Improving production efficiency of farmed Atlantic salmon (Salmo salar L.) by isoenergetic diets with increased dietary protein‐to‐lipid ratio          下载免费PDF全文

Rúni Weihe  Jens‐Erik Dessen  Regin Arge  Magny Sissel Thomassen  Bjarne Hatlen  Kjell‐Arne Rørvik 《Aquaculture Research》2018,49(4):1441-1453

The effects of isoenergetic diets with high (HP) and low (LP) protein‐to‐lipid ratios on feeding rate (SFR), feed conversion (FCR), growth (TGC) and relative‐ and absolute nutrient retention were investigated using both whole‐body weight (BW) and carcass weight (CW) to assess the production efficiency. Three different feeding trials in seawater were conducted: two large‐scale trials with yearling smolt (S1) and under‐yearling smolt (S0) and one small‐scale with S1 smolt. The initial body weights in the trials were 105, 319 and 978 g, respectively, and the fish were fed and monitored until they reached harvest weights. In all three trials, the dietary HP group attained significantly higher (p < .05) CW at harvest based on fish with equal BW. Also, fish fed the HP diets significantly improved FCR (p < .05) when based on CW. In the small‐scale trial, fish fed HP diet, especially during late autumn and spring, significantly (p < .001) improved FCR_BW and FCR_CW. Improved FCR coincided with significantly higher (p < .05) relative energy retention in the dietary HP group. In all three trials, the HP groups had significantly higher (p < .05) TGC with regard to both BW and CW. Taken together, the present studies indicate that growth performance and feed utilization in modern salmon farming has the potential to be further improved by increasing the dietary protein‐to‐lipid ratio. In addition, dietary influence is more precisely assessed when using carcass as the weight denominator when analysing feed utilization and growth performance.  相似文献   

Relationship Between Fecal Indicators in Sediment and Recreational Waters in a Danish Estuary     

Peter Roslev  Søren Bastholm  Niels Iversen 《Water, air, and soil pollution》2008,194(1-4):13-21

The European Union has introduced a new bathing water directive where future classification of recreational waters will be based on the microbial parameters Escherichia coli, and intestinal enterococci. Introduction of enterococci as a new quality parameter may pose a challenge in some areas because relatively less is known about these organisms compared to E. coli. In the present study, the relative abundance of intestinal enterococci, E. coli, and ten fecal sterol and stanol biomarkers were investigated in water and sediment at two estuarine beach sites affected by fecal pollution. In the bathing water, enterococci were relatively more abundant at low E. coli concentrations. In the sediment, enterococci were generally more abundant than E. coli with surface concentrations between 1.0?×?10² and 4.5?×?10³ CFU cm^?3. Enterococci populations were relatively similar in water and sediment, and were phenotypically different from that of nearby pollution sources. The putative human specific genetic marker esp in Enterococcus faecium was not detected in water or sediment samples despite occasional inputs of human waste from storm water overflows. Sterol and stanol profiles suggested a direct link between water and sediment pollution profiles on days with wind conditions that facilitated resuspension. Sediment resuspension may occur at wind speeds exceeding 6–8 m s^?1, and could contribute significantly to enterococci concentrations in the overlying water. The study emphasized that recontamination of the water column due to wind induced resuspension should be considered when evaluating indicator levels and microbial hazards in estuarine recreational waters.  相似文献   

‘David and Goliath’ of the soil food web – Flagellates that kill nematodes     

Lisa Bjørnlund  Regin Rønn 《Soil biology & biochemistry》2008,40(8):2032-2039

Nematodes and flagellates are important bacterial predators in soil and sediments. Generally, these organisms are considered to be competitors for bacterial food. We studied the interaction among flagellates and nematodes using axenic liquid cultures amended with heat-killed bacteria as food and showed for the first time that a small and common soil flagellate (Cercomonas sp.) is able to attack and kill the much larger nematode Caenorhabditis elegans. The killing process is not caused by soluble metabolites but requires direct contact between the flagellate cells and the nematode surface and occurs rapidly (within a few hours) at high flagellate density. At lower flagellate density, adult nematodes sometimes avoid attachment of flagellates, feed on them and become the dominant bacterial predator. Considering that bacterial feeders affect bacterial communities differently, and that one bacterial feeder can control the abundance of another, suggests a new perspective on how bacterial diversity and trophic interactions are linked in the soil food web.  相似文献   

