饲料中添加高剂量有机硒和无机硒对异育银鲫生长性能、组织硒蓄积和血液生化指标的影响

为探究饲料中高剂量的有机硒和无机硒对异育银鲫(Carassius auratus gibelio var. CAS V)的生长性能、硒蓄积和血浆生化指标等方面的影响,以硒代蛋氨酸(有机硒)和亚硒酸钠(无机硒)作为不同类型的硒源,初始体重为(62.95±0.23) g异育银鲫为研究对象,进行了为期90d的养殖实验。实验结果表明,饲料中添加0、10和20 mg/kg的有机硒和无机硒对异育银鲫的存活和饲料干物质的表观消化率无显著影响;有机硒处理组硒的表观消化率随饲料有机硒的添加量增加而显著升高(P<0.05);饲料中添加无机硒对硒消化率无显影响(P>0.05)。在饲料中添加有机硒可以提高异育银鲫的生长(P<0.05),在20 mg/kg处理组中达到最高(P<0.05);而饲料中添加10 mg/kg无机硒处理组未显著改变异育银鲫的特定生长率(P>0.05),但高浓度的无机硒则显著降低了其特定生长率(P<0.05)。饲料中添加有机硒显著降低了异育银鲫的肝体比,添加10 mg/kg无机硒显著降低异育银鲫的肝体比(P<0.05);饲料中添加有机硒和无机硒对异...     

富硒壶瓶碎米荠对青鱼幼鱼生长、生理生化、硒代谢、抗氧化及先天免疫的影响

为探究富硒壶瓶碎米荠(Cardamine hupingshanensis)对青鱼(Mylopharyngodon piceus)幼鱼生长、血清生理生化、肝脏硒代谢、抗氧化能力和先天免疫指标的影响,选取360尾初始体重为(5.51±0.02) g的青鱼幼鱼随机分配至4个实验组中,每组3个重复。在基础饲料中添加富硒壶瓶碎米荠的量为0、0.5、1.0和2.0 g/kg(硒的实际含量分别为0.04、0.43、0.75和1.57 mg/kg),同时添加矿物质混合物(无硒添加)和维生素混合物,配置成4种等氮等能的青鱼幼鱼试验饲料,养殖周期为60d。结果显示:饲料中添加0.5和1.0 g/kg富硒壶瓶碎米荠时,鱼体增重率(WG),特定生长率(SGR)较对照组和过量组(2.0 g/kg)显著升高,饲料系数(FCR)显著降低(P<0.05)。当饲料中富硒壶瓶碎米荠添加量为0.5—1.0 g/kg时,血清中的甘油三酯(TG)、总胆固醇(TCH)和白蛋白(ALB)含量呈上升趋势,而葡萄糖(GLU)含量显著下降(P<0.05)。饲料中添加0.5—1.0 g/kg富硒壶瓶碎米荠时可显著提高肝脏核因子...     

卫星灵芝液体发酵富集硒锌的研究

研究不同浓度的硒、锌对卫星灵芝菌丝体生长的影响,初步探讨卫星灵芝菌丝体生物富集硒、锌的效应。采用平板培养法及液体发酵法研究锌、硒对卫星灵芝菌丝体生长的影响及富集效应。培养基中不同浓度的亚硒酸钠对菌丝体生长均具有不同程度的抑制作用,但灵芝菌丝体的富硒量随着硒浓度的增加而提高,当亚硒酸钠浓度为40 mg/L时,菌丝体中的生物量、富硒量及富硒转化率最高,分别为1.54%、2 131.55 mg/kg、32.91%;培养基中硫酸锌浓度低于150 mg/L的范围内对卫星灵芝菌丝体生长有明显的促进作用,硫酸锌浓度为60 mg/L时菌丝体中的锌含量和富锌转化率最高,分别为1 142.91 mg/kg、1.76%。培养基中同时添加40 mg/L的亚硒酸钠和60 mg/L硫酸锌,菌丝体生长量1.60%,富硒量301.85 mg/kg,富硒率4.84%;富锌量为540.41 mg/kg,富锌率为5.72%。     

德国鸢尾对Cd胁迫的生理生态响应及积累特性

通过盆栽研究了Cd胁迫下德国鸢尾的生长状况、生态效应、生理特性及吸收和富集Cd的能力.结果表明:德国鸢尾对小于5 mg/kg的Cd有较强的耐性,适用于城区土壤修复;Cd浓度大于5 mg/kg时抑制德国鸢尾生长,降低了其生态效应.随着Cd浓度的增大,德国鸢尾根系活力、叶绿素含量和含水量逐渐降低,游离脯氨酸和可溶性糖含量先升高后降低,细胞膜透性逐渐升高.Cd在德国鸢尾体内分布为根系＞地上部分,随着Cd浓度的增大,德国鸢尾根系和地上部分Cd积累浓度逐渐升高、富集系数和转运系数逐渐降低;Cd浓度为20 mg/kg时德国鸢尾对Cd的积累量最大,为2.122 mg/plant.     

