Animal Science 'i Florida Agricultural
Mimeograph Report No. AN64- Experiment Station
EFFECTS OF WHOLE-BODY GAMMA IRRADIATION ON MATURE EWES
J. E. Moore, P. E. Loggins, C. F. Simpson and C. B. Ammermanh/
Studies of the effects of ionizing radiation on farm livestock may
contribute to an understanding of the effects on humans. However, due
to the nature of the digestive system in ruminants, irradiation of
cattle or sheep may result in different physiological effects than those
encountered in swine. Shirley et al. (1962) reported that gamma irradia-
tion increased the liver-copper levels in swine while Goodner et al.
(1955) reported that irradiation of the rat reduced the absorption of
sodium. Dixon (1955) reported that irradiated mice exhibited a reduced
absorption of glucose, but gastric emptying time and intestinal hexo-
kinase activity were not affected. The microflora of the cecal contents
of the rat were found to be altered by x-irradiation (Bell et al., 1955).
The cecal lactobacilli were decreased but coliform organisms were in-
creased in the irradiated rats. However, this effect could not be
related to the rate of food movement through the intestinal tract. In
studies of 200 to 300 lb. calves, Rosenfeld (1958) reported that 600
roentgens (r) from cobalt-60 resulted in a loss of appetite, decreased
rumination rate, and watery diarrhea twelve hours after irradiation.
However, the animals recovered 24 hours after irradiation, continued to
appear normal for about 6 days, but again exhibited loss of appetite,
decreased rumination rate, and watery diarrhea six days after irradia-
In preliminary research at the Florida Station, Meacham and Moore
(1962), observed that the concentration of rumen total volatile fatty
acids (TVFA) were decreased 2 to 4 days after mature sheep were given
200 or 400 r of cobalt-60 gamma irradiation. The present study was
undertaken to further investigate the effects of ionizing irradiation
on sheep with special emphasis on the voluntary consumption of feed and
on rumen TVFA concentration.
Two experiments were conducted, with 8 ewes in experiment I and
10 ewes in experiment II. The mature, open, ewes, from the Station
flock, were taken from pasture and allotted to one of two dietary treat-
ments shown in table 1. Diet A contained a 3:1 hay:corn ratio and 8.5%
protein while diet B contained a 1:1 hay:corn ratio and 9.0co protein.
The ewes were randomly allotted to treatments as shown in table 2. The
ewes were fed the experimental diets in dry lot for at least 9 days
i Moore, Assistant Animal Nutritionist, Department of Animal Science;
Loggins, Assistant Animal Husbandman, Department of Animal Science;
Simpson, Pathologist, Department of Veterinary Science; and Ammerman,
Assistant Animal Nutritionist, Department of Animal Science.
before being transferred to individual metabolism racks. Individual
feed consumption was measured on a daily basis after a 5-day adjustment
period. Voluntary feed consumption was recorded for 7 days prior to
Table 1. Experimental Diets
Feedstuff A B
Bermuda hay, chopped 73.5 49.0
Corn, ground shelled 24.5 49.0
Urea, crystalline 0.5 0.5
Defluorinated phosphate 1.0 1.0
Salt, trace mineralizedl 0.5 0.5
Vitamins A and D2 + +
1 Carey Salt Co., Hutchinson, Kansas; NaC1, 96.2%; Mn,
0.25%; Fe, 0.27%; Cu, 0.033%; Co, 0.01%; Zn, 0.005%;
and I, 0.007%.
2 2000 I.U. of vitamin A palmitate and 500 I.U. of
vitamin D2 added per pound of ration.
Table 2. Experimental Irradiation and Dietary
Treatments and Allotment of Ewes
0 ra 400 r
Experiment Ab B A B
I 1, 4c 5, 8 2, 3 6, 7
II 9 14 10, 11, 12, 13 15, 16, 17, 18
a Irradiation level
c Ewe numbers
In experiment I, two ewes receiving each diet were placed in indi-
vidual wooden crates 13 feet from the cobalt-60 source2 and irradiated
bilaterally. The irradiation rate was 3.67 r per minute, the exposure
time was 54.5 minutes per side, thus giving a total dose of 400 r. In
experiment II, four ewes receiving each diet were irradiated at 3.56 r
per minute for 56.2 minutes per side to give a total dose of 400 r.
