|
Items in cart [0] |
Questions? Call 888-624-8373 |
| Copyright © 2009. National Academy of Sciences. All rights reserved. Terms of Use and Privacy Statement |
Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter.
Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.
OCR for page 421
silicon
Next to oxygen, silicon is the most abundant element on earth, and
quartz (crystalline silica) is the most abundant mineral in the earths
crust (Carlisle, 19741. Silicon is found in the ash of most plant and
animal tissues in small quantities, but it has been generally considered
nonessential for most living organisms. Silica has long been associated
with silicosis, a chronic lung disease caused by inhalation of silica-
bearing dust especially in miners, and with certain types of malignant
tumors (Allison, 1968~. It has been suggested that silicon is an essential
nutrient for animals, based on its effect on bone mineralization in the
laboratory rat, and on the occurrence of a deficiency in the chick
(Carlisle, 1974~.
ESSENTIALITY
It has been shown that silicon is important in formation of young bone
in laboratory rats (Carlisle, 19741. The importance of silicon appears to
lessen as the bone approaches maturity. The element is also present,
along with iron, in blood vessels between metaphyseal trabeculae. It
seems to be involved in endochondrial and periosteal bone formation.
A silicon deficiency resulted in a 37 percent depression in growth rate
of chicks (Carlisle, 1974~. The deficient animals appeared stunted, and
all organs were atrophied. Retarded skeletal development was recorded
for the deficient chicks. Silicon has been shown to be essential for
421
OCR for page 422
422 MINERAL TOLERANCE OF DOMESTIC ANIMALS
growth in rats also (Schwarz, 1973~. Un~ceDular microscopic plants,
diatoms, require silicon for shell formation and net DNA synthesis
(Carlisle, 19743.
METABOLISM
Silicon is usually found in combination with oxygen as silica. Silicon
compounds play an especially sigruf~cant part in some lower organisms
(Carlisle, 19741. At least traces of silicon are found widespread in tis-
sues and fluids of higher animals. The normal human blood level is less
than 5 ppm (Carlisle, 19741. Silicic acid is readily absorbed across the
intestinal wall and is excreted in the urine. Evidence was obtained that
silica was not absorbed in sheep and cattle to a significant extent and
appeared to be useful as an inert indicator to determine digestibility
(Gallup et al., 19451. The amount of silicon in blood and intestinal
tissues in rats is affected by age, sex, castration, adrenalectomy, and
thyroidectomy (Carlisle, 19741. Silica can enter in the respiratory tract,
go to the lung as silicic acid, and is eventually eliminated.
The quantity of silicon present in the active growth areas of the bone
appears to be related to the maturity of the bone (Carlisle, 1974~. In the
early stages of mineralization, silicon is present in small quantities. As
mineralization progresses, silicon increases concomitantly with cal-
cium. Later, the amount of silicon drops, and as the calcium reaches the
level ire apatite, silicon level is at the detection limit.
SOURCES
Silicon is taken up by the roots of plants and deposited in cell walls.
There is considerable variation in silicon content between plant species
(Carlisle, 1974~. Cereal grains high in crude fiber are higher in silicon
than low-fiber grains. The silicon, present as silica, soluble silicates,
and in organic combinations, is bound to the cellulosic cell structure.
Silicon does not appear to be essential for plants, but it produces
beneficial effects on plant growth Cones and Handreck, 19671. Kind of
soil, plant species, transpiration rate, and nutrient supply affect silica
content of plants. Silica is not distributed uniformly among plant parts.
It appears to be deposited in largest quantities in parts from which
water is lost in greatest quantities. Rice hulls contain high concentra-
tions of silica (Van Soest, 1970~. Contamination of feeds with soil,
especially in hay and pasture herbage, elevates the level of silica.
OCR for page 423
Silicon
423
Although silicon has been shown to be a dietary essential, it is not
likely that deficiency would occur in practice due to the wide distribu-
tion of it as a component or contaminant of feed.
TOXICOSIS
Excess dietary silica appears to be involved in depression in digesti-
bility of forages, depression in growth and reproduction rate, and for-
mation of kidney stones in ruminants. Under practical farm or ranch
conditions, silicon toxicosis is not a serious problem.
LOW LEVELS
Silicon in forages has been shown to depress dry matter digestibility in
viva in ruminants (Van Soest and Jones, 1968) and organic matter
digestibility in vitro (Smith et al., 1971~. The depressions amounted to
approximately three units of dry matter digestibility in vivo (Van Soest
and Jones, 1968) and one unit of organic matter digestibility in vitro
(Smith e' al., 1971) per unit of silica in the dry matter of forages.-
Addition of sodium silicate to rumen cultures depressedin vitro organic
matter digestibility of siliceous forages and purified cellulose (Smith
and Nelson, 1975; Smith and Urquhart, 1975~. The effects were amelio-
rated by addition of glucose in a mixture of minerals to the medium
(Smith and Nelson, 1975), which may explain the reason Minson (1971)
did not observe a depressing effect of silicon on in vitro digestion of
neutral detergent solubles.