饲料中铜浓度对异育银鲫和斑点叉尾的影响

通过4周的生长实验,研究饲料中不同铜含量对异育银鲫(Carassius auratus gibelio)[初始体重(128.6±2.0)g]和斑点叉尾(Ictalurus punctatus)[初始体重(159.4±2.0)g]的生长、饲料利用、血液生化以及组织中铜积累量的影响。两种实验鱼的实验饲料均以CuSO4?5H2O为铜源,铜含量分别为3.1(对照)、7.5、49.8、100.5、506.9、965.1和1491.1 mg/kg饲料。实验结果表明,异育银鲫摄食量(FI)随饲料中铜含量的增加无显著影响(P0.05),特定生长率(SGR)随着饲料中铜含量的增加而显著下降,在铜含量为1491.1 mg/kg时出现最低值(P0.05),饲料效率(FE)表现出与特定生长率相似的变化趋势。肝体比(HSI)和脏体比(VSI)均随着饲料中铜含量的增加而显著下降(P0.05),各处理组间的肥满度(CF)差异不显著(P0.05)。血浆中谷草转氨酶(GOT)在铜含量为7.5 mg/kg时达到最低值(P0.05),然而血浆中谷丙转氨酶(GPT)、铜锌超氧化物歧化酶(Cu-ZnSOD)活性及红细胞压积(Hct)、血红蛋白浓度(Hb)均不受饲料中铜含量的影响(P0.05)。肝脏中铜积累量随着饲料中铜含量的增加而无显著影响(P0.05),而肌肉中铜含量没有显著差异(P0.05)。斑点叉尾FI随饲料中铜含量的增加而显著上升(P0.05),SGR随饲料中铜含量的增加表现出下降的趋势,但是差异不显著(P0.05),FE随饲料中铜含量的增加显著降低(P0.05)。HSI和CF随饲料中铜含量的变化而显著下降。Hct随铜含量的增加呈现出先上升后下降的趋势,当铜含量为100.5 mg/kg时达到最大值(P0.05),然而饲料铜水平对血浆中GPT、GOT、Cu-Zn SOD活性及Hb、VSI均无显著影响(P0.05)。铜在各组织中的积累表现出与异育银鲫相同的变化趋势。饲料中较高浓度铜可抑制斑点叉尾和异育银鲫的生长和饲料利用,且异育银鲫对铜的耐受性高于斑点叉尾。     

饲料蛋白源和养殖密度对草鱼生长性能、体成分和血清生化指标的影响

为探究饲料蛋白源和养殖密度对草鱼生长以及生理健康的影响,以初始体质量为(5.36±0.18) g的草鱼(Ctenopharyngodon idella)为试验对象,采用双因素正交实验,研究饲料非粮蛋白源(豆粕、乙醇梭菌蛋白、黄粉虫、棉籽浓缩蛋白和小球藻)和初始养殖密度(0.11、0.16和0.21 kg/m³;对应为20、30和40尾/网箱)及其交互作用对草鱼生长性能、体成分和血清生化指标的影响。养殖试验在池塘网箱(1.0 m×1.0 m×1.5 m)中进行,养殖周期为60d。结果表明:随着养殖密度的增加,各蛋白源组草鱼饲料系数均呈增长趋势,特定生长率、增重率和蛋白质效率和肝体比均呈降低趋势。在不同养殖密度下,黄粉虫组饲料系数均显著高于其他蛋白源组(P<0.05),特定生长率、增重率和蛋白质效率均显著低于其他蛋白源组(P<0.05)。当养殖密度为0.11和0.16 kg/m³时,试验草鱼生长性能接近,其特定生长率显著优于0.21 kg/m³密度组(P<0.05)。饲料蛋白源和养殖密度对草鱼全鱼水分和粗蛋...     

