* Chinese diet demands more protein * American genetics help Chinese breed bigger, healthier animals By P.J. Huffstutter and Niu Shuping ALBION, Indiana/BEIJING, April 20 (Reuters) - Inside a dimly lit barn in northeast Indiana, where the air smells faintly of corn and earth, the future of China's food supply is squealing for attention. A farmhand shuffles through the crowd of pigs inside pen 7E3, patting their fleshy pink backs and checking their water trough. The animals her