Effects of dietary copper concentration and source on performance and copper status of growing and finishing steers

Performance and Cu status were measured in growing and finishing steers supplemented with different copper (Cu) concentrations and sources. Sixty Angus (n = 36) and Angus x Hereford (n = 24) steers were stratified by weight and initial liver Cu concentration within a breed and randomly assigned to treatments. Treatments consisted of 1) control (no supplemental Cu); 2) 20 mg Cu/kg DM from Cu sulfate (CuSO4); 3) 40 mg Cu/kg DM from CuSO4; 4) 20 mg Cu/ kg DM from Cu citrate (C6H4Cu2O7); 5) 20 mg Cu/kg DM from Cu proteinate; and 6) 20 mg Cu/kg DM from tribasic Cu chloride (Cu2(OH)3Cl). A corn silage-soybean meal-based diet that was analyzed to contain 10.2 mg of Cu/kg DM was fed for 56 d. Steers were then switched to a high-concentrate diet that was analyzed to contain 4.9 mg of Cu/kg DM. Equal numbers of steers per treatment were slaughtered after receiving the finishing diets for either 101 or 121 d. Performance was not affected by Cu level or source during the growing phase. Gain, feed intake, and feed efficiency were reduced (P < .05) by Cu supplementation during the finishing phase. Plasma and liver Cu concentrations were higher in steers receiving supplemental Cu at the end of both the growing and finishing phases. Steers supplemented with 40 mg Cu/kg DM from CuSO4 had higher (P < .05) liver Cu concentrations than those supplemented with 20 mg Cu/kg DM from CuSO4. Liver Cu concentrations did not increase over the finishing phase relative to liver Cu concentrations at the end of the growing phase. These results indicate that as little as 20 mg/kg of supplemental Cu can reduce performance in finishing steers.     

Bioavailability of copper from copper glycinate in steers fed high dietary sulfur and molybdenum

Sixty Angus (n = 29) and Angus-Sim-mental cross (n = 31) steers, averaging 9 mo of age and 277 kg of initial BW, were used in a 148-d study to determine the bioavailability of copper glycinate (CuGly) relative to feed-grade copper sulfate (CuSO(4)) when supplemented to diets high in S and Mo. Steers were blocked by weight within breed and randomly assigned to 1 of 5 treatments: 1) control (no supplemental Cu), 2) 5 mg of Cu/kg of DM from CuSO(4), 3) 10 mg of Cu/kg of DM from CuSO(4), 4) 5 mg of Cu/kg of DM from CuGly, and 5) 10 mg of Cu/kg of DM from CuGly. Steers were individually fed a corn silage-based diet (analyzed 8.2 mg of Cu/kg of DM), and supplemented with 2 mg of Mo/kg of diet DM and 0.15% S for 120 d (phase 1). Steers were then supplemented with 6 mg of Mo/kg of diet DM and 0.15% S for an additional 28 d (phase 2). Average daily gain and G:F were improved by Cu supplementation regardless of source (P = 0.01). Final ceruloplasmin, plasma Cu, and liver Cu values were greater (P < 0.05) in steers fed supplemental Cu compared with controls. Plasma Cu, liver Cu, and ceruloplasmin values were greater (P < 0.05) in steers supplemented with 10 mg of Cu/kg of DM vs. those supplemented with 5 mg of Cu/kg of DM. Based on multiple linear regression of final plasma Cu, liver Cu, and ceruloplasmin values on dietary Cu intake in phase 1 (2 mg of Mo/kg of DM), bioavailability of Cu from CuGly relative to CuSO(4) (100%) was 140 (P = 0.10), 131 (P = 0.12), and 140% (P = 0.01), respectively. Relative bio-availability of Cu from CuGly was greater than from CuSO(4) (P = 0.01; 144, 150, and 157%, based on plasma Cu, liver Cu, and ceruloplasmin, respectively) after supplementation of 6 mg of Mo/kg of DM for 28 d. Results of this study suggest that Cu from CuGly may be more available than CuSO(4) when supplemented to diets high in S and Mo.     

