As part of her presidential platform, Elizabeth Warren is not just taking on big agriculture corporations like Bayer AG and Tyson Foods Inc. She’s also going after checkoff programs, which do marketing campaigns for commodities.Slogans like “Got Milk?”, “Beef: It’s What’s For Dinner,” and “Pork: The Other White Meat” are what’s at stake. By law, growers pay a portion of their sales into checkoffs, which then promote the commodities. But that process is rigged against family farmers, the Democratic presidential candidate wrote in a Medium posting Wednesday that detailed her plans for U.S. agriculture.