Liver Iron Depletion Without Copper Loss in
Swine Fed Excess Zinc1
DENNIS H. COX 2 AND OTHO M. HALE
Departments of Animal Diseases and Animal Husbandry, Georgia Coastal
Plain Experiment Station, Tifton, Georgia
In addition to such abnormalities as TABLE 1
anemia, poor growth, and an increase or Composition of basal diet
decrease in the activity of various en
zymes, zinc toxicosis in the rat is mani
Ground yellow corn 79.1
fested by a reduction in liver iron and cop Soybean meal, solvent1 16.0
per (Cox and Harris, '60; Magee and
Downloaded from jn.nutrition.org by guest on October 31, 2011
Matrone, '60; McCall et al., '61). The Alfalfa meal 1.8
Mineral mixture2 2.0
liver iron was reduced preferentially and Vitamin premix3 0.1
Chlorte tracycline4 1.0
it was suggested that the loss of liver iron,
not copper, is responsible for the anemia 1 After 69 days on experiment tankage replaced the
soybean meal.
and the depression of the activity of some 2 Mineral mixture added per 100 pounds of feed:
iron-containing enzymes (Cox and Harris, CaCO3, 273.9 gm; steamed bone meal, 273.9 gm; NaCl.
273.9 gm; Fe2O3, 19.55 gm; CoCOa, 195 mg; MuSO,-
'60). Except for the report (Kulwich et H2O, 3.9 gm; KI, 50 mg; CuSO4-5H20, 3.12 em; cane
al., '53) that a dietary level of 1,000 ppm molasses, 58.69 gm. Zinc oxide was added to supply
40 ppm of zinc.
of zinc did not appear to have an appre 3 Vitamin premix supplied riboflavin, 2 mg; Ca
pantothenate, 4 mg; niacin, 9 mg; and choline chlo
ciable effect upon copper metabolism in ride, 10 mg/pound of feed; 15 /ig of vitamin B12 were
swine, iron and copper data for swine re added/pound of feed.
4 Aurofac 1A, American Cyanamid Company. New
ceiving a toxic level of dietary zinc are York; supplied 18.0 mg of Aureomycin/pound of feed.
lacking. The investigation reported here
in was made to determine the effect of end of each experimental regimen, a por
high levels of dietary zinc on liver iron tion of the liver was dried to a constant
weight of 100 °C.Iron was determined by
and copper in swine. the method of Sideris ('42), copper by
EXPERIMENTAL
the method of Peterson and Bollier ('55),
Eighteen weanling purebred Duroc pigs and zinc by the dithizone procedure (Shir
ley et al., '49).
were randomly separated into three groups
containing two females and 4 males per RESULTS
group. The pigs were housed in concrete- Levels of 0.2 and 0.4% of zinc in a
floor pens, 6 per pen, and received feed soybean protein diet for swine for 69 days
and water ad libitum. The composition did not cause any noticeable sign of a
of the basal diet is presented in table 1. toxicosis, except a slight scouring, and no
Zinc oxide was premixed with a portion gross tissue changes at sacrifice.
of the soybean meal at rates to give either Data demonstrating the effect of high
0.2 or 0.4% of zinc in the diet. Since dietary levels of zinc on growth, feed con
toxic symptoms as described by Brink et sumption, and feed utilization are pre
al. ('59) did not develop after a period of
sented in table 2. For the period of 69
69 days, three pigs from each treatment days, the control pigs gained slightly more;
were killed. The remaining pigs were con the feed consumption was essentially the
tinued for another 27 days with the follow same for the three groups; and the feed
ing dietary modifications: tankage re
Received for publication January 8, 1962.
placed the soybean meal as protein source ' Published with the approval of the Director as
and as premix for the zinc oxide and pigs Journal Series Paper no. 94.
2 Present address : Department of Nutrition, Uni
fed 0.2% of zinc received 0.4%. At the versity Hospitals, University of Iowa, Iowa City, Iowa.
77:
J. NUTRITION, '62 225
Thit Oni
L8D3-NN3-OT39
226 DENNIS H. COX AND OTHO M. HALE
TABLE 2
Effect of zinc on growth, feed consumption, and feed utilization
trialNo. 69 Days' Days'
trial1Basal3147.0181.01.266.254.960.4%
Zn627.7130.31.494.352.9227 Zn23138.6166.01.015.865.800.4%
Zn627.2133.21.544.162.700.4% Zn3131.0164.01.226.495.32
of
pigsAv.
initial weight,
IbAv.
final weight,
IbAv.
daily gain,
Ib.Av.
daily
Ib.Feed feed intake,
required/lb of gain, IbBasal627.7138.51.614.342.700.2%
1Animals were also fed diets for the 69-day period, at which time tankage replaced soybean meal.
2Animals in this group were fed 0.2% of zinc for 69 days.
