Twenty high producing cows of three different age groups (8 at 25 months-first lactation:8 at 41 months-second lactation; 4 at 67 months-fourth lactation) were compared for the First 40 days postpartum via dry matter intake, milk production, body weight change and blood constituents, Concentrate and corn silage were fed at a 1 : 1 ratio on a dry matter basis ad libitum until the daily consumption reached the predetermined levels which differed only in the maintenance allowances between cows. Dry matter intake per metabolic body weight was lowest in the oldest group for the first three weeks and highest thereafter. Milk production per metabolic body weight was clivated as the age advanced (230, 270, 300g/metabolic unit during the sixth week postpartum). The feed efficiency far milk production was tower in the youngest group versus the two older groups (1.82, 2.29. 2.30kg/kg dry matter intake), which was reflected by less postpartum body weight loss in she youngest group versus the two older groups(7, 31, 26kg). Serum calcium and phosphorus were the lowest on day 1 postpartum, with the oldest rows having the lowest value. Serum magnesium was the lowest on day 5 postpartum, with the youngest rows having the lowest values. Serum plateau, were achieved ar days 5, 10 and 15 postpartum for calcium, phosphorus and magnesium, respectively. The results of this experiment lead to the conclusion that there are age differences in the metabolic systems of high producing cows which should be applied to she practice.