Variability in concentrations of zinc in serum and feed when using zinc oxide as a supplement for the prevention of facial eczema

AIMS: To determine the variability of concentrations of Zn in feed, when used as a supplement to prevent facial eczema, and to determine the variability in concentrations of Zn in serum between cows and herds that are being supplemented with ZnO in feed, using in-shed feeders or on a feed pad.

METHODS: Sixteen commercial dairy farms in the Waikato region of New Zealand were enrolled, that were supplementing cows with ZnO in the feed using either an automatic in-shed feeder (ASF) or a feed pad (FP) using a feed-out or mixer wagon. On each farm 10 cows were selected by the farmer, that were assumed to be representative of the age and liveweight of the herd. Four hours after supplement feeding, each cow was weighed and a blood sample collected for measurement of concentrations of Zn in serum. Three samples of feed were collected from each farm for Zn analysis, from the beginning, middle and end of the feed being distributed. Levene’s test for homoscedasticity was used to analyse whether there were differences in variation of individual concentrations of Zn in serum, and in the feed, between the two feeding systems. Multivariable linear regression was used to examine associations between age, feeding method or liveweight and concentrations of Zn in serum, after accounting for the variability between farms.

RESULTS: Of the 163 cows sampled, concentrations of Zn in serum were between 20–35?µmol/L in 75/163 (46 (95% CI=38–54)%) cows; were <20?µmol/L in 71/163 (44 (95% CI=36–52)%) cows, and >35?µmol/L in 17/163 (10 (95% CI=6–16)%) cows. The variation in concentrations of Zn in serum in individual cows differed between farms (p<0.001), and the variability was greater for cows fed using a FP than ASF (p<0.001). There was no difference in the variation of concentrations of Zn in feed between the two feeding methods (p=0.54), but concentrations of Zn in serum were associated with the amount of Zn offered in feed (p=0.008).

CONCLUSIONS AND CLINICIAL RELEVENCE: There was significant variability between farms in the concentrations of Zn in the serum of cows being supplemented with ZnO in feed. Only 46% of cows sampled had concentrations of Zn between 20–35?µmol/L. Effective management of facial eczema should include monitoring Zn in the feed and in serum to ensure cows are receiving the correct dose they require.     

乐果、铜和锌对水生生物的联合毒性研究

为通过不同生物等级的模式生物研究乐果、铜和锌的联合毒性,以明亮发光杆菌和斑马鱼胚胎为受试模式生物,通过混合毒性指数法（MTI法）评价了乐果、铜和锌的联合毒性效应。结果表明：明亮发光杆菌毒性测试显示,暴露测试15 min时,乐果、铜和锌的EC₅₀值分别为123、0.53 mg·L^-1和1.71 mg·L^-1;暴露测试30 min时,EC₅₀值分别为122、0.50 mg·L^-1和1.54 mg·L^-1。乐果-铜和乐果-锌暴露15 min测得的MTI分别为0.69和0.60。斑马鱼胚胎毒性测试显示,暴露72 h后乐果、铜和锌的LC50值分别为0.31、1.67 mg·L^-1和369 mg·L^-1。乐果-铜和乐果-锌暴露72 h后测得的MTI分别为0.70和0.75。研究表明,乐果和铜、锌分别混合后的联合毒性均有所增强,整体毒性表现为部分相加作用,因此两类物质在环境中的残留会对水生生物及其他生物造成潜在危害。     

甘氨酸锌在动物生产中的应用研究

锌是动物体内的必需微量元素之一,在动物生长发育和健康方面起着关键作用.甘氨酸锌作为有机微量元素具有生物利用率高、减排环保等优势.综述了甘氨酸锌对动物的生长性能、繁殖性能、免疫能力及肠道健康的影响,探讨了动物对甘氨酸锌的需要量,旨在为动物生产中科学利用甘氨酸锌改善动物健康,促进动物生长提供理论依据.     

石灰性褐土中磷锌镉相互作用对其有效性的影响

采用室内培养的方法,研究了石灰性褐土中磷、锌、镉相互作用对土壤中磷、锌、镉有效性的影响。结果表明：（1）磷锌共同培养时,施锌提高了土壤速效磷含量,且随培养时间的延长而降低。在相同锌浓度处理下,土壤中的有效锌含量随施磷量的增加而增加,不同锌浓度处理下,有效锌含量随土壤培养时间的延长而显著降低。（2）磷镉共同培养时,施镉对土壤速效磷含量影响不明显;施磷降低了有效镉含量,但效果不显著;且都随时间的延长而降低。（3）锌镉共同培养时,在培养的前30d,土壤中有效锌含量随施镉浓度增加而降低,但在30d后,有效锌含量有增加的趋势。土壤中有效镉含量在不同锌-镉处理下随培养时间变化有较大差异：在Cd3处理下,加入高浓度锌后显著降低土壤有效镉含量;Cd30处理下,在培养前30d,锌的施入对土壤中有效镉含量影响不明显,但30d以后,土壤有效镉含量随施入锌浓度的增加而显著降低。说明两者的竞争机制随时间的延长发生变化,且施锌能明显降低镉的毒性。     

