Epidemiology and control of an outbreak of classical swine fever in wild boar in Switzerland     

Schnyder M  Stärk KD  Vanzetti T  Salman MD  Thor B  Schleiss W  Griot C 《The Veterinary record》2002,150(4):102-109

An outbreak of classical swine fever in wild boar in the southern part of Switzerland (Canton of Ticino) was investigated after the implementation of control measures in a defined infected area (the risk zone), and in a surrounding surveillance zone (the non-risk zone). After the disease had been detected, hunting was not allowed in the risk zone for over six months, during which the disease was left to run its course, but hunting was continued in the non-risk zone for one month. After seven months, a hunting strategy targeted at young animals was implemented in both zones. Between May 1998 and January 2000,1294 wild boar were shot or found dead, and diagnostic and biological data were collected and analysed. Only one animal from the non-risk zone was found to be seropositive for antibodies to the virus, whereas 179 of 528 wild boar from the risk zone were virus positive and 162 were seropositive. The proportion of virus-positive animals decreased from 62.7 per cent to zero over one year. During the first hunting season, seropositive animals were found in all age groups, but 12 months later only animals more than one year old had antibodies against the virus.  相似文献   

Short fallows of Tithonia diversifolia and Crotalaria grahamiana for soil fertility improvement in western Kenya     

B. Thor Smestad  H. Tiessen  R.J. Buresh 《Agroforestry Systems》2002,55(3):181-194

Managed short-duration fallows may have the potential to replace longer fallows in regions where population density no longer permits slow natural fallow successions. The purpose of fallows is not only to improve subsequent crop performance but also to restore soil fertility and organic matter content for the long term. We therefore evaluated the soil organic matter and nutrient flows and fractions in a short fallow experiment managed in the western Kenya highlands, and also compared the experimental area with a 9–12-yr-oldadjacent natural bush fallow. The factorial agroforestry field experiment with four land-use and two P fertilizer treatments on a Kandiudalfic Eutrudox showed that 31-wk managed fallows with Tithonia diversifolia(Hemsley) A. Gray and Crotalaria grahamiana Wight &Arn. improved soil fertility and organic matter content above those of a natural weed fallow and continuous maize (Zea mays L.). Post-fallow maize yields were also improved, although cumulative three-season increases in yield were small (0–1.2 Mg ha⁻¹) when the yield foregone during the fallow season was accounted for. Improvements in yield and soil quality could be traced to quantity or quality of biomass recycled by the managed fallows. The non-woody recycled biomass produced by the continuous maize, weed fallow, and tithonia treatments was near 2Mg ha⁻¹, whereas crotalaria produced three times more recyclable biomass and associated N and P. Increases in topsoil N due to the fallows may have been attributable in part to deep acquisition and recycling of N by the fallows. Particulate macro-organic matter produced by the fallows contained sufficient N(30–50 kg ha⁻¹) to contribute substantially to maize production. Organic Paccumulation (29 kg ha⁻¹) similarly may play a significant role in crop nutrition upon subsequent mineralization. The effect of the P fertilizer application on soil properties and maize yield was constant for all land-use systems (i.e., no land-use system × P fertilizer interactions occurred). There was an indication that tithonia may have stimulated infestation of Striga hermonthica (Del.) Benth., and care must be taken to evaluate the full effects of managed fallows over several seasons. This revised version was published online in June 2006 with corrections to the Cover Date.  相似文献   

Effects of photoperiod, stocking density and diet on growth in young spotted wolffish (Anarhichas minor olafsen)     

Thor M. Jonassen 《Aquaculture International》2002,10(5):411-420

Full scale experiments in tanks were conducted to elucidate the effect of photoperiod regime, dietary fat level and stocking density on growth in spotted wolffish. The study showed that continuous light (LD24:0) did not give a higher final mean weight or faster overall growth rate in spotted wolffish compared to constant 8 h light and 16 h darkness (LD8:16). However, there were indications that the fish needed time to adapt to a new photoperiod regime. The feeding experiment indicated a negative relation between dietary fat level and growth, where fish given 15% fat in the diet had a 13% higher final mean weight compared to fish on a diet with 20% fat. However, no conclusions could be made. The final mean weight was 10% higher at 25 kg/m² compared to 40 kg/m², indicating a negative impact of high stocking density on spotted wolffish.  相似文献   

Digestive capacity, intestinal morphology, and microflora of 1-year and 2-year old Atlantic cod (Gadus morhua) fed standard or bioprocessed soybean meal     

Ståle Refstie  Thor Landsverk  Anne Marie Bakke-McKellep  Einar Ringø  Anne Sundby  Karl D. Shearer 《Aquaculture (Amsterdam, Netherlands)》2006,261(1):269-284

