Iowa State University Veterinarian Records, RS 22/6/0/9, University Archives, Special Collections Department, Iowa State University, http://www.add.lib.iastate.edu/spcl/arch/rgrp/22-6-0-9.html
The billion dollar poultry industry of the United States has grown tremendously in the last three decades. Almost all of the scientific advancement in this field has occurred in this period. The disease control has definitely lagged behind the growth of the industry. In 1920 the death rate among chickens was 10 per cent; in other words, ten birds in every hundred placed in the laying house died. By 1930 the death rate had increased to 15 per cent; by 1934 to 20 per cent and by the end of 1937, it had increased to 24 per cent. These were the laying house mortalities. The brooder house mortality was reported to be about 20 per cent which is another additional loss to the poultry raiser. The Bureau of Animal Industry's 1942 report shows losses in all animals in the United States due to disease to be $418,000,000; of this amount $255,000,000 is reported to be due to poultry disease.
Maddy, K. T.
Iowa State University Veterinarian: Vol. 8
, Article 3.
Available at: http://lib.dr.iastate.edu/iowastate_veterinarian/vol8/iss2/3