Bioavailability of zinc in several sources of zinc oxide, zinc sulfate, and zinc metal.

Three zinc depletion-repletion assays were carried out with chicks to determine Zn bioavailability in five sources of ZnO, three sources of ZnSO4.H2O, and two sources of Zn metal. A standard 23% CP corn-soybean meal diet was fed during the first 3 d posthatching, after which it was replaced with a Zn-deficient soy concentrate diet (13.5 mg Zn/kg) until d 7. On d 8 after an overnight period of feed withdrawal, chicks were fed for 12 d the Zn-deficient basal diet containing 0, 4.76, and 9.90 (Assay 1); 0, 5.06, or 10.12 (Assay 2); or 0, 4.73, or 9.13 (Assay 3) mg/kg supplemental Zn from analytical grade (AG) ZnSO4.7H2O (22.7% Zn) to generate a standard response curve. The AG and feed-grade (FG) Zn sources being evaluated were then provided at a level that would fall within the standard curve. Weight gain (Assays 1, 2, and 3) and total tibia Zn (Assay 1) responded linearly (P<.01) to Zn supplementation from ZnSO4.7H2O. Weight gain regressed on supplemental Zn intake gave standard-curve equations with fits (r2) ranging from .94 to .97. In Assay 1, regression of total tibia Zn (Y, in micrograms) on supplemental Zn intake (X, in milligrams/12 d) gave the equation Y = 13.2+6.74X (r2 = .90). Standard-curve methodology was used to estimate relative Zn bioavailability (RBV), with RBV of Zn in the ZnSO4.7H2O standard set at 100%. Four sources of FG ZnO were evaluated: Source 1 (78.1% Zn, hydrosulfide process, U.S.), Source 2 (74.1% Zn, Waelz process, Mexico), Source 3 (69.4% Zn, China), and Source 4 (78.0% Zn, French process, Mexico). Analytical-grade ZnO (80.3% Zn) was also evaluated. Feed-grade ZnO Sources 1 and 4 as well as AG ZnO produced average RBV values that were not different (P>.10) from the standard, but average RBV values for FG Source 2 and FG Source 3 were only 34 (P<.05) and 46% (P<.05), respectively. All sources of ZnSO4.H2O, which included two FG sources (source 1, 36.5% Zn; source 2, 35.3% Zn) and one food-grade source (36.5% Zn), were not different (P>.10) in RBV from the ZnSO4.7H2O standard. Two Zn metal products, Zn metal dust (100% Zn) and Zn metal fume (91.5% Zn), were also evaluated, and they were found to have Zn RBV values of 67 (P<.05) and 36% (P<.05), respectively. Feed-grade sources of ZnO vary widely in color, texture, Zn content, and Zn bioavailability.     

Methodology for assessing zinc bioavailability: efficacy estimates for zinc-methionine, zinc sulfate, and zinc oxide.

The bioavailability of zinc-methionine (ZnMET) was compared to that of feed-grade ZnSO4.H2O using three different diets: purified (crystalline amino acid [AA]), semipurified (soy isolate), and complex (corn-soybean [C-SBM]) diet. With the Zn-deficient purified or semipurified diet, weight gain and tibia Zn responded linearly to both ZnSO4.H2O and ZnMET supplementation. Common-intercept, multiple linear regression indicated differences in Zn bioavailability between ZnMET and ZnSO4.H2O for both diets as indicated by bone Zn. With the ZnSO4.H2O standard set at 100%, bioavailability of Zn from ZnMET was 117% (P less than .05) in the AA diet and 177% (P less than .01) in the soy isolate diet. The ZnMET was also compared to ZnSO4.H2O in a C-SBM diet containing 117 mg of Zn/kg. When high levels of Zn were added to this diet (0, 250, 500, and 750 mg/kg of supplemental Zn), consistent tissue Zn responses did not occur beyond the first increment. Addition of lower levels of supplemental Zn (0, 5, 10, 20, 30, 40 and 50 mg/kg) to a Zn-unsupplemented C-SBM basal diet (45 mg/kg of Zn), however, resulted in a broken-line, two-slope response in tibia Zn for both ZnMET and ZnSO4.H2O. Inflection points occurred at 60 and 54 mg of Zn/kg of diet for ZnSO4.H2O and ZnMET, respectively. The ratio of slopes (ZnMET:ZnSO4.H2O) below the inflection points was 206% (P less than .01), indicating that Zn was considerably more bioavailable in ZnMET than in ZnSO4.H2O for chicks consuming C-SBM diets. When feed-grade ZnO was compared to feed-grade ZnSO4.H2O in chicks consuming C-SBM diets, bone Zn slopes below the respective inflection points indicated that Zn was 61% bioavailable in ZnO relative to ZnSO4.H2O.     