The objectives of this work were to evaluate how dietary soybean meal (SBM) or a soy meal made by bioprocessing the SBM (BPSBM) to remove anti-nutritional factors affected hydrolytic capacity, amino acid absorption, intestinal morphology, and microflora along the intestinal tract of Atlantic cod at two life stages. Three fish meal based standard cod diets were formulated to contain no soy (FM control), 25% SBM, or 22% BPSBM. Prior to sampling the diets were fed to duplicate groups of 0.5 kg (1-year old) and 1.7 kg (2-year old) cod for a period of 3 months, and the groups reached 0.9 and 2.5 kg, respectively. Digesta was then sampled from different intestinal sections for analyses of trypsin and amylase activity as well as absorption of amino acids, nitrogen, and sulphur. Gastrointestinal sections were sampled for measurements of relative weight (kg^− 1 body weight), and tissues from these sections were sampled for analyses of brush border enzyme (alkaline phosphatase (ALP), leucine aminopeptidase (LAP), and maltase) activity and histological examination. Microflora was sampled from both digesta and the intestinal wall. The SBM diet stimulated relative growth of all gastrointestinal sections except the distal intestine in both age classes. Relative growth of the pyloric intestine was also stimulated by BPSBM. The pyloric caeca and the upper mid intestine were found to be the major sites for enzymatic hydrolysis of protein and starch and for amino acid absorption. Dietary SBM and BPSBM did not alter the activity of trypsin and LAP, but the activity of these enzymes in the proximal intestine was affected by age, being higher in 1-year old than in 2-year old cod. The rate of amino acid, nitrogen, and sulphur absorption along the gastrointestinal tract was not affected by SBM, but was slowed by BPSBM. Dietary SBM or BPSBM did not alter the morphology of the intestinal mucosa in any sections of the cod intestine. The distal-most structure of the intestine, a compartment with inlet and outlet (anus) valves, showed very high microbial colonisation in the mucosal brush border. Inclusion of SBM in the diet changed the intestinal microflora, increasing the population level of transient bacteria in the pyloric and mid intestine, but reducing the population level of adherent bacteria throughout the intestine. To conclude, Atlantic cod appeared to have a robust and flexible digestive system able to adjust to high dietary levels of soy protein meals.  相似文献   

Lymphoid follicles in the gastric mucosa of dogs. Distribution and lymphocyte phenotypes     

yvor Kolbjrnsen  Charles McL. Press  Peter F. Moore  Thor Landsverk 《Veterinary immunology and immunopathology》1994,40(4):299-312

The occurrence and distribution of lymphoid follicles within the stomachs of 36 dogs that dis not have macroscopic gastric lesions are presented. The dogs ranged in age from less than 1 year to over 13 years. The number of follicles varied between the different regions of the stomach, being most numerous (15.6 follicles cm⁻²) and uniform in size (about 1 mm in diameter) in the fundus. The number and size of follicles in the antrum varied widely between dogs. Age-related changes in the distribution of follicles were not found following simple linear regression analysis. The phenotypes of lymphocytes in gastric lymphoid follicles of nine dogs aged from less than 1 year to 5 years were determined using monoclonal antibodies specific for canine leucocyte antigens and an indirect immunoperoxidase technique. The follicles had an organized distribution of lymphocytes subsets in that a predominantly B cell area contained some CD4+ cells and very few CD8+ cells and was adjacent to an area containing mostly T cells. Computer-assisted morphometric analysis was used to quantify the overall presence of the various lymphocyte subpopulations. Follicles in the fundus and body regions possessed similar percentages of lymphocytes averaging 42%, 22% and 3% of the area occupied by B cells, CD4+ and CD8+ cells, respectively. It is concluded that lymphoid follicles are a normal constituent of the canine gastric mucosa and possess a lymphocyte composition similar to that reported by others for solitary intestinal follicles.  相似文献   

The influence of physical watercourse parameters on the degree of anadromy in different lake populations of Arctic charr (Salvelinus alpinus (L.)) in northern Norway   总被引：1，自引：1，他引：0  

K. Kristoffersen 《Ecology of Freshwater Fish》1994,3(2):80-91

The influence of physical watercourse parameters on the degree of anadromy was studied in 15 lake populations of Arctic charr (Salvelinus alpinus (L.)) in northern Norway. The anadromy of the different populations was scored based on the following criteria; marine parasites. fish length and length at maturity. There were significant negative correlations between the anadromy scores and both the length of the outlet rivers of the different lakes and a migration barrier index for the different watercourses (combining migration distance and water velocity). It is hypothsized that these correlations were due to differences in energy expenditure for charr during upstream migration and/or differences in predation pressure on charr during river migration. Short rivers with relatively high water velocity seem to be the most preferable conditions for the anadromous life-history strategy. There were no correlations between the degree of anadromy and mean river slope or minimum summer water discharge.  相似文献   

Factors affecting the phase-out of pesticide use in public areas in Denmark     

Kristoffersen P  Larsen SU  Møller J  Hels T 《Pest management science》2004,60(6):605-612

