Humic acids (HA), a class of compounds resulting from decomposition of organic matter, particularly plants are natural constituents of drinking water, soil and lignite. It inhibit bacterial and fungal growth, thus decrease levels of mycotoxins in feed. Stress management, immune system, anti-inflamatory activity, antiviral properties as well as prevention of intestinal diseases, mainly diarrhoea in humans and animals are described as its beneficial effect. The use of HA and related products in feed improved gut health for better nutrient utilization as well as improved the health status by working against pathogens by developing immunity. Routine use of HA in feed improved growth of broilers by increasing digestion of protein and trace element utilization but a few researches has been conducted in this area. However, also contradictory findings in piglets are described. Most of the literature found is from companies but scientific articles are rather limited. There are also strong limitations in the knowledge of HA uses as feed additive for growth of other species of animal. It is really difficult to compare the actual effects of HA preparations due to different sources and nature as well as because rearing of animal in different region of the world varies as climatic conditions and aspects. So, bio-effect of HA product depends on specification.