Factors Related to Copper Status in Spring-Born Missouri
K. Tessman, DVM*
Jeff W. Tyler, DVM, PhD*†
Stan W. Casteel, DVM, PhD†
Robert L. Larson, DVM, PhD*‡
Richard F. Randle, DVM, MS*‡
Departments of *Veterinary Medicine and Surgery, †Veterinary Pathobiology, and ‡Veterinary
Extension, University of Missouri, Columbia, Missouri
KEY WORDS: copper deficiency, prevalence, risk factors,
cattle diseases, nutrition
This study determined the prevalence of copper deficiency
in Missouri feeder calves and described the relationship between management
factors and copper deficiency. Five hundred twenty-eight beef calves
aged 4 to 10 months were included in the study. Serum samples and survey
data were collected from calves throughout Missouri. Serum copper concentrations
were determined by atomic absorption spectrophotometry. Apparent and
real prevalence of copper deficiency were calculated for each agricultural
district as well as the overall prevalence for the entire state. Regression
models were developed predicting both serum copper concentration and
copper status. Associations between copper status and owner perceptions
of disease were examined with the use of Chi-squared tests. Calculated
real prevalence of the 9 agricultural districts ranged from 0%
to 53.1%. None of the questions regarding animal health
were significantly associated with copper deficiency. A number of management
factors were significantly associated with either serum copper concentration
or copper status (P <0.05). These included a number
of agricultural regions as well as legume-type forages, cow body condition,
and calf age. Access to creep feed and trace mineralized salt were significantly
associated with serum copper concentration and copper status. Copper
deficiency was commonly identified in many of the agricultural districts.
The most consistent risk factor identified in this study was agricultural
region. The relationship between geographic areas of copper deficiency
occurrence and the state’s 2 major rivers, the Missouri and Mississippi,
was the most intriguing factor identified. The true influence of these
rivers could not be determined with this study, but it warrants further
Copper is an essential micronutrient.1,2 Copper deficiency
has been associated with disease states that decrease commercial beef
production. Clinical manifestations of copper deficiency include anemia,
diarrhea, long bone fractures, generalized ill thrift, and decreased
Recent studies have demonstrated that copper deficiency
is common in North American beef cattle.2,5 Dargatz et al. found that
40.6% of the beef cows and heifers were either deficient
or marginally deficient. This study demonstrated that copper deficiency
was common even though half of the producers reported using a copper
supplement. It should be noted that Dargatz et al. used a test end point
of less than 0.65 mg/g serum
copper concentrations to define marginal deficiency. Results of a recent
study suggested that this test end point might have resulted in wholesale
misclassification of copper replete calves as copper deficient.6 A test
end point of less than or equal to 0.45 mg/g
best optimizes test performance.
The primary purpose of this study was to identify management
factors that would affect serum copper concentration and copper deficiency.
In addition, we wanted to determine whether copper status was related
to owner perceptions regarding the occurrence of disease. Although in
this study only herds from Missouri were surveyed, the conclusions reached
should be applicable in other areas. General management practices for
beef herds are similar across the Midwest and the vast majority of Missouri
calves are fed in other states.
MATERIALS AND METHODS
Sample and Survey Data Collection
data collection process was a systematic attempt to determine the copper
status of feeder calves throughout Missouri. The sampling strategy was
premised on geographic localities (counties) rather than proportionate
sampling of cattle populations. Private veterinary practitioner-collaborators
whose practice included a large beef cattle component were identified
throughout the state. Collaborator veterinarians collected blood samples
from 3 representative calves in each enrolled herd and obtained samples
from no more than 3 herds in each county. Sampling was performed at
the time of routine fall processing of calves and was restricted to
calves between the ages of 4 and 10 months. Practitioners completed
a questionnaire summarizing exposure to potential risk factors for copper
deficiency. The survey included questions regarding region, calf age
in months, pasture type, and mineral supplementation practices. Owners
also were asked whether diarrhea of mature cows, calf diarrhea, pneumonia,
fractures, abnormal hair coats, lameness, and cow fertility were perceived
as ongoing health problems in their herd.
Serum Copper Analysis
Serum samples were analyzed by use of atomic absorption
spectrophotometry (Perkin Elmer 2380 Atomic Absorption Spectrophotometer,
Perkin Elmer, Norwalk, CT; wavelength, 324.7 nm). Serum copper determination
was performed with external controls containing 1.99 mg/g copper, and copper standards of 1, 0.5, 0.2, and 0.1 mg/g were prepared by use of calibration reference
solution (Fisher Scientific Co., Fair Lawn, NJ) and 0.5% Triton X-100 (Fisher Scientific Co.). A standard
curve was generated through regression analysis of the copper standards.
