Comparison of the 60-Day Mortality Responses of Lambs and Adult Sheep after Unilateral Exposure to Cobalt-60 Gamma Radiation.
Technical rept. 30 Jun 69-17 Apr 70,
AIR FORCE WEAPONS LAB KIRTLAND AFB N MEX
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Fifty-three lambs and 24 adult sheep were exposed unilaterally right side to potentially lethal doses of cobalt-60 gamma radiation 200 to 500 R, midline air dose. The incidence of mortality during the first 60 days post-exposure was recorded and analyzed. The median lethal dose LD-50 for the lambs was 347 R, and the slope of the probit regression line was 22.24 probits per decade increase in dose. For the adults the LD-50 was 381 R, and the slope was 4.25 probits per decade increase in dose. Compared to other sheep mortality data, the slope of adult line was unusually small and it is questionable as to whether or not it is a close approximation to that of the entire population. The average day of death for those lambs which died within the first 60 days post-exposure was 21.3 days. Both the average and standard deviation were significantly smaller than those reported elsewhere for bilaterally exposed adults. On the basis of the available data, it appears that the difference in averages can be attributed to the youth of the lambs rather than to the exposure aspect. Modified author abstract