The effects of fatty acids on pure cultures of rumen bacteria

Abstract

SummaryThe effects of fatty acids, at low concentrations (0–005-O5 g/1), on the growth of seven species of rumen bacteria were examined.Anaerovibrio lipolytica(strain 5 S),Peptostreptococcus elsdenii(type 2),Bacteroides ruminicola46/52 andSelenomonas ruminantium(strain 17) were unaffected by addition of oleic acid to the medium. Growth ofButyrivibrioB 835 was stimulated by low concentrations of oleic (< 0–01 g/1), lauric (< 0–1 g/1) or capric (< 0–1 g/1) acids while higher concentrations of these acids were inhibitory. Myristic, palmitic and stearic acids were inhibitory at all concentrations tested.Ruminococcus4263/1 was inhibited at all concentrations of the six acids. Production of methane by pure cultures ofMethanobacterium ruminantiumwas also inhibited by the additions of long-chain fatty acids. Oleic acid was the most inhibitory of the series of acids. These results are consistent with the reported effects of lipids on rumen function.