Effects of dietary copper source and concentration on carcass characteristics and lipid and cholesterol metabolism in growing and finishing steers

We conducted an experiment to determine the effects of dietary copper (Cu) source and level on carcass characteristics, longissimus muscle fatty acid composition, and serum and muscle cholesterol concentrations in steers. Sixty Angus and Angus x Hereford steers were stratified by weight and initial liver Cu concentration within a breed and randomly assigned to treatments. Treatments consisted of: 1) control (no supplemental Cu); 2) 20 mg Cu/kg DM from Cu sulfate (CuSO4); 3) 40 mg Cu/kg DM from CuSO4; 4) 20 mg Cu/kg DM from Cu citrate; 5) 20 mg Cu/kg DM from Cu proteinate; and 6) 20 mg Cu/kg DM from tribasic Cu chloride. A corn silage-soybean meal-based diet was fed for 56 d. Steers were then switched to a high-concentrate diet. Equal numbers (n = 5) of steers per treatment were slaughtered after receiving the finishing diets for either 101 or 121 d. Serum cholesterol was not affected by treatment during the growing phase but was decreased (P < .05) in steers supplemented with Cu by d 84 of the finishing period and remained lower (P < . 05) at subsequent sampling periods. Longissimus muscle cholesterol concentration tended to be reduced (P < .11) by Cu supplementation. Hot carcass weight and backfat were lower (P < .05) in animals receiving supplemental Cu. However, Cu-supplemented and control steers had similar marbling scores. Longissimus muscle polyunsaturated fatty acid concentrations (18:2 and 18:3) were increased (P < .07) and saturated fatty acid concentrations tended (P < . 11) to be reduced by Cu supplementation. These results indicate that as little as 20 mg of supplemental Cu/kg diet can reduce backfat and serum cholesterol and increase muscle polyunsaturated fatty acids in steers fed high-concentrate diets.     

Estimated copper requirements of angus and simmental heifers

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.     

Dietary copper effects on lipid metabolism, performance, and ruminal fermentation in finishing steers

Sixty Angus steers (391.1+/-6.1 kg) were used to determine the effects of dietary Cu concentration on lipid metabolism and ruminal fermentation. Steers were stratified by weight and randomly assigned to treatments. Treatments consisted of 0 (control), 10, or 20 mg of supplemental Cu (as CuSO4)/kg diet DM. Steers were housed in pens equipped with individual electronic Calan gate feeders. On d 86 and 92, ruminal fluid was collected from two steers/treatment for IVDMD determination. Equal numbers of steers per treatment were slaughtered after receiving the finishing diets for 96 or 112 d. Gain, feed intake, feed efficiency, IVDMD, and ruminal VFA molar proportions were not affected by Cu supplementation. Copper supplementation increased (P < .05) liver Cu concentrations, and steers supplemented with 20 mg Cu/kg DM had higher (P < .05) liver Cu concentrations than steers supplemented with 10 mg Cu/kg DM. Serum total cholesterol concentrations were reduced by d 56 and at subsequent sampling dates in steers receiving supplemental Cu. Longissimus muscle cholesterol concentrations were lower (P < .10) in steers supplemented with Cu. Backfat depth was less (P < .05) in steers receiving supplemental Cu, but marbling scores were similar across treatments. Unsaturated fatty acid composition of longissimus muscle was increased (P < .05) and saturated fatty acid composition tended (P < .12) to be reduced in Cu-supplemented steers. Polyunsaturated fatty acid concentrations were higher (P < .05) in steers receiving Cu. These results indicate that addition of 10 or 20 mg Cu/kg to a high-concentrate diet containing 4.9 mg Cu/kg DM alters lipid and cholesterol metabolism in steers but does not affect ruminal fermentation.     

Effects of Dietary Phosphorous and Trace Mineral Source on Immune Function,Mineral Status,and Performance of Stressed Steers

Two experiments were conducted to determine the effects of dietary P and trace mineral source on immune response, mineral status, and performance in steers stressed by weaning and disease exposure. In Experiment 1, 24 Angus and 24 Simmental weaned steers were used. Treatments consisted of 1) inorganic trace minerals, 2) organic trace minerals, 3) 0.15% supplemental P + inorganic trace minerals, and 4) 0.15% supplemental P + organic trace minerals. Copper, Mn, and Zn were added to provide 10, 25, and 25 mg/kg DM, respectively. The organic treatments supplied 50% of the supplemental Cu and Mn, and 66% of the supplemental Zn from metal proteinates, with the remainder supplied by inorganic sulfate forms. Inorganic treatments supplied all of the supplemental Zn, Cu, and Mn from sulfate forms. The basal diet was a corn silage-soybean meal-based diet. On d 2 following weaning, steers received an intranasal inoculation of infectious bovine rhinotracheitis virus (IBRV). Rectal temperatures in response to IBRV inoculation were similar across treatments. On d 9, steers were injected with 10 ml of a 25% pig red blood cell (PRBC) suspension. Total Ig titers against PRBC concentrations were higher (P<0.05) in steers receiving no supplemental P on d 7 postinjection. However, IgG and IgM titers were unaffected by treatment. Cell-mediated immune response (CMI) to phytohemagglutinin (PHA), plasma Cu and Zn concentrations, and 38-d performance were unaffected by treatment. In Experiment 2, 35 Angus steers were fed diets containing either inorganic or organic trace minerals. Performance and percent morbidity were unaffected by treatment. Plasma Cu was higher for steers fed organic trace minerals. Results indicate that increasing dietary P or replacing inorganic trace minerals with organic forms had little effect on immunity or performance of steers stressed by weaning.     

