J. Anim. Sci. 2003. 81:865-873
© 2003 American Society of Animal Science
Estimated copper requirements of Angus and Simmental heifers1
L. A. Mullis,
J. W. Spears2 and
R. L. McCraw
Department of Animal Science and Interdepartmental Nutrition Program, North Carolina State University, Raleigh 27695-7621
2 Correspondence:
phone: 919-515-4008; fax: 919-515-4463; E-mail:
Jerry_Spears{at}ncsu.edu.
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Abstract
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In Exp. 1, Simmental (n = 21) and Angus (n = 21) heifers, approximately 9 mo of age, were used in a 160-d study to determine the effect of dietary Cu on growth and Cu status. Two- or three-yr-old first-calf heifers (21 Angus and 21 Simmental) entering into their last trimester of pregnancy were used in Exp. 2 to estimate Cu requirements of the two breeds during gestation and early lactation. Treatments in both studies consisted of 0 (control), 7, or 14 mg of supplemental Cu (as CuSO4)/kg of DM. The control corn silage-based diets contained 6.4 and 4.4 mg of Cu/kg of DM in Exp. 1 and 2, respectively, and 1.2 mg of Mo/kg. Dietary Cu did not affect performance in either breed in Exp. 1. Copper supplementation generally did not affect plasma Cu concentrations in Angus heifers, but increased (P < 0.05) plasma Cu in Simmental heifers from d 37 until the end of Exp. 1. Final liver Cu concentrations were lower (P < 0.05) than initial concentrations in control Angus and Simmental heifers; however, liver Cu increased (P < 0.01) in Cu-supplemented heifers. In Exp. 2, Cu supplementation of the control diet increased (P < 0.05) plasma Cu during gestation and greatly increased (P < 0.01) liver Cu in both breeds. Calves born to cows not supplemented with Cu also had lower plasma Cu concentrations than Cu-supplemented calves by 73 d of age. In both studies, control Simmental heifers had lower (P < 0.05) plasma Cu concentrations than Angus on most sampling dates. When Cu was supplemented at 7 or 14 mg/kg of DM, few differences in plasma Cu concentrations were observed between breeds. Results suggest that Angus heifers have a lower minimal Cu requirement than Simmental. Based on liver Cu, the control diets containing 4.4 or 6.4 mg of Cu/kg of DM did not meet the Cu requirement of either breed during gestation and lactation or growth. Addition of 7 mg of Cu/kg of DM to the control diets met Cu requirements of both breeds.
Key Words: Angus • Copper • Heifers • Simmental
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Introduction
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Copper deficiency can develop in cattle when their diet contains less Cu than is required or when absorption and utilization of dietary Cu is inhibited by other minerals (Wikse et al., 1992). Antagonists, such as Mo, S, and Fe, at high concentrations can increase dietary requirements of Cu (McDowell, 1992).
The Cu requirement of a specific species of animal also may be affected by breed. Weiner et al. (1978) found that Cu repletion rates differed significantly among three breeds of sheep, and Woolliams et al. (1983) reported that Blackface and Welsh sheep differed in liver Cu concentration. Few studies have been conducted to study the effect of breed on Cu status in cattle. Smart and Christensen (1985) found that Simmental-sired heifers had lower plasma Cu concentrations than Hereford- or Angus-sired heifers. In the absence of supplemental Cu, Angus cattle had higher plasma Cu concentrations than Simmental or Charolais cattle (Ward et al., 1995). Simmental steers also had lower liver and plasma Cu concentrations than Angus steers when fed diets high in Fe (Mullis et al., 2003). Gooneratne et al. (1994) reported that biliary Cu excretion was approximately twofold higher in Simmental heifers than in Angus heifers when fed identical diets. The objective of the present experiments was to estimate the Cu requirement of Simmental heifers during growth, gestation, and early lactation and to compare with data from Angus heifers.
