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| Copper
In Nutrition |
The
following sections give an overview of copper as an essential
trace mineral in animal nutrition and a brief introduction
to Micronutrients TBCC®, an improved nutritional
source of copper.
The Role of Copper in Nutrition
Copper (Cu) is an essential trace element for all animals.
Deficiencies of Cu in commercial animal production are rare
in nonruminant animals, but are more common in ruminant animals.
Copper functions in the body as a component of (or cofactor
for) several important enzymes, the most notable of which
are listed below.
| Enzyme |
Function |
| Ceruloplasmin |
Oxidizes
Fe2+ to Fe3+ so iron can be absorbed from the
gut and then bound to transferrin (Fe transport) |
| Superoxide
dismutase (SOD) |
Catalyzes
the removal of superoxide radicals (O2-) |
| Cytochrome
C Oxidase |
Terminal
step in mitochondrial electron transport (ATP
production) |
| Amine
Oxidases |
Catalyzes
the oxidation of biogenic amines such as tyramine,
histamine and dopamine |
| Tyrosinase |
Synthesis
of melanin, norepinephrine and epinephrine |
| Lysyl
Oxidase |
Generates
crosslinking between connective tissue proteins
such as collagen and elastin; catalyzes removal
of the epsilon amino group of lysine |
| Mono-oxygenases |
Amidation
of peptide hormones (e.g., bornbesin, calcitonin,
gastrin, cholecystokinin) that are necessary for
hormone function |
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Because Cu is added in trace-mineral premixes to animal diets,
and because CuSO4·5H2O has been
used to provide pharmacologic levels of Cu for growth promotion
in swine and poultry, bioavailability of Cu in various Cu
sources is very important. The discussion that follows, therefore,
focuses on the relative bioavailability (RBV) of Cu (relative
to CuSO4·5H2O) in various sources
of Cu.
The true absorption efficiency of Cu from a mixed diet consumed
by humans has been estimated to range from 25% (high intakes)
to 50% (low intakes). Copper bioavailability is difficult
to quantify accurately. Hence, Cu accumulation in tissues
(primarily liver) increases only slightly (and curvilinearly)
between deficient levels and a dietary level of about 250
mg Cu/kg diet. Beyond this level, Cu accumulates rapidly and
generally in a linear fashion. Pig and chick work has shown
that the Cu in CuO is almost totally unavailable for absorption
from the gut. Work in D.H. Baker's laboratory at Illinois
established a bioavailability assay for Cu in chicks fed Cu
either above its requirement (liver Cu accumulation) or below
its requirement (gall bladder accumulation). Relative bioavailability
of Cu for various inorganic and feed-ingredient sources of
Cu were in good agreement between the two methods. Relative
to analytical-grade CuSO4·5H2O
, RBV values for Cu were 145% for analytical-grade CuCl and
95 to 115% for feedgrade CuSO4·5H2O,
Cu-lysine, and Cu-methionine. Other RBV values reported in
the Illinois work were 0% for both analytical-grade and feedgrade
CuO, 115% for analytical-grade Cu(OAC)·H2O,
100% for analytical-grade Cu2O and 100% for analytical-grade
CuCO3·Cu(OH)2. Among animal and
plant-source proteins, RBV values ranged from 0% for pork
liver to 115% for chicken liver. Intermediate values were
obtained for poultry by-product meal (90%), beef liver (80%),
corn gluten meal (50%), peanut hulls and soy mill run (45%),
cottonseed meal and dehulled soybean meal (40%), and rat liver
(20%).
Copper is excreted from the body primarily in feces. Thus,
50 to 75% of ingested Cu is unabsorbed, and that which is
absorbed and not incorporated into various proteins (e.g.,
enzymes, metallothionein) reenters the gut, primarily as a
component of bile. The form of Cu in bile is thought to be
unavailable for reabsorption into the body. Copper ingested
from fecal matter appears to be utilized no better than 30
to 50% relative to the Cu in CuSO4·5H2O.
