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 US 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. That’s a bonanza for Canadian farmers, who have almost completely removed the growth drug ractopamine from their pigs’ diet – largely because it is banned in China, which consumes half the world’s pork. US exports to China are limited because only about half of the nation’s herd has been weaned off the drug, according to US hog producers, meat packers and animal feed dealers. But major US-based firms are now moving to produce more ractopamine-free hogs – including the three biggest pork producers. The ascension of Canada’s pork exports underscores the power of the gargantuan Chinese market to influence agricultural practices and profits in supplier countries worldwide. As recently as 2013,…