Mineral concentrations of plasma and liver after injection with a trace mineral complex differ among Angus and Simmental cattle

To examine the effects of cattle breed on the clearance rate of an injectable mineral product, 10 Angus and 10 Simmental steers were blocked by breed and initial BW (332 ± 33 kg) and injected with either Multimin 90 (MM) or sterilized saline (CON) at a dose of 1 mL/45 kg BW. Multimin 90 contains 15 mg Cu/mL (as Cu disodium EDTA), 60 mg Zn/mL (as Zn disodium EDTA), 10 mg Mn/mL (as Mn disodium EDTA), and 5 mg Se/mL (as sodium selenite). Steers received a corn-silage-based diet, and inorganic sources of Cu, Zn, Mn, and Se were supplemented at NRC recommended amounts. Jugular blood was collected immediately before injection and at 8 and 10 h post-injection and on days 1, 8, and 15 post-injection. Liver biopsies were collected 3 d before injection and on days 1, 8, and 15 post-injection. Liver and plasma mineral concentration and glutathione peroxidase (GSH-Px) activity data were analyzed as repeated measures. Plasma concentrations of Zn, Mn, and Se were greater (P = 0.01) and Cu tended to be greater (P = 0.12) post-injection in MM steers compared with the CON steers. Regardless of treatment, Simmental cattle had lower plasma concentrations of Cu, Zn, and Se (P ≤ 0.05) when compared with Angus cattle. Erythrocyte GSH-Px activity was greater (P = 0.01) in MM steers compared with CON steers. Liver concentrations of Cu, Zn, and Se were greater (P = 0.05) in MM steers compared with CON steers post-injection. Liver Mn concentrations tended to be greater (P = 0.06) in MM steers compared with CON steers in the days post-injection. Interestingly, Simmental cattle exhibited greater (P = 0.01) liver Mn concentrations in the days after injection compared with Angus cattle (7.0 and 6.0 mg Mn/kg for Simmental and Angus cattle, respectively), regardless of treatment. It is unclear if this breed difference is biologically relevant; however, these data may suggest that differences in liver excretion of Mn exist between the two breeds. Overall, use of an injectable trace mineral increased liver concentrations of Cu and Se through the 15-d sampling period, suggesting that this injectable mineral is an adequate way to improve Cu and Se status of cattle through at least 15 d.     

Effects of dietary copper on the expression of lipogenic genes and metabolic hormones in steers

An experiment was conducted to determine the effects of Cu supplementation on performance, subcutaneous adipose tissue mRNA expression of acetyl CoA carboxylase (ACC), stearoyl CoA desaturase (SCD), uncoupling protein 2 (UCP2), and leptin in growing and finishing steers. Forty-eight purebred Angus steers were allotted to one of five treatments: 1) control (no supplemental Cu); 2) 10 mg Cu/kg DM from CuSO4; 3) 10 mg Cu/kg DM from a Cu amino acid complex (Availa Cu); 4) 20 mg Cu/kg DM from CuSO4; 5) 20 mg Cu/kg DM from Availa Cu. Steers were fed an alfalfa hay corn-based diet for 56 d (basal diet contained 7.1 mg Cu/kg DM) and switched to a high-concentrate diet for 144 d (basal diet contained 6.1 mg Cu/kg DM). Blood samples were obtained every 28 d throughout the entire experiment. On d 112 of the finishing period, subcutaneous adipose tissue biopsies were obtained from the tailhead of three animals per treatment and analyzed for ACC, SCD, UCP2, and leptin mRNA expression. Animal performance was not affected by Cu supplementation during the growing phase. Steers receiving 10 mg Cu/kg DM from Availa Cu had higher (P < 0.05) ending body weights and tended (P < 0.10) to have higher ADG than steers receiving 10 mg Cu/kg DM from CuSO4 during the finishing phase. Serum concentrations of nonesterified fatty acid and insulin were not affected by Cu supplementation. Steers receiving supplemental Cu tended (P < 0.11) to have less backfat relative to controls. However, dietary Cu did not influence the level of subcutaneous adipose tissue ACC and SCD mRNA. Neither UCP2 nor leptin gene expression was affected by Cu supplementation. These results indicate that dietary Cu supplementation (10 to 20 mg Cu/kg DM diet) may alter lipid metabolism of subcutaneous adipose tissue; however, it does not seem to affect expression of certain lipogenic genes.     