One milliliter of serum was added to 1 mL of 0.5 % Triton X-100 in a plastic tube and processed
through a vortex before analysis. Copper concentrations of individual
samples were determined by comparison to the standard curve.
serum copper concentration was defined as a serum copper concentration
wet weight.6 Adequate serum copper concentrations were defined as >0.45
mg/g wet weight. Only calves for which serum
copper concentration and complete survey data were obtained were included.
Apparent prevalence (the proportion of calves with serum copper concentrations
was reported for each of the 9 agricultural districts (Northeast, North
Central, Northwest, West Central, Central, East Central, Southeast,
South Central, and Southwest) as defined by the Missouri Agriculture
Statistics Service (Missouri Department of Agriculture, Jefferson City,
MO). Additionally, real prevalence was defined using the following equation:
RP = (AP + Sp – 1)/(Se + Sp – 1),7 where
RP is real prevalence, AP is apparent prevalence, Se is sensitivity, and Sp is specificity.
Values used for sensitivity and specificity, 53% and 89%,
respectively, in the calculation were drawn from a previous study.6
Proportions were compared among districts using a 2-¥-9
Chi-squared test (SAS System for Windows, version 8, SAS Institute Inc.,
Cary, NC). Patterns of deficiency were deemed to differ when the calculated
value was less than 0.05. To calculate the statewide proportions of
calves with deficient copper status, we multiplied the proportion of
calves with low serum copper concentrations in each region times the
number of calves in the respective region to get the number of calves
in each region with less-than-optimal copper status. These numbers then
were summed and divided by the total state beef calf population,
yielding statewide weighted proportions.
between owner perceptions of herd health and calf serum copper concentrations
were explored using a series of Chi-squared tests. Observations were
cross-classified using 2-¥-2
tables defined by disease status (0, 1) and serum copper concentrations
Disease status variables included the presence of diarrhea in mature
cows, calf diarrhea, pneumonia, fractures, abnormal hair coats, lameness,
and cow fertility. Forward stepwise logistic regression models were
developed to predict the incidence of low serum copper status (£0.45 mg/g) as a function
of region, calf breed, calf age, animal health and husbandry practices,
pasture type, and mineral supplementation practices. In each regression
model, the independent variable with the smallest P-to-enter
was added at each step until no remaining variable had a P-to-enter
<0.05. Calculations were performed with the aid of a statistical
software package (SAS Institute Inc., Cary, NC).
Of the 528 calves studied, 34%
had access to creep feed and 71%
of the calves had access to trace mineralized salt. Eleven percent of
the calves originated from herds provided with supplemental hay and
16% of the calves originated from herds with supplemental
concentrates. Many of the operations fertilized pastures (84%). Fifty-eight percent of the operations used
only commercial fertilizer, 5%
used only manure from various species, and 21%
used both. The predominant pasture plant was fescue (94% of pastures); however, orchard grass (31%) and red clover (44%) were common. More detailed description of the study population
is available on request.
Serum copper concentrations varied from 0.06 to 2.25 mg/g. Eighteen percent, or 96 of the total number
of calves sampled, had serum copper concentrations less than or equal
to 0.45 mg/g (Fig. 1). Apparent
prevalence of low serum copper concentration (£0.45
mg/g wet weight) varied from
4% to 33%
among the 9 agricultural districts. The calculated real prevalence of
copper-deficient calves varied from 0%
to 53% by agricultural district.
The highest proportion of deficient calves was observed in the Southeast
district. Two districts, Southwest and South Central, were defined as
zero calculated real prevalence because the actual value calculated
was less than zero. The calculated statewide real prevalence of copper
deficiency was 17.1% (Table 1). The proportion of copper-deficient
calves differed among the 9 agricultural districts (P
<0.05). Low serum copper concentrations (£0.45
mg/g) were not significantly
associated with owner perceptions that cow diarrhea, poor hair coats,
infertility, calf diarrhea, pneumonia, fractures, or lameness were problems
in the herd.
regression model predicting serum copper concentration revealed a large
number of associations between serum copper concentration and independent
variables (Table 2). The Southwest and South Central regions, calves
more than 6 months of age, lespedeza pastures, creep feed, and trace
mineralized salt were associated with an increase in serum copper concentration.
The West and East Central regions, poor cow condition, and white clover
pastures were associated with a decrease in serum copper concentration.
The logistic regression model predicting copper deficient
status identified several significant associations with postulated independent
variables (Table 3). Ladino clover pastures were associated with copper-deficient
status. The Southwest and South Central regions, alfalfa pastures, and
providing creep feed and trace mineralized salt were associated with
a decreased likelihood of copper-deficient status.
