解决夏季母猪“饥而不饿”的营养招数

夏季来临，温度是影响猪群健康的第一要素，尤其对于母猪，在高温下其对营养的吸收利用及代谢均会发生改变，导致母猪代谢不畅而不愿采食，这将严重影响猪群健康及繁殖成绩。文章将从营养调节角度分析，并结合生产实践来解决这一问题，以期为猪场夏季母猪健康养殖提供借鉴和参考。     

试论《三国志》裴松之注“凿空语怪”的文学意义

《三国志》裴松之注因为引用了几则具有志怪性质的材料，而被历来史家批评其“凿空语怪”、“坐长烦芜”。事实上，裴松之在引援这些注文时并非是不加选汰而盲目采用的。裴松之用审慎的态度和隐蔽的手段，把自己对历史人物及事实的评价暗蕴于注解之中。而且，其保存小说材料和用小说注史之功，是不可泯没的。《三国志》裴松之注将历史与小说相结合，则对当下的玄幻小说创作具有一定的启迪意义。     

棕紫泥土的养分吸附特征及对作物生长的影响研究

棕紫泥土在四川约有1·6642×106hm2,占石灰性紫色土亚类的39·27%。在四川旱耕地资源中占有重要的地位,其生产潜力大,问题也多。本文运用土壤养分系统研究法探讨了四川棕紫泥土的供肥状况及主要营养影响因子。结果表明N、P是棕紫泥土作物生长的主要影响因子,补充N、P是增产的重要措施;其他营养元素是否成为影响因子要因作物而异。     

Improving minimum detectable differences in the assessment of soil organic matter change in short‐term field experiments

The demand for information on cropping system impact on soil organic matter (SOM) calls for efforts to improve the utilization of short‐term field experiments (e.g., to evaluate the parameterization of cropping systems in models). Those approaches have coped with the problem of determining small SOM changes within a large background mass. Thus, objectives of this survey are (1) the improvement of the minimum detectable difference (MDD) in SOM in the hudycrop short‐term field experiment by methods of sampling design and data treatment, (2) the verification to what extend the hudycrop short‐term field experiment allows for the determination of management induced effects on SOM, and (3) the investigation to what extent the obtained results may be suitable to evaluate the parameterization of a SOM balance model. The design of the hudycrop is suitable for excluding outliers plotwise. The estimation of plot means can be improved by the sampling design. Instead of determining a single plot mean in a mixed sampling procedure, the design provides multiple values for each plot, allowing for the identification of extreme values before calculating plot means. In consequence, minimum detectable differences decrease by a factor of 0.53 for soil organic C (SOC) and 0.63 for soil total N (STN) masses, allowing for detection of changes in the magnitude of 3.7 and 2.6% of background SOC and STN levels, respectively. Differences between treatments, however, are significant with corrected values (after outlier exclusion) for the crop production systems with the highest impact (potatoes and mulched red clover). Determining outliers based on Student's t‐test gives the lowest MDD and is therefore considered to be the most suitable method in this case. Correlations between apparent changes and SOM balances according to the HU‐MOD–2 model, used in this survey, indicate that the experimental design, in principal, is suitable for the evaluation of the parameterization of crop production systems in models. Still, an improved precision in SOM change detection is necessary. Reasonable options for that purpose are discussed in the paper.     