Effects of soybean oil and dietary copper on ruminal and tissue lipid metabolism in finishing steers

An experiment was conducted to determine the effects of Cu and soybean oil (SBO) supplementation on ruminal and tissue lipid metabolism and carcass characteristics in finishing steers. Sixty Angus steers (369.0 +/- 10.1 kg) were stratified by weight and randomly assigned to treatments in a 2 x 2 factorial arrangement, with factors being 0 or 20 mg of supplemental Cu/kg DM from Cu sulfate and 0 or 4% SBO. Steers were fed a high-concentrate basal diet that contained 5.3 mg Cu/kg DM. Average daily gain and feed intake were reduced (P < 0.01) by SBO but were not affected by Cu. Gain:feed ratio was not affected by treatment. Liver Cu concentrations were higher (P < 0.01) in steers receiving supplemental Cu and lower (P < 0.04) in SBO-supplemented steers. Copper supplementation tended to reduce (P < 0.12) and SBO supplementation tended to increase (P < 0.11) serum cholesterol concentrations. Backfat depth was reduced (P < 0.10) by Cu and SBO supplementation. Marbling scores and longissimus muscle lipid content were not affected by Cu supplementation; however, SBO supplementation reduced (P < 0.01) marbling scores. Longissimus muscle polyunsaturated fatty acids tended to be increased (P < 0.14) in Cu-supplemented steers. Longissimus muscle C18-conjugated dienes and the 18:1 trans isomer were increased (P < 0.05) in SBO-supplemented steers. Ruminal fluid 18:3 was increased (P < 0.05) and the 18:1 trans isomer was decreased (P < 0.05) in Cu-supplemented steers. These results indicate that as little as 20 mg of supplemental Cu/kg DM can reduce backfat and may alter lipid metabolism in steers fed high-concentrate diets.     

Performance, carcass characteristics, and lipid metabolism in growing and finishing Simmental steers fed varying concentrations of copper.

An experiment was conducted to determine the effects of dietary copper (Cu) on performance, carcass characteristics, and lipid metabolism in Simmental steers. Thirty-six Simmental steers (329.3 +/-11.4 kg) were stratified by weight and randomly assigned to treatments. Treatments consisted of the following: control (no supplemental Cu) and 10 or 40 mg Cu/kg DM from Cu sulfate. Each treatment consisted of six replicate pens, with each pen containing two steers. A corn silage-soybean meal-based diet was fed for 56 d. Steers were then switched to a high concentrate diet. Performance was not affected by treatment during the growing or finishing phases. Plasma Cu concentrations were higher (P < 0.05) in steers receiving supplemental Cu by d 56 of the growing phase and remained higher (P < 0.05) at all 28-d sampling periods during the finishing phase. Liver Cu concentrations were higher (P < 0.001) in steers receiving supplemental Cu at the end of the growing phase and on d 84 and at the end of the finishing phase. Steers supplemented with 40 mg Cu had higher (P < 0.001) liver Cu concentrations than those supplemented with 10 mg Cu/kg DM. Serum and longissimus muscle cholesterol concentrations were similar between treatments. Longissimus muscle and backfat fatty acid composition was similar between treatments. These results indicate that Cu supplementation given to Simmental steers increased Cu status but had no effect on performance, carcass characteristics, or lipid or cholesterol metabolism.     

Effect of zinc source (zinc oxide vs zinc proteinate) and level on performance,carcass characteristics,and immune response of growing and finishing steers

Sixty Angus and Angus x Hereford steers (246 kg initial BW) were used to determine the effects of Zn level and source on performance, immune response, and carcass characteristics of growing and finishing steers. Treatments consisted of 1) control (no supplemental Zn), 2) ZnO, 3) Zn proteinate-A (ZnProt-A, 10% Zn), and 4) ZnProt-B (15% Zn). Treatments 2, 3, and 4 supplied 25 mg of supplemental Zn/kg diet. Steers were individually fed a corn silage-based diet during the 84-d growing phase and a high corn diet during the finishing phase. Cell-mediated and humoral immune response measurements were obtained between d 67 and 74 of the growing phase. Equal number of steers per treatment were slaughtered after receiving the finishing diets for 84 or 112 d. Performance and carcass measurements were similar in steers fed the two ZnProt sources. Zinc supplementation, regardless of source, increased (P < 0.05) ADG during the growing phase. In the finishing phase, ADG (P = 0.10) and gain/feed (P = 0.07) tended to be higher for steers fed ZnProt compared with those supplemented with ZnO. Gain and feed efficiency were similar for control and ZnO-supplemented steers during the finishing phase. Steers fed ZnProt had heavier (P < 0.05) hot carcass weights and slightly higher (P < 0.05) dressing percentages than those in the control or ZnO treatments. Quality grade, yield grade, marbling, and backfat were increased by Zn supplementation, but were not affected by Zn source. In vitro response of lymphocytes to mitogen stimulation and in vivo swelling response following intradermal injection of phytohemagglutinin were not affected by Zn level or source. Humoral immune response following vaccination with infectious bovine rhinotracheitis also was not affected by treatment. Soluble concentrations of Zn in ruminal fluid were higher (P < 0.05) in steers fed ZnProt compared to ZnO steers. Results indicate that ZnProt may improve performance of finishing steers above that observed with inorganic Zn supplementation.     

