Dietary α‐Ketoglutarate supplementation alleviates harmful effects of high environmental ammonia on grass carp,Ctenopharyngodon idella

Current intensive fish farming usually causes high environmental ammonia (HEA) in ponds that is toxic to fish. α‐Ketoglutarate (α‐KG) can be rapidly transaminated to glutamic acid and further aminated to glutamine. Therefore, we hypothesized that dietary α‐KG supplementation would alleviate HEA toxicity to fish. To test the hypothesis, 270 healthy grass carp (Ctenopharyngodon idella) juveniles were randomly assigned to control, HEA (18.37 mg/L ammonia) and HEA + α‐KG (0.75% of α‐KG) groups. Ammonia and free amino acid content in plasma and brain, liver glutamic pyruvic transaminase and glutamic oxaloacetic transaminase activity, and urea and glycogen content were measured on the first, seventh and 42nd days. Our results showed short‐term HEA exposure (1 day) led to a significant ammonia accumulation in the brain and plasma and significantly decreased glutamic and aspartic acid content in the brain and increased glutamine content in the brain and plasma. The long‐term HEA exposure (42 days) caused significant reductions in glycine and arginine content in the brain tissue. In most cases, dietary α‐KG supplementation alleviated the fluctuations in FAA content in the brain and plasma. Our results suggested dietary α‐KG alleviated HEA toxicity to grass carp.     

Effect of the Pietrain breed used as terminal boar on Post-weaning Multisystemic Wasting Syndrome (PMWS) in the offspring in four PMWS-affected farms

The aim of this study was to determine the potential risk factors for PMWS at the individual pig level and assess the effect of the Pietrain paternal genetic background of the animals in a cohort study. The survey was set up in four PMWS-affected farms with 2 repetitions (batches) per farm. A representative sample of 60 pigs per batch, stratified according to the paternal genetic background (Pietrain: yes vs. no), was randomly selected after farrowing. The representative cohort was divided into 8 batches and the pigs were individually monitored from birth to slaughter. Survival analysis was used to determine the factors related to the time to PMWS. The litter-cluster effect was taken into account using the marginal Cox model (robust estimation of the covariance matrix) and the gamma shared frailty model which were compared.No protective effect of the Pietrain breed on the time to PMWS and the proportion of affected pigs in the offspring was found in this study. Piglets showing low circovirus type 2 (PCV2) titres at 7 weeks-old with no subsequent seroconversion and piglets from PCV2 negative sows were most likely to be affected by PMWS (HR=7.0 and 2.8, respectively). Active infection of the pregnant dams with parvovirus was related to an increased risk of PMWS in the offspring (HR=2.3). Neck injuries due to poorly performed injections in the dams were associated with an increased risk of PMWS with the marginal model (HR=2.1). Oxytocin injection (dams) during farrowing was protective against PMWS in the offspring (HR=0.6).     

气候条件对大白菜产量的影响

大白菜喜温和气候,它主要的生长时期,平均温度大都以16±10℃的条件为宜.采用Cob-Douglas生产函数模型和通径分析方法,探讨气象要素对大白菜产量综合效应的结果表明,大白菜在我地栽培,其生长过程中对气象要素的需求量,与它的生物学特点相吻合.     

义乌游泳馆屋盖风荷载的试验研究

义乌游泳馆采用凹形屋盖,对这种屋盖结构的风荷载研究还比较少.为此,制作了比例为1:100的刚性模型,采用同步测压技术,进行了义乌游泳馆凹形屋盖的风压测量,得到了其屋盖上的平均风压系数分布并与凸形屋盖的试验结果进行比较.结果表明:凹形屋盖上的“吸力”要远大于凸形屋盖上的“吸力”;迎风向挑棚上、下表面压力出现不利的负相关,应引起设计人员的注意;周边建筑对义乌游泳馆屋盖风荷载的影响不大.最后还给出了义乌游泳馆屋盖上的前10个最小极值风压.     

Back-calculation method shows that within-flock transmission of highly pathogenic avian influenza (H7N7) virus in the Netherlands is not influenced by housing risk factors

To optimize control of an avian influenza outbreak knowledge of within-flock transmission is needed. This study used field data to estimate the transmission rate parameter (β) and the influence of risk factors on within-flock transmission of highly pathogenic avian influenza (HPAI) H7N7 virus in the 2003 epidemic in The Netherlands. The estimation is based on back-calculation of daily mortality data to fit a susceptible-infectious-dead format, and these data were analysed with a generalized linear model. This back-calculation method took into account the uncertainty of the length of the latent period, the survival of an infection by some birds and the influence of farm characteristics. After analysing the fit of the different databases created by back-calculation, it could be concluded that an absence of the latency period provided the best fit. The transmission rate parameter (β) from these field data was estimated at 4.50 per infectious chicken per day (95% CI: 2.68–7.57), which was lower than what was reported from experimental data. In contrast to general belief, none of the studied risk factors (housing system, flock size, species, age of the birds in weeks and date of depopulation) had significant influence on the estimated β.     

