Roaring Chinese demand for cheap animal feed helped fuel the largest week of grain sorghum sales seen by U.S. exporters in nearly two decades, U.S. Agriculture Department data. China's appetite for the corn substitute is expected to remain strong for the time being, despite Beijing's recent approval of one GMO corn variety, possibly signaling a renewed appetite for U.S. corn imports and expanding a lucrative market for American farmers. Exporters sold 584,324 tonnes of U.S. sorghum in the week ending Dec. 18, the largest weekly sale since 1995 and the second largest total on records dating back to 1990, USDA data showed. Shipments of 332,867 tonnes, all to China, were the biggest since 1992. The sales underscore months of Chinese interest in sorghum, after the country rejected more than 1 million tonnes of corn that contained an unapproved genetically modified variety developed by Syngenta AG. The drought-resistant grain, also called milo, has long been used as a substitute feedstuff by budget-conscious livestock and poultry producers. In China, it is also used to produce alcohol and other foods. For China's protein sector, sorghum's appeal is clear: it is often cheaper than corn, and is not genetically modified nor subject to corn's import tariffs and quotas. As a result, "the Chinese program is very aggressive. The only thing that would stop it is some type of tariff," said Mike O'Dea, a trader at INTL FCStone Inc. The United States is forecast by USDA to export 5.8 million tonnes of sorghum during the 2014/15 season - more than half of the harvest - with nearly 5 million of that likely heading to China. Sorghum made a comeback among U.S. farmers two years ago during a scorching drought. Sorghum is typically less expensive to plant than corn, but also tends to yield less per acre. There is no sorghum futures contract and the grain is often priced at a discount to Chicago Board of Trade corn. However, on Monday on the Ohio River in Cincinnati where the two crops compete, corn was $4 per bushel while sorghum fetched $4.38, according to USDA. That pricing premium has convinced at least one farmer to change his spring planting strategy. Tom Morton, whose farm is in the top sorghum growing state of Kansas, said he will increase his sorghum this spring by 100 acres. And for the first time in 15 years, Morton will not plant any corn. (Reuters)