Effects of organic zinc and phytase supplementation in a maize-soybean meal diet on the performance and tissue zinc content of broiler chicks

1. The purpose of this study was to investigate the effects of Bioplex Zn (a chelated zinc proteinate) and phytase supplementation in a maize-soybean meal diet on the performance and tissue zinc (Zn) content of broiler chicks. Treatment structure consisted of a 2 x 6 factorial arrangement with two inclusions of phytase (0 or 500 PU/kg) and 6 of Bioplex Zn providing 0, 2, 4, 8, 16 and 32 mg Zn/kg diet. A total of 864 chicks were randomly assigned to each of 12 dietary treatments with 6 replicate cages of 12 chicks. 2. Dietary inclusion of phytase increased feed intake, weight gain, plasma Zn content, tibia Zn content, tibia and ash weight. 3. Dietary supplementation of Bioplex Zn linearly increased feed intake, weight gain, gain to feed ratio, plasma Zn concentration, liver Zn concentration, tibia Zn content, tibia and ash weight. 4. An interactive effect of phytase and Bioplex Zn on feed intake, weight gain, tibia Zn concentration and tibia ash weight was found. 5. One slope, straight broken-line analysis of weight gain regressed on the supplemental Zn level provided as Bioplex Zn indicated that 12 mg/kg supplemental Zn without phytase and 7.4 mg/kg supplemental Zn with phytase were required for the optimal weight gain of chicks.     

Zinc bioavailability in soybean meal

A phytate-containing soy protein concentrate (SPC) diet (13.5 mg Zn/kg) and a phytate-free egg white diet (.3 mg Zn/kg) were used to determine the relative bioavailability (RBV) of Zn in dehulled soybean meal (SBM) based on Zn depletion-repletion growth bioassays in young chicks. After a 4-d Zn depletion period, chick weight gain responded linearly (P < .01) to graded increments of supplemental Zn (0 to 10 mg/kg) from ZnSO4 x 7H2O, whether added to the Zn-deficient SPC or egg white diet. Slope, however, was over twice as great for the standard curve relating weight gain to supplemental Zn intake for the egg white diet as for the SPC diet. Addition of 7 to 10 mg Zn/kg from SBM to either Zn-deficient diet increased (P < .01) weight gain, but a similar SBM addition to either diet made adequate in Zn did not increase weight gain. Using standard-curve methodology, RBV of Zn in SBM was 78% when the the SPC diet was used, but it was only 40% when the egg white diet was used. The phytate contained in the SPC basal diet therefore markedly reduced the efficiency of utilizing the supplemental inorganic Zn from ZnSO4 x 7H2O. This lowered the slope of the standard curve so that, on a relative basis, the Zn in SBM had a higher RBV value than was the case for Zn utilization in SBM with the phytate-free egg white diet. The 78% Zn RBV value in SBM would seem to have the greatest relevance for practical-type corn-SBM diets.     

