Estimation of the relative bioavailability of copper sources in chicks fed on conventional dietary amounts

1. Tissue accumulation of Cu from dietary additions of 0, 5, 10, or 20 mg/kg Cu as reagent grade Cu acetate and feed grade Cu carbonate was determined in day‐old chicks fed on conventional maize‐soyabean meal starter diets (5.41 mg/kg Cu as‐fed basis) for 3 weeks.

2. Average daily food intake, daily weight gain and food conversion were similar among treatments.

3. There were linear increases in plasma and liver Cu concentrations (P< 0.01) as dietary Cu increased.

4. Bioavailability of Cu as carbonate was 0.66 that of Cu in the acetate based on the multiple regression slope ratio of liver Cu concentration on added dietary Cu. Although responses for the two Cu sources did not differ significantly, the relative bioavailability of the Cu carbonate was similar (0.66 vs 0.68) to that obtained in an earlier study (Ledoux et al., 1991) with greater dietary Cu contents (150, 300 and 450 mg/kg) in which the slopes of the equations representing the two sources differed (P<0.05).     

Estimation of the relative biological availability of inorganic selenium sources for ruminants using tissue uptake of selenium

An experiment was conducted to estimate the relative bioavailability of inorganic Se sources based on tissue Se deposition following supplementation at high dietary levels. Twenty-eight crossbred wethers averaging 50 kg initial weight were assigned randomly to seven treatments that were fed for 10 d. The basal diet contained .18 mg/kg Se (DM basis). Dietary Se was added at 0, 3, 6 or 9 mg/kg as reagent grade sodium selenite (Na2SeO3) and 6 mg/kg from either calcium selenite (CaSeO3), Na2SeO3 + fumed amorphous carrier or sodium selenate (Na2SeO4). There were four sheep per treatment group, housed in individual, raised pens with slatted floors. Daily feed intake was restricted to 1,200 g and tap water was available ad libitum. The basal diet was fed for a 10-d adjustment period, then sheep were fed experimental diets for 10 d. At the termination of the experiment, blood samples were taken; sheep were stunned and killed, and livers and kidneys were removed and frozen for Se analysis. There was a linear (P less than .001) uptake of Se in liver, kidney and serum. The CaSeO3 and Na2SeO4 sources resulted in greater (P less than .05) Se concentrations in liver and kidney than did Na2SeO3, but these differences were not significant when the analyzed dietary Se concentrations were used as a covariate in the statistical model. Based on linear and multiple linear regression slopes and average increases in serum, liver and kidney Se concentrations, estimated relative bioavailability values corrected for analyzed dietary concentration, were 100, 101, 90 and 133 for Na2SeO3, CaSeO3, Na2SeO3 + carrier and Na2SeO4, respectively.     

Estimation of the relative bioavailability of manganese sources for sheep

The relative biological availability of Mn in reagent-grade (RG) Mn sources was tested using 41 Rambouillet crossbred wether lambs in a completely randomized design. Lambs were fed a basal corn-soybean meal-cottonseed hull diet (37.6 ppm Mn, DM basis) or this basal diet supplemented with 0, 1,500, 3,000 or 4,500 ppm Mn from RG MnSO4.H20 or 3,000 ppm Mn from RG MnO, MnO2 and MnCO3. Feed intake was restricted to 1,000 g/hd daily during the 21-d experimental period. There was a decrease (P less than .01) in daily feed intake by sheep fed 4,500 ppm Mn from MnSO4. Liver, kidney and bone Mn concentrations increased (P less than .05) with MnSO4 supplementation. Liver was most responsive to dietary Mn, followed by kidney and bone. Based on multiple linear regression slopes for liver, kidney and bone Mn concentrations, relative bioavailability of Mn from MnO, MnO2 and MnCO3 averaged 57.7, 32.9 and 27.8%, compared with 100% for MnSO4.     

