Abstract
To study on the biosynthesis of vitamin B_<12> in the rumen, the rumen contents were fractionated into Infusoria. bacteria, and Infusoria-bacteria free fractions, and the vitamin B_<12> activities of each fraction were measured by using Euglena gracilis as a test organism. The following results were obtained : (1) The vitamin B_<12> activity of total rumen contents was maximum, 4.2〜5.2μg per 100g of fresh matter, 6〜14 hours after feeding. (2) The vitamin B_<12> activities of Infusoria and bacteria fractions were maximum, 0.73μg and 1.53μg per 100g of fresh rumen contents, 14 hours after feeding, respectively. (3) The vitamin B_<12> activity of Infusoria-bacteria free fraction was about 0.1μg per 100g of fresh rumen contents, and there was no remarkable change under fasting.
