Study on Nutrient Composition,Enzymatic Activities and Protein Components in Tibetan Sheep Milk of Different Births

The nutrient composition,enzyme activities and protein components were studied in Tibe-tan sheep milk of different births.The results showed that the contents of milk protein,lactose and fat were 48.45±13.21g/L,41.93±5.06g/L,and 69.43±11.41g/L,respectively;the milk protein contents of 2nd and 4th birth ewe were higher than that of 1st birth ewe significantly(P0.05)and very significantly(P0.01);the differences of lactose content in milk of different births were insignificant(P(0.05));the content of fat were decreasing along with the increasing of births;the milk fat contents of 1st birth ewe were higher than that of 4th birth ewe significantly(P0.05).The activities of γ-glutamyl transpeptidase(γ-GT),alkaline phosphatase(AKP),lactoperoxidase(LP),and amylase(AMY) in milk were 268.25±89.18U/100mL,231.85±107.38U/100mL,3.97±3.68U/mL,and 80.65±73.91U/100mL,respectively.The differences of activity of γ-GT,AKP and LP in milk of different births were insignificant(P0.05).Main protein components in milk comprised α-lactalbumin(α-La),β-lactoglobulin(β-Lg),IgG,casein(CN) et al,the relative percentage of CN was 50%～52% approximately,but the relative content of αLa was low.The relative percentage of main protein components in milk were insignificant(P0.05)in different births.Four kinds of molecular weight type of milk mucin 1(MUC1)were discovered in this study,with molecular weights of 214 kD,209 kD,207 kD and 205 kD,respectively.