Regulators filed a lawsuit Monday to block the nation's third-largest beef packer, Brazilian-based JBS S.A., from buying the fourth-largest, National Beef Packing Co. Here's a look at the implications:

THE SALE:

Regulators say the deal would mean three companies would control more than 80 percent of the nation's fed cattle packing capacity, or the amount of cattle that are processed into beef products. In 2007 packers bought more than 27 million fed cattle for nearly $30 billion.

THE INDUSTRY:

JBS S.A., based in Brazil, is the world's largest beef packer. After the merger, its share of U.S. packing capacity would increase from 20 percent to 35 percent.

TYSON FOODS INC.: Based in Springdale, Ark. Its cattle packing capacity would be between 25 and 30 percent.

CARGILL INC.: Based in Wayazata, Minn. Its packing share would be between 20 and 25 percent.