The effects of low-copper diets with or without supplemental molybdenum on specific immune responses of stressed cattle

Angus bull calves (n = 42; 7 mo of age; 254 kg initial BW) were used to investigate the effects of dietary Cu and Mo on immune function of stressed cattle. Randomly selected calves (n = 22) were injected with 90 mg of Cu as Cu glycinate 28 d before weaning and castrated at weaning. These calves received 7.5 and 5 mg of supplemental Cu/kg of DM during a 41-d receiving phase and a 196-d growing phase, respectively. The remainder of the steers received no supplemental Cu during the experiment. Copper-supplemented steers had adequate Cu status at weaning, whereas unsupplemented calves were marginally Cu-deficient. Cell-mediated response to intradermal injection of phytohemagglutinin was not affected by dietary treatment during the receiving phase. During the growing phase, half of the steers in each Cu treatment were given 5 mg of supplemental Mo/kg of DM. Copper supplementation increased (P<.05) humoral response to ovalbumin injected on d 133 of the growing phase. On d 168 of the growing phase, calves receiving only supplemental Mo were severely Cu-deficient based on plasma and liver Cu concentrations. The other treatment groups had adequate Cu status. Before feeding on d 168 of the growing phase, half of the steers were loaded onto trailers and transported 2.5 h, and they remained on the trailers an additional 9.5 h. Humoral response to porcine erythrocytes (PRBC) and delayed-type hypersensitivity (DTH) to dinitrochlorobenzene was tested at the end of the stress period. There was a Cu x stress interaction for humoral response to PRBC, with Cu decreasing antibody titers in unstressed calves and increasing titers in stressed steers. Stressed steers had lower (P = .03) ADG during the 28 d following stress. The results of this study indicate that Cu deficiency and 5 mg of supplemental Mo/kg of DM do not dramatically alter the specific immunity of stressed cattle.     

Trace mineral source impacts rumen trace mineral metabolism and fiber digestion in steers fed a medium-quality grass hay diet

Twelve Angus steers (BW 452.8 ± 6.1 kg) fitted with ruminal cannulae were used to determine the impact of trace mineral (TM) source on digestibility, ruminal volatile fatty acid (VFA) composition, ruminal soluble concentrations of Cu, Zn, and Mn, and relative binding strength of trace minerals located in the rumen insoluble digesta fraction. Steers were fed a medium-quality grass hay diet (DM basis: 10.8% CP, 63.1% neutral detergent fiber [NDF], 6.9 mg Cu/kg, 65.5 mg Mn/kg, and 39.4 mg Zn/kg) supplemented with protein for 21 d. Treatments consisted of either sulfate (STM) or hydroxy (HTM) sources (n = 6 steers/treatment) to provide 20, 40, and 60 mg supplemental Cu, Mn, and Zn/kg DM, respectively. Following a 21-d adaptation period, total fecal output was collected for 5 d. Dry matter (P < 0.07) and CP (P < 0.06) digestibility tended to be reduced, and NDF (P < 0.04) and acid detergent fiber (ADF) (P < 0.05) digestibility were reduced in STM- vs. HTM-supplemented steers. On day 6, ruminal fluid was collected at 0, 2, and 4 h post-feeding and analyzed for VFA. There were no treatment x time interactions for VFA. Steers receiving HTM had less (P < 0.02) molar proportions of butyric acid and greater (P < 0.05) total VFA concentrations than STM-supplemented steers. Steers were then fed the same diet without supplemental Cu, Zn, or Mn for 14 d. On day 15 steers received a pulse dose of 20 mg Cu, 40 mg Mn, and 60 mg Zn/kg DM from either STM or HTM (n = 6 steers/treatment). Ruminal samples were obtained at 2-h intervals starting at −4 and ending at 24 h relative to dosing. There was a treatment x time interaction (P < 0.03) for ruminal soluble Cu, Mn, and Zn concentrations. Ruminal soluble mineral concentrations were greater (P < 0.05) for Cu at 4, 6, 8, 10, 12, and 14 h; for Mn at 4 and 6 h; and for Zn at 4, 6, and 8 h post-dosing in STM compared with HTM-supplemented steers. Copper concentrations were greater (P < 0.05) at 12 and 24 h and Zn concentrations in ruminal solid digesta were greater at 24 h in HTM-supplemented steers. Upon dialysis against Tris-EDTA, the percent Zn released from digesta was greater (P < 0.05) at 12 h (P < 0.03) and 24 h (P < 0.05), and the percent Cu released was greater (P < 0.02) at 24 h post-dosing in HTM steers when compared with STM-supplemented steers. Results indicate that Cu and Zn from HTM have low solubility in the rumen and appear to be less tightly bound to ruminal solid digesta than Cu and Zn from STM. The lower ruminal soluble concentrations of Cu and Zn in steers given HTM were associated with greater fiber digestibility.     

