Canada has overtaken the United States as the top North American supplier of pork to China as farmers and meat packers in both nations battle for lucrative shares of the biggest global market. Canada’s pork sales to China, after a sharp rise last year, exceeded those of the United States in the first quarter of 2017. That’s only happened a handful of times in two decades, according to U.S. and Canadian government data. Rising affluence is driving China’s voracious appetite for pork, including parts of the pig – feet, elbows, innards – which command little value in most countries. At the same time, tightened environmental standards in China have forced farm closures and boosted demand for cheaper imports.