The study was carried on a total number of 130 calves. From them 53 buffalo calves were held in the animal farm station of Faculty of Veterinary Medicine, Suez Canal University and 77 Frisian cattle calves were held in El-Salhya private farm, Ismailia, Egypt. Two control groups 9 from the faculty farm and 11 for El-Salhya farm were used from each group. All groups were clinically examined for presence of fever, signs of diarrhea and dehydration. Blood with and without anticoagulant and fecal samples were collected from both diseased and control calves at the same time. Heparinized blood was used for blood picture. Clear serum samples were used for biochemical analysis of sodium, potassium, chloride, total proteins, albumin and globulins as well as Protein electrophoresis pattern was performed to detect the level of each protein fraction.  Fecal samples were examined microscopically to detect the presence of parasitic infestation. According to the severity of dehydration the diseased calves were divided into three groups mild, moderate and severe one. Diseased calves showed mild to severe diarrhea and few cases showed signs of dehydration. Hematological findings revealed no significant variations in hemoglobin values and leukocyte counts but RBCs counts showed a significant decrease in mild cases of diarrheic calves; however PCV showed a highly significant increase in severe diarrheic calves in both farms. Biochemical analysis of serum showed no significant differences in sodium and potassium, while chloride showed highly significant increase in severe diarrheic buffalo calves. Total proteins showed a significant increase in severe diarrheic buffalo calves in the faculty farm, while albumin showed a significant increase in severe group of El-salhya farm, also globulin showed a significant increase in all diseased buffalo  calves. Protein electrophoresis revealed that only α1 globulins showed highly significant increase in diseased calves. No severe blood changes were recorded. The obtained result support the idea that mild diarrhea does not affect blood parameters in early stages of the disease.