Chemical characteristics and relative bioavailability of supplemental organic copper sources for poultry

Five commercially available organic Cu products and reagent-grade CuSO4 x 5H2O (Cu Sulf) were evaluated by polarographic analysis and solubility in 0.1 M K2HPO4-KH2PO4 buffer (pH 5), 0.2 M HCl-KCl buffer (pH 2), or deionized water. Fractions from these solubility tests were evaluated by gel filtration chromatography for structural integrity. The organic sources were Cu lysine complex (Cu Lys), Cu amino acid chelate (Cu AA), Cu proteinate A (Cu ProA), Cu proteinate B (Cu ProB), and Cu proteinate C (Cu ProC). Separation of peaks in the chromatograms for the soluble Cu fraction from deionized water indicated that 77, 31, 69, 94, and 16% of the Cu remained chelated for the above sources, respectively. Two experiments were conducted to estimate the relative bioavailability of Cu from the organic Cu supplements for chicks when added at high dietary concentrations to practical corn-soybean meal diets. Liver Cu concentration increased (P < 0.0001) as dietary Cu increased in both experiments. When Cu Sulf was assigned a value of 100% as the standard, linear regression slope ratios of log10 liver Cu concentration regressed on added dietary Cu concentration gave estimated relative bioavailability values of 124 +/- 5.1, 122 +/- 5.3, and 111 +/- 6.0 for Cu Lys, Cu AA, and Cu ProC, respectively, in Exp. 1. The bioavailability estimates for Cu Lys and Cu AA were greater (P < 0.05) than that for Cu Sulf. Values in Exp. 2 were 111 +/- 7.6, 109 +/- 8.4, and 105 +/- 7.5 for Cu Lys, Cu ProA, and Cu ProB, respectively, and all sources were similar in value for chicks. Solubility of Cu in pH 2 buffer provided the best prediction of bioavailability (r2 = 0.924). Other indicators of chelation integrity and solubility had little value as predictors of bioavailability (r2 < or = 0.445).     

Relative bioavailability of organic bis-glycinate bound copper relative to inorganic copper sulfate in beef steers fed a high antagonist growing diet

To assess the relative bioavailability of bis-glycinate bound Cu, 90 Angus-cross steers (265 ± 21 kg) were blocked by body weight (BW) to pens with GrowSafe bunks and randomly assigned to dietary treatments (14 to 18 steers/treatment): 0 mg supplemental Cu/kg dry matter (DM; CON), 5 or 10 mg supplemental Cu/kg DM as Cu sulfate (CS5; CS10) or bis-glycinate bound Cu (GLY5; GLY10). Steers received a high antagonist growing diet (analyzed 4.9 mg Cu/kg DM, 0.48% S, and 5.3 mg Mo/kg DM). Steers were weighed at the beginning (days 1 and 0) and end (days 125 and 126) of the trial to determine average daily gain (ADG) and gain:feed (G:F). Blood was collected from all steers on days 0, 28, 56, 84, and 126. Liver samples were collected on days −3 or −2 and day 123 or 124. Data were analyzed using ProcMixed of SAS (experimental unit = steer; fixed effect = treatment and block). Plasma Cu was analyzed as repeated measures (repeated effect = day). Plasma and liver Cu concentrations were regressed against total Cu intake using ProcGLM to calculate relative bioavailability of GLY. Final BW and overall ADG were greatest for CS5 and CS10 and least for CON and GLY5 (P = 0.01). Overall, DMI was not affected by treatment (P = 0.14), but overall G:F tended to be greatest for CS5, CS10, and GLY5 and least for CON (P = 0.08). Total and supplemental Cu intake was greatest for steers supplemented either source at 10 mg Cu/kg DM and least for CON (P < 0.01). However, total and supplemental Cu intake was greater for CS5 than GLY5 (P < 0.01). Final liver Cu concentrations were greatest for CS10, least for CON, CS5, and CS10, and intermediate for GLY10 (P < 0.01). Final plasma Cu was greatest for steers supplemented either source at 10 mg Cu/kg DM (P < 0.01). Relative bioavailability of GLY was 82% compared to CS based on liver Cu (P < 0.01) but did not differ based on plasma Cu (P = 0.60). The lesser bioavailability of GLY relative to CS could be due to a high concentration of dietary antagonists and lower solubility of GLY (68.9% relative to CS) in pH conditions (5.2) similar to the ruminal pH of a beef animal consuming a high concentrate diet. Future studies should examine the effects of bis-glycinate bound Cu fed in blended combination with inorganic Cu sulfate to determine the most effective blend of sources for feedlot cattle experiencing varying amounts of dietary Cu antagonists.     

