Study on milk composition and milk protein distribution in Romanian Holstein cattle

The aim of this study was to determine milk quality indices as well as the milk protein composition in Romanian Holstein cattle raised under the conditions of experimental farm of INCDBNA-IBNA. The study was carried out on 22 milk samples. The types of different milk proteins were identified by SDS-PAGE technique. Sampling day and milk chemical composition were performed during the milking period of studied cattle. The quality indices were breed-specific for protein (3.38%) and higher for fat (4.39%). Milk proteins analysis of Romanian Holstein cattle separated by SDS-PAGE electrophoresis showed the presence of four major caseins (αs1-, αs2-, β- and k-casein) and two whey proteins (β-lactoglobulin, α-lactalbumin). The caseins accounted 77.28% of the total milk proteins, while the major proteins (β-lactoglobulin, α-lactalbumin) from the whey represented 22.72% of the total proteins. αs1-casein + αs2-casein had a higher expression (36.01%) followed by β-casein (31.45%), β-lactoglobulin (18.16%), k-casein (9.82%) and α-lactalbumin (4.56%). The most of milk samples was characterized by a medium expression level of both caseins and whey proteins