Alternatives to riboflavin (vitamin B2) production by recombinant microorganisms are needed in organic poultry production, but are cost-intensive, so that a demand-oriented riboflavin supply is necessary. Details on the riboflavin requirements of organic poultry are not available. A feed material with high native riboflavin content from fermentation of the filamentous fungus Ashbya gossypii was studied. Two runs with 800 Ranger Gold™ broilers each (40 pens with 20 animals) were conducted.