Relative bioavailability of phosphorus in inorganic phosphorus sources fed to growing pigs

The relative bioavailability of P in 5 sources of inorganic P was determined using growing pigs. The 5 sources of inorganic P were dicalcium phosphate (DCP), monocalcium phosphate (MCP) containing 50% MCP (MCP50), MCP containing 70% MCP (MCP70), MCP containing 100% MCP (MCP100), and monosodium phosphate (MSP). A total of 11 diets were formulated. The basal diet was formulated to contain 0.10% P, and 10 additional diets were formulated by adding 0.07 or 0.14% P from each of the 5 P sources to the basal diet. Growing pigs (n = 44; initial BW: 16.8 ± 4.3 kg) were individually housed and randomly allotted to the 11 experimental diets. Feed was provided on an ad libitum basis throughout the 28-d experimental period. At the conclusion of the experiment, all pigs were killed, and 4 bones (i.e., the third and fourth metacarpals on both front feet) were harvested. Bone-breaking strength, bone ash, and Ca and P concentrations were determined. The concentration of bone ash increased (P < 0.05) as MCP50, MCP70, MCP100, or MSP were added to the basal diet, and the concentration of bone P also increased (P < 0.05) as MCP70, MCP100, or MSP were added to the basal diet. The relative bioavailability of P in each of the feed phosphates was determined using slope ratio methodologies based on breaking strength, and expressed relative to MSP. The slope of the regression line for diets containing MSP or MCP100 was steeper (P < 0.05) than the slope for pigs fed the diet containing DCP, but not different (P > 0.05) from that of pigs fed diets supplemented with MCP50 or MCP70. In conclusion, P in MSP and MCP100 is more bioavailable than P in DCP, but there were no differences within MCP sources.     

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.     

Use of chemical characteristics to predict the relative bioavailability of supplemental organic manganese sources for broilers

Twelve organic Mn sources and MnSO4 were evaluated by polarographic analysis and via solubility in buffers (pH 5 and 2) and deionized water. Fractions from solubility tests were evaluated by gel filtration chromatography for structural integrity. Organic Mn sources included five Mn methionine complexes (Mn Met A to Mn Met E), two Mn proteinates (Mn Pro A and Mn Pro B), and five Mn amino acids (Mn AA A to Mn AA E). Sources varied considerably in chemical characteristics. Chelation strength (Qf) ranged from weak (1.9 Qf-values) to strong complexes (115.4 Qf-values). No complexed Mn was found in filtrates at pH 2.0 or 5.0. A 42-d bioassay was used to estimate relative bioavailability of Mn sources for chicks fed diets supplemented with 60, 120, or 180 mg Mn/kg. Bone Mn, heart Mn, heart manganese-superoxide dismutase activity (MnSOD), and heart MnSOD mRNA increased (P < 0.001) as dietary Mn increased. Only heart MnSOD mRNA tended (P < 0.10) to differ among dietary Mn sources. For bioassays of Mn, the MnSOD mRNA level in heart was more sensitive than the MnSOD activity in heart or other indices. Relative to MnSO4 (assigned 100%), slope ratios of MnSOD mRNA levels in heart gave bioavailabilities of 99, 132, and 113% for Mn Met E, Mn AA B, and Mn AA C sources with weak, moderate, and strong chelation strength, respectively. The bioavailability of Mn was more closely related to chelation strength as measured by polarography than to chemical traits assessed by solubility or structural integrity.     

Effects of dietary substitution of zinc‐methionine for inorganic zinc sources on growth performance,tissue zinc accumulation and some blood parameters in broiler chicks

This study was designed to evaluate the effects of dietary inclusion of zinc‐methionine (ZnMet) as a replacement for conventional inorganic zinc sources on performance, tissue zinc accumulation and some plasma indices in broiler chicks. A total of 450‐day‐old Ross male broiler chicks were randomly assigned to five pen replicates of nine experimental diets. Dietary treatments consisted of two basal diets supplemented with 40 mg/kg added Zn as feed‐grade Zn sulphate or Zn oxide in which, Zn was replaced with that supplied from ZnMet complex by 25, 50, 75 or 100%. At 42 days of age, three randomly selected birds from each pen were bled to measure plasma metabolites; then, the chicks were slaughtered to evaluate carcass characteristics. Results showed that dietary treatments affected (p < 0.05) feed intake during the starter period, and chicks on Zn oxide diets consumed more feed than sulphate counterparts. Furthermore, dietary substitution of inorganic Zn sources by ZnMet caused improvements (p < 0.01) in body weight gain during all experimental periods. Dietary supplementation of ZnMet improved feed conversion efficiency during 1–21 and 1–42, but not in 21–42 days of age. Complete replacement of inorganic Zn by that supplied from ZnMet caused an increase (p < 0.05) in relative liver weight. Similarly, dietary inclusion of ZnMet increased breast meat and carcass yields and reduced abdominal fat percentage (p < 0.05). Incremental levels of ZnMet increased (p < 0.05) zinc concentrations in liver and thymus, and the highest zinc accumulations were seen in 100% ZnMet‐supplemented birds. Interestingly, introduction of ZnMet into the diets partially in place of inorganic sources resulted in decreases (p < 0.01) in plasma uric acid and triglycerides concentrations. The present findings indicated that dietary ZnMet inclusion in replacement of inorganic sources in addition to improving growth performance, reduced plasma uric acid and triglycerides concentrations, consequently decreased abdominal fat pad and increased carcass meat yield.     

