The study was conducted to determine the effect of humic acids added to the diet of lactating cows on their milk productivity and physicochemical parameters of milk. The study was conducted on 14 Holstein cows of German breeding, which were fed 20 g/100 kg of live weight per day of an organic feed mixture containing 40.5% humic acids and 22% fulvic acids to their basic diet for 30 days. Milk samples were taken twice, before the use of the organic feed mixture and after 30 days of use. An increase in milk productivity by 5.8% was observed in 86% of lactating cows, the mass fraction of fat in milk increased A slight increase in milk fat content (p<0.1) is associated with an increase in this indicator in the milk of 72% of experimental cows from 0.2 to 0.92%. In the milk of the rest of the cows, the fat content of the milk did not change, but the average index for the group increased by 0.38%. The mass fraction of proteins after 30 days of using the organic feed mixture, an increase in the mass fraction of proteins in the milk of cows was noted on average for the group by 0.2% (р<0.05), with an average indicator for the group of 3.5±0.06% (3 ,12–4.2%). In the milk of 80% of the examined cows, the mass fraction of proteins increased from 0.12 to 0.9%, in 20% of the cows the mass fraction of protein in milk did not change, but the values corresponded to the basic norm (3.0%). An increase in average daily milk yield from 36.73±0.6 kg (35.43–38.9) at the beginning of the study against 38.85±0.19 kg (37.3–39.9; p<0.01) at the end of the experiment, which is 2.12 kg more and indicates a positive effect of humic acids on milk productivity of cows. The number of somatic cells in the milk of cows after a 30-day use of an organic feed mixture based on humic acids did not change and amounted to 104.78±19.09 thousand/cm3 (20.0–218.0), against 104.47±23, 5 thousand/cm3 (11.0–246.0) at the beginning of the study. In the milk of 28.5% of cows, at the end of the study, a slight decrease in the number of somatic cells was noted from 35 to 55 thousand/cm3, in the milk of 21.4% of cows, the number of somatic cells increased slightly from 19 to 74 thousand/cm3, which corresponds to the physiological norm . Milk urea nitrogen is used to assess the energy-protein balance in feed; a reduced value at the end of the study ranged from 7.1 to 18.5 mg/100 ml, indicating a crude protein deficiency in the diet.

Key words: humic acids, number of somatic cells, mass fraction of fat, mass fraction of proteins, lactose, milk urea nitrogen, milk productivity.