The experiment was carried out on 28 Black-and-White heifers (3 groups of 8-10 animals) from 3 weeks before expected calving to 300 days of lactation. One week before calving and in the first week of lactation, the animals in the control group were fed a diet formulated according to IZ-INRA requirements (2001) to achieve a milk yield 30 kg/d at the peak of lactation. The daily ration for control animals containing 3 kg concentrate was increased for experimental group H₁ and H₂ by 1 or 2 kg concentrate, respectively. The increased feeding level reduced serum non-esterified fatty acids and β-hyroxybutiric acid, and increased the glucose concentration and milk yield during lactation.