Tolerance for excess basic zinc chloride and basic copper chloride in chicks

(1) Four chick experiments were conducted to determine toxicity estimates for basic zinc chloride (BZC) and basic copper chloride (BCC), now being used as sources for these minerals. (2) In experiment 1, New Hampshire x Columbian crossbred chicks were fed 0, 500, 1000, 1500, 3000 and 5000 mg Zn/kg from BZC (Zn5Cl2(OH)8). Broken-line regression analysis showed that the minimal toxic break points for chick weight gain and gain:food were 1720 and 2115 mg Zn/kg, respectively. (3) Crossbred chicks were fed 0, 150, 250, 500, 750 and 1000 mg Cu/kg from BCC (Cu2(OH)3C) in experiment 2. Regression analysis indicated that the minimal toxic break points for chick weight gain and gain:food were 642 and 781 mg Cu/kg, respectively. (4) In experiment 3, commercial broiler chicks were fed 0, 1500, 2000 and 2500 mg supplemental Zn/kg from BZC or 0, 500, 650 and 800 mg supplemental Cu/kg from BCC. Broiler chicks fed those high inclusion rates of Zn did not show reduced weight gain in comparison to chicks fed no supplemental Zn. All high concentrations of supplemental Cu depressed chick weight gain in comparison to control chicks. (5) Experiment 4 involved two separate 4 x 2 factorial designs with supplemental Zn (0, 2500, 3500 and 4500 mg/kg) or Cu (0, 500, 750 and 1000 mg/kg) and two breeds of chicks (crossbred and commercial). Significant interactions for weight gain, food intake, gain:food and liver Cu suggested that the crossbred and commercial chicks responded differently to high concentrations of supplementary dietary Cu.     

Pharmacological zinc levels reduce the phosphorus-releasing efficacy of phytase in young pigs and chickens

A pig trial and a chick trial were done to determine the effect of high levels of Zn and Cu on the P-releasing efficacy of phytase. Ninety-nine individually fed pigs (7.2 kg) were given ad libitum access to one of 11 experimental diets for a period of 21 d. Fibula ash (mg) was regressed against supplemental inorganic P (iP) intake (g) to establish the standard curve, from which phytase treatments were compared to determine P-releasing efficacy. The basal diet was a corn-soybean meal diet with no supplemental P (21% CP, 0.075% estimated available P, 130 mg of Zn/kg, as-fed basis). Diets included three graded levels of supplemental iP (0, 0.075, 0.150%) from reagent-grade KH2PO4, two levels of phytase (500 and 1,000 FTU/kg) from EcoPhos, 1,500 mg of Zn/kg from either Waelz ZnO or basic Zn chloride (Zn5Cl2(OH)8), and all combinations of phytase and Zn. One phytase unit (FTU) was defined as the amount of enzyme required to release 1 micromol of iP per minute from sodium phytate at 37 degrees C and pH 5.5. Phytase supplementation improved (P < 0.01) weight gain, G:F, and fibula ash (% and mg). Bone ash (mg) was highest (P < 0.01) for pigs fed diets containing 1,000 FTU/kg of phytase. Supplemental Zn had no effect (P > 0.50) on growth performance, but decreased (P < 0.05) fibula ash (mg). Comparison of the phytase treatments to the standard curve (r2 = 0.87) revealed P-release values of 0.130 and 0.195% for 500 and 1,000 FTU of phytase/kg, respectively, in the absence of Zn, whereas in the presence of Zn (pooled), P-release values were decreased (P < 0.01) to 0.092 and 0.132%, respectively. The effects of high levels of supplemental Zn (basic Zn chloride) and Cu (CuSO4 x 5H2O) on phytase efficacy also were investigated in a 12-d chick trial. Dietary treatments were arranged according to a 2(3) factorial, with two levels each of supplemental phytase (0 and 500 FTU/kg from EcoPhos), Zn (0 and 800 mg/kg), and Cu (0 and 200 mg/kg). There was a phytase x Zn interaction (P < 0.01) for tibia ash. Thus, Zn supplementation decreased tibia ash in the presence, but not in the absence, of phytase. Supplemental Cu did not affect (P > 0.30) the response to phytase. These results suggest that pharmacological levels of Zn chelate the phytate complex, thereby decreasing its availability for hydrolysis by phytase.     