A siliceous type of urinary calculus was observed in sheep, but added
silica did not have any effects (Beesonet al., 1943~. Feeding wheat bran
appeared to contribute to the disturbance. Beeson et al. obtained evi-
dence that urinary magnesium plays an important part in the limitation
of urinary silica solubility. Addition of sodium silicate to the diet at the
level of 2.2 percent tended to increase the incidence of urinary calculi
in lambs fed a calculi-inducing diet (Schneider et at., 1952~. Incidence
of urinary calculi in grazing steers in Montana was correlated
(r = 0.558) with the silica content of the forages (Parker, 19571. Nega-
tive correlations were reported between the incidence of calculi and the
concentration of phosphorus, calcium, magnesium, and potassium in
the forage. Silica was the main constituent of uroliths in cattle in the
problem area of Canada, but outside the problem area the uroliths
contained little or no silica (Cornell e' al., 19591. Urinary calculi were
found in wethers fed rations containing prairie hay, but not in those fed
OCR for page 424
424 MINERAL TOLERANCE OF DOMESTIC ANIMALS
r
alfalfa hay diets (Emerick et at., 19591. No difference was observed in
number of animals with urolithiasis between cattle fed prairie hay from
two different sources, but animals fed hay from a ranch with a history
of urolithiasis had approximately twice as much urolithic material
present in the urinary organs, compared to those fed hay from the
urolithiasis-free area (Whiting et al., 1958~.
Bailey (1967b) reported a sevenfold greater silica concentration in
urine from cows fed prairie hay than from cows fed alfalfa hay. They
pointed out that the difference was due more to differences in urine
volume than to differences in total silica excreted in the urine. Prairie
hay was found to contain 5.7 percent silica, compared to 0.4 percent for
alfalfa hay (Bailey, 1976a). Although percent silica absorption was
lower in cows fed prairie hay than those fed alfalfa hay, the absolute
amount was obviously much higher for the cows fed prairie hay. Bailey
(1976c) suggested that low water intake was a necessity, but not a
sufficient condition for calculi formations.
Number of offspring born to female rats was decreased by including
600 or 1,200 ppm soluble silica in the water (Smith et al., 19731. Further-
more, the number of offspring surviving until weaning was decreased
by the addition of silica to the drinking water. Longevity of rats started
on treatments after weaning was not affected by the addition of soluble
silica to drinking water.
Administration of dextro- and levorotatory quartz to the lungs of rats
by sufflation produced changes in the lungs, consisting of intraalveolar
modular foci of macrophages containing quartz crystals (King e' al.,
1946b).
HIGH LEVELS
Feeding dogs a semisynthetic diet with 12 percent silicic acid (4.3
percent silicon and 3 percent talc [0.9 percent silicon]) produced fatal
urethral blockage, cystitis, uremia, and systemic infection (McCullagh
and Ehrhart, 1974~. In a subsequent test, 3 of 16 dogs fed the diet
developed urethral blockage, but were treated successfully after the
diet was changed. Silica has been shown to cause hemolysis of eryth-
rocytes in vitro (Staider and Stober, 1965~.
FACTORS INFLUENCING TOXICITY
Sex of animals appeared to be important in the response to high levels
of silica. Adding sodium silicate to the drinking water at a level to
supply 374 ppm silicon increased rate and efficiency of gain in
OCR for page 425
Silicon
425
growin~finishing wethers, but depressed these in ewes (Smith et at.,
1972~. The response in wethers was mostly with those fed an alfalfa-
hay-based diet, with little effect in those fed different proportions of
cottonseed hulls and mile, supplemented with urea. Type of diet did not
influence the response in ewes. Adding 600 ppm sodium silicate (280
ppm silicon) to drinking water depressed gain in female albino rats, but
increased gain in males (Smith et al., 1973~. Phosphorus and nitrogen
retention was increased in male rats given access to water with 1,200
ppm soluble silica.
Type of feed appears to affect the formation of calculi. Incidence was
higher in animals fed prairie hay than in those fed alfalfa hay as the
roughage source (Emerick et al., 1959~. This may be due to the higher
silica content in prairie hay (Bailey, 1976a) or lower urine volume in
cattle fed this roughage (Bailey, 1967b). Also, addition of calcium may
have been important, since a lower calcium-to-phosphorus ratio in-
creased incidence of calculi (Schneider et al., 19S2~. Dietary magne-
sium level may be involved also. Lower urinary magnesium was
observed in sheep fed prairie hay (Emerick et al., 19591. A normal
intake of magnesium had an alleviating effect on incidence of calculi
(Schneider et al., 19521. A negative correlation was reported between
incidence of urinary calculi and magnesium level in the forage (Parker,
1957).
