The weather, coyotes and equipment costs, to name a few. These days, many are also worried the EPA will tax their cows. Here's why: In 2007, the U.S. Supreme Court ruled the EPA has the authority to regulate greenhouse gases. In response, the EPA filed a more than 550-page notice last summer in which it sought public comment on how to proceed. The filing hardly mentioned agriculture, but it noted the methane that livestock produce is a source of greenhouse gas emissions. Ever since, farm and business groups have organized an intense lobbying campaign against what they say is a proposed cow tax. EPA officials say such a proposal doesn't exist. Either way, farmers have caught wind of the idea, and they don't like it.