饲粮锌对肉鸡生长性能、组织含锌酶活性以及金属硫蛋白含量的影响

选用720只1日龄商品代AA肉公鸡进行试验,研究饲粮中添加不同水平无机锌对肉仔鸡生长性能、肝脏铜锌超氧化物歧化酶(CuZnSOD)活性和肾脏金属硫蛋白(MT)含量的影响,以考核这些指标对评价肉仔鸡锌营养状况的意义。将肉鸡按平均体重随机分成8个处理组,分别饲喂不添加锌的玉米-豆粕型基础饲粮(对照组,含锌28.37mg/kg)和在对照组基础饲粮中以无机硫酸锌形式分别添加20、40、60、80、100、120mg/kg和140mg/kg锌的试验饲粮21d。结果表明:肉仔鸡的日增重、日采食量和肾脏MT含量均受到添加锌水平的显著影响(P<0.05),其中肾脏MT含量受锌水平影响极显著(P<0.01),而不同锌水平对肝脏CuZnSOD活性无显著影响(P>0.1)。这表明对于肉仔鸡,肾脏MT可能是评价机体锌营养状况的敏感指标。     

有机锌源对肉鸡生长性能和胫骨软骨症的影响

采用玉米－豆饼型饲粮研究有机锌源对肉鸡生长性能和胫骨软骨症（ＴＤ）的影响。结果表明,有机锌源与硫酸锌对肉鸡生长和饲料采食量均无显著影响,锌的补加提高了胫骨,中趾骨,胰Ｚｎ含量,有机锌源的补加并不影响骨灰含量,胫骨长度,不诱导肉鸡ＴＤ发病率上升。     

Zinc-amino acid complexes for swine

Two experiments were conducted to determine the effect of sources of dietary zinc on gain, feed conversion and blood and bone traits of swine. In the first experiment 96 pigs were used in a 28-d study. The pigs were fed diets with no supplemental Zn or with either 9 or 12 ppm supplemental Zn from zinc sulfate (ZnSO4), zinc methionine (ZnMet) or zinc methionine with picolinic acid (ZnMet w/PA), each with or without 5% added corn oil. There were differences (P less than .05) in average daily gain (ADG) and average daily feed intake (ADFI) between the pigs fed the two organic Zn sources, with those fed ZnMet w/PA showing the better gains and feed conversion. However, neither organic Zn source resulted in pig performance that was different from either the diet with no supplemental Zn or the diets supplemented with Zn from ZnSO4. In the second experiment the same dietary Zn sources and treatments were fed as in Exp. 1 except that corn oil was deleted as a variable. No differences in ADG, ADFI, feed/gain (F/G) or in changes in serum Zn or Cu were observed among treatments during either the 21-d nursery or the 56-d growing periods. During the subsequent 56-d finishing period ADG and ADFI were greater (P less than .01) for pigs fed the Zn-supplemented diets than for those fed the diets without supplemental Zn. There were no differences among treatments in F/G during the finishing period. Zn content of bone ash was lower (P less than .01) in the non-Zn-supplemented pigs. These data suggest that the Zn sources used are of similar biological value and do not support the theory that picolinic acid aids Zn absorption.     

Effects of replacing pharmacological levels of dietary zinc oxide with lower dietary levels of various organic zinc sources for weanling pigs