Invasive Acacia longifolia induce changes in the microbial catabolic diversity of sand dunes     

Elizabete Marchante  Annelise Kjøller  Sten Struwe  Helena Freitas 《Soil biology & biochemistry》2008,40(10):2563-2568

Acacia longifolia is one of the main plant species invading Portuguese dune ecosystems. Areas invaded by this exotic tree have reduced plant diversity and altered soil microbial processes and nutrient pools, but the impacts on microbial functional diversity in the soil have been little explored. Soil samples were collected in areas invaded by A. longifolia for more than 20 years, in areas invaded after 1995 and in non-invaded areas. Respiration responses to 20 different substrates were analysed, in order to assess the catabolic response profile (CRP) as a measure of microbial functional diversity. Five substrate groups were tested: amino acids, carbohydrates, carboxylic acids, plant litters, and plant polymers. CRP clearly discriminated between the three different areas. Respiratory responses to the individual substrates α-ketoglutaric acid, oxalic acid, starch, citric acid, and xylose and to the groups of amino acids and plant polymers were similar in both invaded areas and different in the non-invaded. The responses to tartaric acid, gallic acid, fumaric acid, Cistus litter, and Acacia litter were the same in long- and non-invaded areas, but different from recently invaded areas. The duration of invasion, carbon (C) content, nitrogen (N) content, C/N ratio, pH, and litter quantity explained 39.6% of the variance of catabolic responses. It is concluded that invasion by A. longifolia has substantial effects on the catabolic diversity of the soil microbial communities. These effects may have wider implications for nutrient cycling and ecosystem-level processes and for the invasibility of the system.  相似文献   

Development of a LC-MS/MS method for the analysis of enniatins and beauvericin in whole fresh and ensiled maize     

Sørensen JL  Nielsen KF  Rasmussen PH  Thrane U 《Journal of agricultural and food chemistry》2008,56(21):10439-10443

A LC-MS/MS method for the detection of beauvericin and the four enniatins A, A1, B, and B1 in maize and maize silage was developed. The method uses direct injection of maize extracts without any tedious and laborious cleanup procedures. The limit of quantification was determined at 13 ng g(-1) for beauvericin and at 17, 34, 24, and 26 ng g(-1) for enniatins A, A1, B, and B1, respectively. The method was used in surveys of the compounds in fresh maize samples collected at harvest in 2005 and 2006. All samples had the same distribution of the enniatins: B > B1 > A1 > A. Enniatin B was present in 90% of the samples in 2005 and in 100% in 2006 at levels up to 489 and 2598 ng g(-1), respectively. Beauvericin contamination was more frequently detected in 2006 than in 2005 (89 and 10%, respectively) and in higher amounts (988 and 71 ng g(-1), respectively). The occurrence of beauvericin and the four enniatins was examined in 3-month-old maize silage stacks from 20 different farms. As observed in fresh maize, enniatin B was the most abundant compound in ensiled maize and was found from 19 stacks at levels up to 218 ng g(-1). The stability of enniatin B in maize silage was assessed by analyzing samples from 10 of the silage stacks taken after 3, 7, and 11 months of ensiling. Enniatin B could be detected at all locations after 11 months and appeared to be stable during ensiling.  相似文献   

New esters of okadaic acid in seawater and blue mussels (Mytilus edulis)     

Torgersen T  Miles CO  Rundberget T  Wilkins AL 《Journal of agricultural and food chemistry》2008,56(20):9628-9635

