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91.
92.
Cordia africana Lam. is a commercial timber species that grows naturally throughout sub-Saharan Africa and tropical Arabia. At present very
little is known about genetic variation in this species and baseline information is needed to initiate improvement programs
in Ethiopia. Thus, the objectives of the study were to quantify the inter- and intra-population variations in seed size traits
and germination responses to different constant temperature regimes. Seeds were collected from 30 open-pollinated families
within each of the five populations representing the natural distribution of the species in Ethiopia. To examine seed size
variations, seed length, seed width, and 1,000-seed weight were quantified. Inter- and intra-population variations in seed
germination were investigated under different constant temperature regimes from 20 to 35°C in climate chambers. Significant
variations in seed length, width and weight were detected both at inter- and intra-population levels, and family heritabilities
of 0.63–0.76 showed that much of the phenotypic variation in seed size traits were additive genetic variation. Significant
variation in germination was also found among and within populations as well as between the different constant temperature
regimes. Generally the variation in germination was considerably higher within population than between populations. The optimal
temperature for germination of C. africana seeds was 25–30°C with family heritabilities for germination ranging between 0.20 and 0.33, depending on the germination
temperature. 相似文献
93.
Kim Van Van Truong Dinh Hoai Kurt Buchmann Anders Dalgaard Nguyen Van Tho 《南方农业学报》2012,43(4):520-523
[目的]探讨3种不同药物处理方式对台湾棘带吸虫引起的鲤鱼幼鱼急性鱼鳃传染病(开放性鳃病)的防治效果.[方法]在试验初期,将1620条鲤鱼幼鱼(70日龄)鱼鳃自然感染台湾棘带吸虫,随后分成4组,分别采用CuSO4、福尔马林和吡喹酮不同方式处理6周,与对照(自然喂食、不使用任何化学药剂)比较防治鲤鱼幼鱼急性鳃传染病的效果.[结果]感染台湾棘带吸虫的幼鱼生长缓慢,其身长和体重增长均较慢.施药后,幼鱼台湾棘带吸虫后期囊幼虫感染强度减少.在每千克饲料中分别添加50和75 mg吡喹酮喂食幼鱼5d,可以杀死鱼鳃中所有的台湾棘带吸虫后期囊幼虫,且鱼鳃恢复正常;面使用25 mg吡喹酮,仅有35%的后期囊幼虫死亡.所有不同浓度CuSO4处理(0.3、0.4和0.5mg/kg冲洗浸泡24 h及以3.0、4.0和5.0 mg/kg冲洗浸泡10m)和福尔马林处理(20、25和30 mg/kg冲洗浸泡及200、250和300 mg/kg短时间冲洗浸泡)均不能杀死台湾棘带吸虫后期囊幼虫.[结论]经普通化学药剂CuSO4或福尔马林冲洗浸泡,不能防治由台湾棘带吸虫后期囊幼虫引起的鲤鱼开放性鳃病,但50~75 mg吡喹酮/kg饲料可以在5d内治疗该病. 相似文献
94.
Albert K. D. Imsland Trine Haugen Susanne Håvardstun Anders Mangor-Jensen 《Journal Of Applied Aquaculture》2013,25(3):252-262
Different levels of pressure were investigated to see if it was possible to induce triploidy at a lower pressure than previously used (600 bar) for Atlantic cod (Gadus morhua). Newly fertilized eggs were exposed to different levels of pressure: 400, 500, and 600 bar, and one control group (no pressure). Induction of triploidy occurred at each pressure level used in this experiment. Mean weight and length at the termination of the trial period was significantly lower, in the 400 bar group, compared to the other treatment groups. Microsatellite loci analysis revealed over 90% triploid outcome in each experimental group. Lower incidence of deformities was seen in the 400 bar group compared to the 500 and 600 bar groups. Overall this study demonstrated successful triploid induction at both low (400 bar) and medium (500 bar) pressures. 相似文献
95.