Differences in hemolysis were reported from incubating sheep and
human erythrocytes with silica with different crystalline structures
(Staider and Stober, 19651. Alumina was useful in partly alleviating the
hemolytic effects of quartz. Aluminum dust did not prevent silicosis in
rabbits from administration of silica in the lungs, but the lesions were
less advanced in the animals receiving aluminum (King et al., 1946a).
Siliceous calculi were prevented in calves fed a calculi-inducing diet
by including 4 percent sodium chloride in the diet, which increased
urine volume by 50 percent (Bailey, 1967a). In later work, results were
obtained indicating that consumption of 300 g of salt per day in 300-kg
calves prevented formation of siliceous calculi (Bailey, 1973~. The high-
salt intake increased urine volume. Feeding of ammonium chloride did
not affect water intake or formation of siliceous calculi (Bailey, 1976b).
TISSUE LEVELS
Bovine muscle was reported to contain 1.0 to 1.7 ppm silica, dry basis
(Van Soest, 19701. Levels in liver were 0.2 to 0.5 ppm, dry basis.
Chicken feathers contained 1.6 ppm, dry basis.
OCR for page 426
426 MINERAL TOLERANCE OF DOMESTIC ANIMALS
MAXIMUM TOLERABLE LEVELS
It appears that even tow levels of silica in forages will depress their
digestibility by ruminants. No calculi were observed in sheep fed up to
0.57 percent silicon (Emericket al., 19591. Thus the maximum tolerable
level in sheep appears to be 0.2 percent as soluble salts of high avail-
ability. Higher levels of less soluble forms found in natural substances
can be tolerated.
SUMMARY
Silicon is the most abundant element in the earth's crust, next to oxy-
gen, and has been shown to be essential for bone formation in rats and
growth of chicks. It is widely distributed in plants in the form of silica.
The ha~! effects of an excess of silicon in animals include a depres-
sion in roughage digestibility by ruminants, abnormal reproduction in
rats, and involvement in urinary calculi in sheep. It is toxic when
administered in lungs, which appears to be a more serious problem with
humans than animals. Toxicity does not appear to be a serious problem
.
in animals.
OCR for page 427
A
He
A,
-
ct
E
._
a:
::
e_
o
·_
U.
E
o
.O
-
o
-
Cat
to
rat
o
-
-
._
E
-
-
I:
. - o
-
a
o
u'
O
``
_
_
=m
O ~
~~ —
~ 3
Go
_
TO
C:
o ~ ~ t_
~o ~ ~
_
~ ~ ~ —
8
~ ~ ~ 3 E E
; G C o C
e ~ ~ ~ e ~ O y y i ~e °
5 ~ ~a ~ ~ j i s~ l~ e =° i E 5
a a ~ ~ z, z z c' ~ ~ ~ Z ~ 3~ ~ D ~ 3
Le ~
.~ o~ .o o~ 3 3
o
o
_ _
_
~ ~ ~ a~ lB ja~ ~Or E ~a' E ~
~ ~ ~ ~ E3 E; 53
3~ ~ ~§ $§ ~ ~ °= ~ o
8 ~ ~
~ E E E E E e
m E.e E ~ 3. a ~, ~ ~ · 3 ~ °,
~ ~ Z ~ ~ ~ ~ u~ u~ co ce ~ ~ ~ ~:
427
OCR for page 428
x ·~" ~
~ ~ ~ - &1 9 ~ ~ ~ r 0 ~ .=
._ 0 ~ E A {5 0
E a It a, If.
.~ .
O O Su,
. E ED x ~ a
428
-
~c
._
3
lo
o
D
o
Ct
- o
._
Cal
CO
Ct
~4
._
=
._
Cal
Ct
E ~
ct u,
lo,
_ ct
~ CL
.-
en
._ ~
c `,-
x
0
ED .—
~ c
Zen
~ ~0
OCR for page 429
Silicon
REFERENCES
429
Allison, A. C. 1968. Silicon compounds in biological systems. Proc. R. Soc. 171:17.
Bailey, C. B. 1967a. Siliceous urinary calculi in calves: Prevention by addition of sodium
chloride to the diet. Science lS5:696.
Bailey, C. B. 1967b. Silica excretion in cattle fed a ration predisposing to silica urolithia-
sis: Total excretion and diurnal variations. Am. J. Vet. Res. 28:1743.