Marine algal toxins of the okadaic acid (OA) group can occur as diol esters and sulfated diol esters in algae and as fatty acid esters in shellfish. Several of these ester forms have been identified, but the most common procedure for detecting OA group toxin esters is by measuring the increase in parent toxin after alkaline hydrolysis. Use of this alkaline hydrolysis method led to the discovery of high levels of conjugates of OA and dinophysistoxins-2 (DTX2) in seawater and of OA, DTX1, and DTX2 in blue mussel hepatopancreas (HP) from Fl?devigen, Norway, during a bloom of Dinophysis spp. In the water sample, a C 8-diol ester, a C 9-diol ester, and a previously undescribed C 8-triol ester of OA were characterized using HPLC-MS (2), -MS (3), and -MS (4) in combination with various derivatization procedures. Palmitic acid (16:0) ester derivatives of these diol/triol esters were found in mussel HP and characterized using HPLC-MS (2), -MS (3), and -MS (4). To the authors' knowledge, hybrid diol-fatty acid esters of OA have not been previously described. Mass spectral analysis showed the presence of two forms of hybrid esters: one with the fatty acid conjugated to the 7-OH of the OA moiety and the other with the fatty acid conjugated to the OH group in the "diol" moiety. In the water sample, the C 8-diol ester was the most abundant, whereas in the mussels, the 16:0-C 9-diol hybrid ester was most abundant, and only minor amounts of the 16:0-C 8-diol hybrid ester were detected, suggesting that C 8- and C 9-diol esters of OA may be metabolized differently in blue mussels. 7- O-acyl esters of OA, DTX1, and DTX2 are thought to contribute to shellfish toxicity by being hydrolyzed in the human stomach to the parent toxins, and the newly characterized hybrid esters are likely to contribute similarly.  相似文献   

Genetic variation and inheritance in a 9 × 9 diallel in silver birch (Betula pendula)     

Tore Skrøppa  Thomas Mørtvedt Solvin 《Scandinavian Journal of Forest Research》2019,34(3):178-188

A complete diallel cross was made among nine Betula pendula trees growing in a natural population and a trial was planted on agricultural soil at one site. This exceptional trial has provided estimates of genetic parameters that can only be estimated in complete diallels. Traits measured were height and diameter during a period of 37 years, and assessments were made of bud burst, leaf abscission and rust infection at the early ages. All traits showed genetic variation and the variance components of general combining ability (GCA) effects were dominating, with heritability estimates of 0.16 and 0.23 for height and diameter at age six years. The best-growing families could be identified at that age. At age 37 years, when the trial had been thinned twice, the offspring from the highest and lowest ranked parent for growth contributed with 19% and 6% of the total volume of the stand, respectively. The GCA effects were also highly significant for the assessment traits, but with an interaction with year for bud burst. High values of estimates of genetic correlations proved that bud burst, leaf abscission and rust infection are interrelated, and also to some extent with growth traits. Families with an early bud burst were tallest, were less affected by the rust fungus and kept their leaves later in the autumn.  相似文献   

Suspended matter and associated contaminants in Danish streams: a national analysis     

Thodsen  Hans  Rasmussen  Jes Jessen  Kronvang  Brian  Andersen  Hans Estrup  Nielsen  Anders  Larsen  Søren Erik 《Journal of Soils and Sediments》2019,19(7):3068-3082

Purpose

Suspended matter (SM) in streams is usually considered of minor importance in Danish environmental management. However, SM has some ecological effects as it may (1) clog fish spawning grounds and (2) act as an important agent for transport and exposure of biota to chemical substances, such as phosphorus and toxic inorganic (e.g. heavy metals) and organic (e.g. pesticides) substances.

Materials and methods

A large national data set of >?100,000 water samples analysed for SM and loss on ignition was investigated for spatial concentration patterns, sediment yields and temporal trends. Moreover, the importance of SM as a transport agent for phosphorus and heavy metals in streams was investigated through a correlation analysis.

Results and discussion

The mean suspended matter concentration (SMC) (including organic matter) amounted to 12 mg l^?1, with an organic content of 4.9 mg l^?1 (41%). A clear difference in SMC temporal trends over the sampling period was found between geographical regions. Sediment yields were calculated for all major catchments revealing low sediment yields (1–15 t km^?2 year^?1) compared to neighbouring countries and showed clear geographical patterns. Statistically significant relationships were established between SMCs, suspended sediment concentrations (SSCs) (excluding organic matter) and organic matter concentrations (OMCs) and particulate phosphorus (PP) concentrations, and again spatial patterns appeared. However, it was clearly shown that SMC/SSC/OMC could not be used as a robust, nationwide, indicator for PP concentrations. Analyses of the relationship between SMC and particle-bound heavy metal concentrations generally revealed weak correlations except for Pb and Ni (median R²?>?0.3).

