST VARIANTS AND IMPROVE CHESSE QUALITY

Cristina Lazăr, Rodica Pelmuş, Elena Ghiţă, M.C. Rotar

Abstract
    The main purpose of this study was to identify the proteins polymorphism in Montbéliarde cows to discover and select the best individuals whit casein variants suitable for a very good ability of making cheese. Milk composition was analysed for fat (3.83%) and protein (3.38%). Fat percentage manifested a high variability and ranged between 6.06% and 1.21%, while milk protein didn’t have the same variation with closed limits (3.89 and 3.28%). SDS-PAGE analysis revealed, after electrophoresis, six protein fractions in milk samples: αs1, αs2, β, k-CN, and β-LG, and α-LA. By densitometry analysis, three levels of expressions of the same type of protein fraction were discovered in each milk sample. The casein group, composed by four fractions αs1-, αs2-, β- and k-casein (32.8%, 7.3%, 34.3%, 17.6%) show in fact that they are 92% of the total milk protein and 8% are albumins similar with other studies for cows. First protein fraction αs1-casein, was with medium expression manifested by 54.54% of the cows, followed by that one with strong (31.82%) and low expression (13.64%). On the third place in milk composition is situated β-casein with strong expression for 4.54% of the cows. Medium expression level of the β-casein was manifested by the majority of the analysed Montbéliarde cows (72.73%) and 22.73% of it had low expression level, while only 4.54% of them have recorded strong expression level. Further investigations will be necessary to confirm the results by PCR-RFLP analysis to identify Montbéliarde cows caseins polymorphism with the genetic variants for each protein locus. This will allow keeping the most suitable animals with strong genetic expression and high content in caseins very well correlated with milk.

Key words: Montbéliarde, dairy cows, milk composition, milk proteins polymorphism

COMPOZIŢIA ŞI IDENTIFICAREA POLIMORFISMULUI PROTEINELOR DIN LAPTE LA VACILE MONTBÉLIARDE PENTRU SELECŢIA CELOR MAI BUNE VARIANTE LA ÎNBUNĂTĂŢIREA CALITĂŢII BRÂNZEI

Cristina Lazăr, Rodica Pelmuş, Elena Ghiţă, M.C. Rotar

Rezumat
    Scopul acestui studiu a fost identificarea polimorfismului proteinelor din lapte la vacile Montbéliarde cu variantele de cazeină potrivite la fabricarea de brânzeturi. S-a analizat compoziţia laptelui la grasime (3,83%) şi proteină (3,38%). Procentul de grăsime a manifestat o variabilitate destul de mare cuprinsă între 6,06% şi 1,21%, în timp ce proteina din lapte a avut limite restrânse fără variaţie (3,89% şi 3,28%). Analiza de electroforeză (SDS-PAGE) a evidenţiat şase fracţiuni proteice în probele de lapte αs1, αs2, β, k-CN, and β-LG, and α-LA. S-au determinat prin analiza de densitometrie trei nivele d expresie pentru fiecare fracţiune proteică. Cazeina este compusă din patru fracţiuni proteice αs1-, αs2-, β- and k-CN (32.8 %, 7.3%, 34.3%, 17.6%) care reprezintă 92% din proteina totală, iar 8% sunt albuminele similar cu alte rase de taurine. Prima fracţiune proteică αs1-CN a avut expresie medie la 54,54% din vaci, urmată de cea cu expresie puternică (31,82%) şi cu expresie slabă (13,64%). β-CN se situează pe al III-lea loc în compoziţia laptelui cu expresie puternică la 4,54% din vaci. Un nivel de expresie medie la β-CN s-a înregistrat la majoritatea vacilor analizate (72,73%), în timp ce 22,73% au avut expresie slabă, iar 4,54% expresie puternică. Investigaţii suplimentare sunt necesare la confirmarea rezultatelor obţinute în acest studiu prin PCR-RFLP la vacile Montbéliarde. În acest fel se vor alege cele mai bune animale cu expresie genică puternică şi un conţinut mare de cazeină foarte bine corelat cu calitatea laptelui.

Cuvinte cheie: Montbéliarde, dairy cows, milk composition, milk proteins polymorphism