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Materials and Methods
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Care, handling, and sampling of the animals herein were approved by the North Carolina State University Animal Care and Use Committee.
Experiment 1
Angus (n = 21) and Simmental (n = 21) heifers were used to estimate Cu requirement of the two breeds during growth. Heifers were approximately 9 mo old and had an initial BW of 271.1 kg. Heifers were stratified by initial plasma Cu concentration within breed and randomly assigned to treatments. Treatments consisted of 0, 7, or 14 mg of supplemental Cu/kg of DM. Supplemental Cu was provided in the form of CuSO4. There were 14 animals per treatment and seven heifers per treatment of each breed.
All heifers had been maintained on similar pastures and fed a free-choice mineral (contained 1,000 mg of Cu/kg) that should have provided adequate Cu prior to the study. The basal diet consisted (DM basis) of 90% corn silage (34.7% DM) and 10% of a protein, mineral, and vitamin supplement (Table 1
). The basal diet analyzed 6.4 mg of Cu/kg and 11.1% CP on a DM basis. The diet also analyzed low in Mo (0.2 mg/kg). Therefore, 1 mg of Mo/kg of diet, as sodium molybdate, was added to all diets to simulate a level of Mo that might be expected in grazing situations. Heifers were housed in covered, slotted-floor pens and individually fed using electronic feeders (American Calan, Northwood, NH). Feed was offered once daily with feed offerings based on the amount each heifer would consume in a 24-h period. Two consecutive weights were taken at the beginning and end of the 160-d experiment, with intermediate weights taken on d 37, 65, 93, and 121. Blood samples were obtained on d 0, 37, 65, 93,121, and 149. Blood was taken via jugular venipuncture into heparinized vacuum tubes specifically designated for trace mineral analysis (Vacutainer 9735, Becton Dickinson, Rutherford, NJ). Plasma was frozen until analysis for concentrations of Cu and ceruloplasmin activity. Liver biopsies were obtained for Cu analysis by the method of Erwin et al. (1956) at the beginning and at the termination of the study.
Experiment 2
Forty-two 2- or 3-yr-old first-calf heifers (21 Angus and 21 Simmental) entering the last trimester of gestation were used to estimate Cu requirements of the two breeds during gestation and early lactation. Average initial weights were 534 and 546 kg for Angus and Simmental heifers, respectively. Heifers were blocked by initial plasma Cu concentration and then randomly allotted to the three treatments described for Exp. 1. The diet consisted of 94% corn silage (43.3% DM) and 6% of a protein, mineral, vitamin supplement on a DM basis (Table 1
). The basal diet was analyzed to contain 4.4 mg of Cu/kg and 10.3% CP. Sodium molybdate (1 mg of Mo/kg) was added to the basal diet. Heifers were housed and group-fed in 12 covered, slotted-floor pens containing three or four animals each. The 3-yr-old heifers each received 7.9 kg of diet DM/day prior to calving. The 2-yr-old heifers each received 8.6 kg of DM/d prior to calving. Heifers were moved to small, dry pasture lots when the first calf was born (d 90). All calves were born between d 90 and 137 of the study. During this time, heifers were group-fed by breed and Cu treatment. On d 140, heifers and calves were moved back to covered pens and feed was offered ad libitum. Weights and blood samples for heifers were obtained on d 0, 28, 56, 84, 112, 140, 168, 196, and 224. Weights and blood samples were obtained for the calves on d 168, 196, and 224. Calves averaged 45, 73, and 101 d of age, respectively, when blood samples were obtained. Blood was taken via jugular venipuncture into heparinized vacuum tubes. Plasma was frozen until analyzed for Cu concentration and ceruloplasmin activity. Liver biopsies (Erwin et al., 1956) were taken from the heifers at the beginning and end of the study for liver Cu analysis.