Two 28-d randomized complete block design experiments were conducted to evaluate the effects of concentrations and sources of Zn on growth performance of nursery pigs. Seven stations participated in Exp. 1, which evaluated the efficacy of replacing 2,500 ppm of Zn from ZnO with 125, 250, or 500 ppm of Zn from Zn methionine. A control diet with 125 ppm of supplemental Zn was included at all stations. A total of 615 pigs were used in 26 replicates. Average weaning age was 20.6 d and the average initial BW was 6.3 kg. There were no differences in any growth response among the three supplemental Zn methionine levels fed in Exp. 1. Zinc supplementation from Zn methionine improved ADG compared with the control during all phases (P < 0.05), due primarily to an increase in ADFI. Pigs fed 2,500 ppm of Zn from ZnO gained faster (P < 0.01) than those fed the control diet during all phases, and faster (P < 0.05) than those fed supplemental Zn from Zn methionine for the 28-d experiment. Differences in gain were again due mainly to differences in feed intake. A second experiment compared five sources of supplemental organic Zn (500 ppm of Zn) with 500 and 2,000 ppm supplemental Zn from ZnO and a control (140 ppm total Zn). Six stations used a total of 624 pigs, with an average weaning age of 20.4 d and averaging 6.2 kg BW in 15 replicates. Pigs fed 2,000 ppm of Zn from ZnO gained faster (P < 0.05) than pigs fed the control or any of the 500 ppm of Zn treatments (ZnO or organic Zn). Pigs fed the 2,000 ppm of Zn from ZnO also consumed more feed than those receiving 500 ppm of Zn from ZnO or from any of the organic Zn sources (P < 0.05). Organic sources of Zn did not improve gain, feed intake, or feed efficiency beyond that achieved with the control diet. Supplemental Zn at a concentration of 500 ppm, whether in the form of the oxide or in an organic form, was not as efficacious for improved ADG as 2,000 to 2,500 ppm of Zn from ZnO.     

Zinc methionine for ruminants: relative bioavailability of zinc in lambs and effects of growth and performance of growing heifers

Studies were conducted to evaluate zinc methionine (ZnMet) as a source of Zn for ruminants. Experiment 1 compared the availability of Zn in ZnMet and zinc oxide (ZnO) in lambs fed a semi-purified diet deficient in Zn. Based on growth rate and animal performance, plasma Zn and plasma alkaline phosphatase activity, no differences in Zn availability were detected between the two Zn sources. Apparent absorption of Zn also was similar, but Zn retention was higher (P less than .01) in lambs fed ZnMet because of a tendency for lower urinary Zn excretion (P less than .19) in this group. Zinc absorption and retention by lambs were similar for the two Zn sources in Exp. 2 when 20 mg Zn/kg was added to an orchardgrass hay-based diet containing 30 mg Zn/kg. In Exp. 3, lambs were dosed orally with 300 mg of Zn as ZnO or ZnMet, and the increase in plasma Zn following dosing was monitored. The increase in plasma Zn above predosing values was similar at 6 h but was higher at 12 (P less than .10) and 24 h (P less than .05) postdosing in lambs given ZnMet. Thirty-six Hereford x Simmental heifers (271 kg) were used in Exp. 4 to determine the influence of supplementing Zn (25 mg/kg) as ZnO or ZnMet of growth performance and Zn status. Heifers were fed a corn silage-based diet that contained 23.1 mg Zn/kg during the 126-d study. Zinc supplementation to the basal diet increased (P less than .05) gain and feed/gain during the first 56 d, but not for the entire 126-d study.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of feeding different concentration and forms of zinc on the performance and tissue mineral status of broiler chicks

1. Two studies were conducted to investigate the effect of feeding different concentration and forms of zinc (Zn) on the performance and tibia Zn status of broiler chicks.

2. In Experiment 1, chicks fed on the control or the diet supplemented with 12?mg of Zn as sulphate had lower feed intake, weight gain and tibia Zn content than other treatment groups. Chicks given 12 and 24?mg of organic Zn in starter and grower phases, respectively, had the same performance and tibia Zn content as those fed 40?mg of Zn as sulphate and the same performance but higher tibia Zn content than those given 12?mg of Zn as organic over the 42?d.

3. In Experiment 2, chicks given 24?mg organic Zn had greater weight gain than chicks fed on the other treatment diets in the starter period. Chicks fed on the control diet had lower tibia Zn content than chicks fed other treatment diets. Chicks given 80?mg Zn as sulphate had higher tibia Zn content than chicks fed the other treatment diets except those given 40?mg of Zn as sulphate.

4. The results from these trials indicate that feeding lower concentration of Zn as organic form may better promote the growth performance of broiler chicks.     