Effects of supplementing combinations of inorganic and complexed copper on performance and liver mineral status of beef heifers consuming antagonists.

Performance, immune response, and liver trace mineral status were measured in growing heifers supplemented with different copper (Cu) concentrations and sources when diets contained the Cu antagonists Mo, S, and Fe. Sixty Angus x Hereford heifers were managed in two groups for 112 d and were either individually fed diets and mineral treatments using individual feeding stalls (Stall) or pen-fed grass hay and individually supplemented mineral treatments (Pen). The basal diet of grass hay, rolled barley, and soybean meal was analyzed to contain 6 mg Cu/kg DM. The treatments consisted of 1) no supplemental Cu (Control); 2) 49 mg Cu/kg DM from Cu sulfate (i.e. approximately five times NRC recommendation for Cu from CuSO4) (5X-SO4); 3). 22 mg Cu/kg DM from CuSO4 (2X-SO4); 4). 22 mg Cu/kg DM from a combination of 50% CuSO4 and 50% Cu-amino acid complex (50-50); and 5). 22 mg Cu/kg DM from a combination of 25% CuSO4, 50% Cu-amino acid complex, and 25% Cu oxide (CuG) (25-50-25). All heifers were supplemented with the Cu antagonists Mo (10 mg/kg DM), S (2,900 mg/kg DM), and Fe (500 mg/kg DM). These diets resulted in dietary Cu:Mo ratios that averaged 0.5:1 for Control, 4.5:1 for the 5X-SO4, and 2.4:1 for 2X-SO4, 50-50, and 25-50-25. Rate and efficiencies of gain and cell-mediated immune function were not different (P > 0.10) among treatments. Data suggest supplements containing combinations of inorganic and complexed Cu interacted differently in the presence of Mo, S, and Fe. Heifers consuming the 25-50-25 supplement in the Stall group initially lost hepatic Cu rapidly but this loss slowed from d 50 to d 100 compared to the Control (P = 0.07), 50-50 (P < 0.05), and 2X-SO4 (P < 0.05) heifers and was similar (P > 0.10) to that in the 5X-SO4 heifers. In the Pen group, total hepatic Cu loss tended to be greater for 25-50-25 and 2X-SO4 compared to 5X-SO4 heifers (P = 0.09 and P = 0.06, respectively); Cu loss in the 50-50 heifers was similar (P > 0.10) to that in the 5X-SO4 heifers. This suggests that supplementing combinations of inorganic and amino acid-complexed Cu was as effective in limiting hepatic Cu loss during antagonism as was increasing dietary Cu levels to five times the NRC recommendation. A combination of 25% CuSO4 , 50% Cu-amino acid complex, and 25% CuO limited liver accumulation of Mo compared to supplements without CuO and could provide a strategic supplementation tool in limiting the systemic effects of Cu antagonism in beef cattle.     

Dietary copper effects on lipid metabolism and circulating catecholamine concentrations in finishing steers