Analytical Procedures
For determination of plasma Cu concentration, plasma was diluted 1:3 with deionized water and aspirated into the flame of an atomic absorption spectrophotometer (model 5000, Perkin Elmer, Norwalk, CT). Standards for plasma Cu were prepared in 10% glycerin. Plasma ceruloplasmin activity was determined by the method of Houchin (1958) and is reported as absorbance units at 525 nm. Liver biopsy samples were dried at 100°C for 72 h and wet-ashed in a microwave digester (model MDS-81D, CEM, Matthews, NC). Samples were placed into Teflon-lined digestion vessels, 10 mL of trace mineral grade nitric acid was added, and the samples were allowed to digest for 1 h at room temperature. Sealed vessels were then placed in the microwave digester at 49% power setting for 45 min, 35% power for 45 min, and 0 power for 10 min. Vessels were vented, 2 mL of 30% hydrogen peroxide was added, and unpressurized samples were then placed back in the microwave digester for 5 min at 50% power. Feed samples were ashed in the same manner; however, feed samples were only allowed to digest for 30 min and were placed in the microwave for 5 min at 50% power, 15 min at 70% power, and 10 min at 0 power. After the addition of hydrogen peroxide, samples were placed back in the microwave for 3 min at 50% power and 2 min at 0 power. Ashed samples were analyzed for Cu by atomic absorption spectrophotometry (model 5000, Perkin Elmer).
Statistical Analysis
Data were analyzed by least squares ANOVA using the GLM procedure of SAS (SAS Inst., Inc., Cary, NC). Plasma and liver data were analyzed by repeated measures in the GLM procedure of SAS using main effects of treatment, breed, treatment x breed, time, treatment x time, breed x time, and treatment x breed x time. The model for performance data included treatment, breed, and treatment x breed. Differences among treatment means were determined using the F-protected LSD test.
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Results
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Experiment 1
Plasma Cu concentrations were affected by a treatment x breed x time (P < 0.01) interaction (Table 2). Copper supplementation of the control diet increased (P < 0.01) plasma Cu from d 37 until the end of the study in Simmental heifers. Simmental heifers supplemented with 14 mg of Cu had higher (P < 0.01) plasma Cu concentrations than those supplemented with 7 mg of Cu/kg of DM. Plasma Cu concentrations in Angus heifers were only affected by dietary Cu supplementation on d 93 and 121. On these two sampling days, plasma Cu was higher (P < 0.05) in Angus heifers supplemented with 14 mg of Cu/kg of DM compared to control heifers.
Plasma Cu was also affected by a treatment x breed (P < 0.01) interaction (Table 2). In animals not supplemented with Cu, Simmental heifers had lower (P < 0.01) plasma Cu concentrations than Angus from d 37 until the end of the study. No breed differences were observed when Cu was supplemented at 7 mg/kg; however, when Cu was supplemented at 14 mg/kg of DM, Simmental heifers tended to have higher plasma Cu concentrations than Angus heifers, with breed differences significant (P < 0.05) on d 65 and 121.
Plasma ceruloplasmin activity was affected by a treatment x time (P < 0.01) interaction (Table 3). Simmental heifers in control group had lower ceruloplasmin activity (P < 0.05) than those supplemented with 7 mg of Cu/kg of DM on d 65, 93, and 121, and lower activity (P < 0.01) than those supplemented with 14 mg of Cu/kg of DM on d 37 and at subsequent sampling d. Heifers supplemented with 7 mg of Cu/kg of DM had lower (P < 0.05) ceruloplasmin activity than Simmental heifers fed 14 mg of Cu/kg of DM on d 65 and 121. Dietary copper did not affect ceruloplasmin activity in Angus heifers.
Plasma ceruloplasmin activity was affected by a treatment x breed interaction (P < 0.05; Table 3) at all sampling days (other than d 0). When heifers were given no supplementary Cu, Simmental heifers had lower (P < 0.05 on d 0 and 37; P < 0.01 on d 65, 93, 121, and 149) ceruloplasmin activities than Angus throughout the entire study. However, there were no breed effects on ceruloplasmin activity when heifers were supplemented with 7 or 14 mg of Cu/kg of DM.
