Methane is the second most prevalent greenhouse gas, and plays an important role in global warming. Methane is generated from many sources, including natural production in the environment, by livestock, and as a result of human activity. Approximately one-fourth of anthropogenic methane emission in the United States is from enteric fermentation primarily from livestock, particularly ruminants. While the effects of methane are generally focused on its global warming potential, methane also results in a net loss of feed energy to the animal. There are numerous strategies that have been utilized to potentially reduce methane production in ruminants. Increasing feed efficiency by feeding highly digestible forages is one approach that has been used. Feeding ionophores has also been shown to reduce methane production in the rumen. Grinding and pelleting of forages may also reduce methane emissions, but this practice is not cost effective for producers. Increasing dietary fat has the potential to decrease methane emissions, but this method could negatively affect milk components and producer income. Methane emission inhibitors are chemical compounds with inhibitory effects on rumen methanogenic microorganisms. These compounds have been studied for their efficacy in reducing methane emissions and effects on production in dairy cattle. Among the more efficient methane inhibitors is 3-nitrooxypropanol (3NOP), which blocks an enzyme necessary for microbial production of methane in the rumen. This inhibitor has been shown to decrease methane emission by 30% and increase body weight gain in dairy cattle, with no effects on dry matter intake, milk production, or feed efficiency. Research with dairy cattle, as well as other livestock species, has shown that methane inhibitors as feed supplements could lead to substantial reductions in greenhouse gas emissions. While there are several strategies that have been proven to reduce methane emission from ruminants, the FDA approval of 3NOP could prove to be a more efficacious method of reducing greenhouse gas emission while improving livestock performance.