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1.
Prevalence of Escherichia coli O157 in cattle at the farm level is mostly determined by taking individually rectal samples. From the animal welfare point of view the collection of such samples on the farm is not advisable. The present study evaluated alternative sample types to assess the E. coli O157 status of cattle farms. Twelve closed cattle farms were visited twice with a time interval of 6-8 months. Rectal and hide surface samples (the nose, the neck, the shoulder, the flank, and the round) were collected from beef cattle within the period of 5 months before slaughter and from their environment (overshoes from the pen bedding, swabs from the pen barrier, feed and water). Statistical analysis revealed that from all samples taken only the "overshoe method" might be a good sampling technique to substitute the collection of individual fecal samples to establish the E. coli O157 status of a farm and even a pen. Characterization of the isolates, using pulsed field gel electrophoresis, revealed that on each positive farm only one genotype was presented, even after a period of more than 6 months. 相似文献
2.
We have previously shown that rectally inoculated sheep excrete Escherichia coli O157:H7 during weeks to months without developing a clear antibody response. However, antibodies against this bacterium were observed in naturally infected sheep, which most likely became orally infected. To understand this difference, sheep were orally inoculated with the same Shiga toxin-negative E. coli O157:H7 strain that was used for the rectal inoculation. A primary oral inoculation resulted in shedding of E. coli O157:H7 in the faeces and detection of antibody responses against intimin, EspA and EspB. The antibody titres waned as shedding decreased. A secondary inoculation resulted in longer shedding, even though a booster antibody response occurred. Cellular responses followed a similar pattern as the antibody levels, albeit with a lower secondary response. The presence of antigen-specific antibody-secreting cells indicates involvement of both a systemic response in the spleen and a local immune response in the terminal rectum. These results suggest that E. coli O157:H7 has to pass the small intestine to evoke antibody responses. 相似文献
3.
Nicolas Latte Gilles Colinet Adeline Fayolle Philippe Lejeune Jacques Hébert Hugues Claessens Sébastien Bauwens 《European Journal of Forest Research》2013,132(4):565-577
Forest ecosystems play a major role in atmospheric carbon sequestration and emission. Comparable organic carbon stock estimates at temporal and spatial scales for all forest pools are needed for scientific investigations and political purposes. Therefore, we developed a new carbon stock (CS) estimation procedure that combines forest inventory and soil and litter geodatabases at a regional scale (southern Belgium). This procedure can be implemented in other regions and countries on condition that available external carbon soil and litter data can be linked to forest inventory plots. The presented procedure includes a specific CS estimation method for each of the following forest pools and subpools (in brackets): living biomass (aboveground and belowground), deadwood (dead trees and snags, coarse woody debris and stumps), litter, and soil. The total CS of the forest was estimated at 86 Tg (185 Mg ha?1). Soil up to 0.2 m depth, living biomass, litter, and deadwood CSs account, respectively, for 48, 47, 4, and 1 % of the total CS. The analysis of the CS variation within the pools across ecoregions and forest types revealed in particular that: (1) the living biomass CS of broadleaved forests exceeds that of coniferous forests, (2) the soil and litter CSs of coniferous forest exceed those of broadleaved forests, and (3) beech stands come at the top in carbon stocking capacity. Because our estimates differ sometimes significantly from the previous studies, we compared different methods and their impacts on the estimates. We demonstrated that estimates may vary highly, from ?16 to +12 %, depending on the selected methods. Methodological choices are thus essential especially for estimating CO2 fluxes by the stock change approach. The sources of error and the accuracy of the estimates were discussed extensively. 相似文献
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Microalgal bacterial flocs originating from aquaculture wastewater treatment as diet ingredient for Litopenaeus vannamei (Boone) 下载免费PDF全文
Sofie Van Den Hende Leon Claessens Eric De Muylder Han Vervaeren 《Aquaculture Research》2016,47(4):1075-1089
Microalgal bacterial flocs (MaB‐flocs) in sequencing batch reactors are a novel and promising technology to treat aquaculture wastewater. To improve the economics of this technology, the harvested MaB‐flocs should be valorized. Therefore, we investigated if MaB‐flocs from an outdoor pilot reactor treating pikeperch (Sander lucioperca L.) wastewater can be used as a colour enhancing ingredient for shrimp diets. Considering the nutritional composition and high ash content of MaB‐flocs, five iso‐nitrogenous and iso‐lipidic shrimp diets were formulated by replacing 2–8% of the basal diet ingredients by MaB‐flocs. These diets were continuously fed to juvenile Pacific white shrimps Litopenaeus vannamei (Boone) cultured in a hybrid recirculating aquaculture system. The addition of these relatively low amounts of MaB‐flocs to shrimp diets significantly increased the pigmentation (redness and yellowness) of cooked shrimp tails. The diet modifications did not affect the shrimp survival, weight gain, size distribution and food conversion rate, nor did they affect the proximate composition and fatty acid profile of the raw shrimp muscle. This shows that MaB‐flocs originating from treatment of pikeperch wastewater can substitute 8% of diet ingredients of Pacific white shrimp while enhancing its pigmentation. 相似文献
6.
