Changes of Rumen Microbiota Density and Physicochemical Properties at Different pH北大核心CSCD

The aim of this experiment was to investigate the changes of rumen microbiota density and physicochemical properties at different pH. Five Holstein cows in dry milk period were selected as rumen fluid donors. Using in vitro method, five treatments were set according to the criteria of rumen acidosis, and the pH of culture medium was 6.5, 5.8, 5.5, 5.2 and 5.0, respectively, with five replicates in each treatment. After three hours of incubation, the changes of rumen microbiota density and physicochemical properties were measured. The results showed as follows: 1) with the decrease of pH, the rumen microbiota density showed a fluctuation change of first decreasing, then increasing and then decreasing, and the microbiota density in pH 5.8 treatment was significantly lower than that in pH 6.5 treatment (P<0.05). When pH was 5.2, the rumen microbiota density was the highest, which was significantly higher than that in the other treatments (P<0.05). 2) With the decrease of pH, the intracellular H+-ATPase activity in rumen microbiota was firstly increased and then decreased, but there was no significant difference among all treatments (P>0.05). 3) The intracellular ATP content in rumen microbiota was not significantly affected by different pH treatments (P>0.05). 4) With the decrease of pH, the intracellular protein content in rumen microbiota was gradually increased (P<0.05). 5) With the decrease of pH, the intracellular pH (pHi) and cellular transmembrane pH difference (ΔpH) in rumen microbiota were firstly increased and then decreased, and the pHi and ΔpH in pH 5.5 and 5.2 treatments were significantly higher than those in the other three treatments (P<0.05). 6) With the decrease of pH, the cell membrane permeability of rumen microbiota was gradually increased, except for pH 5.8 treatment, the other treatments were significantly higher than pH 6.5 treatment (P<0.05). In conclusion, the rumen microbiota can increase the intracellular H+-ATPase activity and protein content, consume ATP, and change pHi and ΔpH in response to external pH decline. When pH decreases to 5.5, the membrane permeability and pHi of rumen microbiota increase significantly, indicating that they are running to be subjected to more serious acid stress. The density of rumen microbiota fluctuates with the decrease of pH, and when pH decreases to 5.2, the density of rumen microbiota is the highest. © 2023 Authors. All rights reserved.     

猪源肺炎克雷伯菌荧光定量PCR检测方法的建立与应用

为了实现猪源肺炎克雷伯菌(Klebsiella pneumoniae,Kp)的快速检测,根据GenBank公布的猪源Kp Khe基因保守序列,设计引物和探针,建立了一种Kp荧光定量PCR快速检测方法,并对该方法的灵敏性、特异性及重复性进行评价。结果显示:该方法灵敏度高,最低检测限为10 copies/μL;特异性强,与大肠杆菌、金黄色葡萄球菌、化脓性链球菌、猪2型链球菌、副猪嗜血杆菌、猪坏死杆菌、猪细胞内劳森菌和猪丹毒杆菌等病原均无交叉反应;重复性好,批内及批间变异系数均小于2%。采用本方法检测140份临床送检样品,本方法的阳性检出率高于细菌分离鉴定方法。以上结果表明,本方法特异性强、灵敏度高、重复性好,可为猪源肺炎克雷伯菌病的诊断及防治提供更好的技术支持。     

杨粮间作系统中林木遮荫作用研究

本文报道了利用遮荫指数和遮荫程度 ,描述华北平原农区杨粮间作系统毛白杨对农田的遮荫情况。结果说明 ,毛白杨幼林 (株行距 3m× 2m× 18m) 1～ 7a生的遮荫指数为 1 3%～ 6 7 8% ,遮荫程度是 0 3%～16 5 % ;中龄林—成林 (株行距 4m× 30m) 10～ 14a生的遮荫指数是 5 1 3%～ 76 0 % ,遮荫程度为 2 2 8%～2 8 1%。利用遮荫程度表示林木对农田的遮荫情况比用遮荫指数更符合实际 ,并且提出 15 %的遮荫程度是田间可接受的最大遮荫程度     

日本在无机质复合木材领域的研究进展*

无机质复合木材是近年来木材化学改性领域中研究活跃的主题之一，文中简要叙述了溶胶—凝胶法制备木材—无机质复合材料的基本反应历程，介绍了近年来日本在无机质复合木材研究方面的进展情况。     

不同强度的择伐作业对保留木与幼树幼苗的影响

采用标准地的方式调查不同强度的择伐作业前后常绿阔叶林林分中保留木和幼树幼苗的变化.结果表明:保留木的损伤与采伐木的胸径及择伐强度有关.胸径越大则损伤率越大.择伐强度亦然.择伐作业后幼树的破坏与择伐强度间无明显的关系.这与作业的具体情况有关.择伐后与皆伐未整地经一段时间.林内幼苗数量都有所增加,尤以皆伐作业和弱度择伐为最.     

紫色土流失区造林技术

紫色土流失区造林技术是在划分流失地类型的基础上,采取生物和工程措施相结合的方法,适地适材选择造林树种。流失区适宜造林树种以侧柏为主,辅以建柏、闽粤栲、火力楠等树种。     

毛竹竹根区土壤微生物数量与酶活性研究

采样分析了毛竹竹根区土壤微生物数量和酶活性。结果表明：毛竹竹根区土壤细菌数量明显多于林间土，其R／S值（土壤酶活性比值）平均为1．53；从不同年龄竹来看，Ⅰ、Ⅱ度竹竹根区细菌数量多于Ⅲ度竹。毛竹竹根区土壤真菌数量也明显多于林间土，R／S值平均为2．05；其中Ⅱ度竹竹根区真菌数量显著多于Ⅰ、Ⅲ度竹根区，差异达显著水平。放线菌数量无论是毛竹竹根区与林间土之间还是不同年龄毛竹竹根区土之间均无明显不同。毛竹竹根区土壤过氧化氢酶、脲酶和蔗糖酶的活性明显高于林间土，R／S值分别平均为1.28、1.48、和1．94，但在Ⅰ、Ⅱ、Ⅲ度竹竹根区之间这3类酶的活性无明显差异。毛竹竹根区土壤蛋白酶和磷酸酶的活性也明显高于林间土，其R／S值分别平均为2．00和1．82，并且蛋白酶活性Ⅱ度竹竹根区明显高于Ⅰ、Ⅲ度竹竹根区，磷酸酶活性Ⅱ度竹竹根区也显著高于Ⅲ度竹竹根区，差异均达显著水平。     

温度、光照对南京裂爪螨的影响

南京裂爪螨 (Schizotetranychus nanjingensis Ma et Yan)常与竹缺爪螨 (Aponychuscorpuzae Rimando)、竹裂爪螨 (Schizotetranychus bambusae Recb)等害螨共同或单独在毛竹(Phyllostachys pubescens Mazel et H.de L ehaie)叶背刺吸危害 ,造成竹叶早衰、早落[1～ 3] 。有关其生活习性及其发生与部分环境因子的关系以及防治技术 ,前人已作了研究[3～ 9] ,但未见光照对其存活、发育、繁殖的影响以及温度与其存活的关系等文献报道 ,本文就此作一研究报道。1　材料与方法1 .1　温度试验设置 - 1 0℃± 1℃、2℃± 1℃、2 0℃± 1℃、2 5℃…     

湿地松是营造农田防护林好树种

在平原农田防护林带引种湿地松，通过７ａ试验观察，在成活率、高径生长量上都优于池杉，且长势旺盛，宜于平原农区推广．