a1 Rowett Research Institute, Bucksburn, Aberdeen, AB2 9SB
The 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 and Selenomonas ruminantium(strain 17) were unaffected by addition of oleic acid to the medium. Growth of ButyrivibrioB 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 of Methanobacterium 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.
(Received January 09 1973)