Agency securitization of loans originated by correspondents and mortgage brokers fell 27.9 percent during the first quarter, but there are a number of companies moving in to take up the slack as big-name banks trim down their third-party originator programs. Wells Fargo and Chase remained the biggest sellers of TPO loans to Fannie Mae, Freddie Mac and Ginnie Mae, but their volume was down 41 percent from the fourth quarter ... [Includes one data chart]