Twelve lactating Holstein-Friesian cows and twenty five lactating Egyptian-buffaloes were used in this study. These animals were reared at the experimental Station of Faculty of Agriculture, Assiut University.
Total blood serum protein were estimated by Ab-refractometer method. Serum protein fractions was also determined electro-phoreti cally.
Results obtained can be summarized as follows:
1- Genus had no significant effect on total serum proteins and its fractions except on gamma-globulin frasction. On the other hand, blood serum of Friesian cows contained more total protein (6.43 + 0.02 gm/100 ml) than that of buffaloes (6.20 + 0.02).
2- Blood gamma-globulin was significantly (P/ 0.05) higher in the blood of lactating animals calved at summer months as compa red to those calved at winter months.
3- Albumin: globulin ratio was significantly higher (P/ 0.01) in the blood of both winter calved genus as compared with that of summer calved genus.
4- Blood components other than gamma-globulin and albumin: globulin ratio were not significantly affected by calving season.