Copper deficiency (£0.45
mg/g) was found in 7 of the
9 agricultural districts. Two districts, Southwest and South Central,
with no copper deficiency are located in the Ozark Plateau, a region
of relatively higher elevation. We estimated that more than 300,000
calves were copper-deficient. Inspection of a map of Missouri indicates
that the patterns of most severe copper deficiency were observed in
the Missouri and Mississippi River basins (Fig. 2). This observation
agrees with the observation that river silt pastures could be associated
with trace element deficiencies.8 Explanation of this phenomenon could
lie in a recent report describing the complex interaction of trace elements,
most notably zinc and copper, with dissolved organic matter in fresh
water.9 Highly stable complexes that are resistant to disassociation
Although fescue pastures were the most common forage provided
across the state (94%), this
was not significantly associated with copper status or serum copper
concentration. This is contrary to recent reports of endophyte-infected
fescue being associated with decreased available copper.10 The survey
made no attempt to differentiate endophyte versus non-endophyte-infected
fescue. In addition, the small number of operations (31 herds) that
did not use fescue limits the ability to detect differences.
Pasture types that were significantly associated with
serum copper concentration include lezpedeza (increased concentration)
and white clover pastures (decreased concentration). Pasture types significantly
associated with copper status are ladino clover pasture (positive) and
alfalfa (negative). In general, legumes tend to be higher in copper
concentration than grasses.11 This observation presents a conundrum
because all of these pasture types are legume-type forages. It is possible
that these disparities are the result of random chance. Given the strength
of the associations (Tables 2 and 3), this seems unlikely.
Not surprisingly, access to creep feed and trace mineralized
salt were positively associated with serum copper concentration and
negatively associated with the probability of copper deficiency. Both
of these practices are recommended as therapeutic preventatives for
Older calves had increased serum copper concentrations
and calves in herds with poor cow body condition had decreased serum
copper concentrations. Both of these relationships are intuitively logical.
Older calves will rely more heavily on pasture forage and concentrates.
Therefore, the risk of copper deficiency associated with a cow’s milk
diet will be decreased.12,13 In the instance of cows with poor body
condition, one can intimate that this is a reflection of overall herd
management. The fact that the cows themselves are in poor condition
suggests an overall lack of good-quality available feedstuffs. This
lack of quality feed easily could lead to a copper deficiency as well
as deficiencies in other micronutrients.
None of the health-related questions in the survey are
significantly associated with copper deficiency in this study. This
is of particular interest because most of the questions posed pertain
to disease syndromes that have been historically linked to copper deficiency.1,2,8
It is possible that there were too few of those syndromes observed to
make a statistically significant association. Other explanations could
include a lack of owner awareness to the various disease entities.
This research was
supported in part by United States Department of Agriculture Formula
Funds, the University of Missouri, Agriculture Experiment Station, and
the Department of Veterinary Medicine and Surgery, Committee on Research.
Additional support was provided by the Minority Biomedical Researchers
Training Initiative and the University of Missouri Chancellor’s Gus
T. Ridgel Fellowship for Underrepresented Minority Americans. The authors
acknowledge the technical assistance of private practitioners throughout
the state of Missouri in sample and survey data collection.
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Figure 1. Proportion of calves within each of 8
classes of serum copper concentration. The numbers appearing at the
top of each bar represent the total number of calves in each class.
The vertical dashed line (- - -) represents the test end point for copper
deficiency (£0.45 mg/g).
Classes are intervals of serum copper concentration of 0.15 mg/g, except
for the last class, which is any value greater than 1.05 mg/g.
1. Apparent and Calculated Real Prevalence of Copper Deficiency
by Agricultural Region*
Calves Calves Apparent
Real No. of
at Risk§ No. (£0.45 mg/g) Prevalence
15 0.174 0.153 34,203
North Central 222,000
9 0.188 0.185 40,964
22 0.222 0.267 32,330
West Central 240,000
7 0.194 0.201 48,253
18 0.222 0.267 122,910
East Central 136,000
16 0.291 0.431 58,580
2 0.040 0.000‡ 0
South Central 320,000
2 0.034 0.000‡ 0
5 0.333 0.531 20,738
of Forward Stepping Regression Model Predicting Serum Copper Concentration
(mg/g) as a Function of Various Husbandry
Variable Coefficient P Value
Intercept 0.53997 <0.0001
aged 7 to 10 months 0.07255 0.0019
Lespedeza 0.14705 <0.0001
mineralized salt 0.04573 0.0382
Results of Logistic Regression for Predicting
Copper Deficiency (£0.45
mg/g) in 528 Spring-Born Missouri Feeder
Calves as a Function of Various Husbandry Practices
Parameter Coefficient P Value Odds Ratio
Intercept -0.4945 0.0204
Southwest -1.9913 0.0069
clover 0.6524 0.0225
Alfalfa -2.4606 0.0215
feed -1.0001 0.0004
mineralized salt -0.8770 0.0004
Figure 2. Map of Missouri depicting
the 9 agricultural districts and the Missouri and Mississippi Rivers.
Gray-shaded regions have estimated real prevalence of copper deficiency
greater than 20%. Key for districts; 1 = Northwest, 2 = North
Central, 3 = Northeast, 4 = West Central, 5 = Central, 6 = East Central,
7 = Southwest, 8 = South Central, and 9 = Southeast.