By Hugh Bronstein BUENOS AIRES (Reuters) - China has approved its first shipment of genetically modified Argentine corn, Buenos Aires said on Tuesday. Argentine Agriculture Minister Norberto Yauhar said Chinese health authorities cleared 60,000-tonnes of genetically modified (GMO) Argentine corn. The cargo was already headed inland to be used as hog and chicken feed. Benchmark Chicago corn futures fell briefly after Reuters reported on the shipment. Argentina competes for market share with the United States, the No. 1 world corn exporter. ...