Mega producers have ushered in a new era for Midwest agriculture and amplified the growing environmental concerns associated with concentrated animal agriculture. The combination threatens to undermine the Midwest's long-held dominance in hog production and processing.

Throughout the 1990s, the pork industry has been at the forefront of a revolution in the structure of the U.S. food and agricultural sector. In particular, the pork industry has been rapidly moving away from its traditional structure built on hundreds of thousands of small farms selling hogs at...