Aleksander Handå Trond Nordtug Stein Halstensen Anders Johny Olsen Kjell Inge Reitan Yngvar Olsen Helge Reinertsen 《Aquaculture Research》2013,44(4):645-656
Feed requirements were estimated from specific growth rates in standardized soft tissue dry weight (SGRDW’) and atomic O:N ratios for mussels fed seven rations of microalgae (5–735 μg C h?1 ind?1) at 7 and 14°C respectively. The mean oxygen consumption and ammonia‐N excretion rates were significantly higher at 14°C (0.29 μg O2 and 27.3 μg N ind?1 h1) compared with those at 7°C (0.16 μg O2 and 11.4 μg N ind?1 h?1) (P < 0.05), resulting in O:N ratios between 3 and 45 at 7°C and 7 and 28 at 14°C. Low O:N ratios indicate protein catabolism and an unfavourable condition, whereas high ratios indicate that carbohydrate is the primary energy source. The measured SGRDW’ suggests minimum feed requirements of ~240 and ~570 μg C ind?1 h?1 for weight maintenance at 7 and 14°C, with corresponding O:N ratios of 24 and 16, respectively, indicating a more stressed condition at 14°C. A 0.5% SGRDW’ day?1 was obtained by ~565 (O:N = 29) and ~680 (O:N = 23) μg C ind?1 h?1 at 7 and 14°C respectively. A positive and significantly higher SGRDW’, with the lowest feed ration at 7°C compared with a negative SGRDW’ at 14°C (P < 0.05), indicated that storage time can also possibly be prolonged at low temperatures if the mussels are not fed. 相似文献
96.
Anaesthesia of farmed fish: implications for welfare 总被引:1,自引:0,他引:1
During their life cycle as farmed animals, there are several situations in which fish are subjected to handling and confinement.
Netting, weighing, sorting, vaccination, transport and, at the end, slaughter are frequent events under farming conditions.
As research subjects, fish may also undergo surgical procedures that range from tagging, sampling and small incisions to invasive
procedures. In these situations, treatment with anaesthetic agents may be necessary in order to ensure the welfare of the
fish. The main objective of this paper is to review our knowledge of the effects of anaesthetic agents in farmed fish and
their possible implications for welfare. As wide variations in response to anaesthesia have been observed both between and
within species, special attention has been paid to the importance of secondary factors such as body weight, water temperature
and acute stress. In this review, we have limited ourselves to the anaesthetic agents such as benzocaine, metacaine (MS-222),
metomidate hydrochloride, isoeugenol, 2-phenoxyethanol and quinaldine. Anaesthetic protocols of fish usually refer to one
single agent, whereas protocols of human and veterinary medicine cover combinations of several drugs, each contributing to
the effects needed in the anaesthesia. As stress prior to anaesthesia may result in abnormal reactions, pre-anaesthetic sedation
is regularly used in order to reduce or avoid stress and is an integral part of the veterinary protocols of higher vertebrates.
Furthermore, the anaesthetic agents that are used in order to obtain general anaesthesia are combined with analgesic agents
that target nociception. The increased use of such combinations in fish is therefore included as a special section. Anaesthetic
agents are widely used to avoid stress during various farming procedures. While several studies report that anaesthetics are
effective in reducing the stress associated with confinement and handling, there are indications that anaesthesia may in itself
induce a stress response, measured by elevated levels of cortisol. MS-222 has been reported to elicit high cortisol release
rates immediately following exposure, while benzocaine causes a bimodal response. Metomidate has an inhibitory effect on cortisol
in fish and seems to induce the lowest release of cortisol of the agents reported in the literature. Compared to what is observed
following severe stressors such as handling and confinement, the amount of cortisol released in response to anaesthesia appears
to be low but may represent an extra load under otherwise stressful circumstances. Furthermore, anaesthetics may cause secondary
adverse reactions such as acidosis and osmotic stress due to respiratory arrest and insufficient exchange of gas and ions
between the blood and the water. All in all, anaesthetics may reduce stress and thereby improve welfare but can also have
unwanted side effects that reduce the welfare of the fish and should therefore always be used with caution. Finally, on the
basis of the data reported in the literature and our own experience, we recommend that anaesthetic protocols should always
be tested on a few fish under prevailing conditions in order to ensure an adequate depth of anaesthesia. This recommendation
applies whether a single agent or a combination of agents is used, although it appears that protocols comprising combinations
of agents provide wider safety margins. The analgesic effects of currently used agents, in spite of their proven local effects,
are currently being debated as the agents are administrated to fish via inhalation rather than locally at the target site.
