Early mortality in the young chicken after exposure to fast neutrons or gamma rays.

Two-day-old White Leghorn cockerels were exposed to various doses of / sup 60/Co gamma radiation or high energy (14.5 MeV mean energy) neutrons from the Naval Research Laboratory, Isochronous Cyclotron in Washington DC. Early deaths (within 30 hr of exposure) were observed after exposure to both types of radiation. Chicks exposed to neutrons died in two distinct and sepanate time periods. These two modes of death were not apparent after the gamma irradiations. After either neutron or gamma exposure, survival time decreased as mortality level increased, reaching a minimum of approximately 5 hr. The 30-hr LD/sub 50/ values were 519 plus or minus 5.6 rads of neutrons and 939 plus or minus 8.0 rads of gamma radiation; the relative biological effectiveness (RBE) at this mortality level was 1.81. (auth)