Effect of inorganic and organic manganese supplementation on the performance and tissue manganese content of broiler chicks

The effects of dietary levels of manganese (Mn) in inorganic (MnO) and organic (Mn fumarate) forms were evaluated on cockerel chicks. A basal corn-soybean diet with 23 mg/kg Mn was supplemented with levels of 0, 30, 60 and 240 ppm Mn from both Mn sources. Each treatment was replicated in five pens of 10 chicks. The chicks were fed diets ad libitum from 14 to 49 days of age, after which five birds per treatment were sacrificed for pathomorphological examinations and analysis. The treatments did not exert significant effects on the body weight (BW), the feed/gain (F/G) ratio or the mortality rate. According to the necropsy findings, no growth retardation or emaciation occurred in either of the groups and the differences in the average absolute and relative organ weights were not significant (P > 0.05). Tissue analysis indicated that the tibia showed the greatest response to Mn, followed by the liver and kidney. Accumulation in the tibia was higher (P < 0.05) with supplements of 30, 60 and 240 mg/kg from both Mn sources (3.71, 3.78, 4.44, and 3.68, 4.00, 4.36 mg/kg DM, MnO and Mn fumarate, respectively) compared to the control group (3.21 mg/kg). Accumulation in the liver increased significantly (P < 0.05) only with supplements of 60 and 240 ppm independently of the Mn source (12.7, 14.2, and 14.0, 14.9 mg/kg, respectively) compared to the control (9.8 mg/kg). Similarly, kidney tissue Mn was higher (P < 0.05) only with supplements of 60 and 240 ppm (12.8, 12.8, and 13.1, 12.5 mg/kg, respectively) compared to the control (10.2 mg/kg). At the same level of supplementation of the two Mn sources there were no significant differences (P > 0.05) between the Mn concentrations of organs and tissues. Droppings sensitively reflected the intake, whereas blood plasma and feathers showed only the extreme Mn loading.     

Early growth and environmental implications of dietary zinc and copper concentrations and sources of broiler chicks

1. Environmental accumulation of zinc and copper is becoming a concern in areas having intensive animal production. This study examined performance and excretion of broiler chicks given diets supplemented with graded concentrations of zinc and copper from three different sources. 2. Two experiments were conducted, each utilising 570 1-d-old chicks. In Experiment 1, chicks were given diets containing supplemental zinc concentrations from 40 to 120 mg/kg supplied as zinc sulphate, a zinc amino acid complex (Availa Zn), or a combination of zinc sulphate and Availa Zn with each contributing one-half of the total supplemental zinc. In Experiment 2, broiler chicks were given diets with graded concentrations of supplemental copper ranging from 4 to 12 mg/kg from copper sulphate, a copper amino acid complex (Availa Cu), or a combination of copper sulphate and Availa Cu with each contributing one-half of the total supplemental copper. 3. During the 17-d experimental period, mineral concentration or source did not influence body weight, feed conversion, or the incidence of mortality from 1 to 17 d. 4. Decreasing dietary zinc concentration from 120 to 40 mg/kg reduced zinc excretion by 50%. 5. Copper excretion was decreased by 35% as supplemental copper was reduced from 12 to 4 mg/kg. 6. Reducing dietary zinc and copper concentrations can potentially decrease the accumulation of heavy metals in the environment without compromising bird performance.     

Toxicity and tissue accumulation of copper in chicks fed casein and soy-based diets.

Experiments were conducted to study Cu toxicity in chicks fed casein or soy-containing diets containing graded levels of excess CuSO4.5H2O. Differences between diets in measures of Cu toxicity were pronounced. Addition of 800 mg of Cu/kg to a casein-dextrose semipurified diet decreased weight gains by 63%, but the same addition of Cu to a corn-soybean meal complex diet decreased gains by only 8%. At all levels of Cu supplementation (100, 200, 400 or 800 mg/kg), Cu deposition in the liver was increased markedly in chicks fed casein diets compared with those fed the complex diet. Substituting soy-protein concentrate for casein in the semipurified diet resulted in a marked decrease in Cu toxicity as measured by weight gain reductions and tissue accumulation of Cu.     

