Effect of fulvic acid and humic acid. Part 1. Economic indexes, immunostimulant effect

Effect of fulvic acid (FA) and humic acid (HA) on production parameters (feed intake, weight gain, feed conversion ratio) and immune response of rats were investigated in two experiments. The aims of the experiments were to detect the optimal dose of FA and HA and to determine whether the test materials (FA, HA) are direct or indirect growth promoters. First experiment: control or 0.1%, 0.2%, 0.4%, 0.8% FA or HA supplemented diets. Second experiment: control and 0.4% FA or HA supplemented diets. 26-day-long feeding period was used in both experiments. No significant changes were observed in the production parameters. Ovalbumine antibody titre of rats on HA or FA supplemented diets showed dose dependent (up to 0.4% supplementation) and significant (p < 0.05) increase (350 and 418% respectively) over the control (100%). Both FA and HA stimulated the immune response and lengthened the persistence of the antibodies in time (14th day geometrical means: 685.79 (control); 1131.37 (FA); 1055.61 (HA); 26th day geometrical means: 544.31 (control); 1969.83 (FA); 1600.00 (HA)). Based on the results, it can be said that the growth promoting effect of humic substances reported in the scientific literature is an indirect effect and it may be based on the strong humoral immune-stimulatory effect of both FA and HA.