Effects of dietary yeast inclusion and acute stress on post-prandial whole blood profiles of dorsal aorta-cannulated rainbow trout

Yeast is a potential alternative to fish meal in diets for farmed fish, yet replacing more than 50 % of fish meal results in reduced fish growth. In a 4-week experiment, 15 rainbow trout (Oncorhynchus mykiss) were cannulated and fed three diets each week: 30 % fish meal as a control (FM); 60 % replacement of fish meal protein, on a digestible basis, with Saccharomyces cerevisiae (SC); and 60 % replacement with Wickerhamomyces anomalus and S. cerevisiae mix (WA). Blood was collected at 0, 3, 6, 12 and 24 h after feeding. In the final week, fish were exposed to a 1-min netting stressor to evaluate possible diet–stress interactions. Significant increases in pH, TCO₂, HCO₃ and base excess were found after fish were fed the SC and WA diets compared with FM, which elevated blood alkaline tides. Yeast ingredients had lower buffering capacity and ash content than fish meal, which explained the increase in alkaline tides. In addition, fish fed the WA diet had significantly reduced erythrocyte area and fish fed SC and WA diets had increased mean corpuscular haemoglobin levels, indicating haemolytic anaemia. Higher levels of nucleic acid in yeast-based diets and potentially higher production of reactive oxygen species were suspected of damaging haemoglobin, which require replacement by smaller immature erythrocytes. Acute stress caused the expected rise in cortisol and glucose levels, but no interaction with diet was found. These results show that replacing 60 % of fish meal protein with yeasts can induce haemolytic anaemia in rainbow trout, which may limit yeast inclusion in diets for farmed fish.     

基于15N示踪技术的干旱区滴灌葡萄氮素利用分析

为研究水氮调控对干旱区滴灌葡萄氮素吸收利用的影响,以新疆鲜食葡萄弗雷为试验材料,利用¹⁵N 示踪技术,设置2种灌水处理(灌水量为4 950、5 400 m³·hm^-2,分别记作W1、W2),3种施氮处理(施氮量为177、235、292 kg·hm^-2,分别记作F1、F2、F3)进行大田试验。结果表明,各处理土壤全氮含量和¹⁵N丰度差异极显著(P<0.01),并且在0~20 cm土层出现富集现象。各器官征调氮素能力随水氮投入加大极显著增强(P<0.01)。根系、茎秆、叶片器官的生物量随着吸氮量的增加极显著提高(P<0.01),而较高施氮量(F3)不利于果实器官生物量的积累。果树吸收的肥料氮量随水氮投入的加大逐渐增加,受水氮调控影响极显著(P<0.01),果树吸收的土壤氮量大于肥料氮量。W2F1的¹⁵N标记氮肥利用率和¹⁵N标记氮肥偏生产力最高,分别为38.36%和114.20 kg·kg^-1,W2F2的产量最高,为20 253 kg·hm^-2,但与W2F1差异不显著。表明水氮投入过多会引起茎秆和叶片器官徒长且不利于提高¹⁵N标记氮肥利用率。综上所述,灌水量5 400 m³·hm^-2、施氮量177 kg·hm^-2(W2F1)是兼顾经济效益与生态效应的可行水氮运筹模式。本研究结果为干旱区滴灌葡萄高产高效种植提供了参考。     

植保无人机低空低量施药雾滴沉积飘移分布立体测试方法

随着植保无人机在中国的广泛使用,植保无人机的沉积分布均匀性与雾滴飘移流失也引起各方面的重视。目前,针对植保无人机施药雾滴沉积飘移的测试方法较少,且着重于从沉积或飘移中某一方面分析植保无人机雾滴沉积飘移规律,未对作业中全方位的雾滴的沉积飘失规律进行系统测试。该文基于国际标准ISO22866和ISO24253建了1套针对低空低量植保无人机的立体测试方法,分别在地面布置沉积和飘移收集器,在空中架设立体沉积和空中飘移收集器,结合航拍影像所获取的植保无人机准确作业参数,对4个型号植保无人机分别搭载德国Lechler公司的IDK120-015和TR80-0067喷头进行了测试,系统分析了无人机周边的总沉积以验证方法准确性,计算了总地面沉降以表征可利用部分和空中耗散以评估环境风险。结果表明,各植保无人机地面沉积率在53.6%~76.6%,地面飘移率最高17.4%,空中飘移率可高达14.7%;该测试系统可收集62.4%~101.7%无人机喷洒出的雾滴。测试的4种植保无人机在搭载IDK喷头后均明显降低了雾滴飘移,但也同时降低地面沉积率;各植保无人机在搭载2种喷头时沉积规律不同,不同植保无人机设计需要选择不同喷头。该测试方法能够有效的收集并分析植保无人机在作业区域的雾滴立体分布状态,可为植保无人机综合评估提供新的参考依据。     

Heat,wheat and CO2: The relevance of timing and the mode of temperature stress on biomass and yield

