The object of the invention relates to a feed supplement additive containing humic acids, zinc and copper compounds for use in the prevention and/or treatment of diarrhoea diseases in suckling and weaned piglets, which substantially reduces the piglets' excretion of zinc and, through this, the soil load without the clinical effect of the generally used zinc oxide treatment being reduced. The mass ratio of the humic acids, zinc and copper in the preparation according to the invention, calculating for elemental zinc and copper, is 100:2.5-10:2.5-12, preferably 100:3.3-7, 5: 3.5-9, most preferably 100:4-6.5:4.5-7.5. At a characteristic therapeutic amount of the product according to the invention, the zinc content is between 100-160 ppm, instead of the currently recommended 2800 ppm.