镉在土壤-香根草系统中的迁移及转化特征

以无植物组处理为对照,采用盆栽试验方式探讨不同Cd浓度胁迫条件下香根草根际土壤中重金属Cd的积累、迁移及转化特征。土壤Cd处理设4个浓度梯度,分别为0、2、20、80 mg/kg土壤干重。结果表明:(1)香根草可以显著降低土壤中生物有效态Cd和总Cd含量。(2)香根草各部分Cd积累量随处理浓度的增加和处理时间的延长而增加,90 d时80 mg/kg处理组地上部分和根的Cd积累量分别高达180.42 mg/kg和241.54 mg/kg。(3)各浓度Cd处理下,富集系数随着Cd处理浓度的增加而显著降低,随处理时间的延长而升高。(4)香根草地上部分Cd含量小于根部,各处理转移系数均小于1。随着处理时间的延长,中低浓度处理组的转移系数稍有降低,高浓度处理组的转移系数则显著上升。(5)种植香根草使其根际土中残渣态的Cd转化为生物有效态Cd,提高Cd清除效率。研究结果表明,香根草能够有效地吸收土壤中的Cd,降低土壤中总Cd含量,提高土壤安全性,可作为Cd污染地区植物修复的备选物种。     

重金属镉与铜在棕尾别麻蝇体内的积累和排泄研究

为了研究镉(Cadmium,Cd)和铜(Copper,Cu)在棕尾别麻蝇Boettcherisca peregrina (Diptera:Sarcophagidae)生长发育过程中积累和排泄的动态变化,在室内给棕尾别麻蝇初产幼虫连续饲喂含不同浓度Cd2'或Cu2+的人工饲料,每隔24 h测定幼虫对Cd2+或Cu2+积累和排泄及变态过程中的变化.结果表明:棕尾别麻蝇幼虫取食含有Cd2+的饲料后,大部分Cd2+积累在体内,少部分通过排泄系统排出.Cd2+在幼虫体内的积累量随着取食时间的延长而增加,幼虫取食含200 μg/g Cd2+饲料后,体内Cd2+积累量高于取食含100 μg/g、400 μg/g和800 μg/g Cd2+饲料后体内Cd2+积累量,幼虫对Cd2+排泄量亦有相同的规律.Cd2+在幼虫、蛹和刚羽化成虫中的含量依次降低.棕尾别麻蝇幼虫取食含Cu2+的饲料后,其体内Cu2+积累量小于排泄量,而且体内积累量和排泄量随着取食时间的延长而增加,Cu2+积累量和排泄量与取食饲料中的Cu2+浓度均不成正比.在变态过程中,Cu2+也不断被排泄,体内Cu2+含量随之下降.     

秋华柳和枫杨幼苗对镉的积累和耐受性

以秋华柳和枫杨当年实生幼苗为研究对象,采用向土壤添加外源镉(CdCl₂ · 2.5H₂O)的形式设置了0(对照组)、10 、20 、50、100 mg/kg 5个处理,研究了镉胁迫下秋华柳和枫杨幼苗的生长、生物量变化和根茎叶镉含量,并评价了两树种的耐性指数(Ti)、转移系数(Tf)和生物富集系数(BCF)。结果表明:(1)在镉含量为10 mg/kg时,秋华柳和枫杨幼苗基于生长和生物量参数的耐性指数(Ti)分别为91.72和91.62,与对照组相比无显著变化,其余各组(20、50、100 mg/kg)则显著低于对照植株(P<0.05);(2) 土壤镉浓度小于20mg/kg时,秋华柳植株茎、叶镉积累量分别高达61.73 mg/kg、163.04 mg/kg,根镉积累量为91.05 mg/kg;枫杨植株茎、叶镉积累量最高分别为7.9 mg/kg、5.25 mg/kg,仅为秋华柳茎、叶的12.8%和3.2%,根镉积累量高达190.68 mg/kg;(3) 除对照外,秋华柳幼苗各部分镉含量为叶＞根＞茎,转移系数(Tf)介于0.789-1.513之间,枫杨幼苗各部分镉含量为根＞茎＞叶,转移系数(Tf)介于0.037-0.044之间,远远小于秋华柳Tf;(4)秋华柳和枫杨幼苗在土壤镉浓度为10 mg/kg时具有很高的生长适应性和耐性,秋华柳根吸收的镉向地上部分转移能力、地上部分积累镉的能力都远远大于枫杨,生物富集系数(BCF)进一步证实了这一特性。研究证明,秋华柳植株具有很高的镉耐性、镉转移能力及地上部分积累镉的能力,适合于镉污染严重区域的植物修复。     