不同锰源与锰水平对肉仔鸡生产性能和组织矿物元素沉积的影响

为研究不同锰源与锰水平对肉仔鸡的生产性能与组织矿物元素沉积的影响,试验采用2×5完全随机试验设计,在玉米—豆粕型基础日粮(锰含量为37.66mg/kg)中添加0、45、90、130、180mg/kg(5个锰添加水平)的复合氨基酸锰和硫酸锰(2种锰源),构成10个日粮处理组,将540只1日龄健康艾维茵肉仔鸡随机分为10个处理组,开展肉仔鸡饲养试验(共42d)。于35日龄时测定其生产性能指标,计算料肉比;于42日龄时测定其胫骨、肝脏、肾脏组织中铜、铁、锌浓度以及胫骨灰分、钙及磷含量。结果表明,在上述日粮中,锰添加量在45~130mg/kg时,无论是添加复合氨基酸锰组还是添加硫酸锰组35日龄肉仔鸡体重和采食量较未添加组差异显著(P≤0.05),经分析,锰水平对其平均体重及采食量有极显著影响(P<0.01);不同锰源的35日龄肉仔鸡体重、采食量、料肉比差异不显著(P >0.05)。42日龄肉仔鸡胫骨、肝脏、肾脏组织中铜、锌、铁含量及胫骨灰分、钙磷含量未受锰源和锰水平及两者互作的显著影响(P >0.05)。由以上结果可以得出,锰水平对肉仔鸡生长性能有极显著影响(P<0.01);锰源对肉仔鸡生产性能无显著影响(P >0.05);锰源和锰水平及两者互作对肉仔鸡组织矿物元素沉积无显著影响(P >0.05)。     

Growth-promoting efficacy in young pigs of two sources of zinc oxide having either a high or a low bioavailability of zinc

Commercial sources of zinc oxide (ZnO) differ widely in Zn relative bioavailability (RBV), but it is unknown whether growth-promoting efficacy in young pigs is influenced by RBV of the ZnO sources used. We compared a low-RBV (39%) ZnO manufactured by the Waelz process (W) to a high-RBV (93%) ZnO manufactured by the hydrosulfide process (HS). Antibacterial agents were included in the diet in only one of the four trials (Exp. 4). In Exp. 1, pigs (n = 36, 6.5 kg, 28 d of age) were randomly assigned in three replicates to receive 0, 1,500, or 3,000 mg Zn/kg from HS Zn in a 21-d growth assay. Growth rates and feed intake responded linearly (P < 0.01) to incremental doses of Zn. In Exp. 2, pigs (n = 60, 6.1 kg, 28 d of age) were randomly assigned in five replicates to receive either 0 or 1,500 mg W or HS Zn/kg during a 21-d feeding period. Growth performance was improved (P < 0.01) by the addition of ZnO. During wk 1, however, pigs receiving HS Zn grew faster (P < 0.03) than those receiving W Zn, but the difference diminished to a trend (P < 0.08) during wk 2. Morphology of duodenal, jejunal, and ileal intestinal sections was examined at d 21 of the assay, but neither source of ZnO had an effect on crypt depth or on villus height or width. In Exp. 3, weaned pigs (n = 48, 5.4 kg, 21 d of age) were randomly assigned in four replicates to the same dietary treatments as in Exp. 2 for a 17-d growth assay. Growth performance was improved (P < 0.05) by the addition of ZnO, but no difference was detected between the two sources. In Exp. 4, pigs (n = 60, 6.2 kg, 28 d of age) were randomly assigned in five replicates to receive either 0 or 1,500 mg/kg W or HS Zn in an 11-d growth assay wherein antimicrobial agents were included in the basal diet. Growth rates during the first 6-d were improved (P < 0.06) by the addition of ZnO, with a trend (P < 0.10) for greater weight gain in pigs receiving HS than in those fed W Zn. During the entire 11-d, however, there was no difference in growth rates between pigs fed the two sources of ZnO. In conclusion, RBV of Zn in ZnO did not substantially affect the growth-promoting efficacy of ZnO in young pigs fed diets with or without antimicrobial agents.     

