Requirement-oriented supply of organic broilers with riboflavin from fermentation of Ashbya gossypii

The required riboflavin (vitamin B2) demand of poultry is hardly met by the native contents of grains and legumes. A supplementation is consequently necessary to avoid deficiency in this vitamin, which has detrimentous effects on performance, health and welfare. In organic production riboflavin supplementation must origin from GMO-free sources. A dried product from fermentation of the yeast-like fungi Ashbya gossypii with a high native content of riboflavin was tested in two trials with 800 mixed-sex one day old Ranger Gold™ chicken. Four different riboflavin concentrations were tested in each run. In the first trial, a control diet contained only native riboflavin contents without supplementation (2.9 mg riboflavin/kg), the other diets were supplemented at graded dosages up to contents of 9.2 mg/kg. In the second trial, starter feeds contained 4.0 mg and 5.6 mg riboflavin/kg, whereas contents at the later fattening stages were reduced. Body weight and feed consumption were measured weekly. Additionally, slaughter parameters were assessed (dressing, proportion of valuable cuts, abdominal fat, liver, heart and gizzard). In the first trial, the native riboflavin contents did not meet the requirements of the slow-growing broilers and resulted in deficiency symptoms. High supplementations, however, did not have positive effects on performance and slaughter parameters. Consequently, a reduction of the riboflavin supplementation particularly during the later fattening period seems to be possible to compensate higher production costs of the tested product compared to conventional vitamin production by GMO.