Lactation has a great impact on biochemical parameters in the blood of cows, reflecting on metabolic demands. A part of that test is determining enzyme activities in the serum. This study was conducted on 40 head of Friesian dairy cows apparently healthy, were divided into two groups the first is the early lactation  (15 days to 2 months), and the second group is mid lactation (75 days to 4 months) collected blood samples and draw blood serum purified to measure some routine biochemical changes as total protein, albumin, globulin mathematically and total bilirubin are generally used for the evaluation of metabolic status and activity of enzymes Aspartate aminotransferase (AST), Alanine aminotransferase (ALT), Gamma-glutamyl-transferase (GGT), and Alkaline phosphatase (ALP). Milk samples were taken from cows under study to measure the activity of enzymes (AST, ALT, ALP, GGT), The study showed the presence of significant differences in both total protein, globulin mathematically, total bilirubin in two group, and a significant difference in the activity of AST, ALP in the blood serum in two stages and no significant difference in the activity of enzymes in the whey in two stage with the existence of marked  increase activity of (ALT, ALP, GGT), and decrease activity of AST in milk than blood serum. The results indicated that AST activity appeared significantly lower in milk than that in blood (p < /em>= 0.0002) and =0.0035) in two stage of lactation respectively, also ALT, ALP, GGT was highly significant in milk than blood serum (P=0.0290, < 0.0001, <0.0001) in early lactation, and (p < /em> =0.0102, < 0.0001, < 0.0001) in mid lactation.