The present invention relates to a food and feed supplement, and its use, where the supplement comprise as the basic component at least one carboxylic acid and/or its salt, an iron component and vitamins B6, B9 and B12 in amounts corresponding to at least that which theoretically can be consumed during the metabolism of the COOH-groups present. The supplement may also contain a desiccant and an antioxidant. The supplement will have a pH in the range 2.0-6.0 when dissolved in water. The supplement is characterized in that the amounts of the vitamins B6, B9 and B12 are in the range of 0.5-30 mg, 0.1-10 mg and 1-1500 &mu；g/gram dry weight of the content of the pure carboxylic acids in the supplement, respectively. The supplement can be used in animal feed in amounts of 0.5-15 grams dry supplement/kg dry feed.