用最小可检测差异技术评估耕作方式对土壤C固定的影响

Three long-term field trials in humid regions of Canada and the USA were used to evaluate the influence of soil depth and sample numbers on soil organic carbon （SOC） sequestration in no-tillage （NT） and moldboard plow （MP） corn （Zea mays L.） and soybean （Glycine max L.） production systems. The first trial was conducted on a Maryhill silt loam （Typic Hapludalf） at Elora, Ontario, Canada, the second on a Brookston clay loam （Typic Argiaquoll） at Woodslee, Ontario, Canada, and the third on a Thorp silt loam （Argiaquic Argialboll） at Urbana, Illinois, USA. No-tillage led to significantly higher SOC concentrations in the top 5 cm compared to MP at all 3 sites. However, NT resulted in significantly lower SOC in sub-surface soils as compared to MP at Woodslee （10-20 cm, P =0.01） and Urbana （20-30 cm, P 〈 0.10）. No-tillage had significantly more SOC storage than MP at the Elora site （3.3 Mg C ha^-1） and at the Woodslee site （6.2 Mg C ha^-1） on an equivalent mass basis （1 350 Mg ha^-1 soil equivalent mass）. Similarly, NT had greater SOC storage than MP at the Urbana site （2.7 Mg C ha^-1） on an equivalent mass basis of 675 Mg ha^-1 soil. However, these differences disappeared when the entire plow layer was evaluated for both the Woodslee and Urbana sites as a result of the higher SOC concentrations in MP than in NT at depth. Using the minimum detectable difference technique, we observed that up to 1 500 soil sample per tillage treatment comparison will have to be collected and analyzed for the Elora and Woodslee sites and over 40 soil samples per tillage treatment comparison for the Urbana to statistically separate significant differences in the SOC contents of sub-plow depth soils. Therefore, it is impracticable, and at the least prohibitively expensive, to detect tillage-induced differences in soil C beyond the plow layer in various soils.     

Breeding for increased grain protein and micronutrient content in wheat: Ten years of the GPC-B1 gene

To provide food and nutrition security for a growing world population, continued improvements in the yield and nutritional quality of agricultural crops will be required. Wheat is an important source of calories, protein and micronutrients and is thus a priority to breed for improvements in these traits. The GRAIN PROTEIN CONTENT-B1 (GPC-B1) gene is a positive regulator of nutrient translocation which increases protein, iron and zinc concentration in the wheat grain. In the ten years since it was cloned, the impacts of GPC-B1 allelic variation on quality and yield traits have been extensively analyzed in diverse genetic backgrounds in field studies spanning forty environments and seven countries. In this review, we compile data from twenty-five studies to summarize the impact of GPC-B1 allelic variation on fifty different traits. Taken together, the results demonstrate that the functional copy of the GPC-B1 gene is associated with consistent positive effects on grain protein, Fe and Zn content with only marginally negative impacts on yield. We conclude that the GPC-B1 gene has the potential to increase nutritional and end use quality in a wide range of modern cultivars and environments and discuss the possibilities for its application in wheat breeding.     

Deficit irrigation based on drought tolerance and root signalling in potatoes and tomatoes

Agriculture is a big consumer of fresh water in competition with other sectors of the society. Within the EU-project SAFIR new water-saving irrigation strategies were developed based on pot, semi-field and field experiments with potatoes (Solanum tuberosum L.), fresh tomatoes (Lycopersicon esculentum Mill.) and processing tomatoes as model plants. From the pot and semi-field experiments an ABA production model was developed for potatoes to optimize the ABA signalling; this was obtained by modelling the optimal level of soil drying for ABA production before re-irrigation in a crop growth model. The field irrigation guidelines were developed under temperate (Denmark), Mediterranean (Greece, Italy) and continental (Serbia, China) climatic conditions during summer. The field investigations on processing tomatoes were undertaken only in the Po valley (North Italy) on fine, textured soil. The investigations from several studies showed that gradual soil drying imposed by deficit irrigation (DI) or partial root zone drying irrigation (PRD) induced hydraulic and chemical signals from the root system resulting in partial stomatal closure, an increase in photosynthetic water use efficiency, and a slight reduction in top vegetative growth. Further PRD increased N-mineralization significantly beyond that from DI, causing a stay-green effect late in the growing season. In field potato and tomato experiments the water-saving irrigation strategies DI and PRD were able to save about 20-30% of the water used in fully irrigated plants. PRD increased marketable yield in potatoes significantly by 15% due to improved tuber size distribution. PRD increased antioxidant content significantly by approximately 10% in both potatoes and fresh tomatoes. Under a high temperature regime, full irrigation (FI) should be undertaken, as was clear from field observations in tomatoes. For tomatoes full irrigation should be undertaken for cooling effects when the night/day average temperature >26.5 °C or when air temperature >40 °C to avoid flower-dropping. The temperature threshold for potatoes is not clear. From three-year field drip irrigation experiments we found that under the establishment phase, both potatoes and tomatoes should be fully irrigated; however, during the later phases deficit irrigation might be applied as outlined below without causing significant yield reduction:

