When you're pushing a shopping cart through the chilled air of the Whole Foods Market meat department, past rows of neatly packaged poultry and a glass case of butchered pork chops, the supermarket wants you to imagine the idyllic pastures on a place such as Sweet Stem Farm. Nestled on a handful of acres in scenic Lancaster County, Pa., the farm is run by a young couple who set out to create a grass-fed "farming oasis" for chickens, turkeys, lambs, cattle and heritage-breed pigs, according to a video on the website of Whole Foods, which the farm supplies.