胎次和泌乳阶段对奶牛体细胞数和乳损失量的影响

通过奶牛生产性能（dairy herd improvement,DHI）测定体细胞数,探究奶牛的胎次及其不同泌乳阶段对其乳体细胞数（somatic cell count,SCC）和乳损失量的影响。通过对某养殖场泌乳期奶牛DHI的测定进行分析,结果表明：体细胞评分（somatic cell score,SCS）随奶牛胎次的增加而增加,但SCS在不同胎次的不同泌乳阶段表现有所不同。一胎牛SCS随着泌乳期的延长而增加,前期、中期与后期的SCS呈显著性差异（P＜0.05）;二胎牛与三胎牛SCS呈现相同变化规律,泌乳前期的SCS较泌乳中期高,而泌乳后期SCS显著高于前2个泌乳阶段（P＜0.05）。乳损失量随胎次的增加整体呈现增加趋势,且泌乳早期和泌乳后期乳损失量高于泌乳中期。     

从皮尔格林公司重组看美国肉鸡业战略取向

皮尔格林公司的前世今生 1曾经的世界第一位于美国德克萨斯州匹兹堡的世界最大鸡肉生产商皮尔格林公司（Pilgrim’s Pride）控制着鸡禽的培育、     

影响当前狂犬病防制的因素及对策

狂犬病是由狂犬病病毒引起的一种古老的人畜共患传染病，除犬和人外，它还可以感染猫、牛、马、羊、猪、狐、狼、蝙蝠等动物，人类常由带毒犬咬伤而感染。人一旦感染狂犬病，死亡率几乎达100％。近年来，我国狂犬病发病数逐年上升。据卫生部2003年7月份发布的消息称，狂犬病已成为我国传染病中     

戊唑醇在苹果和土壤中的残留分析方法

本文建立了戊唑醇在苹果和土壤中残留的液相色谱分析方法.该方法仪器最低检出量为4×10-11g;最低检出浓度为0.002mg/kg;平均回收率为85.6%～102.2%;变异系数为2.85%～9.47%。     

A molecular mechanism of resistance to streptomycin in <Emphasis Type="Italic">Xanthomonas oryzae</Emphasis> pv. <Emphasis Type="Italic">oryzicola</Emphasis>

Xanthomonas oryzae pv. oryzicola, the causal agent of rice leaf streak disease, was found to be sensitive to streptomycin (an aminocyclitol glycoside antibiotic), by inhibition of protein synthesis resulting from interference with translational proofreading. This study aimed to determine the molecular resistance mechanism of X. oryzae pv. oryzicola to streptomycin. Seven streptomycin-resistant mutants were obtained by UV induction or streptomycin selection. These mutants can grow at 100 μg ml⁻¹ of streptomycin while the wild-type strain (RS105) cannot grow at 5 μg ml⁻¹. Sequencing indicated that the rpsL gene encoding ribosomal protein S12 has 375 bp encoding 125 amino acid residues. In all resistant strains, a mutation in which AAG was substituted for AGG (Lys→Arg) occurred either at codon 43 or 88. Two plasmids, pUFRRS and pUFRRX, were constructed by ligating the rpsL gene into the cosmid pUFR034. The plasmids pUFRRS and pUFRRX containing the Lys→Arg mutation of the rpsL gene conferred streptomycin resistance to the sensitive wild-type strain by electroporation. Both transformants, RS1 and RS2, could grow in the medium containing 50 μg ml⁻¹ of streptomycin. A mutation at codon 43 or 88 in rpsL can result in resistance of Xanthomonas oryzae pv. oryzicola to streptomycin.     

NaCI胁迫对塔里木河下游罗布麻抗性酶的影响

研究了不同盐浓度胁迫下罗布麻种子的抗性酶活性及含量.罗布麻种子萌发采用盐溶液水培方法,设0、0.05、0.1、0.2、0.3、0.4、0.5、0.6mol/L8个盐梯度.分析罗布麻丙二醛(MDA)、超氧化物歧化酶(SOD)和游离脯氨酸(Pro)三种酶的含量和活性随盐浓度的变化趋势.得出结论:MDA含量和SOD活性变化趋...     