Liver Cu concentrations were affected by time (P < 0.01), time x treatment (P < 0.01) and a time x breed interaction (P < 0.10; Table 4). Initial liver Cu concentrations were not significantly affected by breed, although Simmental heifers tended (P < 0.15) to have lower liver Cu than Angus. Copper supplementation greatly increased (P < 0.01) final liver Cu and heifers supplemented with 14 mg of Cu had higher (P < 0.01) liver Cu concentrations than those receiving 7 mg of Cu/kg of DM. Compared with initial concentrations, final liver Cu concentrations decreased (P < 0.01) in controls, but increased (P < 0.01) in Cu-supplemented heifers. Final liver Cu concentrations were not affected by breed because of the variation in liver Cu concentrations observed in animals supplemented with Cu. An ANOVA of final liver Cu using only data from heifers not supplemented with Cu indicated that liver Cu was lower (P < 0.01) in Simmental (21.1 ± 3.7) vs. Angus (48.3 ± 7.0) heifers. However, in heifers supplemented with 7 or 14 mg of Cu/kg of DM, liver Cu was not affected by breed.
Performance of heifers is shown in Table 5. There were no significant differences among Cu treatments or between Angus and Simmental heifers in daily gain, feed intake, or gain/feed.
Experiment 2
Ten heifers were removed from the study due to loss of calf at birth, abortion, or being open. Three Angus heifers were open (one from each treatment). Three Angus heifers had calves that were dead at birth or died shortly after birth in the 7 mg-Cu treatment and one Angus heifer in the 14 mg-Cu treatment aborted. Three Simmental heifers, all from the control group, were removed because of one being open, one abortion, and one stillborn calf.
Birth weights were heavier (P < 0.01) for Simmental (40.8 vs. 34.8 kg, SEM = 1.2) compared to Angus calves. Simmental calves also had higher (P < 0.05; 145 vs. 120, SEM = 7.5) final weights than Angus when adjusted for sex and age. Calves averaged 112 d of age at the termination of the study. Dietary Cu did not affect birth weights, final weights, or ADG of calves. Cow weight change during the study was not affected by Cu or breed.
Plasma Cu concentrations in heifers were affected by a treatment x breed x time (P < 0.01) interaction (Table 6). Supplementing Angus heifers with 7 mg of Cu/kg of DM increased (P < 0.05) plasma Cu concentrations over that observed in control Angus heifers on d 28, 84, 112, 140, and 224. Angus heifers supplemented with 14 mg of Cu/kg of DM had higher (P < 0.05) plasma Cu concentrations than control heifers on d 28, 56, 84, 112, 140, and 224. Simmental heifers fed the control diet had lower (P < 0.05) plasma Cu concentrations than Cu-supplemented heifers on all sampling dates with the exception of d 0, 56, and 224. Plasma Cu concentrations in control Simmental heifers decreased to levels (<0.5 mg/L) indicative of Cu deficiency by d 112. After calving, plasma Cu concentrations began to rise and reached concentrations of 0.93 mg/L on d 224. Plasma Cu concentrations did not differ between heifers supplemented with 7 mg of Cu and those supplemented with 14 mg of Cu/kg of DM for either breed.
Control Simmental heifers had lower (P < 0.05) plasma Cu concentrations than control Angus heifers on d 0, 28, 84, 112, 140, and 168 (Table 6). Angus heifers maintained normal-range plasma Cu concentrations throughout the study, whereas control Simmental heifers experienced a drop in plasma Cu concentrations from d 84 to 168. When heifers were supplemented with 7 mg of Cu/kg of DM, there were no breed differences with the exception of d 0 (P < 0.05) and 28 (P < 0.01) when Simmental heifers were lower than Angus. When 14 mg of Cu/kg of DM was supplemented there were breed differences on d 0 (P < 0.01) and d 28 and 84 (P < 0.05) with Simmental heifers having slightly lower plasma Cu concentrations.
