添加吡啶羧酸铬对肉仔鸡生产性能的影响研究

选用144只1日龄体重均匀、健康的艾维茵肉仔鸡,随机分成6个日粮处理组:1组为对照组,喂基础日粮;2～6组为试验组,分别在基础日粮中添加0.5mg/kg、1mg/kg、1.5mg/kg、2mg/kg、2.5mg/kg铬(以吡啶羧酸铬形式),研究在日粮中添加不同浓度的吡啶羧酸铬对肉仔鸡生产性能的影响.试验结果表明:①日粮中添加铬浓度为0.5～1mg/kg的吡啶羧酸铬时,能显著提高肉仔鸡增重,明显改善肉仔鸡的饲料效率(P＜0.05);②日粮中添加铬(吡啶羧酸铬形式)能够提高经济效益.     

四种市售鸡饲料中铜,锌,铬含量的测定与分析

用原子吸收分光光度法测定了四种市售鸡饲料中铜、锌、铬的含量,通过分析发现各饲料产品中铬的含量均超过标准,其中有一厂家的两种饲料严重超标。另有三种饲料样品中的锌含量超过推荐量,各产品中铜的含量基本正常。笔者认为目前各饲料生产企业较为普遍地存在着滥用重金属类微量元素的现象,希望引起各有关生产企业的重视     

砖红壤中铬的溶出和外源三价铬的氧化转化*

砖红壤铬（Cr）的背景值和锰氧化物的含量均较高,当土壤中Cr溶出或者受到Cr(III)污染,可能被氧化生成毒性较高的Cr(VI),从而对周围的环境造成威胁。为考察砖红壤中Cr的环境风险,以云南、海南和广东采集的部分砖红壤为对象,研究土壤中Cr的溶出和外源Cr(III)的氧化。连二亚硫酸钠-柠檬酸钠-重碳酸钠法提取和电子探针扫描分析的结果表明,砖红壤中的Cr主要与铁氧化物和硅酸盐矿物结合,呈非活性状态。盐酸和柠檬酸的酸化和络合作用促进了Cr的溶出,但即使1 mol?L-1的盐酸也仅使海南3和广东9砖红壤中3.68%和3.54%的Cr溶出。向砖红壤中添加Cr(III)并培养42 d,发现少量添加的Cr(III)氧化为Cr(VI),但不同土壤中Cr(VI)的生成量与亚锰的净产生量不一致,说明土壤中Cr(III)氧化生成的Cr(VI)可能会被土壤有机质重新还原为Cr(III)。去除土壤有机质后,一次平衡实验中观察到外源添加的Cr(III)氧化为Cr(VI),氧化量与土壤易还原锰的含量一致。随着溶液pH的增加,Cr(III)的氧化量呈先上升后降低的趋势,在pH4.5时Cr(III)氧化量达最大值,但Cr(III)的氧化转化量在Cr(III)添加量中的占比很小,外源Cr(III)在土壤中氧化转化的风险也很低。虽然砖红壤的背景Cr和易还原锰的含量较高,但自然条件下Cr的溶解和Cr(III)的氧化反应很难发生,Cr(III)不易转化为Cr(VI),因此不需要过度担忧砖红壤中Cr的风险。     

吡啶羧酸铬、L-肉碱和甜菜碱对天府肉鸭生产性能和胴体品质的影响

640只21日龄健康天府肉鸭,按体重相近的原则随机分为4组,对照组饲喂基础日粮,试验组分别在基础日粮中添加吡啶羧酸铬500μg/kg、L-肉碱50mg/kg和甜菜碱1000mg/kg。试验结束后,屠宰测定胸肌率、腿肌率、腹脂率和皮脂厚。结果表明,吡啶羧酸铬能显著提高增重,L-肉碱和甜菜碱对天府肉鸭增重、采食量和料肉比无显著影响。吡啶羧酸铬使肉鸭皮脂厚降低2.08%、腿肌率提高2.52%。L-肉碱有降低胸肌率的趋势。甜菜碱使肉鸭皮脂厚、腹脂率分别降低5.96%、7.25%,而有提高胸肌率的趋势。综上可见,本试验条件下,在生长后期日粮中添加吡啶羧酸铬、L-肉碱或甜菜碱对天府肉鸭生产性能和胴体品质有一定改善作用。     

铜、锌、铬金属离子对黄金鲫的急性毒性研究

为研究黄金鲫对铜(Cu2+)、锌(Zn2+)和铬(Cr6+)3种重金属离子的耐受性,试验分别设定不同浓度梯度的重金属离子处理组,进行急性毒性试验。结果表明,Cu2+半致死浓度(LC50)在24、48、72 h分别为2.63、0.80、0.73 mg/L,安全浓度(SC)为0.022 mg/L。Zn2+和Cr6+在24、48、72、96 h的LC50分别为72.74、59.75、58.05、57.80和519.05、391.05、375.53、347.03 mg/L,二者的SC依次为12.040和66.660 mg/L。3种重金属对黄金鲫的毒性大小依次为Cu2+Zn2+Cr6+。     