2/ University of Florida Agricultural Irradiation Facility, Gainesville.
Originally 6000 curies of cobalt-60.
In experiment II, the non-irradiated ewes were transported to the irra-
diation facility and kept there during the irradiation, but were
shielded from the source. After irradiation the ewes were returned
immediately to their individual metabolism racks and feed consumption
observations were continued. In the following, the use of the phrase
"days after irradiation" will refer to the time elapsed from the day
that the irradiated ewes were exposed and applies also to the non-
irradiated ewes. Negative figures refer to days before the day of
Total white blood cell counts were made -3, 4, 14, 21 and 30 days
after irradiation in experiment I, and 7 days after irradiation in
experiment II. In experiment I, rumen fluid samples were taken by
stomach tube -7, -5, -3, 2, 4, 7, 14 and 21 days after irradiation for
determination of total volatile fatty acids (TVFA). The samples were
centrifuged, the protein precipitated with Zn(OH)2 and the filtrate was
acidified and steam distilled. The distillate was titrated with 0.01 N
NaOH and the milliequivalents of TVFA per 100 mls of rumen fluid were
calculated. Rumen fluid samples were not taken in experiment II; how-
ever, the ewes were subjected to the passage of a stomach tube 16 and
18 days after irradiation in order to determine if this procedure
affected feed consumption.
Feed consumption records were continued for the control ewes for
16 days after irradiation in experiment I and for 20 days after irradia-
tion in experiment II. The surviving irradiated ewes were held in the
metabolism racks for 29 days after irradiation in experiment I and for
20 days after irradiation in experiment II. After removal from the
racks the ewes were returned to pasture where they were periodically
observed until 60 days after irradiation.
The effect of 400 r of cobalt-60 gamma irradiation on the total
white blood cell counts of mature ewes in experiment I is presented in
table 3. Gamma irradiation reduced total white blood cell counts with-
in 4 days after irradiation, and recovery in the surviving ewes did
not begin until 14 to 21 days post-irradiation. The reduction in total
white blood cell counts by irradiation was also observed in experiment
II in samples taken 7 days after irradiation. The two control ewes had
values of 6,900 and 7,200 cells per cumn respectively, while the irra-
diated ewes had an average value of 3,320 cells per cumm with a range
of 2,200 to 4,250.
The effect of irradiation on average daily feed consumption in
experiment I is presented in table 4. Three of the non-irradiated ewes
exhibited some loss of appetite 3 to 6 days after the day of irradiation
but had recovered by the seventh day. However, the irradiated ewes
exhibited an immediate loss of appetite after irradiation, and three of
the four also exhibited a recovery after 7 days. One ewe, (No. 2; 400
r) developed anorexia 2 days before irradiation and did not consume feed
for a total of 18 days of daily observation. Sixteen days after irradia-
tion it was removed from the rack and death occurred 5 days later. Post-
mortem examination revealed diffuse abscessation in the mouth which may
have contributed to the loss of appetite. Ewe number 6 partially
recovered its appetite and ate 2.1 Ibs. on day 18. However, it consumed
only 0.6 lb. on day 19, refused to eat on day 20 and was sacrificed on
day 21. It was depressed and had bloody feces.
Table 3. Effect of Irradiation on
Cell Counts of Mature
Days after A
Irradiation 1 4
-a 9,650 6,350 10,550
Total White Blood
6,400 7,500 6,650
b Cells per cubic millimeter
c Ewe number 2 died day 21
d Ewe number 6 sacrificed day 21, post-mortem sample
Table 4. Effect of Irradiation on Average Daily Feed
Consumption of Mature Ewes, by Perioda
Period 0 r 400 r
(Days after A B A B
Irradiation) 1 4 5 8 2 3 6 7
-7 to -1 1.8 1.4 2.2 2.7 1.3 2.2 2.5 2.6
0 to 2 2.1 1.9 2.5 2.8 0.1 1.4 0 0
3 to 6 1.5 0.8 0.6 2.8 0 1.5 0.2 0.1
7 to 11 2.0 1.7 2.6 2.8 0 2.0 1.7 1.2
12 to 16 2.1 1.6 1.9 2.9 0b 2.0 1.8 1.9
17 to 20 -- -- -- 2.1 1.3c 1.9
21 to 29 -- -- -- -- 2.0 -- 2.2
a Pounds/day, average over period indicated
b Ewe number 2 removed from rack on day 16, and died on day 21
c Ec nuumbe:.: 6 sacrificed on Tay 21
The results of the rumen total volatile fatty acid analyses in
experiment I are presented in table 5. These values tended to reflect
the changes in voluntary feed consumption.
