Ruminants are significant contributors to global greenhouse gas (GHG) emissions. Mitigating enteric and manure methane (CH4) production have been explored, but often in isolation of other GHG. Lowering enteric CH4 emissions can cause unintended increases in GHG from manure. Considering the complexity of rumen and the impact that it can have on manure composition, a whole systems approach is required to assess the value of additives that mitigate enteric CH4 emissions. This chapter summarizes a range of nutritional strategies available for enteric- and manure-CH4 abatement. Dietary additives including alternative electron acceptors, inhibitors, plant secondary compounds, and carbon (C) derived materials will be reviewed for their efficacy as mitigants of overall GHG emissions and evaluated for how they alter rumen and manure microbiomes. A compilation of current research will identify gaps in knowledge and reinforce the need to further examine dietary mitigation strategies in ruminant production systems at a whole farm level.