Cu2+、Zn2+、Cd2+对黑水虻幼虫生长的影响 及在虫体和虫粪的积累

为研究不同金属离子对黑水虻幼虫生长的影响及在虫体和虫粪中的积累分布规律,通过在黑水虻幼虫饲料中加入不同浓度的Cu~(2+)、Zn~(2+)、Cd~(2+),分析观测了幼虫增重、虫体和虫粪中金属含量等情况。结果表明,适量的Cu~(2+)、Zn~(2+)、Cd~(2+)可以促进黑水虻幼虫的生长,Zn~(2+)浓度在400 mg/kg时黑水虻幼虫的体重最高。Cu~(2+)、Zn~(2+)、Cd~(2+)在黑水虻幼虫体内和虫粪中的残留随着饲料中Cu~(2+)、Zn~(2+)、Cd~(2+)浓度的升高而增加。Cu~(2+)、Zn~(2+)在虫体中的残留比例都小于50%,大部分残留在虫粪中,Cd~(2+)在10、20、40 mg/kg处理中虫体的残留比例大于50%,最高达到了91.3%,而在80、160 mg/kg处理中虫体残留量比例小于50%。各重金属在虫粪中的残留主要以残渣态存在,且各形态的含量顺序在高浓度处理中都为残渣态酸溶态水溶态碱溶态。说明饲料中适量金属离子的添加有利于黑水虻幼虫生长,但过量的添加会抑制黑水虻幼虫生长,并造成金属离子的积累。     

Bioaccumulation and Excretion of Enantiomers of Myclobutanil in Tenebrio molitor Larvae Through Dietary Exposure

The bioaccumulation and excretion of enantiomers of myclobutanil in Tenebrio molitor larvae through dietary exposure under laboratory conditions were investigated using high‐performance liquid chromatography tandem mass spectrometry (HPLC‐MS/MS) based on a ChiralcelOD‐3R [cellulosetris‐tris‐(3, 5‐dichlorophenyl‐carbamate)] column. The wheat bran fed to Tenebrio molitor larvae was spiked with racemic myclobutanil at two dose levels of 20 mg/kg and 2 mg/kg (dry weight). The results showed that there was a significant trend of enantioselective bioaccumulation in the larvae with a preferential accumulation of (?)‐myclobutanil in 20 mg/kg dose exposure, but it was not obviously observed in the 2 mg/kg dose group. A kinetic model considering enantiomerization between the two enantiomers based on first‐order reactions was built and the rate constants were estimated to discuss the kinetic reason for the different concentrations of individual enantiomers in the larvae. The approximations implied an inversion between the two enantiomers with a relatively higher rate of the inversion from (?)‐myclobutanil to (+)‐myclobutanil. Meanwhile, analysis of data of excretion samples suggested the active excretion is probably an important pathway for the insect to eliminate myclobutanil rapidly with nonenantioselectivity as a passive transport process, which was consistent with the low accumulation efficiency of myclobutanil measured by BAF (bioaccumulation factor). Chirality 25:890–896, 2013. © 2013 Wiley Periodicals, Inc.     

The effect of selenium and organic material in lake sediments on the bioaccumulation of methylmercury by Lumbriculus variegatus (oligochaeta)

The accumulation of methylmercury (MeHg) to an oligochaete worm Lumbriculus variegatus (Müller) was measured in two different lake sediments in the laboratory. ¹⁴C-labelled MeHg was added to sediments at the nominal concentration of 95 ng/g dw sediment. Groups of six oligochaete worms were exposed in glass beakers to 35 g of spiked sediment for 14 days. The two sediments had organic carbon concentrations of 3.4% and 9.9% and natural selenium concentrations of 1.45 and 0.28 mg/kg (dw), respectively. After two weeks exposure, both the accumulation rate of MeHg and the body residue in the worms were much lower in the sediment having a high organic carbon content. The effect of selenium concentration in the sediment on bioaccumulation of MeHg in Lumbriculus variegatus was measured in one sediment (organic carbon 3.4% and Se 1.45 mg/kg) by adding sodiumselenite (Na₂SeO₃) at different concentrations. The added amounts of selenium were 0, 0.1, 0.5, 2.5, 15.0, and 50.0 mg Se/kg dry sediment. In this exposure the nominal concentration of MeHg was 102 ng/g dw sediment. The two lowest selenium concentrations did not affect the bioaccumulation of MeHg. But, the dose of 2.5 mg Se/kg resulted in a 25% reduction in the body residue after two weeks exposure. When 15 and 50 mg Se/kg were added to the sediment the accumulation of MeHg in the organisms was decreased by 75% and 86%, respectively, as compared to the reference.     

