维生素营养的新概念   总被引：1，自引：0，他引：1  

刘建辉 《国外畜牧学(猪与禽)》2001,(2):19-20

动物的维生素需要量是动态的 ,是随其基因型、生产性能高低、所用生产体系的不同而不同的 ,还随着人们对维生素功能更加深入的了解而不同。这意味着 ,维生素推荐量和维生素添加指南都需要经常更新。现在已经有了新的指南 ,其中的推荐量是根据“最佳维生素营养”的长期概念加以更新的 ,这有助于营养师保证动物的健康和性能目标不因维生素供应量的问题而受害。只有当动物有效利用了为生长、健康、繁殖和存活而通过日粮提供的养分以后才算是实现了最佳营养。虽然所有的养分 ,如蛋白质、矿物质和水 ,对于动物的功能都极为重要 ,但维生素却另有其…  相似文献   

Long-term vegetational history of a Picea abies stand in south-eastern Norway: Implications for the conservation of biological values     

Chiara Molinari  Ole Risbøl  Mikael Ohlson 《Biological conservation》2005,126(2):155-165

The development of a forest stand in south-eastern Norway during the last 9000 years is investigated by pollen and charcoal analyses. The aims are to identify factors that have influenced current biodiversity, which includes the lichen Usnea longissima, and examine the immigration and establishment of the current dominant tree Picea abies. Fire has been a variable but major disturbance factor at the site throughout the study period but has ceased during the last 100 years. Picea immigration was primarily a natural process but local establishment occurred after a major disturbance. Cultural impact began 3500 years ago during the Bronze Age, but was most intensive between AD 1600 and AD 1900. It led to the local extinction of deciduous trees and created a biodiversity bottleneck that facilitated the rise to dominance of Picea. Guidelines are proposed for future management designed to preserve and enhance local biological values.  相似文献   

How representatively can we sample soil mineral nitrogen?     

Antje Giebel  Ole Wendroth  Hannes Isaak Reuter  Kurt‐Christian Kersebaum  Jürgen Schwarz 《植物养料与土壤学杂志》2006,169(1):52-59

Spatial distribution of soil mineral‐N content (N_min) is a scale‐variant process. Precision farming assumes knowledge about the spatial distribution of N_min. Moreover, sampling in management zones is based on the assumption of spatial dependence between sampling points. In the present study, variability structure of N_min and the sources of variability were investigated. Within an agricultural landscape, N_min was investigated across a field in a nested design over four consecutive years. Temporally unstable structure of individual nests require a sampling with several nests in the field. In the investigated field, 35%–49% of the total variability derived from small‐scale variability observed at spatial distances of <5 m and from sampling and analytical errors. Differences between 10 and 26 kg N ha^–1 for the soil depth increment 0–60 cm can be expected. Uncertainty due to analytical errors were in the order of 5–10 kg N ha^–1 for a 0–60 cm layer.  相似文献   

Landscape research — exploring ecosystem processes and their relationships at different scales in space and time     

Chris van Kessel  Ole Wendroth 《Soil & Tillage Research》2001,58(3-4):97-98

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Deposition characteristics and biological effectiveness of fungicides applied to winter wheat and the hazards of drift when using different types of hydraulic nozzles   总被引：1，自引：0，他引：1  

Ole Permin  L. N. J  rgensen  K. Persson 《Crop Protection》1992,11(6):541-546

Hydraulic-fan cone, low-pressure fan and two-chamber cone nozzles were used at 1.5, 3.0 and 6.0 bar (150, 300 and 600 kPa) to deliver 140, 200 and 3001 ha⁻¹ respectively of a fungicide spray to control mildew and yellow rust in winter wheat. No significant differences in biological effect were obtained although fan nozzles deposited significantly more on the upper parts of the stems, and two-chamber cone nozzles deposited less on the flag leaf and on the upper part of the stems. Because of their higher deposit and more even distribution, fan nozzles should be preferred, operated at a pressure of 1.5–3 bar to deliver a spray volume of 140–190 lha⁻¹ at 7 km h⁻¹ and to obtain an acceptable biological effect. Higher pressure (6 bar) and volume rates gave no improvement in fungicide performance. Adding a surfactant or penetration oil did not change the volume median diameter or proportion of spray liquid in droplets < 150 μm. Less drift was found when using two-chamber cone nozzles at 3 bar than with flat-fan spray nozzles at 1.5 bar. It is concluded that the two-chamber cone nozzle is useful for fungicide application when drift must be avoided.  相似文献   

Role of EphA4 and EphrinB3 in local neuronal circuits that control walking     

Kullander K  Butt SJ  Lebret JM  Lundfald L  Restrepo CE  Rydström A  Klein R  Kiehn O 《Science (New York, N.Y.)》2003,299(5614):1889-1892

Local circuits in the spinal cord that generate locomotion are termed central pattern generators (CPGs). These provide coordinated bilateral control over the normal limb alternation that underlies walking. The molecules that organize the mammalian CPG are unknown. Isolated spinal cords from mice lacking either the EphA4 receptor or its ligand ephrinB3 have lost left-right limb alternation and instead exhibit synchrony. We identified EphA4-positive neurons as an excitatory component of the locomotor CPG. Our study shows that dramatic locomotor changes can occur as a consequence of local genetic rewiring and identifies genes required for the development of normal locomotor behavior.  相似文献   

