Photoperiod in recirculation aquaculture systems and timing of seawater transfer affect seawater growth performance of Atlantic salmon (Salmo salar)

Production of Atlantic salmon smolts in recirculation aquaculture systems (RAS) is growing, and novel production protocols using continuous light in RAS are being implemented in the industry. In the present study, Atlantic Salmon parr were exposed to either a traditional protocol (short-day winter signal [12:12 L:D] for 6 weeks) or to continuous light. Both photoperiods were applied in freshwater (FW) and brackish water RAS. Salmon from all treatments were transferred to seawater pens at 200 and 600 g and grown until slaughter size. A control group was smoltified with a 6-week short-day winter signal and kept in FW until sea transfer at 100 g. Continuous light gave a higher growth rate in RAS but reduced feed intake and growth and increased feed conversion ratio during the first 8 weeks in seawater. However, at slaughter, fish exposed to continuous light was bigger than fish given a winter signal because of the higher growth rate in RAS. Slaughter weight was lowest in fish transferred to sea at 600 g, despite having the highest day-degree sum during their life span. The best performing group was the control group transferred at 100 g. All treatments handled transfer to seawater and survival and maturation were not affected by the treatments in RAS. The immune status was examined with a multigene expression assay on BioMark HD platform from parr stage to 5–7 months after seawater transfer. Overall, there was no significant effect of photoperiod or salinity on the expression of the selected immune genes. In sum, the results from this study indicate that using continuous light in RAS may have negative effects on performance shortly after transfer in fish transferred to sea at 200 g, whereas at 600 g, all treatments had reduced growth after transfer irrespective of treatment in RAS.     

基于三轴旋转的旋转光纤捷联惯性导航系统

介绍了基于旋转惯性器件的惯性导航系统的工作原理。根据该方案的思想对捷联惯性导航系统加以改进,设计了可绕三轴旋转的IMU机构,建立了旋转机构误差模型。仿真结果表明,该机构符合最初对它的设计要求,即提高了导航系统关于横滚、俯仰姿态的精度,同时也达到了通过三轴旋转提高航向角跟踪精度的目的,故弥补了目前研究的旋转惯导系统无法调制航向角精度的缺陷。此外。这该绕三轴旋转的惯导系统还可以根据六位置旋转法原理实现实时标定功能,从而进一步改善系统性能。     

Milk-production potential of different sward types in a temperate southern Australian environment

The milk-production potential of different sward types was measured in each of the four seasons of the year in a replicated experiment in south-west Victoria, Australia. Dairy cows were offered ad libitum allowances of a 'short-term winter' sward, based on Italian ryegrass (treatment STW), a 'long-term winter' sward, based on a winter-active tall fescue (treatment LTW), a 'long-term summer' sward, based on a summer-active tall fescue (treatment LTS) and a Control sward (perennial ryegrass) in four seasons (days in milk in parentheses): spring (November dairy cows, 124), summer (February, 227), autumn (May, 234) and winter (August, sixty-four). A 'short-term summer' sward, based on chicory and white clover (treatment STS), was also included in summer. There was a significant season × treatment interaction caused by a more gradual decline in milk yield from peak for cows grazing treatment LTS compared to the Control treatment in the transition period from spring to summer. In summer, cows grazing treatment STS produced more milk (1·41 kg fat plus protein per cow d⁻¹) than cows grazing all other treatments (0·92 kg per cow d⁻¹) because of the superior nutritive value of herbage of pre-grazing pasture and higher apparent dry-matter intakes. Swards based on alternative species to perennial ryegrass are capable of supporting milk production that is at least comparable over an annual cycle.     

人工嗅觉研究进展及其在食品香气评定中的应用展望

概述了人工嗅觉系统的研究历史与应用现状,详细介绍了人工嗅觉系统的基本原理,阐述了基于神经网络的人工嗅觉系统在食品香气质量评定中的广阔应用前景     

农业利益系统分析与有效性评价

农业利益系统分析与有效性评价是一个复杂的农业系统工程问题。该文在分析农业利益及其春系统构成的基础上,根据现有统计资料,从不同角度对吉林省农业利益进行了系统分析,指出了存在的问题,提出了相应的对策。在明确农业投入产出构成的农业利益系统的基础上,分析了ＤＥＡ方法及其春模型,确定了模型的输入输出指标,进行了中国农业利益系统有效性评价,获得了许多信息。为农业利益系统分析与有效性评价提供了思路和依据。     