美人蕉（Canna indica Linn.）和芦苇（Phragmites australisL.）人工湿地对含铬生活污水的净化效果及植物的生理生态变化

选取美人蕉(Canna indica Linn.)、芦苇(Phragmites australis L.)为植物材料.以不同浓度K2Cr2O7(分别含0、1、20、50 mg·-1Cr6+)的生活污水作为Cr6+染源,研究了不同浓度Cr6+及处理时间下两种湿地对污水净化效果、植物体Cr6+积累量及根系活力(TTC)、叶片超氧化歧化酶(SOD)活性、过氧化物酶(POD)活性、净光合速率(Pn)和丙二醛(MDA)等生理指标的影响.结果表明:(1)在试验的初期30 d内,随处理时间的延长,两种人工湿地COD、氨氮去除率均呈逐渐上升的趋势,30 d后,随着Cr6+处理时间的延长及Cr6+浓度的逐渐升高,两种湿地系统对COD、氨氮去除率均逐渐下降.在20、50 mg·L-1Cr6+处理条件下,两种湿地对COD、氨氮的净化效果显著低于对照及1 mg·L-1Cr6+处理,对照与1 mg·L-1Cr6+处理条件下差异不显著.(2)在不同Cr6+浓度处理下,两种人工湿地对TP净化效果的能力较为稳定,同时随处理时间的延长,美人蕉、芦苇体内Cr6+积累量逐渐加大.(3)1 mg·L-1Cr6+处理可提高美人蕉和芦苇的TTC、叶片的SOD、POD、Pn,而20、50mg·L-1Cr6+处理对以上指标均有不同程度的抑制作用,且抑制效果与处理浓度、时间呈正相关.(4)MDA含量随处理时间的延长和浓度升高呈逐渐增加趋势.可见,低浓度Cr6+能有效促进美人蕉、芦苇生长,使之能够维持正常的净化功能,因此,利用它们作为人工湿地植物来修复Cr6+亏染具有一定的实用价值.     

Cr6+胁迫下小麦幼苗地上部分生长及DNA损伤效应的研究

[目的]阐明Cr6+影响小麦幼苗生长发育的毒理机制。[方法]研究5~100 mg/LCr6+胁迫72 h对3 d和10 d龄小麦幼苗地上部分生长的影响及DNA损伤效应。[结果]5~100 mg/LCr6+均表现出降低两苗龄幼苗苗高、地上部分鲜重、干重的效应;3 d龄幼苗比10 d龄幼苗对Cr6+胁迫更敏感;Cr6+导致小麦幼苗叶片DNA含量显著降低,3 d龄幼苗叶片DNA含量下降的幅度大于10 d龄幼苗;5~100mg/LCr6+均引起3 d和10 d龄幼苗地上部分DNA的增色效应值高于对照值。[结论]Cr6+造成的DNA损伤可能是影响不同龄期小麦幼苗生长的主要原因之一。     

Dietary nano chromium picolinate can ameliorate some of the impacts of heat stress in cross-bred sheep

Two studies were conducted to evaluate the effect of nano chromium picolinate (nCrPic) during heat stress (HS) in sheep. In the initial study, 36 Merino × Poll cross-bred sheep were individually penned and allocated to 3 dietary treatments (0, 400 and 800 μg/kg nCrPic) for 8 wk. Body composition was determined at the beginning and end of the experiment using dual energy X-ray absorptiometry. The sheep remained in their dietary groups but were then placed in metabolic cages and randomly allocated within the dietary group to differing ambient temperature regimes, i.e., thermo-neutral (TN) (n = 18) and HS (n = 18), for 3 wk. Dietary nCrPic had no effect on growth performance and body composition during the initial study conducted under TN conditions. Heat stress decreased average daily feed intake (ADFI) (P = 0.002) whereas sheep under HS had reduced average daily gain (ADG) and indeed lost weight (P < 0.001). Dietary nCrPic increased both ADFI (P = 0.041) and ADG (P = 0.049) under both TH and HS conditions such that the performance of sheep receiving supplemental nCrPic and exposed to HS was similar to that of control sheep maintained under TN conditions. Heat stress increased rectal temperature (P < 0.001) and respiration rate (P < 0.001), particularly during the hottest parts of the day as indicated by interactions (P < 0.001) between time of day and thermal treatment. Rectal temperature was lower in sheep fed nCrPic (P = 0.050), particularly under peak HS conditions during the afternoon as indicated by the interactions between dietary nCrPic and time of day (P < 0.001) and dietary nCrPic, thermal treatment and time of day (P = 0.010). Similarly, respiration rate was lower in sheep fed nCrPic under peak HS conditions during the afternoon as indicated by the interactions between dietary nCrPic and thermal treatment (P < 0.001) and dietary nCrPic and time of day (P = 0.030). In conclusion, dietary nCrPic can partially ameliorate the negative effects of HS as indicated by the maintenance of ADFI and decreased physiological responses, such as elevations in rectal temperature and respiration rate.     

电弧喷涂3Cr13修复齿轮泵轴试验研究

为获得性能优良的3Cr13电弧喷涂层，采用正交试验、极差分析和方差分析研究了电弧喷涂工艺参数对3Cr13涂层结合强度和耐磨性的影响。试验结果表明：影响涂层结合强度的工艺参数主次排列为喷涂电流、喷涂气压和喷涂距离，而影响涂层耐磨性的工艺参数主次排列为喷涂电流、喷涂距离和喷涂气压。考虑试验因素对结合强度和耐磨性影响程度的大小以及它们在涂层使用中所起作用的重要程度，优化的3Cr13电弧喷涂工艺规范为喷涂电压35 V；喷涂电流180 A；喷涂距离180 mm；喷涂气压0.6 MPa。齿轮泵轴修复实践表明,优化的电喷涂工艺规范用于修复齿轮泵磨损件是可行的。     

Design on the Welding Technology for 0Cr18Ni9 Production Separator

According to the structural characters and the using properties of the big thick stainless steel chemical separator, a new welding process of the MAG welding is employed in this paper. The product's welding quality meets the design standard. The high productivity and profit are obtained with the new welding methods. The labor intensity of welding is reduced also.