TABLE 3
Excess dietary zinc and swine liver iron, copper, and zinc and blood hemoglobin
Diet Hemo Iron' Copper1 Zinc1
globin
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days429.8diet 69
Basal
(3)«0.2% ±53.93348.1 ±0.616.1 ±
31.6587.2
Zn(3)0.4% ±44.9149. ±4.417.3 ±
65.9«2998.7
(3)Basal
Zn 8 ±
7.3sFed ±4.819.1 ±369.2«132.7
diet
days7595.2 96
(3)0.4% +
80.2496.4 ±
±2.821.0±3.929.8 4.8829.1
(3)«0.4%Zn ±60.5188.5±71.0519.9 ±232.3421
Zn (3)12.914.814.3Fed ±6.2216.2 72.0 ±749.3«
1Micrograms per gram of dry weight of tissue.
2Figures in parentheses show number of animals assayed.
3 Standard error of mean.
* Significantly greater than basal (P < 0.01).
- Significantly less than basal and 0.2% zinc pigs and pigs changed from 0.2 to 0.4% of zinc.
(P < 0.01).
6 Significantly greater than basal and pigs fed 0.2% of zinc and those changed from 0.2% to
0.4% (P < 0.01).
7For 69 days soybean meal was the protein source at which time tankage replaced it.
«Animals in this group were fed 0.2% of zinc for a period of 69 days.
required per pound of gain was the same mia was not produced in pigs receiving
for the controls and pigs fed 0.2% of the high levels of zinc.
zinc, with slightly more required by the Symptoms of a toxicosis did not de
pigs receiving 0.4% of zinc. velop in the pigs that received the high
Data showing the effect of high dietary zinc-tankage diet for 27 days. Growth,
levels of zinc on iron, copper, and zinc in feed consumption, and feed utilization
the liver and blood hemoglobin are pre were about the same for the three groups,
sented in table 3. A lowered (P<0.01) except that the pigs that were originally
liver iron was found in pigs receiving fed 0.2% of zinc and raised to 0.4%
0.4% of zinc as compared with the con gained less weight than the pigs fed 0.4%
trols and pigs fed 0.2% of zinc. The iron of zinc for the entire 96 days (table 2).
content of the liver of pigs fed 0.2% of Similar results were noted for liver iron,
zinc was not significantly different from
the controls. This latter observation is of copper, and zinc in the pigs fed the tank
particular interest since a significant (P < age protein diet as noted for the pigs fed
0.01) accumulation of zinc was found in the soybean protein diet (table 3). How
the liver of these pigs. However, the zinc ever, although a slight elevation of liver
content in the liver of the animals receiv copper occurred in the pigs receiving a
ing 0.4% of zinc was significantly greater high dietary level of zinc, this was not of
(P < 0.01) than those fed 0.2% of zinc. statistical significance. Blood hemoglobin
Liver copper was not reduced in the pigs values were not obtained since the blood
fed either level of high dietary zinc. Ane samples were accidentally lost.
FE AND CU IN SWINE FED EXCESS ZINC 227
DISCUSSION present investigation the results showed
The results of the experiment described that liver copper was not reduced in swine
here demonstrate that, as with the rat, a fed high levels of dietary zinc for an ex
high level (0.4% ) of zinc in the diet re tended period of time. The following rea
sults in an increased level of zinc in the sons may be considered in explaining why
liver and a markedly reduced liver iron. a reduction of liver copper in the swine
Of particular significance was the obser was not produced: (a) species difference
vation that liver copper was not reduced. in copper metabolism, (b) the pigs were
These results substantiate the view (Cox on the high zinc diets for an insufficient
and Harris, ('60) that high levels of die length of time, and (c) liver iron was not
tary zinc cause a preferential loss of liver reduced to the critical level to affect cop
iron and not copper. per metabolism as was suggested from
Of interest was the lack of a significant data obtained for the rat.
reduction of liver iron in the pigs fed 0.2% It was unexpected that reduced hemo
of zinc in which there was a significant in globin values were not found in the pigs
crease in liver zinc. These results suggest receiving 0.4% of zinc for 69 days, espe
that the zinc level in the liver of swine cially since the animals had a markedly
Downloaded from jn.nutrition.org by guest on October 31, 2011
must attain a critical level before produc reduced liver iron. Evidently the iron
ing the liver iron anomaly or that swine stores were not depleted to a critical level
can tolerate a relatively high accumulation to affect hematopoesis.