Cu^2＋、Zn^2＋复合条件下Cd^2＋在陕西5种土壤中的吸附

通过平衡吸附的方法,研究了Cd2＋在单一及与Cu2＋、Zn2＋复合条件下,在陕西塿土、黄绵土、黑垆土、黄褐土、砂土5种土壤中的吸附特征,并通过多重相关分析探讨了其吸附机制。结果表明,在20、30℃条件下,Cd2＋在各供试土样中吸附等温线总体上呈H或L型等温线形式,黑垆土对Cd2＋总是吸附最强,而砂土的吸附总是最弱;Cd2＋吸附的温度效应呈现升温负效应特征,塿土土样中,Cu2＋的共存对其温度效应影响较大,而在其他4种土样中Zn2＋的共存具有较大影响;Cu2＋、Zn2＋的共存均降低了Cd2＋的吸附量,具有显著的拮抗作用;Freundlich模型是描述Cd2＋吸附等温线最佳模型。相关分析结果表明,Cd2＋在土壤中的吸附主要以电性引力吸附为主,Cu2＋的共存主要和其与土壤有机质之间的络和吸附等化学吸附作用有关,因此其对Cd2＋以化学竞争性吸附的影响相对较弱,而Zn2＋共存吸附与Cd2＋吸附机制类似,因此表现出Zn2＋共存对Cd2＋吸附影响较大的特点。     

草酸对不同土壤中Cd Zn吸附及其交互作用影响的初步研究

研究了草酸对Cd2＋、Zn2＋单一及复合条件下在陕西塿土、黄绵土、黑垆土、黄褐土、砂土5种土壤中的吸附特征,并探讨了草酸的影响机制。结果表明,除在低Zn2＋平衡浓度下,5种土壤中草酸促进了Zn2＋的吸附外,总体上在Cd2＋、Zn2＋单一处理及其复合处理中,草酸降低了土壤对Cd2＋、Zn2＋的吸附。草酸既没有改变塿土、黑垆土吸附能力最强、砂土吸附能力最弱的结果,也没有改变Cd2＋、Zn2＋之间的相互拮抗作用。草酸对Cd2＋、Zn2＋吸附的影响机制主要在于其与Cd2＋、Zn2＋形成络合物。草酸主要通过降低电性引力的方式减弱土壤对Cd2＋的吸附能力,而对于Zn2＋,在低平衡浓度下,草酸对Zn2＋吸附的促进作用来源于在土壤氧化物矿物表面形成少量的三元表面络合物的桥键合效应,在高平衡浓度下,对Zn2＋吸附的抑制作用来源于草酸对土壤有机质化学吸附点位的竞争。对Cd2＋、Zn2＋吸附起决定作用的依然是土壤本身性质。     

Effect of Conditioning Zinc Sulfate Heptahydrate (ZnSHH) with Zinc Oxide (ZnO) and Neem Oil on Growth,Productivity, Zinc Biofortification of Grain and Zinc Uptake by Basmati Rice

Commercial grade zinc (Zn) sulfate hepta hydrate (ZnSHH) is the most widely used source of Zn in India and several other countries for amelioration of Zn deficiency in crops. However, it releases water of hydration at temperature above 30°C and forms lumps on storage, which make it difficult to handle it and apply in fields. Therefore, conditioning of ZnSHH with ZnO and neem oil reduces the release of water of hydration and prevents lumps formation and can be well stored. Field experiments were conducted at the research farm of the Indian Agricultural Research Institute, New Delhi, India during rice growing seasons (July-November) of 2009 and 2010 to study the effect of conditioning ZnSHH with ZnO and neem oil on growth, productivity and Zn fortification of rice (Oryza sativa) grain and uptake by Basmati rice ‘Pusa 1121’. The experiment was conducted in a randomized block design with 3 replications comprised of 9 treatments of Zn fertilization. The present study shows that when conditioned with 2% ZnO and 4% neem oil ZnSHH improved yield attributes, grain and straw yields, Zn uptake and partial factor productivity (PFP), agronomic efficiency (AE), recovery efficiency (RE), and physiological efficiency (PE) of Zn in Basmati rice ‘Pusa 1121’. In general, ZnO was inferior to ZnSHH. Application of ZnSHH conditioned with 2% ZnO and 4% neem oil can be a better source of Zn for transplanted puddled Basmati rice on Zn deficient soils.     

Mycorrhizal (Rhizophagus Intraradices) Symbiosis and Fe and Zn Availability in Calcareous Soil

Greenhouse experiment was conducted to assess the iron (Fe) and zinc (Zn) fractionation patterns in soils of arbuscular mycorrhizal (AM) fungus-inoculated and uninoculated maize plants fertilized with varying levels of Fe and Zn. Soil samples were collected for Fe and Zn fractions and available Fe, Zn and phosphorus (P) contents besides organic and biomass carbon (BMC), soil enzymes and glomalin. Major portion of Fe and Zn fractionations was found to occur in the residual form. Mycorrhizal symbiosis increased the organically bound forms of Fe and Zn while reducing the crystalline oxide, residual Fe and Zn fractions, indicating the transformation of unavailable forms into available forms. Soil enzymes, viz. dehydrogenase and acid phosphatase activities in M+ soils, were significantly higher than M? soil consistently. Overall, the data suggest that mycorrhizal symbiosis enhanced the availability of Fe and Zn as a result of preferential fractionation and biochemical changes that may alleviate micronutrient deficiencies in calcareous soil.

Abbreviations: AM: arbuscular mycorrhiza; Fe: Iron; Zn: Zinc; P: Phosphorous; Amox-Zn: amorphous oxide bound zinc; Cryox-Zn: crystalline oxide bound zinc; DAS: days after sowing; DTPA: diethylene Triamine Penta Acetic Acid; MnO₂-Zn: manganese oxide bound zinc; OC-Zn: organically bound zinc; WSEX: water soluble plus exchangeable zinc; MnO₂ Fe: manganese oxide bound iron; OC-Fe: Organically bound iron; WSEX Fe: water soluble plus exchangeable iron.