Plasma ceruloplasmin activity was affected (P < 0.05) by a treatment x breed and a treatment x breed x time interaction (Table 7). Copper-supplemented Simmental heifers had higher (P < 0.05) ceruloplasmin activity than controls on d 28, 84, 112, 140, and 168. Ceruloplasmin activity in Angus heifers did not differ among treatments except on d 140 and 224 when control heifers were lower (P < 0.01) than those supplemented with 7 mg of Cu/kg of DM.
When heifers were provided with no supplemental Cu, Simmental heifers tended to have lower ceruloplasmin activity than Angus heifers (Table 7). There were significant differences (P < 0.01) between the two breeds on d 28, 84, 112, 140, and 168. When Cu was supplemented at 7 mg/kg of DM, Simmental heifers had lower (P < 0.05) ceruloplasmin activity than Angus only on d 28 and 224. At the higher level of Cu supplementation, ceruloplasmin activity differed among breeds only on d 28, with Simmental heifers being lower (P < 0.05) than Angus heifers.
Liver Cu concentrations were affected by breed (P < 0.07) time (P < 0.01) and time x treatment (P < 0.01; Table 8). Simmental heifers had lower (P < 0.01) initial liver Cu concentrations than Angus. Breed did not affect final liver Cu concentrations. Only four control Simmental heifers finished the experiment and liver Cu was highly variable in these animals. Final liver Cu concentrations for these heifers were 84.0, 59.3, 9.4 and 9.1 mg/kg of DM. Copper supplementation greatly increased (P < 0.01) final liver Cu concentrations and heifers supplemented with 14 mg of Cu had higher liver Cu than those receiving 7 mg of Cu/kg of DM.
Calf plasma Cu concentrations were affected by a treatment x breed x time (P < 0.05) interaction (Table 9). Angus control calves had lower (P < 0.05) plasma Cu concentrations than those supplemented with either 7 or 14 mg of Cu/kg of DM on d 45, 73, and 101 after calving. Simmental calves had similar plasma Cu concentrations on d 45 after calving; however, on d 73 after calving, there were significant differences (P < 0.05) among all three treatments. Control calves were lower (P < 0.05) than calves supplemented with either 7 or 14 mg of Cu/kg of DM. Calves supplemented with 7 mg of Cu/kg of DM also had lower (P < 0.05) plasma Cu concentrations than those supplemented with the higher level of Cu. At the end of the study (101 d after calving), Simmental calves fed the control diet had lower (P < 0.01) plasma Cu concentrations than calves being supplemented with Cu. In unsupplemented calves, Simmental had lower (P < 0.07) plasma Cu concentrations than Angus calves on d 73 and 101 after calving. When calves were fed 7 mg of Cu/kg, Simmentals had lower (P < 0.01) plasma Cu levels on d 73 and 101 after calving. Plasma Cu concentrations were similar in the two breeds when calves and their dams were supplemented with 14 mg of Cu/kg of DM.
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Table 9. Effect of dietary copper on plasma copper concentrations in nursing Angus and Simmental calves (Exp. 2)a
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Discussion
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In the present studies, plasma Cu, plasma ceruloplasmin activity and liver Cu concentration were used to estimate Cu requirements. Plasma Cu and ceruloplasmin activity followed the same pattern in both experiments. This was expected because 80 to 90% of Cu in plasma occurs as ceruloplasmin (Underwood and Suttle, 1999). Plasma Cu concentrations in Simmental heifers not supplemented with Cu declined during both experiments to levels indicative of at least marginal deficiency. All Angus heifers and Cu-supplemented Simmental heifers maintained plasma Cu concentrations above 0.8 mg/L, which is considered to be in the adequate range (Underwood, 1977). Gestation is the likely cause of the rapid decline in plasma Cu and ceruloplasmin activity from d 84 to 140 in Simmental heifers not supplemented with Cu in Exp. 2. Large quantities of Cu are deposited in the fetus during late gestation, and this can decrease Cu status of the dam if dietary Cu is low (Gooneratne and Christensen, 1989). Plasma Cu increased in control Simmental heifers following calving. During lactation, only small amounts of Cu are secreted in milk. This may explain the rise in plasma Cu postpartum. Genglebach et al. (1994) also observed a decline during gestation and an increase in plasma Cu during lactation in heifers fed low-Cu diets.
