Chicago Board of Trade corn futures closed slightly lower on Thursday. Traders said plentiful supplies following a bumper harvest in the US Midwest limited follow-through buying from Wednesday's gains. But the market felt oversold after hitting contract lows on Tuesday, traders said. The US Agriculture Department reported weekly corn export sales of 866,900 tonnes, down slightly from a week earlier. Analysts had estimated corn export sales in a range from 700,000 to 1.2 million tonnes.