Table 5. Effect of Irradiation on Rumen Total
Volatile Fatty Acids (TVFA) of Mature Ewes
0 r 400 r
Days after A B A B
Irradiation 1 4 8 2 3 6 7
-7 8.0a 9.6 8.6 10.0 10.4 9.4 10.0 10.7
-5 5.5 7.1 7.0 9.0 9.0 6.8 8.4 8.2
-3 7.5 8.1 8.4 9.8 7.2 8.5 8.0 9.7
2 7.5 8.9 9.6 8.9 4.5 7.2 4.8 5.2
4 6.1 8.2 5.1 8.3 3.9 5.4 2.4 2.1
7 6.0 7.2 7.8 9.0 3.9 6.8 7.3 5.0
14 7.2 6.9 8.4 10.0 --b 7.3 9.0 7.9
21 -- -- -- 8.3 7.oc 8.0
a Milliequivalents per 100 ml
b Ewe number 2 off-feed, died day 21
c Ewe number 6 sacrificed day 21, post-mortem sample
Since examination of the individual daily feed consumption data in
experiment I had indicated that feed consumption was reduced on the day
after the rumen fluid samples were taken, passage of the stomach tube
was not carried out in experiment II until 16 days after irradiation.
The feed consumption data of experiment.II, as presented in table 6,
showed that feed consumption by each of the irradiated ewes was reduced
during the 4 days after irradiation. All but one of the ewes recovered
its appetite and was eating at least half of the pre-irradiation level
on day 15. However, passage of the stomach tube on the sixteenth day
markedly reduced feed consumption in the irradiated ewes and partially
reduced feed consumption in the non-irradiated ewes. In experiment II,
it appeared that there might have been an interaction between diet com-
position, irradiation and stomach tube passage. The irradiated ewes
receiving the high grain diet (B) exhibited a more marked decrease in
feed consumption following passage of the stomach tube and consumed less
than 0.2 lb. on days 19 and 20.
Five of the 8 irradiated ewes (Nos. 11, 12, 13, 17, 18) in experi-
ment II died between the 20th and 28th day after irradiation. Since a
total of 7 of 12 irradiated ewes in both experiments died within 30 days
after irradiation it is suggested that 400 r of total body gamma irradia-
tion at a rate of 3.67 to 3.56 r per minute is near the dose level lethal
- 6 -
to 50% of the ewes within 30 days after irradiation (LD50:30o) In each
case in which death ensued the feces were stained with varied amounts
of blood, from slight to massive, during the 24-hour period prior to
death. No external signs of radiation sickness, except generalized
depression, were observed.
Table 6. Effect of Irradiation on Average Daily Feed
Consumption of Mature Ewes, by Period
Period 0 r 400 r
(Days after A B A B
Irradiation) 9 -l7 10 11 12 13 15 16 17 18
-7 to -1 2.3a 2.9 2.9 2.7 2.4 3.0 2.2 2.7 2.7 2.7
0 to 3 2.3 2.7 2.4 1.9 0.2 1.6 1.1 1.9 0.8 1.5
4 to 9 2.7 2.3 2.8 2.2 1.2 2.7 1.6 2.3 0.1 2.7
10 to 15 2.3 2.4 2.9 2.4 1.6 2.1 1.8 1.9 0.1 2.7
16 to 20b 1.7 1.7 0.6 0.9c 0.7c 1.7c 0.2 0.1 Oc 0.8C
a Pounds/day, average over period indicated
b Stomach tube passed on days 16 and 18
c Died within 30 days after irradiation
The most prominent post-mortem findings in the sheep dying as a
result of the lethal doses of total body irradiation were hemorrhages.
These lesions occurred throughout the body, but usually involved the
heart, stomach, intestinal tract, lungs and urinary system. Varying
manifestations of hemorrhaging were seen at death. These included
pronounced dilatations of the blood vessels supplying the affected
part, small or large hemorrhages, or blood clots. Commonly, large
hemorrhages were found in the renal cortices and pelves. The inner and
outer aspects of the stomach and intestines were often blood-stained.
