China has barred pork imports from six US processing plants and six cold storage facilities effective from Wednesday to enforce its ban on the use of a feed additive that promotes lean muscle growth, Reuters reported, citing the US Department of Agriculture. China currently requires third-party verification that US pork shipped to the country is free of the additive ractopamine, which is sold for hog farm use under the name Paylean. Pork packing plants now ineligible to export to China include Tyson Foods (NYSE.TSN) plants in Perry and Storm Lake, Iowa, along with the company’s facility in Logansport, Indiana.