The present study investigated the effect of various dietary riboflavin supplementations (0 to 4000 mg/kg) during lactation on riboflavin concentrations of liver, carcass (bled body without intestine and liver), and milk in the rat. The experiment was conducted until the 14th day of lactation; milk samples were drawn on the 7th and 13th day of lactation. Riboflavin concentrations of milk raised continuously with increasing riboflavin supplementation; in the range between 0 and 10 mg/kg riboflavin supplementation, there was a linear relationship, and in the range between 12 and 4000 mg/kg there was a logarithmic relationship between riboflavin supplementation and riboflavin concentration in the milk. Maximum riboflavin concentration of milk obtained by supplementation with 4000 mg/kg was twelve-fold higher than without riboflavin supplementation. For riboflavin supplementation up to 12 mg/kg, riboflavin concentrations in milk on the 7th day of lactation and that on the 13th day of lactation were not different. In contrast, in rats fed diets with higher riboflavin supplementation, riboflavin concentrations were higher by 25% in average in milk on the 13th day of lactation than in milk on the 7th day of lactation. Contrary to the milk, riboflavin concentrations in liver and carcass exhibited a saturation, which was achieved at a supplementation of 6 mg/kg (liver) and 10 mg/kg (carcass), respectively. Maximum riboflavin concentrations obtained at a supplementation of 4000 mg/ kg were 1.9- and 2.3-fold higher for liver and carcass, respectively, than concentrations obtained without riboflavin supplementation. The dose-response relationship using riboflavin concentrations of liver and carcass as response factors indicates a riboflavin requirement of 8 to 9 mg/kg for lactating rats fed a semisynthetic diet with 17.4 MJ ME/kg dry matter and 20.8% protein in dry matter.

Summary The present study investigated the effect of various maternal dietary riboflavin supplementations during gravidity and lactation on riboflavin concentrations in blood, liver, and total body of their offspring. Therefore, two experiments with a total of 154 female rats were conducted. In the first experiment the animals received a semisynthetic diet (basal riboflavin concentration of 0.9 mg/kg diet) with various riboflavin supplementations during lactation (0, 2, 4, 6, 8, 10, 12, 40, 400, 4000 mg riboflavin/kg diet). In the second experiment, during gravidity, the rats were fed supplements of 1 or 20 mg riboflavin/kg diet. After parturition each group was divided into three subgroups that received 1, 5 or 20 mg riboflavin/kg with their feed during the following lactation. Both investigations continued until the 14th day of the lactation period just before the pups would start to eat the diets. The total body weights of the offspring in the first experiment only showed an effect of the riboflavin supplementation during lactation in the riboflavin‐deficient group (supplementation of 0 mg/kg diet). Regarding the second experiment, the total body and liver weights of the offspring on the 14th day of lactation were not significantly influenced by the various maternal riboflavin supplements during gravidity and lactation. The data of the first experiment clearly show that there exists a slight dose‐response relationship between the maternal dietary riboflavin supplementation during lactation and the riboflavin concentration in the blood and total body of the offspring. However, a riboflavin supplementation over 8 mg/kg diet led to a saturation of the riboflavin concentration in the body. Also, a dietary supplementation above 2 mg riboflavin/kg diet had no influence on the liver riboflavin concentration. The second investigation showed that the riboflavin concentration in all samples was influenced predominantly by the maternal riboflavin supply during lactation. The riboflavin supply during gravidity had no or only a very slight effect on the riboflavin concentrations in blood, liver, and total body of the offspring. In conclusion, these results indicate the necessity of a sufficient maternal dietary riboflavin supply (8–9 mg/kg diet) during lactation in regard to the health of their offspring and that a high riboflavin supply during gravidity cannot compensate for a deficient supply during lactation.

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. Zusammenfassung Zum Einfluß der Riboflavinversorgung während Gravidität und Laktation auf die Riboflavinkon‐zentrationen von Milch, Leber und Restkörper laktierender Ratten Die vorliegende Arbeit hatte zum Ziel, den Einfluß unterschiedlicher Riboflavinzulagen der Diät während Gravidität und Laktation auf den Riboflavinstatus nach Gravidität und Laktation zu untersuchen. Dazu wurde ein Versuch mit insgesamt 81 weiblichen Ratten durchgeführt. Der Einfluß der Riboflavinversorgung auf den Riboflavinstatus nach der Gravidität wurde untersucht, indem während der Gravidität ein Futter mit unterschiedlichen Riboflavinzulag...

In two experiments with 160 female Sprague-Dawley rats the influence of various dietary riboflavin supplementations during lactation and during pregnancy and lactation were examined on food intake, body mass, reproduction, hematologic profile and the erythrocyte glutathione reductase activity coefficient (EGR-AC). In the first trial rats were fed a semisynthetic, riboflavin-deficient diet, based on casein and corn starch with various riboflavin supplementations during lactation (0, 2, 4, 6, 8, 10, 12, 40, 400, 4000 mg riboflavin/kg diet). In the second experiment the rats received supplements of 1 and 20 mg riboflavin/kg diet, respectively, during pregnancy. After parturition each group was divided into three sub-groups with riboflavin supplementations during lactation of 1, 5 and 20 mg/kg diet, respectively. Both investigations ended at the 14th day of lactation. Food intake was decreased significantly by 25% and 11% in the groups without riboflavin supplementation or 1 mg riboflavin/kg diet. In the same groups body mass was reduced by 11% and 4%, respectively. With regard to the reproduction parameters the riboflavin supply influenced only the litter mass at the 14th day of lactation and only lactational supply was relevant. In both trials the results of the hematologic profile showed no differences. In riboflavin deficiency (0 or 1 mg riboflavin/kg diet, respectively) the EGR-AC was increased significantly to 1.9 and 1.8, respectively. At the supplementation of 4-5 mg riboflavin/kg diet EGR-AC reached a plateau of 1.45, which was not improved by higher supplements. Concerning the whole reproduction cycle (trial II) there was a stronger influence of the actual lactation-supply on EGR-AC, on the other hand a riboflavin deficiency in pregnancy could be compensated only partially by an optimal supply in lactation. Therefore, based on the parameter EGR-AC an optimal riboflavin supply is recommended for each part of the reproduction cycle. By means of EGR-AC also the riboflavin requirement for lactating rats was derived. Feeding a semisynthetic diet (17.4 MJ ME/kg DM, 20.8% crude protein in DM) a supplementation of 5-6 mg riboflavin/kg or a total content of 6-7 mg/kg diet is recommended.