Calculations of apparent ruminal synthesis and intestinal absorption of biotin in dairy cows as influenced by the extraction method

Abstract

Biotin is present in nature either free or as biocytin, which is only degraded under the action of a specific enzyme: biotinidase. This enzyme is not included in analytical assays generally used. A method for sample preparation using biotinidase was developed in our laboratory before analysis by ELISA. Three cows equipped with duodenal and ileal cannulae were used to compare the effects of methods of sample preparation on calculations of apparent ruminal synthesis and intestinal absorption of biotin. There was no apparent ruminal synthesis of biotin, no matter whether free or total biotin was measured (p = 0.84). Results also suggested that rumen microbes cannot utilize nor degrade biocytin present in the feed. Estimates of apparent intestinal absorption were influenced by the sample preparation method (p = 0.002). Analysis of free biotin caused an artefact, suggesting intestinal synthesis of this vitamin; whereas determination of total biotin concentrations showed that absorption was taking place in the small intestine.