Riboflavin for laying hens fed organic winter diets: effects of different supplementation rates on health, performance and egg quality

For reasons of aspired naturalness and cost reduction, vitamin additions should be kept low in organic livestock systems. To define safe lower threshold levels riboflavin supplementation poultry feeding, 135 hybrid layers were allocated to three dietary treatments supplemented with either 4.5 (R4.5), 3.0 (R3.0) or 1.5 mg (R1.5) GMO-free added per kg feed. This resulted total measured concentration averages 5.0, 4.5, 3.1 kg?1 feed for R4.5, R3.0 R1.5, respectively. 18 weeks, each treatment was replicated groups 15 hens. Feed consumption, laying performance, egg quality, the yolk, clinical health scores assessed. Two hens group (six treatment) slaughtered weeks 11 18, respectively, measurement pancreas, spleen, liver heart weights, determination riboflavin. No effects on body weight, eggshell strength yolk colour plumage keel bone integrity observed. symptoms lameness footpad damage found. The yolks R1.5 than other treatments. Liver increased between week all treatments, but it also R1.5. Based these results, addition 3 appeared sufficient respect performance Supplementation only some metabolic signs deficiency. These results apply winter diets.