黑龙江省农村产业结构发展的灰色关联动态分析

应用灰色关联度进行黑龙江省农村产业结构情况的动态分析,得出１９８５～１９９３年和１９８５～１９９５年农村经济收入关联树,对比分析后,进而得出第一产业（农业）是农村经济收入的主要来源,其次是第三产业（交通运输业、商品流通业和餐饮业）、第二产业（农村工业和建筑业）,但经过近几年的产业结构调整,第三、二产业在农村经济收入中所占份额增长很快。在第一产业中,种植业是主要来源,其中畜牧业发展较快;在第二产业中,农村工业是其主要来源,发展较快;在第三产业中,各产业较均衡发展,因此农村产业结构经过几年调整趋于合理。     

Nutrients in the West African Sudano-Sahelian zone: Losses,transfers and role of external inputs

Crop growth on acid sandy soils of the Sudano-Sahelian zone is primarily limited by the low amounts of organic matter and available mineral nutrients in the topsoil. The shortening of fallow periods with population growth, the exploitation of fire wood, spatial nutrient transfers by wind and water and net nutrient exports with crop yields in the order of 15 kg nitrogen (N) 2 kg phosphorus (P) and 15 kg potassium (K) ha⁻¹ yr⁻¹ for traditional fields planted to pearl millet (Pennisetum glaucum L.) in the southern Sahel have exhausted these resources. Large productivity declines in the prevailing agro-pastoral systems are the consequence. Data are presented to show bow nutrient exports at the level of individual fields, through grain yields and biomass removal as forage, firewood, construction material, and also through run-off, wind and water erosion, leaching and volatilisation, are either losses for the ecosystem or sources of nutrients transferred within the ecosystem. Livestock is a vector of nutrients from rangelands to manured fields through forage intake and excretion and helps to shortcut nutrient cycles, but it is also a net consumer of organic matter and minerals. Through the effects of trampling on the soil and of grazing on the vegetation composition and production, livestock also indirectly affects the cycling and transfer of nutrients. Net nutrient inputs by heavy rains causing overland flow, dust deposition and through biological nitrogen fixation, are also unequally distributed and thus aggravate the fertility gradient from large nutrient ‘source’ areas such as rangelands to small ‘sink’ areas such as fallows, low lands, temporary lakes and river benches. At a finer resolution, shrubs and trees with their alternating periods of nutrient storage and recycling in leaves and wood, micro-depressions, termite mounts and ant nests become localised points of nutrient concentration and high crop productivity. To balance losses of nutrients in these integrated systems and to obtain sustainable increases in production, external inputs of nutrients are necessary. These may be introduced by two different pathways, either via mineral fertilisers applied to croplands or via externally produced supplements fed to livestock. These pathways are complementary and each one has direct effects on the other. Fertiliser application to croplands affect livestock through the increase in available forage and crop residue feed, whereas feed supplementation affects crop production through higher amounts and better quality of manure. The adoption of either strategy by farmers requires a high nutrient use efficiency at low cost. Data from regional field trials revealed increases in total dry matter (TDM) of cereals with broadcast annual P application at 13 kg ha⁻¹ ranging across three years from 19 to 88% for rockphosphate and from 34 to 102% for single superphosphate (SSP). Still, a low-external input approach seemed more advantageous to farmers. The placement of NPK fertiliser at 4 kg P ha⁻¹ with the seed at or shortly after planting caused average TDM increases of 70% for millet, sorghum, maize, cowpea and groundnut and showed an up to three-fold higher phosphorus use efficiency than broadcast P. On the other hand, late dry season supplementation of grazing steers with millet bran not only decreased animal weight losses but also increased N and P concentrations in the faeces. The larger nutrient concentrations in the manure increased millet grain yield by 28% and stover yield by 21% on a field manured at a rate of 3 t DM ha⁻¹. However, even with such approaches the current trends of declining soil productivity can only be reversed, if local policy makers are willing to support agricultural change through better terms of trade for agricultural products.     

开放核心群育种体系(ONBS)研究 Ⅴ.家禽ONBS的育种效果: 血液遗传标记监测

从血型因子频率和蛋白（酶）多态遗传监测了开放核心群育种体系培育工业化蛋鸡品系的效果．结果表明,培育育种过程中,各品系遗传结构没有发生显著变化,ＯＮＢＳ可以缓冲育种中突出的遗传抽样所导致的抽样偏差问题,因此引进鸡优秀的遗传背景仍被培育后的群体所维系．Ｃ系的基因频率与Ａ,Ｂ,Ｄ系均存在显著的差异性,说明该鸡祖代四系中Ｃ系有其遗传特殊性．     

Parallels and potentials in animal and human ethnomedical technique

In all cultures, ethnomedical practices are largely the same for animals and people, whether in mode of administration of materia medica, in the materials themselves, or in surgical, mechanical, behavioral, medico-religious, and other realms. Below, parallels between veterinary and human ethnomedical techniques are outlined. Taken together, they suggest that a number of benefits could be gained by closer collaboration between veterinary and human medicine in the delivery of basic healthcare information and services.