Study of peculiar features of protein metabolism of healthy colts in the first three months of life was realized in the conditions of the Republic of Belarus. Research results showed that there was a tendency of increasing of hemoglobin concentration up to 150,270+/- 4,73 g/l, number of total protein of blood serum – up to 60,33 +/- 1,33 g/l, and the decreasing of uric acid up to 97,33 +/- 10,72 micromole /l. Quantity of beta-1 and alpha globulin fractions of serum protein fluctuated a little – from 10,78 +/- 3,69% up to 8,44 +/- 1,24% and from 25,12 +/- 4,84% up to 22,06 +/- 4,93%, respectively. The most essential changes of protein metabolism were stated at two month old colts, which had urea concentration of 5,25 +/- 0,23 micromole/l, alanine aminotransferase activity – 66,92 +/- 3,16 units/l, creatine content increased up to 77,37 +/- 5,83 micromole /l; and there was the lowering of aspartate transaminase level up t159,5 +/- 8,1units/l. There was stated the lowering of albumin quantity up to 32,07 +/- 2,19%, and increasing of alpha-1, alpha2- and beta2- globulin fractions up to 7,52 +/- 1,23%, 14,98 +/- 1,41%, 11,82 +/- 1,04%, respectively. At the age of three months the quantity of urea and creatinine in blood serum of colts remained at the same level, alanine aminotransferase activity decreased on 21,56%, and aspartate transaminase increased up to 204,33 +/- 10,37 units/l. At this period the quantity of albumin fractions was 44,56 +/- 6,59%., concentration of alpha-1, alpha2- and beta2- globulins decreased on 10,64%, 30,04% and 34,52%, respectively