Atmospheric CO₂ enrichment affects C3 crops both directly via increased carbon gain and improved water use efficiency and indirectly via higher temperatures and more frequent climatic extremes. Here we investigated the response of spring wheat (Triticum aestivum L. cv. Triso) to CO₂ enrichment (550 vs. 380 µmol/mol) and heat, applied as a constant +4°C increase or a typical heat wave either before or after anthesis, or as two typical heat waves before and after anthesis. We applied a climate chamber approach closely mimicking ambient conditions. CO₂ enrichment increased above‐ground biomass and yield by c. 7 and 10%, but was not able to compensate for adverse heat stress effects, neither before nor after anthesis, with few exceptions only. Yield depression due to heat stress was most severe when two heat waves were applied (?19%). This adverse effect was, however, compensated by CO₂ enrichment. Applying heat stress before or after anthesis did not exert different effects on yield for both +4°C warming and heat wave application. However, +4°C depressed yield more than a heat wave at ambient CO₂, but not so at elevated CO₂. Thus, the interactive effects were complex and prediction of future wheat yield under CO₂ enrichment and climate extremes deserves more attention.     

稻田免耕年限与复耕次数对土壤容重和水稻生长的影响

试验以免耕1~10年稻田和免耕3~6年后复耕1次、复耕2次、复耕3次稻田为对象,探索不同免耕年限与复耕次数对稻田土壤容重和水稻生长的影响,以期为因地制宜推广免耕技术提供科学依据。结果表明：无论土壤表层还是下层,免耕土壤容重总是大于翻耕土壤,且随着免耕时间的延长,其土壤容重逐渐加重,免耕3年及以后处理土壤容重显著大于翻耕处理(P<0.05),随着复耕次数的增加,土壤容重逐渐降低。连续免耕1~5年的田块,免耕栽培处理水稻最高苗和有效穗以及产量均表现为比翻耕栽培处理高,免耕6年处理表现相对平缓稳定,免耕7年及以后分蘖能力和产量明显下降。免耕3~5年后进行复耕处理水稻分蘖能力和产量总是低于对应的免耕4~6年处理,且随着复耕次数的增加差距逐渐扩大,免耕7年处理水稻分蘖能力和产量与免耕6年后进行复耕1次处理基本持平。结论为稻田免耕应以6年内为宜,当稻田连续免耕超过最适年限后,需要进行复耕作业,复耕1次即可。     

Associations among Haemophilus parasuis,Mycoplasma hyorhinis,and porcine reproductive and respiratory syndrome virus infections in pigs with polyserositis

The objective of this study was to determine the associations among Haemophilus parasuis, Mycoplasma hyorhinis, and porcine reproductive and respiratory syndrome (PRRS) virus (EU-field strain) infections in 95 pigs with polyserositis. A significant association between H. parasuis and M. hyorhinis was identified. H. parasuis and M. hyorhinis were significantly more often detected in PRRS virus positive pigs.     

云南主要核桃品种的ISSR分子鉴别

以核桃当年萌发的新叶为材料,在建立了良好的反应体系基础上,筛选出8条引物对云南省11个主要栽培和推广的核桃品种进行了ISSR分子标记研究。结果表明:8个ISSR引物共检测出位点102个,其中多态性位点62个,占60.78%,参试样品具有较高的多态比率;用其中的两条引物建立了11个品种的指纹图谱,并可用之鉴别参试品种;POPGENE 32软件的计算结果有效等位基因数、基因的多样性和Shannon信息指数分别为1.370 7,0.214 3和0.321 6,供试的云南核桃品种在分子水平上存在比较丰富的遗传变异。     

漾濞核桃叶片基因组DNA的两种提取方法效果比较

以漾濞核桃不同生长期的叶片为材料，采用高盐低pH法和改良CTAB法作提取其基因组DNA的效果比较实验。通过琼脂糖凝胶电泳、紫外分光光度计和RAPD扩增对所提取的DNA样品进行检测，比较所得DNA的产量、质量，认为从漾濞核桃不同发育时期叶片中获得DNA的提取效果不同。4种叶样以冬芽和新叶的效果为好，老叶最差；用两种提取方法从叶片中得到的DNA产量和质量有所不同，高盐低pH法提取的DNA纯度高，但是产量较低；而改良CTAB法则相反，产量高，纯度低。     

Modeling spatial variability in the life-cycle costs of low-volume forest roads

Cost estimation is probably the most decisive factor in the process of computer-aided, preliminary planning for low-volume road networks. However, the cost of construction is normally assumed to be route-independent for a specific project area, resulting in sub-optimal layouts. This is especially true for mountainous terrain and in areas with unstable subsoil. Here, we present a model for more accurately estimating spatial variability in road life-cycle costs, based on terrain surface properties as well as geological properties of the subsoil. This parametric model incorporates four structural components: embankment, retaining structures, pavement, and drainage and stream-crossing structures. It is linked to a geo-database that allows users to derive location-specific parameter values as input. In applying this model, we have demonstrated that variability in costs ranges widely for mountainous areas, with the most expensive construction being approximately five times greater there than on more favorable sites. This variability strongly affects the optimal layout of a road network. First, when location-specific slope gradients are considered, costs are reduced by about 17% from those calculated via currently available engineering practices; when both slope gradient and geotechnical formations are included, those costs are decreased by about 20%. Second, the length of the road network is increased by about 4% and 10% respectively, compared with current practices.