The Influence of Diet on Nitrogen and Amino Acid Content of Mixed Rumen Bacteria

Abstract

Rumen bacteria were isolated from rumen fluid collected 3 hours after feeding from cows fed 24 different diets. The bacteria isolated were analysed for nitrogen and amino acid nitrogen (AA-N) content. The nitrogen content in the bacterial dry matter varied between 6.2% and 9.0% with a mean value of 7.8%. This variation could not be related to any dietary components analysed for. The proportion of AA-N in total bacterial nitrogen varied between 62.1% and 72.3% with a mean value of 67.4% and a significant relation was obtained both to the crude fibre and LHK (sugar + starch) content in the diets. The proportion of AA-N found in the bacteria is discussed in relation to the proportion of AA-N found in duodenal content in 18 published reports, and it is concluded that a proportion of AA-N in bacterial nitrogen of approximately 70% seems justified.