Bailey, C. B. 1973. Formation of siliceous urinary calculi in calves given supplements
containing large amounts of sodium chloride. Can. J. Anim. Sci. 53:55.
Bailey, C. B. 1976a. Fate of the silica in prairie hay and alfalfa hay consumed by cattle.
Can. J. Anim. Sci. 56:213.
Bailey, C. B. 1976b. Effects of ammonium chloride on formation of siliceous urinary
calculi in calves. Can. J. Anim. Sci. 56:359.
Bailey, C. B. 1976c. Relation of water turnover to formation of siliceous calculi in calves
given high-salt supplements on range. Can. J. Anim. Sci. 56:745.
Beeson, W. M., J. W. Pence, and G. C. Holm. 1943. Urinary calculi in sheep. Am. J. Vet.
Res. 4:120.
Carlisle, E. M. 1974. Silicon as an essential element. Fed. Proc. 33:1758.
Connell, R., F. Whiting, and S. A. Forman. 1959. Silica urolithiasis in beef cattle. I.
Observation on its occurrence. Can. J. Comp. Vet. Sci. 23:41.
Emerick, R. J., L. 8. Embry, and O. E. Olson. 1959. Effect of sodium silicate on the
development of urinary calculi and the excretion of various urinary constituents in
sheep. J. Anim. Sci. 18:1025.
Gallup, W. D., C. S. Hobbs, and H. M. Briggs. 1945. The use of silica as a reference
substance in digestion trials with ruminants. J. Anim. Sci. 4:68.
Jones, L. H. P., and K. A. Handreck. 1967. Silica in soils, plants, and animals. Adv.
Agron. 19:107.
King, E. J., N. Rogers, and M. Gilchrist. 1946a. Attempts to prevent silicosis with
aluminum. J. Pathol. Bacterial. 57:281
King, E. J., N. Rogers, M. Gilchrist, and G. Nagelschudt. 1946b. A comparison of the
effects of laevorotatory and dextro-rotatory quartz on flee lungs of rats. J. Pathol.
Bacterial. 57:491.
McCullagh, K. G., and L. A. Ehrhart. 1974. Silica urolithiasis in laboratory dogs fed
semisynthetic diets. J. Am. Vet. Med. Assoc. 164:712.
Minson, D. J. 1971. Influence of lignin and silicon on a summative system for assessing
the organic matter digestibility of panicum. Aust. J. Agric. Res. 22:589.
Parker, G. 1957. "Water-belly" (urolithiasis) in range steers in relation to some charac-
teristics of rangeland. J. Range Manage. 10:105.
Schneider, B. H., E. D. Tayson, and W. E. Ham. ~Q52. Urinary Calculi in Male Farm
Animals. Wash. Agric. Exp. Stn. Circ. 203.
Schwarz, K. 1973. A bound form of silicon in glycosaminoglycans and polyuronides.
Proc. Natl. Acad. Sci. 70:1608.
Smith, G. S., and A. B. Nelson. 1975. Effects of sodium silicate added to Amen cultures
on forage digestion with interactions of glucose, urea and minerals. J. Anim. Sci.
41:891.
Smith, G. S., and N. S. Urquhart. 197S. Effect of sodium silicate added to rumen
cultures on digestion of siliceous forages. J. Anim. Sci. 41:882.
Smith. G. S., A. B. Nelson, and E. J. A. Boggino. 1971. Digestibility of forages in vitro
as affected by content of "silica." J. Anim. Sci. 33:466.
OCR for page 430
430 MINERAL TOLERANCE OF DOMESTIC ANIMALS
Smith, G. S., A. L. Neumann, A. B. Nelson, and E. E. Ray. 1972. Effects of"soluble
silica" upon growth of lambs. J. Anim. Sci. 34:839.
Smith, G. S., A. L. Neumann, V. H. Gledhill, and C. Z. Arzola. 1973. Effects of "soluble
silica" on growth, nutrient balance and reproductive performance of albino rats. J.
Anim. Sci. 34:839.
Staider, K., and W. Stober. 1965. Haemolytic activity of suspensions of different silica
modifications and inert dusts. Nature 207:874.
Van Soest, P. J. 1970. The role of silicon in the nutrition of plants and animals, p. 103.
In Proc. Cornell Univ. Conf. Feed Manuf.
Van Soest, P. J., and L. H. P. Jones. 1968. Effect of silica in forages upon digestibility.
J. Dairy Sci. 51:1644.
Whiting, F., R. Connell, and S. A. Forman. 1958. Silica urolithiasis in beef cattle. Can.
J. Comp. Pathol. 22:332.
Representative terms from entire chapter:
prairie hay
