猪流感的再认识

猪流感是由流感病毒引起猪的急性呼吸道传染病。本文评述了猪流 进化、种间传播、公共卫生意义,认为猪流感在人流感和禽流感之间发挥着关键性作用,堪作研究人流感的动物模型和流感大流行的预警信号,建议重亲高猪流感。     

The Use of Direct‐Fed Microbials to Reduce Shedding of Escherichia coli O157 in Beef Cattle: A Systematic Review and Meta‐analysis

Human illness due to infections with Escherichia coli O157 is a serious health concern. Infection occurs through direct contact with infected animals or their faeces, through contaminated food or water and/or through person‐to‐person transmission. A reduction in faecal E. coli O157 shedding in cattle might reduce the burden of human infections. We used systematic review and meta‐analysis to assess the efficacy of direct‐fed microbials (DFM), compared with placebo or no treatment, fed during the pre‐harvest stage of production in reducing faecal E. coli O157 shedding in beef cattle during field trials. Four electronic databases, Nebraska Beef Reports and review article reference lists were searched. A total of 16 publications assessing faecal shedding at the end of the trial and/or throughout the trial period were included. The majority of publicly disseminated trials evaluated the prevalence of E. coli O157 faecal shedding; only two evaluated the concentration of organisms in faeces. The prevalence of faecal E. coli O157 shedding in cattle is significantly reduced by DFM treatments (summary effect size for all DFM – OR = 0.46; CI = 0.36–0.60). The DFM combination Lactobacillus acidophilus (NP51) and Propionibacterium freudenreichii (NP24) was more efficacious in reducing the prevalence of faecal E. coli O157 shedding at the time of harvest and throughout the trial period compared with the group of other DFM, although this difference was not statistically significant. Furthermore, we found that the combination [NP51 and NP24] treatment was more efficacious in reducing the prevalence of faecal E. coli O157 shedding at the time of harvest and throughout the trial period when fed at the dose of 10⁹ CFU/animal/day than any lesser amount, although this difference was not statistically significant. Feeding beef cattle DFM during the pre‐harvest stage of production reduces the prevalence of E. coli O157 faecal shedding and might effectively reduce human infections.     

Prevalence and Risk Factors for Bacterial Food‐Borne Zoonotic Hazards in Slaughter Pigs: A Review

The Hygiene Package and Regulation EC‐2160/2003 require information flow from farm to slaughterhouse to enhance European consumers protection in a ‘farm to fork’ approach. This obligation especially concerns food‐borne zoonotic hazards transmitted to humans through pork consumption, such as thermophilic Campylobacter spp., Listeria monocytogenes, Salmonella enterica and Yersinia enterocolitica. Prevalence estimates of these four hazards are affected by the sampling strategy and diagnostic procedure. Individual prevalence estimates for pig carriage (from digestive contents or lymph nodes collected at slaughterhouse) were higher than individual prevalence estimates for pig shedding (from faeces). Among risk factors described in the literature, poor pen cleaning and disinfection after pig departure to slaughterhouse and poor bio‐security measures are of major significance. Moreover, whereas wet feed increases the risk of pig infection by L. monocytogenes, dry feed is a risk factor for Salm. enterica. Mixing batches of pigs, notably in fattening herds, represents a risk for the transmission of Salm. enterica and Y. enterocolitica. Whereas small herds are more infected by thermophilic campylobacters and Y. enterocolitica, higher prevalence of Salmonella is observed in large herds due to a more frequent mixing of batches. Antibiotic treatment during the finishing period increases the risk of transmission of Salm. enterica. The forenamed elements should be taken into account to characterize farms in a risk assessment approach and to improve zoonotic hazard management in the pork food chain.     

基于复合函数变换的GM(1,1)模型及其应用

基于函数变换理论,本文提出了对建模数据进行复合函数变换,理论上证明了这种变换可以有效提高建模数据序列的光滑度。并把此方法应用于我国国内人均生产总值的建模中,应用结果表明,该方法所建模型的精度优于传统GM(11,)模型和对数函数变换GM(1,1)模型的精度,从而拓宽了灰色模型的应用范围。     

The analysis on pre splitting blasting to improve permeability draining rate in heading excavation

Aiming at the problem of low excavation speed and high risk of coal and gas outburst because of low gas draining rate in heading excavation,and taking an excavation heading of a mine for example,the test of deep hole pre splitting blasting is processed.The amount of gas draining after pre splitting is compared with the amount of direct draining,and the effective radius of draining is surveyed.The test result shows that the draining rate of K1 coal seam reaches 37.13 %,which reduces the draining time by 60%,10 days after pre splitting,and the gas desorption index exceeds the standards until the fifth blasting.The draining rate of K4 needs 12 days to reach 34.28 %,which reduces the draining time by 60%,and the gas desorption index exceeds the standards when the third blasting processes.Obviously,the effect of gas draining is improved by pre splitting blasting.The effective draining radius of K1 and K4 are 4.5 and 5.2 m respectively after pre splitting blasting.The research can provide reference for the fieldwork of pre splitting blasting.     

