BILLINGS— Montana blood banks are urging people to donate blood after the American Red Cross declared a national blood supply crisis July 27 for the second time in its history. Watch the report below:'Big deal': Montana blood banks encourage donations amid national shortage“We saw the nation's blood supply drop about 25% in June, and that's significant,” said Matt Ochsner, communications director for Red Cross of Idaho, Montana and East Oregon. Vitalant, a blood donation center that serves Billings, has declared a critical blood supply shortage of type O blood. “To be in a critical shortage across the country is a really big deal,” said Emily Sannar, Vitalant donor recruitment manager. Vanessa Willardson/Q2 Vitalant blood donation centerType O is the most transfused blood type.