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| Copper
Improves Poultry Production At Various Levels of Stress |
These three experiments represent a series with progressively
increasing challenge to the immune systems of the broilers.
Since they were done at different times and with different
strains of birds, these confounding factors prevent direct
performance comparisons between the tests. Nevertheless, the
patterns in copper source x level interaction and their impact
on bird performance within the studies are likely to be affected
primarily by the degree to which immune system challenges
were present.
Low Stress - Trial 99-MIC-04a-BB
In this trial, the Ross x Cobb birds were on wire. Three levels
of copper (125, 188 and 250 ppm) were added from each source
above the basal nutritional level provided to the control
birds by the mineral premix.
On TBCC, all elevated levels of copper gave significantly
better results (P<0.05) than the controls and than copper
sulfate at corresponding levels. 188 ppm was better than the
lower and higher levels, but differences between the three
were small.
On copper sulfate, those receiving 125 ppm copper performed
better than the control birds, but the two higher levels progressively
deteriorated performance until it was not different than the
controls.
Medium
Stress - Trial 97-MIC-07-B
These
Ross x HiY birds were grown on previously used litter, presumably
giving a higher level of ingestion of pathogenic microorganisms,
including Eimeria oocysts. Three levels of copper (125, 188
and 250 ppm) were added from each source.
For TBCC, performance at 188 ppm was again better than the
low and high levels, and was also better than copper sulfate
at any level.
On copper sulfate, performance at 125 ppm was not different
than controls. There was a progressive improvement with higher
copper levels, indicating that, under this disease challenge,
250 ppm is needed to get best performance.
High
Stress - Trial 99-MIC-03-BB
Cobb x Cobb birds were raised on previously used litter and
inoculated on Day 3 with both coccidia and Candida albicans
to induce crop mycosis. Two levels of copper (125 and 250
ppm) were added from each source above the basal nutritional
level provided to the control birds by the mineral premix.
Both levels of copper from both sources were better than controls.
250 ppm gave better performance than 125 ppm for both sources.
Discussion of Results
This work shows that the best economic performance level for
copper depends on the extent to which birds are exposed to
immune system challenge. This may help explain the range of
practical experience within the industry on a desirable level
of copper utilization. In this series of trials, Trial 97-MIC-07-B
is the closest approximation of field conditions in the industry
(healthy chicks on built-up litter). Under these conditions,
the optimum level of copper appears to be 188 ppm from
TBCC or 250 ppm from copper sulfate.
Use of 125 ppm copper from copper sulfate gives little or
no improvement over negative controls on built-up litter or
with a high level of immune system challenge. Conversely,
use of 250 ppm from that source is no better than negative
controls with a low challenge. The use of 188 ppm copper from
that source is a compromise that gives up considerable performance
under both low and high stress levels.
TBCC gives consistently good performance at 188 ppm copper
at low to medium stress levels. Data are not available for
that copper concentration with high stress, but interpolation
of the trends indicates it would be at least as good at 188
ppm as copper sulfate at 250 ppm copper.
In general commercial practice, copper is not used as a growth
promotant for birds grown on wire (such as replacement pullets),
since copper is often regarded as a means to counteract the
potentially negative effects of litter. This work shows that
there would be economic benefit to using 125 ppm of copper
from TBCC in such situations.
Presumed Mode of Action
TBCC is virtually insoluble in water. When used at high dietary
levels, it does not have sufficient time to completely dissolve
in the acidic environment of the stomach. In the intestine,
undissolved TBCC will continue to slowly solubilize due to
the action of natural organic complexing agents in digestive
fluids. Thus it displays a form of controlled release, giving
effectiveness over a long path-length of the intestine.
Copper sulfate is highly water soluble. Any copper not quickly
absorbed across intestinal membranes will be precipitated
in the neutral environment of the intestine as hydroxide and/or
sulfide salts. Both of these chemical forms of copper are
considerably less reactive than TBCC, giving less downstream
effectiveness against pathogenic organisms.
In healthy birds, the high soluble copper level provided by
copper sulfate actually reduces rate of gain and feed conversion
efficiency at levels above 125 ppm. The slow release provided
by TBCC minimizes this negative effect in unstressed birds.
Under moderate immune stress typical of commercial conditions,
higher copper is helpful, but the high solubility of copper
sulfate means that 33% more copper must be fed to achieve
the same effect as TBCC.
Impact
of Disease Stress
Feed Conversion vs. Copper Concentration |
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Body Weight vs. Copper Concentration |
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