Conclusions

Relatively low SM concentrations and sediment yields were found. SM is, in some geographical regions, an important transport agent for PP. Clear geographical patterns occurred in the relationships between SMC/SSC/OMC and both river water discharge and PP, as well as for sediment yields and for temporal trends in SMC.

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Estimation of sensitivity, specificity and predictive values of two serologic tests for the detection of antibodies against Actinobacillus pleuropneumoniae serotype 2 in the absence of a reference test (gold standard)   总被引：2，自引：0，他引：2  

Enøe C  Andersen S  Sørensen V  Willeberg P 《Preventive veterinary medicine》2001,51(3-4):227-243

Latent-class models were used to determine the sensitivity, specificity and predictive values of a polyclonal blocking enzyme-linked immunosorbent assay (ELISA) and a modified complement-fixation test (CFT) when there was no reference test. The tests were used for detection of antibodies against Actinobacillus pleuropneumoniae serotype 2 in a survey of respiratory diseases in Danish finishing pigs. The estimates were obtained by maximum-likelihood and also by a Bayesian method (implemented with Gibbs sampling). Possible dependence of diagnostic errors was investigated by comparing models where independence was assumed to models allowing for conditional dependence, given the true disease status.

No strong evidence of conditional dependence in either test sensitivity or specificity was found. Assuming independence, maximum-likelihood estimates and 95% confidence intervals of the sensitivity and specificity of the ELISA were 100% and 92.8% (90.1–95.5%) and the corresponding values of the CFT were 90.6% (85.8–95.4%) and 98.6% (98.0–99.3%), respectively. Bayesian estimates and posterior 95% credible intervals of the sensitivity and specificity of the ELISA were 99.7% (98.7–100%) and 92.7% (89.9–95.3%) and of the CFT were 90.6% (86.0–95.3%) and 98.7% (98.0–99.3%). The sensitivity and specificity of a combined test, where the CFT is subsequently applied to the pig sera that test positive in the ELISA, were estimated at 90.2% (85.6–95.0%) and 99.9% (99.8–100%), respectively. The cost of the combined test was less than the cost of the use of the CFT alone, at prevalences <54%. Prevalences and predictive values and their 95% limits were estimated in six sub-samples of data. The estimates of sensitivity and specificity obtained in the present investigation generally validate those reported from other sources.  相似文献   

Factor analysis of the interrelationships between clinical variables in horses with colic     

Thoefner MB  Ersbøll AK  Jensen AL  Hesselholt M 《Preventive veterinary medicine》2001,48(3):201-214

A prospective survey of horses with colic referred to the Large Animal Hospital at the Royal Veterinary and Agricultural University of Copenhagen, Denmark, was undertaken between August 1994 and December 1997. The interrelationships between 17 clinical variables were analysed using factor analysis. Factor analysis uncovers the structure of the variability in data and therefore detects multicollinearity. A total of 528 horses were admitted in the study period. Of these, 16 were excluded from the analysis as a result of miscellaneous conditions. Only 205 horses had observations for all 17 variables. Because no major change occurred in the main diagnostic categories, this population was considered as a representative subset. Factor analysis confirmed the clinical impression of correlation between variables, but the multicollinearity turned out not to be strong. Four factors were extracted, and these accounted for 51% of the total variance. The retained factors were interpreted by integrating previously reported clinical research. The first factor, which was interpreted as endotoxaemia, had high loadings on capillary refill time, mucous-membrane colour, degree of pain, heart rate, packed-cell volume and abdominal sounds. In the second factor, cecal decompression, admission month and gastric reflux had the predominant influence, and this factor was explained as cecal tympany. The third factor was simply interpreted as age because it had high loadings on gender, age and temperature. In the fourth factor, the interpretation was not straightforward, although breed had the greatest influence in the formation of this factor. Subsequently, the extracted factors were used in a logistic-regression analysis to determine their association with outcome (survival/death). The two factors interpreted as endotoxaemia and age were related to the outcome.  相似文献