Enteric methane emissions from dairy cows fed different proportions of highly digestible grass silage

Abstract

Enteric methane (CH₄) emissions were measured from six lactating dairy cows using the sulfur hexafluoride tracer technique. Three diets with different proportions of highly digestible grass silage/concentrates were fed: 500/500, 700/300, or 900/100 g kg^–1 dry matter (DM). The average daily CH₄ emissions were 282, 300, and 321 g animal^–1, respectively and the methane conversion factor (Y _m ) from gross energy (GE) ranged from 0.051 to 0.056. However, the statistical power of the study was weak and the differences between diets were not significant (p=0.149 and p=0.293, respectively). A linear regression analysis showed a trend (p=0.08) toward higher enteric CH₄ emissions with higher proportion of high quality grass silage in the diet. A definite conclusion is not possible and further studies are needed as a base for concrete advice on how to mitigate enteric CH₄ emissions from high yielding dairy cows in Scandinavia.

Keywords:

• Greenhouse gases (GHG)
• forage-concentrate ratio
• ruminal volatile fatty acids (VFA)
• sulfur hexafluoride

Acknowledgements

The experiment was funded by FORMAS – the Swedish Research Council for Environment, Agricultural Sciences, and Spatial Planning. Authors wish to thank technician Edward J. Birkedal at AAFC-SPARC for making all the equipment for methane measurements, the staff in the barn at Kungsängen research center for taking care of the animals and the staff in the Kungsängen laboratory for performing analyses.