Effects of ensiling cereal grains (barley,wheat, triticale and rye) on total and pre‐caecal digestibility of proximate nutrients and amino acids in pigs

Inclemency of weather frequently causes critical water contents in cereal grains above 15%. Ensiling in pre‐mature condition may be an alternative to other techniques of preservation. Aim of this study was to compare apparent total tract digestibility (D_t; barley, wheat, triticale, rye) of proximate nutrients and pre‐caecal digestibility (D_pc; barley, wheat) of amino acids (AA), respectively, from cereal grains in ensiled and almost dry condition. Moistly harvested cereal grains (67–73% dry matter) were milled through a 4‐mm sieve and ensiled with lactic acid bacteria (LAB, 3 × 10⁵ colony forming units/g Lactobacillus plantarum DSMZ 8862 and 8866). To investigate D_t, two trials were conducted with six Mini‐Lewe pigs and four German Landrace pigs, respectively. D_pc of AA was determined using four German Landrace pigs with ileo‐rectal anastomosis. D_t of proximate nutrients did not differ between cereal grains and their silages, except for ether extract, which was more digestible in ensiled than dry wheat, triticale and rye (p < 0.05). Lysine content was lower in ensiled than dry barley and wheat. In barley, ensiling was accompanied by reduced D_pc of lysine and histidine (p < 0.05). In wheat, ensiling increased D_pc of lysine, methionine, threonine and leucin (p < 0.05). Ensiling of pre‐mature cereal grains with LAB can serve as a reasonable storage alternative. However, as limited data are yet available, further research is required to understand completely the impact of ensiling on nutritional value as indicated, for example, by the lysine content and the D_pc of certain AA.     

前处理及低温贮藏对百合(Lilium)鲜切花寿命的影响

采用不同的前处理液对百合品种‘ＧｒａｎＰａｒａｄｉｓｏ’进行处理,然后分别在２℃和４℃低温下贮藏,观察其瓶插寿命,结果表明,用２号前处理液处理、在室温下瓶插的切花寿命最长;如果经过低温贮藏,用２号前处理液处理、在２℃低温贮藏的切花瓶插寿命最长。     

芽前除草剂和地膜对杂草防除和牛至生长的影响

牛至Orianum vulgare是唇形科多年生草本植物,牛至精油具有抗菌消炎功效,是重要的中兽药和饲料添加剂.牛至在苗期生长缓慢,杂草防除是牛至田建植的基础.本研究分析了芽前除草剂和地膜对牛至田杂草防控和牛至生长的影响.结果 表明,除草剂和地膜覆盖对杂草防除和牛至生长的交互效应显著.其中,覆盖黑色地膜并喷施960 g...     

授粉方式对牡丹和芍药远缘杂交受精前障碍的影响

【目的】探寻克服牡丹与芍药远缘杂交受精前障碍的授粉方式,为克服牡丹、芍药远缘杂交不亲和提供理论依据。【方法】以芍药品种粉玉奴(Paeonia lactiflora‘Fenyunu’)为母本,牡丹品种凤丹白(Paeonia ostii‘Fengdanbai’)、洛阳红(Paeonia suffruticos a‘Luoyanghong’)为父本分别进行远缘杂交,采用常规授粉、延迟授粉、重复授粉、切割柱头授粉和蒙导授粉5种不同授粉方法,对授粉后花粉萌发及花粉管伸长过程进行荧光显微观察,研究母本心皮形态学特征,统计杂交组合结实率。【结果】杂交组合粉玉奴×凤丹白、粉玉奴×洛阳红采用重复授粉、蒙导授粉、延迟授粉的效果均优于常规授粉,在花粉萌发量、花粉管伸长及单花结实率方面表现为延迟授粉重复授粉蒙导授粉常规授粉切割柱头授粉,说明延迟授粉对于克服受精前障碍效果最佳,为最佳授粉方式。切割柱头授粉虽效果不佳,但对克服受精前障碍有一定影响。【结论】在牡丹、芍药远缘杂交育种中,可以采取延迟授粉的方法,减缓甚至克服母本柱头或花柱对异源花粉萌发及花粉管生长的抑制,克服受精前障碍,提高育种效率。