延迟收获对长江中游春玉米农艺性状及机收质量的影响

为探明长江中游玉米籽粒机械直收适宜品种与配套农艺措施,2018—2019年选用不同玉米品种,测定不同机收时间下玉米关键农艺性状、产量及机收质量指标。结果表明,收获时间对春玉米机收产量与机收质量均有显著影响。延迟1周收获后籽粒容重显著增加,机收产量显著提高,2年平均提高9.72%;而延迟2周收获则有降低机收产量的趋势。2年收获时杂质率总体≤3%,而机收籽粒破碎率与损失率均>5%,是该区域春玉米籽粒机收面临的主要问题。籽粒厚度、籽粒含水率和百粒重是影响机收籽粒破碎率的关键性状,三者与机收籽粒破碎率均呈显著的倒二次曲线关系;玉米的倒伏率、穗位高和重心高度是影响机收损失率的关键性状,倒伏率与机收损失率呈显著正相关,而穗位高和重心高度与机收损失率均呈显著的二次曲线关系。延迟收获能显著降低籽粒含水量,从而降低籽粒破碎率,但继续延迟收获有增加倒伏的风险。综上,长江中游春玉米成熟后适时延迟7~10 d收获,可有效降低籽粒含水量与机收籽粒破碎率,提高玉米籽粒机收产量。     

基于离散元法的油莎豆降阻挖掘装置设计与试验

目前油莎豆机械化收获方式以正旋旋耕挖掘为主,但工作过程中存在工作阻力大、碎土率低、埋果率高等问题,本文针对油莎豆旋耕挖掘方式进行反旋运动学分析,建立了旋耕刀与油莎豆团聚体离散元模型,结合EDEM进行挖掘过程离散元仿真试验,确定影响旋耕刀工作阻力和刀轴扭矩的结构参数和取值范围,利用Design-Expert进行试验优化与回归分析,确定旋耕刀的最佳结构参数为：弯折角130°、工作幅宽45 mm,在相同参数设置下与正旋旋耕方式进行对比试验,工作阻力降低了8.6%,刀轴扭矩降低了5.9%,证明反旋挖掘具有降阻作用。为检验优化设计的旋耕刀作业性能,以埋果率和土壤破碎率作为试验指标进行对比试验,结果表明：反旋作业方式埋果率1.07%,土壤破碎率93.48%,与标准旋耕刀相比,新型旋耕刀油莎豆块茎埋果率减低了1.2个百分点,土壤破碎率提高了1.3个百分点。     

水流驱动下不同灌草格局对泥沙分选特征的影响

泥沙的颗粒大小分布体现了土壤侵蚀的基本信息,分析泥沙分选特征有助于解释坡面土壤的侵蚀过程及其作用机理。通过野外冲刷试验(流量为15,20,30L/min),以砒砂岩区灌丛位于坡上(SU)、坡中(SM)、坡下(SL)的灌草地和无灌丛草地(GL)为研究对象,裸地(BL)为对照,探讨水流驱动条件不同灌草格局泥沙分选特征及其作用机理。结果表明:(1)植被可以通过影响水动力参数来影响泥沙颗粒的分布,不同格局泥沙颗粒随冲刷时间及流量的增大呈粗化趋势,粉、砂粒是该区侵蚀泥沙的主要颗粒。(2)水流剪切力、水流功率和单位水流功率均与泥沙DV呈负相关关系,与D0、D1呈正相关关系;3种冲刷流量下,泥沙DV均值分别为2.422,2.381和2.348,不同灌草格局下DV表现为GL相似文献   

Potential of indigenous Bacillus spp. as probiotic feed supplements in an extruded low‐fish‐meal diet for juvenile olive flounder,Paralichthys olivaceus

A 12‐week feeding trial was designed to assess the probiotic potential of indigenous Bacillus amyloliquefaciens and/or Bacillus subtilis singly or in combination with Bacillus licheniformis in an extruded feed for olive flounder (Paralichthys olivaceus) juveniles. A high fish meal (FM) diet (control) and a low‐FM diet containing an alternative protein blend (30% FM replacement, FM30) were formulated. Three other experimental diets were prepared by inclusion of B. amyloliquefaciens (BA), B. subtilis (BS), or a mixture of B. amyloliquefaciens, B. subtilis, and B. licheniformis (BASL) into FM30 diet, with a final concentration of 10⁶ CFU/g diet. Results indicated that the FM30 diet was well tolerated by flounder, and the overall performance was not affected by dietary treatments. Lysozyme activity and total immunoglobulin level were significantly reduced in flounders when fed with the FM30 diet compared with the BASL and BA diets, respectively. The Bacillus additives neither enriched the relative abundance of the corresponding Bacillus spp. in the relevant gut microbiota of olive flounder nor modulated the presumptive gene functions of the gut microbiome. Despite the absence of growth‐promoting effect, the tested probiotics could still be economically viable for use as immunostimulants in commercial flounder diets with partial FM replacement.     