That pesticide use in public areas in Denmark has been significantly reduced during the period 1995 to 2002 is shown when comparing three surveys carried out by the Danish Forest and Landscape Research Institute (DFLRI) with funding from the Danish Environmental Protection Agency. During that period, the total registered public use of pesticides was reduced from 28.8 tonnes active ingredients to 6.3 tonnes, corresponding to a 78% reduction. In 2002, the Danish counties and state institutions had reduced their total pesticide use by 80% and 73%, respectively, compared to 1995 figures. Similarly, the Danish municipalities reduced their use by 83% from 1995 to 2002. Surveys of municipal pesticide use carried out in 1995, 2000 and 2002 have been used as the basis for determining the factors that have influenced municipal reductions of pesticide use. The 2000 and 2002 trends can be explained partly on the basis of the figures for 1995 use. The trend for 2002 can also be partially explained by the political parties in power in the municipalities during the phase-out period. The models used account for up to 30% of the total variations, meaning that the pesticide use of individual municipalities is very much influenced by other, non-definable factors such as tradition.  相似文献   

Palmar or plantar process fractures of the distal phalanx in riding horses: 22 cases (1994–2003)     

K. E. Robson  M. Kristoffersen  S. J. Dyson 《Equine Veterinary Education》2008,20(1):40-46

No case series exists in the literature describing palmar/plantar process fractures (PPFs) of the distal phalanx in a nonracehorse population. We aim to describe the distribution of these injuries, together with their clinical, radiographic and scintigraphic features. In a retrospective case study, horses were selected based on radiographic evidence of a PPF. Data were collected relating to clinical and lameness examination, radiography, scintigraphy, management and follow‐up information. Oblique and flexed oblique radiographic views of the distal phalanx are the most sensitive in detecting PPFs of the distal phalanx and this study concluded that fractures of palmar or plantar process are likely to be missed in horses showing mild lameness if oblique radiographic views of the palmar process are not included.  相似文献   

Nonlocal wind-driven fjord–coast advection and its potential effect on plankton and fish recruitment     

Lars Asplin  Anne Gro Vea Salvanes  & Jon Bent Kristoffersen 《Fisheries Oceanography》1999,8(4):255-263

The Bergen Ocean Model (BOM), a three-dimensional physical coastal ocean model, was used for a numerical simulation experiment to investigate short-term effects of wind-generated coastal upwelling and downwelling on the dynamics of adjacent large outer and smaller inner fjords. The effect of the real alongshore wind regime on advection for an idealized fjord topography, resembling Masfjorden, western Norway, is used as an example. This modelling exercise is a supplement to, and its predictions support, the various hypotheses investigated in ecosystem simulation studies of the Masfjorden. The model predicts that coastal winds from the north cause upwelling and transport the upper water layer out from the fjords. Winds from the south cause downwelling and transport the upper water layer into the fjords. The transport is rapid and ≈50% of the upper water layer may be replaced within 1–2 days. Implications of these physical processes for the dispersal and retention of planktonic organisms and the early life stages of fish are discussed. If strong southerly winds occur frequently, this will transport planktonic organisms into the fjord and may increase the carrying capacity for planktivorous fish. In contrast, frequent strong northerly winds may reduce the abundance of planktonic organisms, including the early life stages of marine fish, and thus possibly reduce recruitment to fjord fish populations. Frequent shifts between southerly and northerly winds would cause an exchange of early life stages between neighbouring fjords and thus enhance genetic exchange.  相似文献   

Is the winter period a severe bottleneck of anadromous riverine Arctic charr parr?     

S. I. Siikavuopio  R. Knudsen  A. C. Winger  R. Kristoffersen 《Ecology of Freshwater Fish》2009,18(1):126-131

Abstract –  Winter growth and survival of wild individually tagged juvenile Arctic charr (1+ age) from a riverine anadromous stock, were studied in a small ice-covered (∼6 months) ground water brook (temperature ∼1 °C) connected to Skibotnelva in subarctic northern Norway. The overall winter survival was estimated to be 68% from late October 2005 to early May 2006. The recaptured charr were not significantly different in initial length or weight compared with the nonrecaptured fish suggesting low size-dependent mortality. The majority (98%) of the recaptured charr showed significant increase in size, with a mean increment of 62% from their initial bodyweight and 12% of the charr parr had more than doubled their weight. The mean specific growth rate was calculated to be slightly lower (0.27) than estimated values from a growth model (∼0.35). In addition, the condition factor increased significantly during the field experiment. These results are the first individual growth data on riverine anadromous Arctic charr parr under natural winter conditions, and indicate that charr can grow relatively fast during periods with low temperature and also that ground water brooks can be good over-wintering habitat for juvenile Arctic charr. These results suggest that the winter period is perhaps a less severe bottleneck than previously recognised for the cold-adapted Arctic charr.  相似文献