山东省农民对创业培训的需求及影响因素分析——以烟台地区为例

以山东省烟台地区农民创业培训及培训需求影响因素为研究内容,通过问卷及实地调研,研究了农民参加创业培训后的基本状况,运用多元Logit回归模型,分析了当前烟台地区农民参与创业培训需求的主要影响因素,同时,针对实际情况提出了农民创业培训工作的可行性建议。     

敌百虫胁迫对克氏原螯虾免疫学相关指标的影响

在不同质量浓度(0、0.132、0.264、0.528 mg/L)敌百虫胁迫条件下,研究克氏原螯虾(Procambarus clarkii)肝胰腺T-SOD、CAT、ACP、AKP及肌肉Na+,K+-ATPase、TChE的活性变化。结果表明,敌百虫对各免疫因子影响各异;0.132 mg/L和0.528 mg/L浓度组克氏原螯虾的肝胰腺T-SOD活性分别于药浴4 d和1 d时显著高于对照组(P0.05);0.132 mg/L和0.264 mg/L浓度组克氏原螯虾的CAT活性于药浴2 d后显著高于对照组(P0.05);12 d内各浓度组ACP及AKP活性随药浴时间的延长而一直低于对照组,其中ACP在4 d内逐渐降低;肌肉TChE在0.132 mg/L和0.264 mg/L浓度组中分别于药浴1 d和4 d后活性显著高于对照组(P0.05);而Na+,K+-ATPase只有0.528 mg/L浓度组在2 d内活性显著高于对照组(P0.05),其余各组未出现诱导现象;试验组各免疫因子活性在药浴12 d时均显著低于对照组(P0.05);表明敌百虫胁迫并非仅仅作用于TChE,其对克氏原螯虾机体T-SOD、CAT、ACP、AKP及Na+,K+-ATPase均有影响,12 d后各免疫因子活性均难以恢复至对照水平。     

基于BP神经网络的阿根廷滑柔鱼资源CPUE标准化研究

西南大西洋阿根廷滑柔鱼(Illex angentinus)是世界上重要的经济柔鱼类,也是我国远洋鱿钓的主要捕捞对象之一.单位努力量渔获量(CPUE)是渔业中广泛使用的表达种群丰度的指标,但CPUE易受到其他因素的影响,需对其进行标准化.本研究利用2012-2017年1-4月中国大陆西南大西洋阿根廷滑柔鱼鱿钓生产统计数据...     

植物响应环境胁迫过程中的蛋白质组变化规律研究进展

植物在生长过程中可能会受到来自环境的多种胁迫,包括以高温、低温、干旱、水涝、高盐、臭氧、光照、矿物质、酸雨、辐射、重金属和机械损伤为代表的非生物因素环境胁迫和以诱导子、细菌、真菌、病毒和植食性动物为代表的生物因素环境胁迫。植物通过改变自身的蛋白质表达水平来对各种环境胁迫作出响应,因此蛋白质组学技术方法能够更好地揭示植物耐受胁迫相关的重要蛋白质群组的动态变化规律,发现植物响应环境胁迫的重要标志物。对近年来植物应答环境胁迫的蛋白质组学研究进行综述,以期从组学角度拓展植物耐受胁迫机制的认识。     

基于脆弱性和退化驱动力分析的环境质量评价

 针对淮河流域伏牛山区不同区域的自然环境及社会经济特征,以县级行政区为评价单元,建立环境质量评价指标体系,然后使用层次分析法评价该地区环境脆弱性,并在同一指标体系下采用主成分分析法分析影响该区环境脆弱性的驱动力。结果表明:中度、强度和极强度脆弱区占淮河流域伏牛山区总面积的2/3以上,主要分布在研究区的中东部地区,而轻度和微度脆弱区分布在西部和南部的山区;影响该区环境脆弱性的6大驱动力为土地过度垦殖、土壤密度与枯落物量、降雨量、农业发展与产业结构水平、地形与植被覆盖、文化素质。