DNA markers provide insight about common lime in historical plantings – An example from the Royal Danish Gardens     

Ole K. Hansen  Pernille Thomsen  Christine Waage Rasmussen 《Urban Forestry & Urban Greening》2014,13(3):543-552

As part of the restoration process of an avenue of common lime (Tilia × europaea) from 1760 in the Royal Danish Gardens, all remaining trees were genotyped with DNA markers before they were felled. As such, information about the nature of the plant material (clonal versus non-clonal) and mode of propagation was obtained, revealing that a single clone constituted 92% of the remaining trees (106 out of 115). Five trees were of another clone, while the remaining four trees had unique genotypes. Mode of clonal propagation was most likely layering since the genotype of the crown and the roots of a subsample of the trees had the same genotype. Trees from four other locations with historical avenues/plantings from the 17th century were also genotyped. The two clones registered in the first location were also found at the other four locations. Of 76 trees from the other historical avenues/plantings, only two trees did not belong to either of the two clones. Genotyping of commercial common lime trees that would be planted in place of the felled trees during the restoration project was also performed. Samples of 20 newly planted trees all possessed the same genotype as the majority of the old felled trees and, thereby, were the same clone as the trees planted nearly 250 years ago. Altogether, the current study shows that the genetic diversity of common lime planted in Danish historical plantings is extremely narrow, and that the same clones have been produced for decades/centuries by private nurseries in the Netherlands and Germany. It also provides evidence that it is possible to obtain the same genetic material as originally planted when common lime trees are to be replaced in historical plantings. Furthermore, the utility of DNA markers in the management of plant material in parks is demonstrated.  相似文献   

Trans fatty acid analyses in samples of marine origin: the risk of false positives     

Mjøs SA  Haugsgjerd BO 《Journal of agricultural and food chemistry》2011,59(8):3520-3531

At conditions commonly applied for trans fatty analyses by gas chromatography, fatty acids naturally occurring in marine lipids may overlap chromatographically with C16 and C18 trans fatty acids and lead to false positives. Elution patterns were studied by tracking retention indices at shifting temperature conditions on two cyanopropyl-coated capillary columns. Most overlaps can be avoided by selecting the right chromatographic conditions, but it was not possible to find a single condition that eliminates the risk of overlap between trans fatty acids and interferents. In total, 17 compounds were identified as potential interferents, and the amounts of these compounds were quantified in various samples of marine origin. The interferents that will most likely contribute to incorrect assessments of trans fatty acids in marine lipids are probably 18:3 n-4 and 18:1 n-11.  相似文献   

Intracellular acidosis enhances the excitability of working muscle     

Pedersen TH  Nielsen OB  Lamb GD  Stephenson DG 《Science (New York, N.Y.)》2004,305(5687):1144-1147

Intracellular acidification of skeletal muscles is commonly thought to contribute to muscle fatigue. However, intracellular acidosis also acts to preserve muscle excitability when muscles become depolarized, which occurs with working muscles. Here, we show that this process may be mediated by decreased chloride permeability, which enables action potentials to still be propagated along the internal network of tubules in a muscle fiber (the T system) despite muscle depolarization. These results implicate chloride ion channels in muscle function and emphasize that intracellular acidosis of muscle has protective effects during muscle fatigue.  相似文献   

Hydraulic energy indices reveal spatial dependence in a subtropical soil under maize crop in Southern Brazil     

Maria Eliza TUREK  Robson André ARMINDO  Ole WENDROTH 《土壤圈》2021,31(5):771-782

Soil physical quality (SPQ) assessment is an important part in the evaluation of soil use, management, and conservation. It can be assessed using several physical properties, hydraulic indices, and functions. Soils from tropical and temperate regions represent different physical behaviors, and the quantification of their physical properties is important to support soil evaluation and modelling. The objective of this study was to evaluate the SPQ in a subtropical field under maize crop cultivation according to its physical properties, hydraulic indices, and functions in an attempt to infer the spatial variability and to determine the behavior of soil physical structure across a spatial domain. Commonly used soil key physical variables, such as texture, bulk density, total porosity, saturated hydraulic conductivity, and organic carbon content, were measured in a regular grid with a soil sampling density of 30 points per hectare, covering an area of 0.5 ha. Saturated hydraulic conductivity varied strongly between subsamples and in the field, suggesting the heterogeneity of the soil structure regarding water drainage. The physical variables were combined with other indicators, which were based on the soil water retention curve and the pore size distribution (PSD) function. Correlation analysis was performed to verify the relationship between the measured and calculated variables, and some strong linear correlations were revealed, such as between aeration energy index and microporosity (r = 0.608) and water retention energy index with microporosity (r = 0.532) and with bulk density (r = 0.541). For most sampled locations, the shape and location parameters of PSD showed results outside of the optimum ranges, whereas the hydraulic energy indices and cumulative hydraulic energy functions presented values that were similar to those found for some tropical soils described in the literature. The spatial variability of these indices was described using semivariograms and kriged maps, indicating the variability of the SPQ in this field.  相似文献