The Chinese central government, famously sensitive to domestic instability of all sorts, created the pork reserve in 2007 with an official mandate to "stabilize live hog prices, prevent excessive hog price drops, which damage the interests of farmers and to ease the negative effects of the cyclical nature of hog production and market prices."

When hogs get too expensive in China, the reserve releases animals onto the market, trying to hold down prices for consumers. When hogs get too cheap, the reserve buys up pigs, trying to keep farmers profitable.

Not an Exact Science

Pork prices have gyrated in China since 2006 as the country has lurched from traditional farming to large-scale agriculture. Small "backyard" farms have disappeared as big, commercial farms have been brought along to replace them.

Only about 37 percent of live hogs in China came from backyard farms last year, compared with about 74 percent in 2001, according to research from Rabobank International.

The Smithfield acquisition is largely seen by China-watchers and commodities experts as a move to help accelerate the development of Chinese mega-farms by grabbing U.S. know-how.

For now, at least, it's also about grabbing U.S. pork: Even though 95 percent of the hogs eaten in China are home-grown, 11 percent of all the pork produced in the United States in the first four months of 2013 wound up getting shipped to China (including Hong Kong) as well, according to the U.S. Meat Export Federation (USMEF).