Effects of increasing zinc supplementation in drinking water on growth and thyroid gland function and histology in broiler chicks

The aim of the study was to examine the effects of increasing zinc supplementation on growth, feed efficiency and thyroid function and histology in broiler chicks. Sixty new born male broiler chicks were randomly allotted into one of four treatment groups and fed for 60 d. Zinc (Zn) was added into drinking water at the levels of 0, 125, 500, and 1000 mg Zn/L. Body weight gain were significantly higher and feed efficiency were significantly lower in chicks supplemented with 125 mg Zn/L compared with chicks supplemented with 500 or 1000 mg Zn/L at the end of the experiment. Serum Zn concentration linearly increased with the increasing level of Zn intake. Serum triiodothyronine and thyroxine levels and the diameters of follicles of thyroid gland were significantly reduced with high levels (500 and 1000 mg Zn/L) of Zn intake at the end of the experiment. It was concluded that chick receiving 1000 mg Zn/L as ZnSO4.7H2O in drinking water showed signs of Zn toxicity.     

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)     

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.     

Effects of breed (Angus vs Simmental) and copper and zinc source on mineral status of steers fed high dietary iron

Forty-four Angus (n = 24) and Simmental (n = 20) steers, averaging 301 kg initially, were used to determine the effects of breed and Cu and Zn source (SO4 or proteinate (Prot) form) on Cu and Zn status of steers fed high dietary iron (Fe). Steers were stratified by weight within breed and randomly assigned to treatments. Treatments consisted of: 1) CuSO4 + ZnSO4 ,2) CuSO4 + ZnProt, 3) CuProt + ZnSO4, and 4) CuProt + ZnProt. Copper and Zn sources were added to provide 5 mg Cu and 25 mg supplemental Zn/kg DM. All steers were individually fed a corn silage-based diet supplemented with 1,000 mg Fe (from FeSO4)/kg DM. Liver biopsy samples were obtained at the beginning and end of the 149-d study. Serum samples were collected initially and at 28-d intervals for determination of ceruloplasmin activity and Zn and Cu concentrations. Copper and Zn source did not affect performance, serum or liver Cu and Zn concentrations, or ceruloplasmin activity. Copper status decreased (P < 0.01) in all steers with time, and increasing the level of supplemental Cu from 5 to 10 mg/kg DM on d 84 did not prevent further drops in serum Cu and ceruloplasmin. Simmental steers had lower (P < 0.05) serum and liver Cu concentrations, and serum ceruloplasmin activity throughout the study. These results indicate that neither CuSO4 nor CuProt were effective at the supplemental concentrations evaluated in alleviating the adverse effect of high Fe on Cu status. Simmental steers had lower Cu status than Angus, suggesting a higher Cu requirement.     

Chemical characteristics and relative bioavailability of supplemental organic zinc sources for poultry and ruminants