We therefore recommend that all protocols of procedures requiring general anaesthesia should be complemented by administration
of agents with analgesic effect at the site of tissue trauma. 相似文献
97.
Promoting sustainable intensification in precision agriculture: review of decision support systems development and strategies 总被引:1,自引:0,他引:1
Jessica Lindblom Christina Lundström Magnus Ljung Anders Jonsson 《Precision Agriculture》2017,18(3):309-331
Precision agriculture provides important issues toward a more sustainable agriculture. Many farmers have the necessary technology to operate site-specifically, but they do not use it in practice, and thus available information and communications technology (ICT) systems are not used to their full potential. This paper addresses how to reduce the so-called “problem of implementation”, based on the knowledge that participatory approaches during the design and development process is one of the most important factors to frame technology adoption. The development of sustainable ICT systems through theories and methodologies from the fields of human computer interaction and user-centered design (UCD) is presented and an ongoing Swedish project for development of an agricultural decision support system (AgriDSS) for nitrogen fertilization is used as an example to frame the issue. The overreaching aim is to develop AgriDSSs that are sustainable in design as well as through design by stressing the importance of participatory approaches for the successful development of AgriDSSs. The Swedish project has the intention to apply a UCD approach, and some pitfalls on starting to use this way of working is identified as well as some suggestions on how to reduce them through co-learning processes. Despite the challenges presented in this paper, ICT can contribute significantly to long-term sustainable development. Thus, several competences and scientific disciplines need to act in concert to help develop a sustainable development of agriculture via a transdisciplinary approach that can make an impact on society at many levels. 相似文献
98.
99.
The present investigation was undertaken to identify and characterize the tetracycline resistance determinant in 22 Gallibacterium anatis strains for which no determinant was identified using primers specific for tet(A, B, C, D, E, G, H, K, L, M, O). A recent study found tet(B) to be the most prevalent tetracycline resistance determinant in a larger collection of G. anatis field strains from Mexico and Denmark. However, in 41% of the tetracycline resistant strains no determinant could be assigned. Here we demonstrate that tet(31) is a common determinant in G. anatis originating from chickens from very different production systems and localities. In addition, tet(31) was identified in strains isolated over a 30-year period. This is the first report on tet(31) since its original identification in Aeromonas salmonicida. 相似文献
100.
Impact of Urban Stormwater on Sediment Quality in an Enclosed Bay of the Lule River, Northern Sweden
Ralf Rentz Anders Widerlund Maria Viklander Bj?rn ?hlander 《Water, air, and soil pollution》2011,218(1-4):651-666
Sediment and porewater samples from an enclosed bay receiving stormwater discharge (Skutviken) near the centre of Lule?, northern Sweden were analysed for major and trace elements and 16 polycyclic aromatic hydrocarbons (PAHs). Among the studied metals Cd, Cu, Pb and Zn were enriched at Skutviken. Also, the PAH content was enriched, in particular for phenantrene, anthracene, fluoranthene and pyrene which are regarded as common constituents in stormwater. The use of trace metal ratios provided indications about pollutant sources for the sediment. Cs-137 dating was used to determine historical changes in metal and PAH fixation in the sediment. The bay Skutviken is enclosed through the construction of a road bank since 1962. The enclosure led to reduced water circulation in the bay that promotes the occurrence of anoxic conditions with sulphate reduction within the bay. As a consequence of these conditions, metals are trapped in the sediments as sulphides. This study suggests that enclosed bays with restricted water circulation may be efficient traps for urban pollutants, reducing the present-day input of pollutants to the sea. In areas with postglacial land uplift, where such bays are common, bay sediments are a potential future source of pollutants when uplift results in erosion and oxidation of the sediments. 相似文献