When heifers in both studies were not supplemented with Cu, Simmental heifers consistently had lower plasma Cu concentrations than Angus heifers. Ward et al. (1995) reported that Angus heifers had greater plasma Cu concentrations than Charolais and Simmental heifers when fed diets low in Cu. Simmental steers also had lower serum and liver Cu concentrations than Angus steers when fed diets high in Fe (Mullis et al., 2003). The lower plasma Cu concentrations in Simmental cattle may relate to increased excretion of absorbed Cu via bile. Bile is the major route of excretion of absorbed Cu (Gooneratne et al., 1989), and biliary Cu excretion has been reported to be much greater in Simmental than in Angus heifers (Gooneratne et al., 1994). In the present study, breed differences in Cu status were generally not seen when the control diets were supplemented with 7 or 14 mg of Cu/kg of DM.
Heifers in Exp. 1 began the study with adequate liver Cu status; however, final liver Cu concentrations (21.1 mg/kg of DM) of unsupplemented Simmentals had declined to levels indicative of a Cu deficiency (Underwood, 1977). This result, coupled with decreased plasma Cu and ceruloplasmin, indicates that 6.4 mg of Cu/kg of DM in the basal diet was not adequate for growing Simmental heifers. The control diet, containing 4.4 mg of Cu/kg of DM, also did not meet the Cu requirements of pregnant Simmental heifers in Exp. 2 based on reduced dam plasma Cu concentrations in late gestation and low plasma Cu in calves by at least 73 d of age. The declining plasma Cu in control calves with increasing age suggests that these calves were born with low liver Cu concentrations. The liver serves as a major Cu store in ruminants and plasma Cu does not generally decrease in cattle until liver Cu concentrations decline to 40 mg/kg of DM or lower (Claypool et al., 1975).
Although plasma Cu concentrations remained in the adequate range for unsupplemented Angus heifers, liver Cu concentrations decreased for heifers in both experiments. The decrease in liver Cu observed in control Angus heifers during the 160- (Exp. 1) and 224-d (Exp. 2) experiments indicates that basal diets in both experiments were inadequate in Cu to maintain initial liver Cu stores.
Results of these studies suggest that Angus females have a lower minimal Cu requirement than Simmental heifers. Plasma Cu concentration declined during the studies in Simmental heifers fed the control diets but not in Angus heifers. Growth and feed efficiency were not affected by the low plasma and liver Cu concentrations observed in Simmental heifers. Therefore, it is possible that Simmental cattle may have a lower metabolic requirement for Cu than Angus. Based on liver Cu status, the basal diets containing 4.4 or 6.4 mg of Cu/kg of DM did not meet the Cu requirement of Simmental or Angus heifers during gestation and lactation, or growth. Addition of 7 mg of Cu/kg of DM to the basal diet met the Cu requirements of both breeds and resulted in increases in liver Cu. This indicates that with diets containing approximately 1.2 mg of Mo/kg of DM and 0.26% S, total dietary Cu (basal + supplemental) concentrations of 11.4 and 13.4 mg/kg of DM were adequate for first calf heifers and growing heifers, respectively.
