The application of the extract of a brown coal as a natural supplement to the calf diet and its influence on the blood acidbase balance was investigated. The effect of the brown coal extract was compared to the effects of the pharmaceutical preparate „Acinormin-Polfa” (Poland). The control group received water only. It was found that both preparations accelerated compensations of respiratory acidosis when compared to the control group. However, there is a danger that a prolonged application of these additives (Acinormin for more than 20 days and the brown coal extract for more than 40 days) can cause alkalosis.