The lymph nodes draining these parts were frequently dark in color.
The heart frequently exhibited hemorrhages, particularly on its exter-
nal surface. The lungs frequently contained large hemorrhages. The
muscles of the body also were frequently hemorrhagic. The bone marrow
was yellow in color, rather than having a normal pink tint. Fibrinous
shreds were often attached to organs which were most severely affected
by radiation damage. These observed lesions of irradiation in sheep,
however, were not as severe as those found in swine by Meacham, et al.
It was apparent that the 400 r level of irradiation, at 3.56 to
3.67 r per minute, was sufficient to bring about physiological changes
in mature ewes. These changes were especially illustrated by the
effects on total white blood cell counts, voluntary consumption of feed,
and lesions observed in post-mortem examination. Since 7 of 12 irra-
diated ewes died within 30 days, it is suggested that this level of gamma
irradiation is near the LD50:30 when administered at a rate of 3.56-3.67
r per minute.
Since the feed consumption of irradiated ewes in experiment I was
less than that in experiment II, it may be suggested that the passage
of the stomach tube in experiment I contributed to a more marked loss
of appetite in the irradiated ewes. This was clearly demonstrated in
experiment II when the use of the stomach tube was delayed until 16 days
after irradiation at which time it markedly reduced feed consumption,
especially in the irradiated ewes. The observation that the ewes on
the ration with a 1:1 hay:corn ratio were affected by irradiation and
passage of the stomach tube more than those on the ration with a 3:1
hay:corn ratio, may suggest that ruminants fed high concentrate rations
are under more stress than ruminants consuming a high roughage ration.
Further experiments are required to test this hypothesis.
The influence of irradiation on rumen total volatile fatty acid
(TVFA) concentration in experiment I could not be separated from the
effect on feed consumption. Examination of the relationship between
TVFA concentration and the consumption of feed during the two days
prior to sampling indicated that TVFA concentrations were reduced due
to a lower amount of substrate available for the rumen microorganisms.
However, more detailed physiological and microbiological studies are
necessary to reject a possible direct effect of irradiation on the
metabolism of rumen microorganisms or on the rate of absorption of the
volatile fatty acids.
Four hundred r of total body gamma irradiation of mature ewes
resulted in depressed feed intake for approximately 4 days after irra-
diation. The rate and degree of appetite recovery was unrelated to the
incidence of death losses. The death of 7 of 12 ewes within 30 days
after irradiation suggested that this level may be near the LD50:30 for
sheep. A depression in rumen total volatile fatty acid concentration
occurred simultaneously with a loss of appetite. Obtaining rumen samples
by stomach tube appeared to depress the appetite of the ewes, however,
the non-irradiated ewes were not as adversely affected by the use of the
Bell, Emily J., J. G. Coniglio and G. W. Hudson. 1955. Effect of
x-irradiation on cecal flora of the rat. Proc. Soc. Exptl. Biol. Med.
Dickson, H. M. 1955. Effect of x-irradiation on glucose absorp-
tion. Am. J. Physiol. 182: 477.
Goodner, C. J., T. E. Moore, Jr., J. Z. Bowers and W. D. Armstrong,
1955. Effect of acute whole-body x-irradiation on the absorption and
distribution of Na-22 and H-3 OH from the gastrointestinal tract of the
fasted rat. Am. J. Physiol. 183: 4T5.
Meacham, T. N., T. J. Cunha, G. E, Combs, H. D. Wallace, A. C.
Warnick, R. L. Shirley and C. F. Simpson. 1962. Effect of gamma irra-
diation on pigs fed low vitamin A rations. Proc. Soc. Exptl. Biol. Med.
Meacham, T. N. and J. E. Moore. 1962. Unpublished research, Fla.
Agr. Exp. Sta.
Rosenfeld, G. 1958. Effects of a single lethal dose of total-body
cobalt-60 gamma irradiation on calves. Radiation Res. 9: 346.
Shirley, R. L., T. N. Meacham, A. C. Warnick, H. D. Wallace, J. F.
Easley, G. K. Davis and T. J. Cunha. 1962. Gamma irradiation and
interrelation of dietary vitamin A and copper on their deposition in
the liver of swine. J. Nutr. 78: 454.