Development of a loop-mediated isothermal amplification assay for rapid, sensitive and specific detection of a Campylobacter jejuni clone

Loop-mediated isothermal amplification (LAMP) assay is a simple, rapid and specific detection method and has been used for detection and identification of different Campylobacter species. In this study, we develop a LAMP assay specific for detection of a particular clone (clone SA) of Campylobacter jejuni, associated with the vast majority of recent sheep abortions in the U.S. Using a set of specific primers for C. jejuni IA3902 (a clone SA isolate) and genomic DNA or boiled cell extract as template, the target DNA was amplified at 63 °C for 50 min in a water bath. A positive reaction was identified visually as white precipitate or fluorescence under UV, and confirmed by gel electrophoresis. Detection limit of the assay was comparable to that of conventional PCR. The LAMP was shown to be specific for detection of clone SA when tested on a number of C. jejuni strains of different genetic backgrounds. Applicability of the LAMP assay for specific detection of clone SA was demonstrated in animal tissues experimentally infected with IA3902 or genetically diverse C. jejuni strains. Since clone SA is the predominant cause of sheep abortions in the U.S. and is a zoonotic pathogen, the LAMP assay may be a valuable detection tool in future epidemiological studies.     

气相色谱-串联质谱法检测猪肉组织中的磺胺二甲嘧啶残留量

利用气相色谱-串联质谱法分析猪肉组织中的磺胺二甲嘧啶残留量。样品脱脂后,采用二氯甲烷提取样品中的目标化合物,经萃取、硅烷化衍生后,用气相色谱-串联质谱法检测,根据保留时间和质谱图谱与对照品比较进行定性与确认。所检测的磺胺二甲嘧啶的二级质谱图与标准的二级质谱图匹配良好,方法快速准确,干扰较少。该法测定磺胺二甲嘧啶的回收率为76%～110%,检出限为0.01mg/kg,适用于磺胺二甲嘧啶残留量的检测。利用气相色谱-串联质谱法分析猪肉组织中的磺胺二甲嘧啶残留量。样品脱脂后,采用二氯甲烷提取样品中的目标化合物,经萃取、硅烷化衍生后,用气相色谱-串联质谱法检测,根据保留时间和质谱图谱与对照品比较进行定性与确认。所检测的磺胺二甲嘧啶的二级质谱图与标准的二级质谱图匹配良好,方法快速准确,干扰较少。该法测定磺胺二甲嘧啶的回收率为76%～110%,检出限为0.01mg/kg,适用于磺胺二甲嘧啶残留量的检测。     

雏鸭饲粮锰适宜水平的研究

采用玉米-豆饼型饲粮(含Mn19ppm),对210只1日龄北京雏鸭进行补锰试验,试验分7组,锰添加水平(试剂级MnSO_4·H_2O)按1～7组顺序依次为0,20,45,60,85,110,135ppm,试验期3周,研究雏鸭饲粮锰适宜水平。结果为,饲粮锰水平不影响雏鸭体增重,日采食量和饲料转化率(P>0.05);胫骨锰浓度随饲粮锰水平增加呈线性上升(P<0.01);肝、肾、胰、心组织锰浓度和肝脏含锰的SOD酶活性可与饲粮锰水平拟合为相应的二次曲线模式(P<0.001),上述软组织锰浓度和肝SOD酶活性达到平衡时,所需饲粮锰依次为110.05,100.00,122.91,113.99和116.00ppm。综合试验结果考虑,雏鸭饲粮锰适宜水平为110ppm。     

农业本体构建方法研究

介绍了本体论的有关概念和理论,然后将本体论的思想和方法应用于农业领域研究,指出现有本体构建方法的不足之处,并在现有研究的基础上提出构建农业本体的原则、基本流程、模型和方法。最后,以水稻为例构建出病虫害防治知识本体。