Forty-eight Angus and Hereford x Angus steers were used to determine the effects of copper (Cu) on lipid and catecholamine metabolism. Steers were stratified by weight within breed and randomly assigned to treatments. Treatments consisted of 0 (control, no supplemental Cu), 10, or 40 mg of supplemental Cu (from Cu2(OH)3Cl)/kg DM. Steers were fed a corn silage-soybean meal-based growing diet for 42 d. Animals were then switched to a high-concentrate finishing diet and remained on the same dietary treatments. On d 70, indwelling jugular catheters were nonsurgically inserted into five steers per treatment. Blood samples were obtained from steers after a 24-h period of feed withdrawal, 1 h after feeding, and after i.v. administration of norepinephrine and were subsequently analyzed for nonesterified fatty acid (NEFA) and catecholamine concentrations. Average daily gain over the finishing period was higher (P < 0.06) in steers receiving supplemental Cu. Serum total cholesterol concentrations were reduced (P < 0.05) on d 84 and 112 in steers supplemented with Cu. Serum norepinephrine (P < 0.14) and NEFA concentrations following feed withdrawal tended (P < 0.12) to be higher in Cu-supplemented steers. Postfeeding norepinephrine concentrations tended to be higher (P < 0.14) in Cu-supplemented steers. Nonesterifled fatty acid concentrations were lower (P < 0.10) in Cu-supplemented steers after norepinephrine administration. Backfat depth was decreased (P < 0.10) and longissimus muscle polyunsaturated fatty acid percentages were increased (P < 0.10) in steers receiving supplemental Cu. These results indicate that Cu addition to a finishing diet containing 5 mg Cu/kg DM alters lipid metabolism. The reduction in backfat depth may be due to copper altering catecholamine metabolism in steers.     

Effects of supplemental zinc concentration and source on performance, carcass characteristics, and serum values in finishing beef steers

Three studies were conducted to examine the effects of zinc concentration or source in diets of finishing beef steers. In Exp. 1, 108 (British x Continental) beef steers were supplemented with concentrations of added zinc (as ZnSO4) at 20, 100, or 200 mg/kg of dietary DM. No differences (P > 0.10) were noted among treatments for ADG or gain:feed for the 112-d finishing period. However, a linear (P < 0.10) decrease was noted in daily DMI with increasing zinc concentrations for the overall finishing period. No differences (P > 0.10) were noted in hot carcass weight; dressing percentage; longissimus muscle area; percentage of kidney, pelvic, and heart fat; or marbling score. There were, however, quadratic increases in s.c. fat thickness (P < 0.05) and yield grade (P < 0.01) with added zinc. In Exp. 2, 12 beef steers were used to examine effects of added dietary zinc on serum concentrations of cholesterol and fatty acid profiles. No differences (P > 0.10) were observed in cholesterol or fatty acids among the supplemental zinc levels. In Exp. 3, 84 Brangus- and Angus-sired steers were fed a steam-flaked corn-based diet containing 30 mg of supplemental zinc per kilogram of dietary DM from one of the following sources: 1) ZnSO4, 2) Zn amino acid complex, or 3) a zinc polysaccharide complex. No differences (P > 0.10) were noted for the overall 126-d trial for ADG, DMI, or gain:feed ratio. Percentage kidney, pelvic, and heart fat was increased (P < 0.10) in steers supplemented with ZnSO4 vs the average of Zn amino acid and Zn polysaccharide complexes. However, s.c. fat thickness was greater (P < 0.10) in steers supplemented with Zn amino acid and Zn polysaccharide complexes vs ZnSO4. Serum zinc concentration did not differ (P > 0.10) among zinc sources. Supplemental zinc concentration in finishing diets did not seem to influence feedlot performance and had a minimal impact on carcass quality. Either the organic or inorganic source can be included in finishing diets without affecting feedlot performance.     

Effects of copper and zinc source on performance and humoral immune response of newly received, lightweight beef heifers

Two experiments were conducted to evaluate the effects of Cu and Zn source on performance, morbidity, and humoral immune response in lightweight, newly received beef heifers. A 2 x 2 factorial arrangement of treatments was used in both experiments, with either a sulfate or a polysaccharide mineral complex (SQM) source of both Cu and Zn as the factors. Supplemental Cu and Zn were included in the receiving diet at concentrations designed to provide 10 mg of Cu/kg and 75 mg of Zn/kg (DM basis). In Exp. 1, 219 newly received beef heifers (British x Continental, average initial BW = 208 kg) were given ad libitum access to a 65% concentrate diet for 35 d to determine treatment effects on DMI, ADG, G:F, and bovine respiratory disease (BRD) morbidity. In Exp. 2, 24 heifers (average initial BW = 272 kg) were fed a diet with no supplemental Cu or Zn for 35 d, followed by fasting-refeeding-fasting stress, after which the same treatment diets used in Exp. 1 were fed for 21 d to examine the effects on humoral immune response (plasma IgG titer determined by ELISA on d 7, 14, and 21) to an ovalbumin (OVA) vaccine given on d 0 and 14. Copper source x Zn source interactions were not detected in either experiment. In Exp. 1, neither Cu nor Zn source affected (P > 0.10) DMI, ADG, G:F, or BRD morbidity. In Exp. 2, d 14 (P = 0.02) and 21 (P = 0.06) OVA titers were greater for heifers that received SQM Zn compared with heifers receiving ZnSO4, but heifers receiving CuSO4 had greater OVA titers than did heifers on the SQM Cu treatment on d 14 (P = 0.01) and 21 (P = 0.001). In summary, neither supplemental Cu nor Zn source affected performance or morbidity of lightweight, newly received heifers; however, source of both Cu or Zn affected the humoral immune response to OVA, although source effects were not consistent for the two minerals.     

