Cattle milk proteins are composed of casein components (Cn) such as α, β and κ-Cn, and whey components such as β-lactoglobulin (Lg). These milk protein components were separated by two-dimensional electrophoresis and compared with the separation patterns of yak, goat, sheep, deer, camel, llama, pig, horse and human milk. Based on our results, cattle and yak, goat and sheep, and camel and llama had very similar patterns, respectively.
As for components like β-Lg in deer, were separated at the same location as that of cattle, components like α- and β-Cn resembled the patterns of goat and sheep. Also, the separation patterns of κ-Cn were divided into two groups: animals (cattle, yak, goat, sheep and llama) whose milk separated near pI6.3, and animals (deer, horse and human) whose milk separated near pI6.9.