肉仔鸡对不同铁源生物学利用率的研究

试验采用1日龄AVAIN肉仔鸡200只研究不同铁源的生物学效价。采用3×3因子试验设计,3种铁源分别为硫酸亚铁、柠檬酸铁和酵母铁,试验日粮在玉米-豆粕型基础日粮(对照组)的基础上分别添加40、80、160mg/kg铁构成,试验共10个处理,每个处理4个重复。在本试验条件下,试验各组铁源对肉仔鸡生产性能、脾脏以及血红蛋白铁含量、红细胞计数、血细胞压积、血清总铁结合力影响不显著;对肝脏、肾脏铁浓度影响显著或极显著;随日粮铁水平的增加,肉仔鸡生产性能没有表现出规律性变化,脾脏铁、肝脏铁、胰脏铁浓度以及血红蛋白含量极显著增加,肾脏、肝脏铁浓度以及血红蛋白、红细胞计数显著增加,而血清总铁结合力极显著降低。利用斜率比法,不同判断指标得到的柠檬酸铁和酵母铁的相对生物学效价不同;综合所获得的回归方程的显著性和日粮铁水平对各测定指标的影响,本次试验所测指标均可作为适合本试验条件的评价不同铁源生物学利用率指标。     

肉仔鸡对不同锰源生物学效价的研究

试验采用1日龄AVAINS肉仔鸡200只研究不同锰源的生物学效价。试验采用3×3因子试验设计,3种锰源分别为硫酸锰、乙酸锰和酵母锰,3个锰水平分别为60、120、180mg/kg,试验共10个处理,每个处理4个重复。在本试验条件下,试验组各组锰源日粮锰源对肉仔鸡生产性能、心肌、肝脏、肾脏、胫骨锰含量以及心肌MnSOD活力影响不显著。日粮中添加酵母锰有改善肉仔鸡生产性能的趋势,但随日粮锰水平的增加,肉仔鸡生产性能没有表现出规律性变化,心肌、肝脏、肾脏及胫骨锰含量极显著增加,而血红蛋白含量显著降低。综合考虑本试验获得的回归方程的显著性和日粮锰水平对各测定指标的影响,本次试验所测指标均可以作为适合本试验条件的评价不同锰源生物学利用率指标。     

Superior growth performance in broiler chicks fed chelated compared to inorganic zinc in presence of elevated dietary copper

Background: The goal of this study was to compare the antagonism of elevated dietary Cu(250 mg/kg) from Cu SO4 on three different Zn sources(Zn SO4· H2O; [Zn bis(-2-hydroxy-4-(methylthio)butanoic acid)], Zn(HMTBa)2,a chelated Zn methionine hydroxy analogue; and Zn-Methionine), as measured using multiple indices of animal performance in ROSS 308 broilers.Methods: Three experiments were conducted in broiler chicks fed a semi-purified diet. Al birds were fed a Zn-deficient diet(8.5 mg/kg diet) for 1 wk, and then provided with the experimental diets for 2 wks.Results: Experiment 1 was a 2 × 2 factorial design with two levels of Cu(8 vs. 250 mg/kg diet from Cu SO4) and two Zn sources at 30 mg/kg [Zn SO4· H2 O vs. Zn(HMTBa)2]. Elevated Cu impaired growth performance only in birds fed Zn SO4.Compared to Zn SO4· H2 O, Zn(HMTBa)2improved feed intake(12 %; P 0.001) and weight gain(12 %, P 0.001) and the benefits were more pronounced in the presence of 250 mg/kg diet Cu. Experiment 2 was a dose titration of Zn SO4· H2 O and Zn(HMTBa)2at 30, 45, 60, and 75 mg/kg diet in the presence of 250 mg/kg Cu SO4. Feed:gain was decreased and tibia Zn was increased with increasing Zn levels from 30 to 75 mg/kg. Birds fed Zn(HMTBa)2consumed more food and gained more weight compared to birds fed Zn SO4, especially at lower supplementation levels(30 and45 mg/kg; interaction P 0,05). Experiment 3 compared two organic Zn sources(Zn(HMTBa)2vs. Zn-Methionine)at 30 mg/kg with or without 250 mg/kg Cu SO4. No interactions were observed between Zn sources and Cu levels on performance or tissue mineral concentrations. High dietary Cu decreased weight gain(P 0.01). Tibia Cu and liver Cu were significantly increased with 250 mg/kg dietary Cu supplementation(P 0.01). No difference was observed between the two Zn sources.Conclusions: Dietary 250 mg/kg Cu significantly impaired feed intake and weight gain in birds fed Zn SO4· H2 O,but had less impact in birds fed Zn(HMTBa)2. No difference was observed between the two organic zinc sources.These results are consistent with the hypothesis that chelated organic Zn is better utilized than inorganic zinc in the presence of elevated Cu.     