Eight commercially available organic Zn products and reagent-grade ZnSO4 x 7H2O (Zn Sulf) were evaluated by polarographic analysis, and solubility in .1 M K2HPO4-KH2PO4 buffer (pH 5), .2 M HCl-KCl buffer (pH 2), and deionized water. Fractions from these solubility tests were evaluated by gel filtration chromatography for structural integrity. Degree of chelation was generally positively related to chelation effectiveness determined by polarography. The organic sources were Zn methionine complex A (Zn MetA), Zn methionine complex B (Zn MetB), Zn polysaccharide complex (Zn Poly), Zn lysine complex (Zn Lys), Zn amino acid chelate (Zn AA), Zn proteinate A (Zn ProA), Zn proteinate B (Zn ProB), and Zn proteinate C (Zn ProC). Three experiments were conducted to estimate the relative bioavailability of Zn from the organic Zn supplements for chicks and lambs when added at high dietary levels to practical diets. Bone Zn concentration increased (P < .001) as dietary Zn increased in both experiments. When Zn Sulf was assigned a value of 100% as the standard, multiple linear regression slope ratios of bone Zn from chicks fed 3 wk regressed on dietary Zn intake gave estimated relative bioavailability values of 83 +/- 14.6 and 139 +/- 16.9 for Zn AA and Zn ProA, respectively, in Exp. 1 and 94 +/- 11.6, 99 +/- 8.8, and 108 +/- 11.4 for Zn Poly, Zn ProB, and Zn ProC, respectively, in Exp. 2. In Exp. 3, 42 lambs were fed diets containing Zn Sulf, Zn ProA, Zn AA, or Zn MetB for 21 d. Based on multiple linear regression slope ratios of liver, kidney, and pancreas Zn and liver metallothionein concentrations on added dietary Zn, bioavailability estimates relative to 100% for Zn Sulf were 130, 110, and 113 for Zn ProA, Zn AA, and Zn MetB, respectively. Except for Zn ProA, which was greater, the organic Zn supplements had bioavailability values similar to that of Zn Sulf for chicks and lambs. Bioavailability of organic Zn products was inversely related to solubility of Zn in pH 5 buffer in chicks (r2 = .91) and pH 2 buffer in lambs (r2 = .91), but not to an estimate of degree of chelation.     

Effects of organic forms of zinc on growth performance,tissue zinc distribution,and immune response of weanling pigs

This study was conducted to determine the effect of zinc level and source on growth performance, tissue Zn concentrations, intracellular distribution of Zn, and immune response in weanling pigs. Ninety-six 3-wk-old crossbred weanling pigs (BW = 6.45 +/- 0.17 kg) were assigned to one of six dietary treatments (four pigs per pen, four replicates per treatment) based on weight and litter origin. Treatments consisted of the following: 1) a corn-soybean meal-whey diet (1.2% lysine) with a basal level of 80 ppm of supplemental Zn from ZnSO4 (control; contained 104 ppm total Zn); 2) control + 80 ppm added Zn from ZnSO4; 3) control + 80 ppm added Zn from Zn methionine (ZnMet); 4) control + 80 ppm added Zn from Zn lysine (ZnLys); 5) control + 40 ppm added Zn from ZnMet and 40 ppm added Zn from ZnLys (ZnML); and 6) control + 160 ppm added Zn from ZnSO4. Zinc supplementation of the control diet had no effect on ADG or ADFI. Gain efficiency was less (P < 0.05) for pigs fed 80 ppm of Zn from ZnSO4 than for control pigs and pigs fed 160 ppm of Zn from ZnSO4. Organ weights, Zn concentration, and intracellular distribution of Zn in the liver, pancreas, and spleen were not affected (P = 0.12) by Zn level or source. Skin thickness response to phytohemagglutinin (PHA) was not affected (P = 0.53) by dietary treatment. Lymphocyte proliferation in response to PHA was greater (P < 0.05) in pigs fed ZnLys than in pigs fed the control diet or the ZnML diet; however, when pokeweed mitogen was used, lymphocyte proliferation was greatest (P < 0.05) in pigs fed the ZnMet diet than pigs fed the control, ZnLys, ZnML, or 160 ppm ZnSO4 diets. Antibody response to sheep red blood cells was not affected by dietary treatments. Supplementation of 80 ppm of Zn from ZnSO4 or ZnMet and 160 ppm of Zn from ZnSO4 decreased (P < 0.05) the antibody response to ovalbumin on d 7 compared with control pigs, but not on d 14. Phagocytic capability of peritoneal exudate cells was increased (P < 0.05) when 160 ppm of Zn from ZnSO4 was supplemented to the diet. The number of red blood cells ingested per phagocytic cell was increased (P < 0.05) in pigs fed the diet supplemented with a combination of ZnMet and ZnLys and the diet with 160 ppm of Zn from ZnSO4. Results suggest that the level of Zn recommended by NRC for weanling pigs was sufficient for optimal growth performance and immune responses, although macrophage function may be enhanced at greater levels of Zn. Source of Zn did not alter these measurements.