铅胁迫对斜纹夜蛾生长发育与生殖的影响

在植食性昆虫斜纹夜蛾幼虫标准人工饲料中添加不同浓度的重金属铅(Pb),研究Pb胁迫对其生长发育与生殖的影响.结果表明:斜纹夜蛾不同发育阶段(幼虫、蛹和成虫)的存活率和体质量随着饲料中Pb浓度的增加而下降,引起存活率显著下降的最低Pb胁迫浓度是100 mg·kg-1,引起体质量显著减少的最低Pb胁迫浓度是50 mg·kg-1.在取食Pb浓度为25～ 200 mg·kg-1的人工饲料后,斜纹夜蛾成虫的产卵天数显著减少;产卵力和生育力随着饲料中Pb浓度的增加而显著下降;1000粒卵的平均质量显著低于对照;卵孵化率显著下降.重金属Pb胁迫对斜纹夜蛾生长发育和生殖具有显著的抑制作用.     

Changes in elemental content in fronds of Azolla filiculoides due to arsenic accumulation

This study analyzed the accumulation of arsenic and its influence on the content of P, Mn, Fe, Cu, Zn, S, Ca, Cl, and K in fronds of Azolla filiculoides via X-ray fluorescence (XRF). Azolla was exposed to increased concentrations of sodium arsenate (0, 5, 10, 20, and 30 μg ml ^? 1) in Yoshida's nutrient solution. After 96 h, fronds were collected and taken to constant weight to calculate the relative growth rate (RGR), the biomass duplication rate, the bioaccumulation factor (BAF), and the elemental concentration via XRF analysis. By increasing As concentrations the RGR and BAF were reduced. The greatest accumulation of As in fronds was achieved at 20 μg As ml ^? 1, which did not show significant differences with the highest concentration. Accumulation of As in fronds diminished concentrations of Mn, Fe, Zn, S, Ca, and K, while the concentration of P remained low but unchanging. The P content was significantly lower than the As content, thus the As:P ratio in fronds enhanced as the As concentration increased. Concentrations of Cl and Cu were unaffected due to As. This is one of the first reports about the influence of As-accumulation on the elemental content in Azolla fronds.     

大黄鱼幼鱼对饲料硒的需求量

为确定大黄鱼(Larimichthys croceus)对饲料硒的需求量, 以Na2SeO3为饲料硒源, 配制6种饲料, 硒的添加水平分别为0(对照组)、0.05、0.2、0.4、0.6和0.9 mg/kg, 实测值分别为0.08、0.16、0.27、0.44、0.66和0.96 mg/kg。在海水浮式网箱中养殖初始体重为(9.140.09) g的大黄鱼幼鱼10周, 结果表明增重率(WG)、全鱼和骨骼中的硒含量随着饲料硒含量的升高而显著升高(P0.05)。当饲料硒含量分别超过0.27、0.66、0.66 mg/kg时, 这些指标的变化趋于平稳。饲料硒含量对存活率(SR)、饲料效率(FE)、体组成、肝体比(HSI)、脏体比(VSI)和肥满度(CF)都没有显著影响(P0.05)。在血清中谷胱甘肽过氧化物酶(GPX)活性、超氧化物歧化酶(SOD)活性和总抗氧化力(T-AOC)随着饲料硒含量的升高呈现先升高后稳定的趋势(P0.05), 并分别在饲料硒含量为0.44、0.44、0.16 mg/kg时达到最大值。肝脏中GPX活性、SOD活性、T-AOC、过氧化氢酶(CAT)活性和谷胱甘肽还原酶(GR)活性与血清中相应酶的活性有相同的趋势。在肝脏中谷胱甘肽硫转移酶(GST)活性随着饲料硒含量的升高呈现先降低后升高的趋势(P0.05), 并在饲料硒含量最高(0.96 mg/kg)时其活力取得最大值。以WG为评价指标, 得出大黄鱼幼鱼对饲料中硒的需求量为0.178 mg/kg。以全鱼和骨骼中硒含量、肝脏GPX活性为评价指标, 得出大黄鱼幼鱼对饲料中硒的最小需求量分别为0.575、0.387和0.440 mg/kg。       

