Ruminal methanogenesis as influenced by individual fatty acids supplemented to complete ruminant diets

The objective of the present study was to investigate the effects of seven different pure fatty acids on rumen fermentation using the rumen simulation technique (RUSITEC). The fatty acids were supplied to a complete ruminant diet at a proportion of 50 g kg(-1) dietary dry matter and compared with an unsupplemented control. Methane release and methanogenic counts were suppr essed by the fatty acids C-12 : 0, C-14 : 0 and C-18 : 2 whereas C-8 : 0, C -10 : 0, C-16 : 0 and C-18 : 0 showed no corresponding effects. Apart from C-12 : 0 and C-18 : 2, C-8 : 0 and C-10 : 0 also adversely affected ciliate protozoa suggesting independence from the methane-suppressing effect of me dium-chain fatty acids (MCFA). Although MCFA but not C-18 : 2 reduced rumin al fibre degradation, the influence on other fermentation traits remained l ow. In conclusion, the supply of certain fatty acids to ruminant diets seem s to have the potential to reduce methane release.