This study’s objective was to determine the impact of dietary humic substances on immune response and blood profiles in piglets. A total of 24 crossbred piglets (Slovakian White × Landrace; 35 days old; average body weight of 11.67 kg) were allotted to two dietary groups with (experimental; 5 g·kg⁻¹) or without (control; 0 g·kg⁻¹) natural humic substances supplementation. In this study, we observed a significant increase of the proportion of CD4+CD8- lymphocytes (p < 0.001) in the experimental group. The results also showed a tendency for an increase of the phagocytic activity and the engulfing capacity of phagocytes and the numbers of the other monitored lymphocyte subpopulations (CD3+, CD21+, CD4-D8+, CD4+CD8+, CD4+CD25+) in piglets in the experimental group compared to the control group. Supplementation of humic substances increased serum alkaline phosphatase compared to the control group (p < 0.05). Other monitored blood parameters were not significantly affected by dietary treatment. It concluded that inclusion of humic substances in the diet of piglets could have a stimulating effect on cellular immunity, without a negative effect on haematological and biochemical parameters.

The effect of humic substances on growth performance, excretion, and the digestive organs was studied in pheasant chickens. Three hundred 1-day-old pheasant chicks were assigned to two equal groups. Chicks in the experimental group were fed diets supplemented with humic substances (5 g/kg). Chickens in the experimental group reached significantly higher average daily weight gains (p ˂ 0.05) in the second phase of rearing (29–49 d) at a significantly better feed conversion ratio (p ˂ 0.05). The supplementation of humic substances led to a significant increase in the average body weight of pheasants at the end of the experiment (p ˂ 0.05), and to a significant increase in average daily weight gains for the entire monitored period (p ˂ 0.05). In the experimental group, significantly higher relative weights of the gizzard (p ˂ 0.05), small intestine (p ˂ 0.05), and jejunum (p ˂ 0.05), along with a significantly larger relative length of the duodenum (p ˂ 0.05), were recorded. A significantly higher concentration of dry matter in the droppings of pheasants was found in the experimental group than in the control group (p ˂ 0.05). According to our results, feeding humic substances had the most beneficial effect on pheasant growth performance during the growing phase. Humic substances can also have a positive effect on the microclimate within the breeding facility. Reductions in the water content of droppings contribute to a reduction in the humidity of the litter, thus limiting the activity of nitrogenic bacteria.