不同镁源相对生物学利用率的评价

360只1日龄的AA肉仔鸡随机分成10组(3×3 1),每组设6个重复,每个重复6只公雏,研究3种镁源的相对生物学利用。三种镁源:氧化镁(MgO)、天门冬氨酸镁(MgAsp)、天门冬氨酸螯合镁(MgdiAsp),每种镁的添加水平为0.9、1.8、2.7g/kg,不加镁的处理组做为对照。试验结果表明,血清镁的浓度随各镁源添加水平提高线性提高(P<0.01)。肝脏镁的含量随日粮中MgO、MgAsp添加量的提高呈二次曲线性提高(P<0.01)。MgAsp比MgO更有效提高血清和肝脏中的镁含量(P<0.01)。MgdiAsp添加组肉仔鸡血清和肝脏中的镁含量最高。肝脏过氧化氢酶(CAT)的活性随MgAsp或MgdiAsp添加量的增加线性提高(P<0.01),而随MgO添加量的增加呈二次曲线性提高(P<0.05)。MgAsp比MgO更有效地提高肝脏CAT的活性,MgdiAsp供应组肉仔鸡肝脏中CAT的活性最高(P<0.01)。肝脏丙二醛(MDA)的含量随日粮镁添加量的增加线性降低(P<0.05),有机镁比无机镁更有利于降低肝脏中MDA的含量(P<0.01)。本研究结果表明,日粮中添加镁可以改善肉仔鸡的镁营养状态,提高肉仔鸡肝脏抗氧化酶的活性,降低脂质过氧化水平,有机镁的效果优于无机镁。     

Zinc bioavailability in feed-grade sources of zinc

Chick bioassays were used to assess bioavailability of zinc (Zn) from inorganic Zn sources. A soy isolate-dextrose diet containing 13 mg Zn/kg diet was supplemented with feed-grade sources of ZnSO4.H2O (ZnSO4) or ZnO and fed for 2 wk after a 7-d Zn-depletion protest period. Bioavailability of Zn in ZnO relative to ZnSO4 (set at 100%) was determined by multiple regression slope-ratio methodology, using both growth and tibia Zn accumulation in chicks fed graded levels of ZnO and ZnSO4. Linear responses for gain and tibia Zn occurred at dietary Zn levels (ZnSO4.7H2O) between 13 mg/kg (basal) and 33 mg/kg (gain) or 53 mg/kg (total tibia Zn). Therefore, two bioavailability assays were conducted using supplemental Zn levels of 0, 7.5 and 15 mg/kg from each Zn source. When weight gain was regressed on supplemental Zn intake, bioavailability of Zn in ZnO was only 61.2% (P less than .01) that of ZnSO4. When total tibia Zn was regressed on supplemental Zn intake, bioavailability of Zn compared with ZnSO4 (set at 100.0%) was 44.1% (P less than .001) for ZnO. With chicks fed soy-based diets, bioavailability of Zn from ZnO was less than that of ZnSO4.     

Rabbit model for estimating relative bioavailability, residues and tissue tolerance of intramuscular products: comparison of two ampicillin products

A rabbit model for simultaneous investigation of the bioavailability, tissue residues and tissue tolerance of intramuscularly administered veterinary medicines is described. The bioavailability of ampicillin from two intramuscular products, which had been found to be different in calves, were compared in a two-way crossover design. The ampicillin levels in plasma, ampicillin residues in tissues, the plasma creatine kinase activity and the tissue damage at the injection sites were studied. The absolute bioavailabilities for the products were 100% and 40%. Differences in pharmacokinetics of ampicillin between sexes were observed after intravenous and intramuscular administration. Only slight tissue damage could be detected at the injection sites after intramuscular administration of these products. The results were compared with those obtained previously in calves and were found to be similar. Further investigations with other intramuscular drug products to validate this model are under way.