Effects of dietary iron on performance and mineral utilization in lambs fed a forage-based diet

Twenty-four lambs, averaging 29 kg, were used to determine the effect of supplemental dietary Fe on performance and Cu, P, Zn and Mn utilization. Treatments consisted of supplemental Fe at 0, 300, 600 or 1,200 mg/kg diet as ferrous carbonate. The basal diet contained 154 mg Fe/kg diet and consisted of 90% Coastal bermudagrass pellets, 9.45% group corn, .5% sodium chloride and .05% vitamin mix. Lambs were slaughtered after having ad libitum access to diets for 98 to 121 d. Dietary Fe did not affect lamb gain or feed intake. Supplemental Fe increased Fe concentrations in liver (P less than .01), spleen (P less than .01) and bone (P less than .10), but not in kidney and muscle. Serum Fe concentrations and percentage transferrin saturation in serum were increased (P less than .01) by supplemental Fe at 28 and 84 d, but not at the termination of the study. Plasma Cu was decreased (P less than .01) at 56 d, whereas serum ceruloplasmin activity was reduced (P less than .01) at 28 d in lambs fed 1,200 mg Fe/kg diet compared with lambs fed 600 mg Fe/kg diet. Lower levels of Fe (300 and 600) reduced (P less than .01) ceruloplasmin by 56 d and plasma Cu by 84 d compared with controls. Liver Cu also was decreased (P less than .05) by supplemental Fe. Plasma P was decreased slightly (P less than .10) by 28 d and significantly (P less than .01) at the other sampling dates by supplemental Fe.(ABSTRACT TRUNCATED AT 250 WORDS)     

Growth, reproductive performance, and manganese status of heifers fed varying concentrations of manganese

An experiment was conducted to examine the effects of dietary Mn on growth, reproductive performance, and Mn status of beef heifers. Eighty Angus (n = 40) and Simmental (n = 40) heifers, averaging 249 kg, were stratified by BW within a breed and randomly assigned to 1 of 4 treatments providing 0 (control), 10, 30, or 50 mg of supplemental Mn/kg of DM from MnSO(4). Heifers were individually fed a diet containing cottonseed hulls, corn gluten feed, citrus pulp, and ground corn, and the control diet contained 15.8 mg of Mn/kg of DM by analysis. Average daily gain, DMI, and G:F for the 196-d period were not affected by Mn supplementation. Control heifers had reduced (P = 0.04) liver Mn when contrasted with the 3 levels of supplemental Mn. Serum cholesterol was greater (P = 0.001) in Angus compared with Simmental heifers over the course of the 196-d experiment but was not affected by treatment. Dietary Mn did not significantly affect measures of reproductive performance. Results of this study indicate that 15.8 mg of Mn/kg of diet DM should be adequate for growth, onset of estrus, and conception of beef heifers.     

肉用仔鸡日粮中添加蛋氨酸铜、锌和锰对粪便微量元素排放的研究

为了比较肉用仔鸡日粮中添加不同有机微量元素后粪便中铜、锰、锌、排放的影响,试验选择1日龄AA肉仔鸡,分为7个处理,对照组添加无机硫酸盐（锌50mg/kg;铜10mg/kg;锰50 mg/kg）,试验组分别用Mintrex-Cu替代5 mg/kg或全部替代硫酸铜;以Min-trex-Zn代替20 mg/kg硫酸锌,以Mintrex-Mn代替20 mg/kg硫酸锰,或在对照组基础上添加20mg/kg的Mintrex-Mn或Mintrex-Zn。42日龄时,采用全收粪法收集粪样72h,用原子吸收分光光度计测定粪样中铜、锰、锌的含量。结果表明：Mintrex-Cu代替50%或100%硫酸铜,对粪便中铜、锌和锰的排泄量没有显著影响（P〉0.05）,Mintrex-Zn/Mn替代40%无机锌、锰对锌、锰排泄量没有显著影响（P〉0.05）。在基础日粮中额外添加20mg/kgMintrex-Zn/Mn显著提高了粪便中锌、锰的排泄量（P〈0.05）,但添加20mg/kgMintrex-Mn降低铜排泄量20%以上（P〈0.05）。研究说明,在基础日粮微量元素水平低于需要量的情况下,采用有机微量元素替代无机微量元素对粪便中微量元素排泄量的影响很小,额外添加有机微量元素则提高粪便微量元素的排泄。