•

Potatoes

°

After the end of tuber initiation, DI or PRD is applied at 70% of FI. During the last 14 days of the growth period, DI or PRD is applied at 50% of FI.

•

Fresh tomatoes

°

From the moment the 1st truce is developed, DI is applied at 85-80% of FI for two weeks. In the middle period, DI or PRD is applied at 70% of FI. During the last 14 days of the growth period, DI or PRD is applied at 50% of FI.

•

Processing tomatoes

°

From transplanting to fruit setting at 4th-5th cluster, the PRD and DI threshold for re-irrigation is when the plant-available soil water content (ASWC) equals 0.7 (soil water potential, Ψ_soil = −90 kPa). During the late fruit development/ripening stage, 10% of red fruits, the threshold for re-irrigation for DI is when ASWC = 0.5 (Ψ_soil = −185 kPa) and for PRD when ASWC (dry side) = 0.4 (Ψ_{soil, dry side} = −270 kPa).

The findings during the SAFIR project might be used as a framework for implementing water-saving deficit irrigation under different local soil and climatic conditions.     

对虾白斑综合征病毒囊膜蛋白VP110在中国明对虾鳃细胞中结合蛋白的鉴定与特性

为了鉴定对虾白斑病综合征病毒(WSSV)囊膜蛋白VP110在中国明对虾(Fenneropenaeus chinensis)鳃细胞中的结合蛋白, 运用pET-32(a)+载体构建了1段含RGD模体的截短VP110原核重组表达质粒, 转化大肠杆菌诱导表达后获得分子量为41 kD的截短重组VP110蛋白(rVP110)。以rVP110作为诱饵蛋白, 运用pull-down实验结合蛋白质谱分析鉴定rVP110结合蛋白, 结果显示, 中国明对虾鳃细胞中的肌动蛋白和精氨酸激酶(arginine kinase,AK)与rVP110具有结合作用。利用PCR扩增中国明对虾AK编码基因, 将其与表达载体pGEX-4T-1连接后转化大肠杆菌诱导表达获得重组AK蛋白(rAK), 通过pull-down实验进一步证实rAK可与rVP110发生结合。克氏原螯虾(Procambarus clarkia)体内中和实验结果显示, rAK对WSSV感染克氏原螯虾具有一定的中和作用, 能延缓螯虾的死亡进程。另外, 中国明对虾在人工感染WSSV后, 荧光定量PCR检测结果显示, AK基因表达水平显著上调, 18 h时达到峰值, 然后下降至正常水平; 酶底物法检测结果同样显示, 鳃细胞中AK酶活性在感染WSSV后发生显著上调。本研究旨在为深入了解WSSV囊膜蛋白VP110在WSSV感染宿主过程中的作用提供基础依据。

     

如何在湖泊水库中进行不投饵网箱养殖鲢鳙鱼

从不投饵网箱养殖鲢鳙鱼的优点以及相关的技术2个方面,论述在湖泊水库中进行不投饵鲢鳙鱼的网箱养殖技术方法。     

对大学生自愿性不就业现象的研究

在大学生就业压力越来越大的形势下,出现了部分毕业生自愿不就业的现象。本文对当前大学生就业中出现的特殊现象——自愿性不就业进行分类探讨,并对产生这些现象的外界环境和主观因素进行分析,最后阐述了大学毕业生自愿性不就业的负面影响。