To determine the changes in milk protein profile at different stages of lactation, milk samples from six (6) multiparous Holstein Friesian-Sahiwal cows were collected at 50 and 150 d of lactation.  The milk samples were subjected to ammonium sulfate (AS) precipitation and sodium dodecyl sulfate-polyacrylamid gel electrophoresis (SDS-PAGE).  Protein content of the AS precipitate was determined by Bradford method. Results show that the total true protein concentration at the early stage is greater than the mid stage of lactation with an average of 1.89 ± .90 mg/ml of milk.  SDS-PAGE was able to purify and separate 13 proteins bands including unique bioactive peptides β-casein with MW of   ̴24,250 Da,  ƙ-casein with    ̴19,843 Da and β-lactoglobulin with   ̴16,900 Da, respectively, compared to only 10 distinct protein bands on the mid stage of lactation.  Under the conditions from which the study was conducted, it can be concluded that based from protein electrophoresis, milk present at early stage of lactation contains greater bioactive proteins such as ƙ-casein and β-lactoglobulin.