Metabolic transformation and urinary excretion of selenium (Se) in rats fed a Se-enriched defatted rapeseed (Brassica napus, L.) diet.

Se-Enriched defatted rapeseed (Se-DRS), a by-product of rapeseed oil production, is high in Se. This study aimed to detect possible changes in Se-metabolism after Se-DRS consumption and to assess its suitability as a Se supplement in monogaster feed. In this experiment, rats were fed three types of diets differing in Se-form: soybean meal, Se-salt and Se-DRS. Potential differences in Se-metabolism were evaluated based on the total Se concentrations along with non-protein Se speciation patterns in the urine and blood serum of the rats. The total Se concentrations were determined using inductively coupled plasma-mass spectrometry (ICP-MS). Se compounds in the samples were identified through high-performance liquid chromatography/ICP-MS. The total Se excretion rate was dose-dependent, and excess of dietary Se was eliminated in the form of Se-sugar 1, regardless of the administered Se-form. The excretion dynamics of dietary selenomethionine (soybean meal) and methylselenocysteine (Se-DRS) were different to that of the mineral Se (Se-salt). The proportions of Se species in the urine were significantly influenced by the Se source. A specific metabolic pathway, resulting in urinary excretion of Se-sugar 2, was observed in animals fed Se-DRS. Neither the total Se concentrations nor the serum Se speciation patterns differed between the animals fed the conventional diet and those fed the Se-DRS-enriched diet. Based on these results, Se-DRS can be considered a suitable Se supplement for monogaster nutrition in Se-deficient regions.