The effect of dietary riboflavin supplementation during pregnancy and lactation on riboflavin concentrations of milk, liver and carcass of lactating rats

SUMMARY: The aim of the present study was to investigate the effect of riboflavin supply during pregnancy and lactation on the riboflavin status of rats after pregnancy and lactation. Therefore, an experiment with a total of 81 female rats was conducted. The effect of riboflavin supplementation during pregnancy on riboflavin status after pregnancy was investigated by feeding diets with various riboflavin supplements (1, 5 or 20 mg riboflavin per kg diet) and the determination of riboflavin concentrations in liver and carcass (bled whole body without intestine and liver). The study shows a marked influence of dietary riboflavin supplementation during pregnancy on riboflavin concentrations of liver and body after pregnancy. Liver exhibited maximum riboflavin concentrations at a supplementary level of 5 mg/kg diet whereas riboflavin concentrations in the carcass were raised by increasing the supplementary level from 5 to 20 mg/kg diet. The riboflavin status after lactation has been studied in response to the riboflavin supplementation during pregnancy (1 or 20 mg/kg diet) and lactation (1, 5 and 20 mg/kg diet). In order to assess the riboflavin status, riboflavin concentrations in the liver and carcass (at the 14th day of lactation) and milk (7th and 13th day of lactation) were determined. The study shows that the riboflavin concentrations of all the samples are influenced predominately by the riboflavin supply during lactation; the riboflavin supply during pregnancy had only a slight effect on the riboflavin concentrations of milk, liver and carcass. Moreover, the riboflavin concentration in milk was more influenced by the riboflavin supply during lactation than the riboflavin concentrations of the liver and carcass. Increasing the riboflavin supplementation during lactation from 1 to 20 mg/kg diet caused a five-fold increase of riboflavin concentrations in milk, whereas riboflavin concentrations in the liver and carcass increased only by ≅ 80%. Those results demonstrate that the riboflavin concentration in milk can be varied over a wide range by the riboflavin supply during lactation whereas the riboflavin concentrations of tissues are under homeostatic control. Moreover, the study shows that a high riboflavin supply during pregnancy cannot compensate for a deficient supply during lactation. Therefore, particular attention has to be given to the dietary riboflavin supply during both physiological states.