The U.S. Department of Agriculture confirmed that it found a case of mad cow disease in a dairy cow in central California.<br/> <br />It is the nation's fourth case.<br/> <br />John Clifford, the USDA's chief veterinary officer<br/> <br />(SOUNDBITE) (English) JOHN CLIFFORD, THE USDA'S CHIEF VETERINARY OFFICER SAYING:<br/> <br />"We will complete an investigation into this particular case. But there should be no concern as indicated about safety of our food supply."<br/> <br />U.S. cattle markets plunged on rumors of the case earlier in the trading day.<br/> <br />The first outbreak of mad cow in the United States occurred in late 2003, roiling global trade in beef.<br/> <br />Deborah Lutterbeck, Reuters.
