What was done
The authors studied the effects of two types and seven levels of fish-oil feed additives on methane production associated with the rumen fermentation of sheep by means of both in vitro and in vivo experiments.

What was learned
A maximal 80% decline in ruminant methane production was observed with fish oil containing n-3-eicosapentanoic acid.

What it means
The results of this study suggest it may be possible to dramatically reduce the amount of methane emitted to the atmosphere by domestic ruminants by means of a simple feed additive.  This natural dietary intervention represents an important approach to reducing the overall impetus for global warming without reducing anthropogenic CO2 emissions and thereby denying ourselves the biological benefits (enhanced plant growth and water use efficiency) that are needed to avoid the significant food shortfall that is otherwise calculated to confront the world about fifty years hence (Idso and Idso, 2000; Tilman et al., 2001).  And with methane having a current climatic impact that is fully half that of CO2 (Hansen, 2002), this approach to the hypothetical global warming problem and the much-more-real food security problem is most appealing.

References
Hansen, J.E.  2002.  A brighter future.  Climatic Change 52: 435-440.

Idso, C.D. and Idso, K.E.  2000.  Forecasting world food supplies: The impact of the rising atmospheric CO2 concentration.  Technology 7S: 33-56.

Tilman, D., Fargione, J., Wolff, B., D'Antonio, C., Dobson, A., Howarth, R., Schindler, D., Schlesinger, W.H., Simberloff, D. and Swackhamer, D.  2001.  Forecasting agriculturally driven global environmental change.  Science 292: 281-284.