公英翘芦散治疗亚临床型奶牛乳房炎的效果研究

本研究旨在初步考察公英翘芦散对亚临床奶牛乳房炎的临床治疗效果。试验选取78头发病牛,其中38头牛为散发,用公英翘芦散治疗;40头牛集中对比治疗,随机分成2组,每组20头,分别用公英翘芦散和公英散进行治疗。用加州乳房炎检验（California mastitis trial,CMT）法检测公英翘芦散治疗后乳区患病状态并判定其治疗效果;用体细胞计数（somatic cell count,SCC）法检测公英翘芦散和公英散治疗后牛奶体细胞数并判定其治疗效果。结果显示,公英翘芦散给药7 d后,患病乳区由75个减少到28个,治疗效果非常显著,治愈率达到62.67%,有效率达到90.67%。与治疗前相比,公英翘芦散和公英散用药1 d后体细胞数均极显著降低（P<0.01）,且公英翘芦散组SCC下降幅度明显超过公英散组。公英翘芦散组在给药2 d后体细胞数显著低于公英散组（P<0.05）,给药3 d之后均极显著低于公英散组（P<0.01）。用药7 d后,公英翘芦散组治愈率可达68.29%,而公英散组治愈率只达到20.00%,差异极显著（P<0.01）;公英翘芦散组有效率可达97.56%,而公英散组有效率为67.50%,差异极显著（P<0.01）,说明公英翘芦散的治疗效果极显著优于公英散（P<0.01）。以上结果说明,公英翘芦散可以作为治疗亚临床奶牛乳房炎的有效药物,为奶牛乳房炎药物的开发提供参考。     

具有非单调发生率的传染病模型的动力学研究

假设恢复者所获得免疫力并不是永久的而是在一段时间后会减弱并丧失，建立了一类具有非单调发生率的传染病动力学方程.利用微分方程的基本理论和数值仿真的方法，将对此模型进行动力学性质的分析，得到无病平衡点稳定性和一致持久性的条件.对于该问题有效的措施，即研究使疾病以非单调发生率传染的情形，建立相应的SEIRS传染病模型，得到其无病平衡点的全局稳定性的与之条件以及系统一致持久的充分条件，并进行系统的数值仿真分析.     

The Extraction,Isolation and Identification of Exudates from the Roots of Flaveria bidentis

Large amounts ofFlaveria bidentis＇s root culturing solution were obtained by using DFT （deep flow technique） equipment and these solution which was vacuum concentrated （10, 20 mg mL-~） can have a certain inhibition on Triticum aestivum, Cucumis sativus, Raphanus sativus, Amaranthus retroflexus, Setaria viridis, Chenopodium album, Echinochloa crusgalli and Chloris virgata. This outcome suggested some active compounds in the root exudates ofFIaveria bidentis can inhibit the germination, seedling elongation and root length. The dichloromethane extract of root exudates was identificated by GC-MS, and 29 kinds of compounds, including esters, hydrocarbons, ketones, thiazole, amines, etc. were obtained and the phthalate n-octyl ester, phthalate 2-ethylhexyl ester were proved to be allelochemicals. The culturing solution of root exudates was separated through the resin column and silica gel column and a component inhibiting seedling height, root length and fresh weight of wheat was got. There were 6 kinds of organic compounds in this component including dioctyl phthalate, 1,2-phthalate, mono（2-ethylhexyl） ester by GC-MS.     

安泰粉针剂治疗犊牛腹泻的临床试验

采用临床对比观察的方法,试验安泰粉针剂对83头犊牛腹泻的治疗效果.治疗组口服安泰粉针剂1.5万单位/kg体重,1次/d,连用3～5 d;对照组肌肉注射氟哌酸注射液4.0～8.0 mg/kg体重,2次/d,连用3～5 d,或口服氟哌酸片,10片/次,2～3次/d,连用3～5 d.安泰粉针剂对犊牛腹泻的治疗效果好于临床常用药物氟哌酸,但无统计学意义(P＞0.05).     

商品猪场确定种猪及精液配种价值的生物经济学方法

商品猪场选购种猪或精液时 ,需要考虑其配种的综合效果 ,这些包括配种后母猪受胎率、窝产活仔数及商品猪的日增重、饲料转化率及瘦肉率等。本文通过建立生物经济学模型模拟商品猪群生产过程 ,利用差额法计算这些指标对出栏猪利润的影响 ,确定其边际效益 ,在此基础上提出“相对配种价值”指数的概念 ,用来估计种猪及精液的综合利用价值 ,为商品猪场选择适当的种猪、精液及配种方法提供参考