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Implications
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A diet containing 4.4 mg of copper/kg of dry matter did not meet the copper requirement of Simmental or Angus heifers during gestation and early lactation. Similarly, based on a decrease in liver copper over time, a diet containing 6.4 mg of copper/kg of dry matter did not meet the copper requirement of growing Angus or Simmental heifers. Simmental heifers seem to have a higher minimal copper requirement than Angus. However, supplementing the basal diets with 7 mg of copper/kg of dry matter met the copper requirement of both breeds.
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Footnotes
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1 Use of trade names in this publication does not imply endorsement by the North Carolina ARS or criticism of similar products not mentioned. 
Received for publication September 6, 2002.
Accepted for publication December 17, 2002.
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Literature Cited
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Claypool, D. W., F. W. Adams, H. W. Pendell, N. A. Hartmann, and J. F. Bone. 1975. Relationship between the level of copper in the blood plasma and liver of cattle. J. Anim. Sci. 41:911–914.
Erwin, E. S., I. A. Dyer, T. O. Meyer, and K. W. Scott. 1956. Uses of aspiration biopsy technique. J. Anim. Sci. 15:428–434.[Abstract/Free Full Text]
Gengelbach, G. P., J. D. Ward, and J. W. Spears. 1994. Effect of dietary copper, iron and molybdenum on growth and copper status of beef cows and calves. J. Anim. Sci. 72:2722–2727.[Abstract]
Gooneratne, S. R., and D. A. Christensen. 1989. A survey of maternal copper status and fetal tissue copper concentrations in Saskatchewan bovine. Can. J. Anim. Sci. 69:141–150.
Gooneratne, S. R., W. T. Buckley, and D. A. Christensen. 1989. Review of copper deficiency and metabolism in ruminants. Can. J. Anim. Sci. 69:819–845.
Gooneratne, S. R., H. W. Symonds, J. V. Bailey, and D. A. Christensen. 1994. Effects of dietary copper, molybdenum and sulfur on biliary copper and zinc excretion in Simmental and Angus cattle. Can. J. Anim. Sci. 74:315–325.
Houchin, O. B. 1958. A rapid colorimetric method for the quantitative determination of copper oxidase activity. (ceruloplasmin). Clin. Chem. 4:519–523.[Abstract]
McDowell, L. R. 1992. Minerals in Animal and Human Nutrition. Academic Press, San Diego, CA.
Mullis, L. A., J. W. Spears, and R. L. McCraw. 2003. Effect of breed (Angus vs Simmental) and copper and zinc source on mineral status of steers fed high dietary iron. J. Anim. Sci. 81:318–322.[Abstract/Free Full Text]
Smart, M. E., and D. A. Christensen. 1985. The effect of cow’s dietary copper intake, sire breed, and age on her copper status and that of her fetus in the first ninety days of gestation. Can. J. Comp. Med. 49:156–158.[Medline]
Underwood, E. J. 1977. Trace Elements in Human and Animal Nutrition. 4th ed. Academic Press, New York.
Underwood, E. J., and N. F. Suttle. 1999. The Mineral Nutrition of Livestock. 3rd ed. CABI Publishing, New York.
Ward, J. D., J. W. Spears, and G. P. Genglebach. 1995. Differences in copper status and copper metabolism among Angus, Simmental, and Charolais cattle. J. Anim. Sci. 73:571–577.[Abstract]
Wiener, G., N. F. Suttle, A. C. Field, J. G. Herbert, and J. A. Woolliams. 1978. Breed differences in copper metabolism in sheep. J. Agric. Sci. 91:433–441.
Wikse, S. E., D. Herd, R. Field, and P. Holland. 1992. Diagnosis of copper deficiency in cattle. J. Am. Vet. Med. Assoc. 200:1625–1629.[Medline]
Woolliams, J. A., N. F. Suttle, G. Wiener, A. C. Field, and C. Woolliams. 1983. The long-term accumulation and depletion of copper in the liver of different breeds of sheep fed diets of differing copper content. J. Agric. Sci. 100:441–449.
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Abstract
Introduction