of zinc in the liver before the iron is ad Brink et al., ('59) reported that the
versely affected. McCall et al., ('61) pro addition of 0.1% of zinc as zinc carbonate
posed that specific protein compounds in to the diet of weanling pigs was the maxi
soybean meal form stable chelates with mal level tolerated and higher levels pro
zinc which decrease the accumulation of duced a toxicosis. It was, therefore, very
zinc in the liver when otherwise toxic unexpected that a marked toxicosis was
levels are ingested and eliminate the ad not found using 0.2 and 0.4% of zinc as
verse interaction with copper and iron. zinc oxide. Investigations on poultry
This proposal may explain why the level (Moeller and Scott, '58; Morrison and
of zinc in the liver did not attain a critical Sarett, '58; O'Dell and Savage, '57), the
level to affect liver iron in the swine fed rat (Forbes and Yohe, '60), and swine
0.2% of zinc. But with 0.4% of zinc in (Smith et al., '60) showed that soybean
the diet a critical level of zinc was at meal in the diet increased the require
tained in the liver as indicated by the sig ment for zinc. McCall et al. ('61) pre
nificant depletion of liver iron. This was sented evidence to show that the amount
further demonstrated by the data which of zinc required to produce toxic symp
showed a significantly greater amount of toms in the rat and the severity of the
zinc in the liver of the swine fed 0.4% symptoms depend upon the source and
of zinc as compared with those fed 0.2%. level of dietary protein. Rats fed exces
Whereas 0.4% of dietary zinc produced a sive zinc in soybean protein diets were
greater accumulation of zinc in the liver heavier, showed higher hemoglobin values,
and a significant loss of liver iron, the lack and less total zinc in the liver than those
of a loss of liver iron in the pigs fed 0.2% animals fed casein. It could be inferred,
of zinc suggests that zinc alters iron me therefore, that the lack of a marked tox
tabolism in the liver rather than iron ab icosis in the present investigation was the
sorption. result of a binding of the zinc by the soy
Cox and Harris ('60) have reported
bean meal and, hence, less available zinc
that rats fed high levels of dietary zinc during the critical stage when the pig is
exhibited an early loss of liver iron and, young. But the level of soybean meal used
after a relatively longer period of time, a in the present study was less than that
reduction in liver copper. The data sug used by Brink et al. ('59). However, our
gested that the reduction of liver copper procedure of premixing zinc oxide with a
was a result of reduced liver iron rather portion of the soybean meal, which they
than an effect of zinc. In contrast, in the did not state was their method, could pos-
228 DENNIS H. COX AND OTHO M. HALE
sibly be a factor in not producing a tox LITERATURE CITED
icosis. The failure to produce a toxicosis Brink, M. F., D. E. Becker, S. W. Terill and A. H.
after tankage replaced the soybean meal Jensen 1959 Zinc toxicity in the weanling
could be due to the short duration the ani pig. J. Animal Sci., 18: 836.
Cox, D. H., and D. L. Harris 1960 Effect of
mals were fed the diet or the age of the excess dietary zinc on iron and copper in the
animals. Whereas zinc carbonate was rat. J. Nutrition, 70: 514.
used in the study of Brink et al. ('59), the Forbes, R. M., and M. Yohe 1960 Zinc require
ment and balance studies with the rat. Ibid.,
use of zinc oxide in the present investiga 70: 53.
tion could be a factor in the lack of pro Kulwich, R., S. L. Hansard, C. L. Comar and G. K.
ducing a toxicosis. However, Magee and Davis 1953 Copper, molybdenum and zinc
Matrone ('60) have reported that excess interrelationships in rat and swine. Proc. Soc.
Exp. Biol. Med., 84: 487.
zinc in the forms of the carbonate, chlo Magee, A. C., and G. Matrone 1960 Studies
ride, and oxide reacted similarly on on growth, copper metabolism and iron metab
growth, hemoglobin formation, liver cop olism of rats fed high levels of zinc. J. Nutri
tion, 72: 233.
per, iron, and zinc, and heart cytochrome McCall, J. T., J. V. Mason and G. K. Davis 1961
oxidase activity in the rat. Effect of source and level of dietary protein on
the toxicity of zinc to the rat. Ibid., 74: 51.
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SUMMARY
Moeller, M., and H. M. Scott 1958 Studies
with purified diets. 3. Zinc requirements.
Weanling pigs were placed on experi Poultry Sci., 37: 1227.
Morrison, A. B., and H. P. Sarett 1958 Studies
ment to study the influence of high levels on zinc deficiency in the chick. J. Nutrition,
of dietary zinc on liver iron, copper, and 65: B.
O'Dell,267.L., and J. E. Savage 1957 Potassium,
zinc.
zinc and distillers dried solubles as supple
Zinc levels of 0.2 and 0.4% in a soy ments to a purified diet. Poultry Sci., 36: 459.
bean meal diet produced neither signs of Peterson, R. E., and M. E. Bollier 1955 Spec-
a marked toxicosis nor an adverse effect trophotometric determination of serum cop
on growth or feed consumption. per with biscyclohexanoneoxalyldihydrazone.
Anal. Chem., 27: 1195.
Evidence was obtained demonstrating Shirley, R. L., E. J. Benne and E. J. Mille 1949
that 0.4% of zinc in the diet of swine re Report on zinc in plants. J. Assoc. Off. Agrie.
Chem., 32.- 276.
sults in a significant reduction in liver Sideris, C. P. 1942 Colorimetrie microdeter-
iron without a concomitant loss of liver mination of iron. Ind. Eng. Chem. (Anal, ed.),
copper. On the other hand, although 0.2% 14: 756.
of zinc in the diet caused a significant in Smith, W. H., M. P. Plumlee and W. M. Beeson
crease of liver zinc, the iron content in the 1961 Zinc requirement of the growing pig
fed isolated soybean protein semi-purified ra
liver was not decreased. tions. J. Animal Sci., 20: 128.