Utilization by sheep of dried pig faeces containing a high concentration of copper

Seven groups of three sheep were given pelleted diets as follows: A, 97% hay + 3% molasses; B, C, D, 82% hay + 3% molasses + 15% dried pig faeces; E, F, G, 67% hay + 3% molasses + 30% dried pig faeces. In an attempt to counteract potential toxic effects of copper in the pig faeces (613 mg/kg dry matter), molybdenum was added to diets C and F at the rate of 90 mg/kg diet, and to diets D and G at the rate of 175 mg/kg diet. Sulphate was included in all diets at the rate of 1.08% of diet. Measurements were made of digestibility, copper retention, and plasma glutamic oxaloacetic transaminase (GOT) values during a 70-day feeding period, after which the animals were slaughtered.Dry matter digestibility coefficients were : diet A, 49.2; diets B, C, D, 44.4; diets E, F, G, 42.5, from which the coefficient for pig faeces alone is calculated to be < 30. Mean copper retention over the 70 days ranged from 210 mg for diet A to 1225 mg for diet G (excluding diet E which showed an aberrant retention of 53 ± 185 mg). Plasma GOT values fluctuated between diets and between sheep with a maximum value of 182 units/ml. Mean liver copper concentrations ranged from 718 mg/kg dry matter for diet A to 1740 mg/kg for diet E. Necrotic lesions occurred in some livers. Kidneys were apparently normal. There were no clear differences in copper status of animals receiving 15% versus 30% pig faeces except for a tendency for liver damage to be greater in the latter. There were no apparent effects of additions of molybdenum.The pig faeces were poorly utilized and, because of the high copper content, potentially hazardous to the health of the sheep.     

Histological Lesion of Spleen and Inhibition of Splenocyte Proliferation in Broilers Fed on Diets Excess in Selenium

The purpose of this 42-day study was to investigate the effects of excess dietary selenium on immune function by determining morphological changes of spleen and cell cycle of splenocyte. Three hundred 1-day-old avian broilers were fed on a basic diet (0.2 mg/kg selenium) or the same diet amended to contain 1, 5, 10, and 15 mg/kg selenium (Se) supplied as sodium selenite (n = 60/group). Anatomically, the spleens were shrinked in volume with pallecent color. Histopathologically, lymphopenia in splenic nodules and periarterial lymphatic sheaths and congestion of the red pulp were observed in 5, 10, and 15 mg/kg Se group. By flow cytometry method, the percentage of G₀/G₁ phase splenocytes was significantly increased, whereas the percentages of S phase and G₂+M phase splenocytes and the proliferation index were markedly decreased in 5, 10, and 15 mg/kg Se groups when compared with those of 0.2 mg/kg group. The results confirmed that excess dietary Se as sodium selenite in the range of 5∼15 mg/kg caused growth retardation of spleen by cell cycle blockage in young chickens.     

The effects of dietary selenium on the biotransformation of 7,21-dimethylbenz[a]anthracene

The influence of dietary selenium on the mutagenic activation of 7,12-dimethylbenz[a]anthracene (DMBA) by rat liver S9 was studied using the Ames test. Rats received supplemental selenium, as sodium selenite, in the drinking water or in the diet. All rats additionally received 0, 20, 50, 100, or 500 mg Aroclor 1254 per kg body weight. Revertant counts decreased 72 and 31% at the 20- and 100-mg/kg induction levels, respectively, with S9 preparations from rats given selenium supplementation, compared to controls. No significant effects of selenium on S9 preparations was observed in rats treated with 500 mg/kg Aroclor. Preparations of S9 from rats receiving 2.5 ppm Se in their diet produced 46, 84 and 70% less revertants than controls at the 20-, 50- and 100-mg/kg induction levels. Increasing the selenium concentration in the diet to 5 ppm reduced the revertant counts by 71, 68 and 65%, at the 20-, 50- and 100-mg/kg induction level of Aroclor, respectively. Dietary selenium supplementation was shown to decrease the mutagenic activation of DMBA by liver microsomes. These studies indicate that in vivo selenium supplementation may reduce susceptibility to the action of various carcinogens.