RADIATION STUDIES WITH SWINE 
D. G. Brown' 
Swine are one of the most popular species among 
large animals in biomedical research. In the field of 
radiation biology, more data are available on swine 
than on other large domestic animals. The LD50/30 values 
reported for swine range from 225 to 710 rads (tissue 
dose in air). These values reflect the influence of a 
number of variables such as dose rate, type and quality 
of radiation, age, size, and breed of swine. The ability 
of swine to recover from irradiation injury has been 
demonstrated by relative effectiveness of dose rate, by 
repeated exposures in the LD50/30 range, and especially 
by the relatively large accumulated gamma radiation 
doses when given in fractions of 50 and 100 R/day to 
mortality. Although swine appear to have the highest 
rate of recovery from radiation injury among the large 
animal species, the early clinical syndrome and patho- 
logical manifestations were similar to those of other 
large animals. 
Late effects observed in swine after exposure to 
bomb radiation were an increase in the incidence of 
genital, intestinal and hepatic neoplasms and a decrease 
(3% per 100 rads) of life span. Neoplasms have not 
been a factor relative to late effects of irradiation in 
mortality of cattle and burros. 
INTRODUCTION** 
The intent of this paper is to review the gen- 
eral response of swine after total-body exposure 
to X- and gamma-radiation and to mixed neu- 
tron-gamma radiation. Data reported by scien- 
tists from other laboratories will be included in 
this report, but the information presented will 
be comprised principally of data compiled at the 
UT-AEC Agricultural Research Laboratory. I 
shall deal specifically with dose-mortality inter- 
relationships and with variables having an ap- 
parent effect on the end results. Consideration 
will be given to both early and late effects. 
* Agricultural Research Laboratory of the University of Tennessee, 
Oak Ridge, Tennessee. 
** This manuscript is published with the permission of the Dean 
of the University of Tennessee Agricultural Experiment Station, 
Knoxville. Operated by the Tennessee Agricultural Station for the 
U.S. Atomic Energy Commission under Contract No. AT-40-1- 
GEN-242. 
EARLY MORTALITY 
There is a rather large range of LD50/30 
values published for swine (Table I). This range 
of values is undoubtedly due primarily to a 
number of variables which were different in 
each experiment. There was also the problem 
of possible variable dosimetry among the 
laboratories. 
The radiation variables which seemed to in- 
fluence considerably the 30-day mortality of 
swine were type of radiation, exposure aspect 
(unilateral and bilateral) and dose rate. Bio- 
logic variables which appeared to be of sig- 
nificance were genotype, age, and size. The 
interrelationship of radiation and biologic var- 
iables complicates interpretation of effects of a 
specific variable; therefore, one can evaluate a 
variable only with reservation. 
Type of Radiation 
The relative biological effect (RBE) for neu- 
trons when compared with gamma or X-rays in 
causing 30-day mortality appears to be approxi- 
mately 1. Values of RBE will vary considerably 
with the dose parameters used for comparisons 
(Table II). 
The average survival time of swine after 
single exposures in the LD50/30 range was ap- 
proximately 14 days for either neutron or pho- 
ton radiation. ^-^'^ The cause of death within 30 
days was usually associated with damage to the 
bone marrow (hemorrhagic syndrome), but the 
general behavior of the swine varied with type 
of radiation. Swine exposed to gamma radia- 
tion were usually active during the first 10 days 
after exposure with only a slight decrease in 
ingestion of food and water. Swine irradiated 
with fission® or 14-MeV neutrons'' were de- 
pressed and lethargic during the first week with 
a pronounced decrease in consumption of food 
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