Abstract: The objective of present study was to reveal the biochemical characteristics of milk from Tibetan Yellow cattle at highlant,milk protein composition and casein polymorphisms. Tibetan Yellow cattle contains low protein content in minds. A total of 43 Tibetan Yellow cattle at Jiulong county of Sichuan province were used to assay milk protein contelk (only about 29 g/L);skim milk protein composition was similar to that of cow as revealed by electrophoresis. Main milk protein components include casein,α-lactalbumin,and β-lactoglobulin. The ratio of milk β-Lg to α-La content was lower that that of yak. The relative percentage of casein was approximately 70%,including α_s-casein and β-casein. Three and two genotypes of αs-casein and β-casein were detected,respectively. Our results indicated that there was difference in milk composition between Jiulong Titetan Yellow cattle and Jiulong yaks that live in similar ecological environment.

Key words: Tibetan Yellow cattle; milk; genetic polymorphism; hypoxia