This is of greatest importance for sheep grazing pastures
that have been treated with Cu-containing manure. Because
biliary excretion of Cu is inefficient in sheep, Cu toxicity
can be a problem in this species.
Copper absorption from the gut is reduced substantially if
Na2S (or other sulfides) are present in the diet. In ruminant
animals, excess Mo in forage can result in thiomolybdate formation
in the rumen. Thiomolybdates can bind Cu and reduce its absorption.
Other factors that reduce gut absorption of Cu are excess
dietary Zn and the presence of reducing agents in the diet,
such as ascorbic acid or cysteine. The extent to which phytate
complexes bind Cu is controversial. The absorption efficiency
of inorganic Cu may be up to three times greater when semi-purified
diets (e.g., casein-based diets) are fed as when conventional
corn-soybean meal diets are fed.
Micronutrients TBCC® - an Improved Copper
Source
The product trade name is derived from Tri-Basic Copper Chloride,
which can be thought of as a hybrid between copper chloride
(strongly acidic) and copper hydroxide (strongly alkaline),
in which three-fourths of the acidity has been neutralized.
The result is a salt that is totally insoluble in water and
yet very easily and quickly soluble in an animal's gut (a
low pH and complexing environment).
The low water solubility results in reduced reactivity in
a food or feed mixture, thus improving stability of vitamins
as well as fats and oils as shown both by vitamin assays done
directly on feed samples and by in vivo assays done on liver
tissue.
The solubility in gastric fluids is demonstrated by the fact
that ten of thirteen bioavailability assays that have been
conducted in nine different animal feeding studies gave RBV
values higher than analytical grade copper sulfate. Of the
remaining three, two gave equal RBV values, while one was
lower. Statistical analysis shows that, in the two studies
adequately designed and large enough to resolve differences
between the sources with a high degree of certainty, TBCC
had RBV's 120% and 138% (both at P<0.001) compared to copper
sulfate. In addition, several growth studies in swine and
chickens have shown that TBCC improves rate of gain and/or
feed:gain more that copper sulfate. The studies in cattle
showed that TBCC's low water solubility allowed it to bypass
the rumen, improving subsequent availability, thus simplifying
the challenge of maintaining a healthy copper status when
cattle are on diets antagonistic to copper absorption.
Suggested References
Aoyagi, S. and D.H. Baker. 1993. Bioavailability of copper
in analytical-grade and feed-grade inorganic copper sources
when fed to provide copper at levels below the chick's requirement.
Poultry Sci. 72:1075-1083.
Aoyagi, S., K.J. Wedekind and D.H. Baker. 1993. Estimates
of copper bioavailability from liver of different animal species
and from feed ingredients derived from plants and animals.
Poultry Sci. 72:1746-1755.
Baker, D.H. and C.B. Ammerman. 1995. Copper bioavailability.
In: Bioavailability of Nutrients for Animals: Amino Acids,
Minerals and Vitamins (Eds. C.B. Ammerman, D.H. Baker
and A.J. Lewis). Academic Press, pp. 127-157.
Funk, M.A. and D.H. Baker. 1991. Toxicity and tissue accumulation
of copper in chicks fed casein and soy-based diets. J. Anim.
Sci. 69:4505-4511.
Ledoux, D.R., P.R. Henry, C.B. Ammerman, P.V. Rao, and R.D.
Miles. 1991. Estimation of the relative bioavailability of
inorganic copper sources for chicks using tissue uptake of
copper. J. Anim. Sci. 69:215-222.
Miles, R.D., S.F. O'Keefe, P.R. Henry, C.B. Ammerman, and
X.G. Luo. 1998. The effect of dietary supplementation with
copper sulfate or tribasic copper chloride on broiler performance,
relative copper bioavailability, and dietary prooxidant activity.
Poultry Sci. 77:416-425.
Stahly, T.S., G.L. Cromwell, and H.J. Monegue. 1980. Effects
of the dietary inclusion of copper and(or) antibiotics on
the performance of weanling pigs. J. Anim. Sci. 51:1347-1351.
U.S. Patents Number 5,451,414; 5,534,043; and 6,265,438
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