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141.

The aim of this study was to estimate genetic and phenotypic parameters for the three mortality traits crushing, stillbirth and total mortality in piglets, and their respective correlations with birth weight. Records were available from 11 016 Yorkshire piglets from 1046 first parity litters in a Swedish experimental herd. Each mortality trait was analysed jointly with birth weight, using bivariate models. Both mixed linear models and threshold models were used. The threshold models took environmental and maternal genetic effects into account, whereas the linear models also included a direct genetic effect of the piglet on its birth weight. The estimated heritabilities were low for all mortality traits (0.01-0.15), with the lowest estimate for crushing and the highest for stillbirth. The estimated environmental correlations between the different mortality traits and birth weight were negative. The estimated genetic correlations between crushing and birth weight (both direct and maternal effect) were also negative in both models, indicating that sows with low-weight piglets are more likely to crush piglets. However, the genetic correlations between stillbirth and birth weight (both direct and maternal effect) were positive. These results suggest that stillbirth and crushing are traits with different genetic backgrounds, and that genetically increasing the birth weight of the piglets may result in more stillborn piglets.  相似文献   
142.

The nutritional effects of two barley mutant lines with an altered phosphorus (P) profile and phytate content (13 and 43% of total P, respectively) were studied. Because grain quantities were limited, rats served as a model for the pig in a feeding trail. Four groups of five Wistar rats (weighing 65 g) were fed the low-phytate lines, the mother variety and a mixture of barley varieties. All diets were supplemented with vitamins and minerals except for P, calcium, zinc and copper. The apparent digestibility of P was improved by up to 13% in the mutant lines. Although all diets were very similar in their zinc content, only rats fed the mutant lines had a net absorption and a positive zinc balance, indicating the improved availability of this mineral. Rats appear to be a suitable model for P utilization in pigs and can thus provide plant breeders with a mineral bioavailability assay for use at an early stage.  相似文献   
143.
Pulse‐labelling of plants in a 14CO2 or 13CO2 atmosphere is a useful tool for investigating C allocation in plants and soils, revelation of C sources in soil organisms, as well as for CO2 partitioning studies. Recently, these labelling experiments have been used to produce isotopically labelled biomass of plants or microorganisms for the investigation of C dynamics in these organisms or in soil. However, it remains unknown whether these labelling approaches may affect the composition of plant constituents that react to modifications of environmental conditions during biosynthesis. Lipids as primary biosynthesis products and main components of plant waxes are well known to react fast to environmental changes resulting in a modified lipid composition. In this study, we demonstrate that lipid composition may be only slightly affected by the labelling procedure, especially, when only short pulses (only a few hours) are applied and when the sampling does not occur immediately after the labelling. While the differences of plant lipid compositions are obviously modified not as a result of isotopic pulses, the environmental conditions of plants grown under controlled laboratory conditions have a significant effect leading to a shift of the distribution pattern of plant lipids compared to the lipid composition of plants grown under field conditions.  相似文献   
144.
Rising levels of atmospheric CO2 have often been found to increase above and belowground biomass production of C3 plants. The additional translocation of organic matter into soils by increased root mass and exudates are supposed to possibly increase C pools in terrestrial ecosystems. Corresponding investigations were mostly conducted under more or less artificial indoor conditions with disturbed soils. To overcome these limitations, we conducted a 14CO2 pulse-labelling experiment within the German FACE project to elucidate the role of an arable crop system in carbon sequestration under elevated CO2. We cultivated spring wheat cv. “Minaret” with usual fertilisation and ample water supply in stainless steel cylinders forced into the soil of a control and a FACE plot. Between stem elongation and beginning of ripening the plants were repeatedly pulse-labelled with 14CO2 in the field. Soil born total CO2 and 14CO2 was monitored daily till harvest. Thereafter, the distribution of 14C was analysed in all plant parts, soil, soil mineral fractions and soil microbial biomass. Due to the small number of grown wheat plants (40) in each ring and the inherent low statistical power, no significant above and belowground growth effect of elevated CO2 was detected at harvest. But in comparison to ambient conditions, 28% more 14CO2 and 12% more total CO2 was evolved from soil under elevated CO2 (550 μmol CO2 mol−1). In the root-free soil 27% more residual 14C was found in the FACE soil than in the soil from the ambient ring. In soil samples from both treatments about 80% of residual 14C was found in the clay fraction and 7% in the silt fraction. Very low 14C contents in the CFE extracts of microbial biomass in the soil from both CO2 treatments did not allow assessing their influence on this parameter. Since the calculated specific radioactivity of soil born 14CO2 gave no indication of an accelerated priming effect in the FACE soil, we conclude that wheat plants grown under elevated CO2 can contribute to an additional net carbon gain in soils.  相似文献   
145.

