The invention relates to an antimicrobial composition comprising a mixture of at least 20 wt. % lactic acid or a derivative thereof and an inorganic acid selected from a nitrogen, sulfur, and phosphorous acid, and mixtures thereof for use in animal nutrition. In one of the embodiments the composition further comprises at least one other acid selected from acetic acid, fumaric acid, gluconic acid, (iso)butyric acid, sorbic acid, (iso)valeric acid, maleic acid, malic acid, capronic acid, benzoic acid, and citric acid. In a special embodiment the composition comprises lactic acid or polylactide, which is attached to a support.