Tom Hellebuyck Kris Baert Frank Pasmans Lieven Van Waeyenberghe Lies Beernaert Koen Chiers Patrick De Backer Freddy Haesebrouck An Martel 《Veterinary dermatology》2010,21(4):429-433
The Chrysosporium anamorph of Nannizziopsis vriesii was associated with dermatomycosis and high mortality in a group of captive giant girdled lizards (Cordylus giganteus). Treatment of one of the infected girdled lizards with voriconazole, which was selected on the basis of in vitro sensitivity testing of the isolate, resulted in resolution of lesions and negative fungal cultures from the skin. Three hours after oral administration of 10 mg/kg, the plasma level of voriconazole exceeded the 0.25‐μg/mL minimal inhibitory concentration tenfold. In conclusion, administration of voriconazole at 10 mg/kg of body weight once daily for 10 weeks resulted in clinical cure and was well tolerated. A longer follow‐up time and larger studies will be necessary to determine the long‐term efficacy and safety of this treatment in giant girdled lizards. 相似文献
7.
C. Van Nieuwenhove R. Merckx Lieven Van Holm Karel Vlassak 《Biology and Fertility of Soils》2001,33(1):25-32
Azorhizobium caulinodans was directly inoculated onto rice plants in three short-term pot trials. Addition of increasing amounts of sucrose (23, 46,
92 kg ha–1) did not influence the N economy of the A. caulinodans-rice association during the early vegetative growth stage. A. caulinodans inoculation alone and in combination with the highest amount of sucrose had a significantly positive effect on the N balance,
with small but significant N gains in the system. Application of 60 kg urea-N ha–1 had a negative impact on the N economy of the inoculated treatments. N losses increased and the amount of atmospheric N2 fixed and incorporated decreased significantly as compared to the amounts under the 20 kg urea-N ha–1 regime. However, N losses were low – a maximum of 8% – at the early vegetative growth stage under the conditions of the experiments.
C limitation does not seem to be a limiting factor for the incorporation of fixed N2 in this bacteria-plant association. Biological N2 fixation caused by A. caulinodans inoculation was responsible for 14% of the plant N at the vegetative growth stage and under low N conditions.
Received: 30 January 2000 相似文献
8.
This study investigated the relationship between the current size of endangered bullhead (Cottus gobio) populations and microsatellite genetic variability. Additionally, the microsatellite data were used to evaluate whether a genetic test for population bottlenecks was able to provide evidence of recent severe population declines. Finally, our results were used to develop conservation priorities and measures. Population size appears to be a crucial parameter in determining the amount of genetic diversity that can be preserved in bullheads, since a significant positive correlation was observed between both variables. Furthermore, in some populations we were able to detect genetic signatures of the documented decline in population size. We suggest that the most immediate goal for bullhead conservation should be to increase the size and the range of the populations, and in doing so minimise or even reverse further genetic erosion. Potential management actions like habitat quality improvement, reduction of river fragmentation and supplementation programmes (translocation, supportive breeding) are discussed. 相似文献
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Van Meulebroek L Vanhaecke L De Swaef T Steppe K De Brabander H 《Journal of agricultural and food chemistry》2012,60(2):566-573
The growing interest of consumers in healthy food challenges growers to continuously improve the nutritional quality of their crops. In this research, the potential of a more saline growth environment for improved antioxidant concentration in tomato fruit was studied, and an U-HPLC-MS/MS method for the determination of lycopene, β-carotene, and α-tocopherol was optimized. Analytes were thereby separated on a 1.9 μm Hypersil GOLD C(18) column and quantified on a TSQ Vantage triple-quadropole mass spectrometer. The method displayed a short analysis time (6 min), a high specificity, and an excellent repeatability (≤6.39%). Furthermore, it was demonstrated that the electrical conductivity level of the applied nutrient solution did not unambiguously influence antioxidant concentration in tomato fruits. Future research should focus on moderate salt stress only and should aim at reducing natural variation by more closely controlling the growth environment and a more objective determination of the ripening degree. 相似文献