Purpose

The utilization of dredged material in dike construction as a substitute for traditionally used aged marsh sediment is considered an advisable option with respect to ecological as well as economic aspects. As a prerequisite to the application, the equivalency with respect to soil physical and mechanical properties of the materials has to be verified. Previous investigations on the compactibility of dredged materials used for dike construction had shown that the bulk densities of these materials were considerably lower than bulk densities of aged marsh sediments. The aim of the investigations presented in this paper was to analyze whether the compactibility of the processed dredged material could be improved by enhanced dewatering of the material prior to construction. It was hypothesized that a decreased water content of the material would allow higher bulk densities to be achieved during construction and hence the soil physical properties would become more comparable to those of the aged marsh sediments.

Materials and methods

To examine whether the compactibility of dredged material can be enhanced by pre-drying, Proctor tests were carried out at different initial water contents. Moreover, it was examined whether the temperature of oven-drying at 30 and 105 °C affects the compactibility of these materials and whether ripening, i.e., the repeated drying and wetting of the dredged material under natural and laboratory conditions, can improve their compactibility.

Results and discussion

The investigations on the effect of the various further processing methods showed that the compactibility and therefore the suitability of processed dredged material for dike construction can be improved by air-drying. A linear relationship between dehydration and Proctor density was found. Air-drying to water contents of 10% dry weight (DW) resulted in an improvement of the Proctor density of up to 11%. However, the tests on the effect of the drying temperature on the compactibility showed that oven-drying had no additional effect on the compactibility of the dredged materials. Ripening under laboratory and natural conditions did not lead to statistically significant changes in the compactibility of the processed dredged material either.

Conclusions

Air-drying of processed dredged material to water contents less than 10% DW is considered to be a useful pre-treatment option to improve the compaction behavior of processed dredged material and to obtain a better functional equivalency with traditionally used dike construction materials such as fine-grained aged marsh sediments.
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146.
Our understanding of the interactions between minerals, organic matter, and microorganisms at so-called biogeochemical interfaces in soil is still hampered by the inherent complexity of these systems. Artificial soil maturation experiments can help to bridge a gap in complexity between simple abiotic sorption experiments and larger-scale field experiments. By controlling other soil-forming factors, the effect of a particular variable can be identified in a simplified system. Here, we review the findings of a series of artificial soil incubation experiments with the aim of revealing general trends and conclusions. The artificial soils were designed to determine the effect of mineral composition and charcoal presence on the development of abiotic and biotic soil properties during maturation. In particular, the development of soil aggregates, organic matter (OM) composition and turnover, sorption properties, and the establishment of microbial community composition and function were considered. The main objectives of the research were to determine (1) how surface properties and sorption of chemicals modify biogeochemical interfaces; (2) how much time is required to form aggregates from mixtures of pure minerals, OM, and a microbial inoculum; and (3) how the presence of different mineral and charcoal surfaces affects aggregation, OM turnover, and the development of microbial community composition.  相似文献   
147.
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148.
Analysing food webs in agricultural habitats is essential for the development of natural control strategies. Several molecular tools to investigate trophic interactions on a species-specific level have been developed in recent years and their advantages and limitations have been discussed. With this study we introduce another tool, terminal restriction fragment length polymorphism (tRFLP). Generalist predators found in Australian brassica crops, their prey and abundant parasitoids were chosen as a model system to adapt and evaluate the tRFLP approach. Using general primers and selecting six restriction enzymes, we obtained species-specific tRF patterns for 21 of the most abundant arthropods in brassica crops. We detected up to three prey species in the gut contents of laboratory-fed predators. Detection rates differed among predators, ranging between 28 and 100%. The identification of a species-specific tRF pattern was strongly affected by the presence and concentrations of DNA from other species. In a preliminary field study, prey could be identified from 20% of the collected brown lacewings. The advantage of the tRFLP method is the possibility of identifying multiple species at once. This advantage is counterbalanced by methodological limitations, among which the most critical one is the fact that it will be difficult to maintain specificity in highly diverse ecosystems. However, if species diversity is limited and the target sequence and the primers are chosen to increase detection success, the tRFLP method can be used to study trophic interactions in the field.  相似文献   
149.
Tolerance is a type of defense that allows plants to attenuate the negative effects of herbivory. Tolerance has been shown to be context-dependent, contingent on abiotic and biotic factors such as nutrients and plant age. Here, we determine the simultaneous effect of herbivory at different phenological stages and nitrogen regimen on the potato’s ability to tolerate herbivory. We subjected young and blooming plants of two potato varieties to 50% injury by Colorado Potato Beetle in low and high nitrogen environments to determine their effects on tuber yield and plant tolerance. All plants in the high nitrogen treatment expressed higher yield and tolerance compared to those in the low nitrogen treatment. Control plants expressed higher yield than plants in either herbivory treatment. There was a variety by phenological stage of herbivory interaction showing that phenological-based tolerance expression within species is genotype dependent.  相似文献   
150.
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