Preliminary study on milk composition and milk protein polymorphism in the Romanian local sheep breed Teleorman Black Head Tsigai

摘要

There is an international interest for preservation and improvement of local animal breeds, due to their superior biological traits: rusticity, resistance and adaptability to very different local environment. The local Romanian Teleorman Black Head Tsigai sheep breed fits very well the current economic demands, such as milk production and prolificacy. The purpose of our study was to determine milk quality indices as well as milk protein polymorphism in local sheep breed, using 24 milk samples. The types of different milk proteins were identified by SDS-PAGE. The test day milk yield and chemical composition assays performed during the milking period of studied sheep showed that the yield of milk fat and protein ranged within the quality indices specific to breed (6.56% fat and 5.9% protein), described in literature. Milk samples were further analyzed for milk protein polymorphism. The electrophoretic pattern of milk samples showed the presence of four major caseins variants (as1-, as2- B- and k-casein) and two whey proteins (B-lactoglobulin, a-lactalbumin). Our study on percentage analysis of protein fractions of interest revealed that caseins represented 74.16% of the total protein of sheep milk, followed by whey proteins. SDS-PAGE analysis showed that majority of milk samples is characterised by a medium expression level of both caseins and whey proteins (66.67-79.17%) followed by higher level of expression (12.6-29.17%). Further studies (Real Time qPCR) are requisite for certitude of the results on the polymorphic genes of proteins from sheep milk, in order to identify the genetic variants from the locus of each protein.