Measurement and dynamic modeling of trace metal mobilization in soils using DGT and DIFS

The technique of diffusive gradients in thin-films (DGT) accumulates metals on a Chelex resin after their diffusive transport through a hydrogel. It lowers metal concentrations in soil solution adjacent to the device and induces resupply of metal associated with the solid phase. DGT devices were deployed in an alluvial gley soil for 21 different time periods between 4 h and 19.5 d. The accumulated masses of Cu, Cd, Ni, and Zn were used to calculate the distribution coefficient for labile metal, Kdl, and adsorption and desorption rate constants. Calculations were performed using a dynamic numerical model of DGT-induced fluxes in soils (DIFS). It assumes first-order exchange between solid phase and solution and diffusional transport in both the soil solution and the hydrogel. The DIFS model fitted changes in accumulated mass with time very well. Values of Kdl calculated from DIFS of 100 (Cd), 250 (Cu), 150 (Ni), and 150 (Zn) were larger than values of distribution coefficients estimated by exchange with Ca(NO3)2 but similar to those estimated by isotopic exchange (Cd and Zn only). These results suggest that the solid-phase pool of metal affected by the removal of labile metal by DGT, which operates on a time scale of minutes, is similar to the solid-phase pool of metal that can isotopically exchange with solution on a time scale of 2 d. Response times of minutes were consistent with interaction rates with surfaces, and desorption rate constants agreed with other reported values. An appraisal of the DIFS model demonstrated the importance of the labile pool size in the solid phase for controlling supply to a sink, such as DGT or a plant. As values of Kdl and kinetic parameters are obtained using DGT with minimal soil disturbance and by a similar mechanism to that involved in plant uptake, they may be pertinent to bioavailability studies.     

International genetic evaluation of dairy sires using a multiple-trait model with individual animal performance records

The objectives of this study were to estimate variance components and predict sire breeding values for milk, fat, and protein yield by using a multiple-trait model in which lactation yield in each country was considered as a different trait. Data included first lactation records of 16,145,832 Holstein-sired cows that calved between January 1, 1990, and December 31, 1997, in 243,466 herds in Australia, Austria, Belgium, Canada, the Czech Republic, Estonia, Finland, Germany, Hungary, Ireland, Israel, Italy, The Netherlands, New Zealand, South Africa, Switzerland, and the USA. Milk, fat, and protein were analyzed separately by using a 17-trait sire model; in this case, "traits" refer to measurements of the same biological parameter in different production systems. Our genetic model included the systematic effects of herd-year-season of calving, age at calving, milking frequency, and heterosis class (i.e., breed composition). Heritability estimates ranged from 0.24 in Australia (protein) to 0.34 in Israel (milk) and The Netherlands (fat). Genetic correlations between countries ranged from 0.77 for Austria-Czech Republic (protein), Estonia-Finland (fat), Estonia-Ireland (milk), Estonia-Israel (milk), and Hungary-New Zealand (fat), to 0.96 for Australia-Ireland (milk), Australia-New Zealand (milk), Belgium-Netherlands (milk), and Belgium-USA (fat). Correlations differed markedly from parameters used currently in international sire evaluations. In particular, genetic correlations were 0.91 to 0.96 between Australia, Ireland, and New Zealand; all of these countries rely heavily on rotational grazing. Correlations were also 0.91 to 0.96 between Belgium, Canada, Italy, The Netherlands, and the USA; all of these countries use intensive management systems. Correlations between these two groups of countries were 0.80 to 0.90. The percentage of elite bulls (top 1% for milk yield) selected in common by each pair of countries ranged from 0.42 for Germany-Estonia and Germany-Israel to 0.78 for Belgium-Netherlands.     

An exploratory study on the influence of orange juice on gut microbiota using a dynamic colonic model

The aim of this research was to evaluate the influence of fresh orange juice (FOJ) and pasteurized orange juice (POJ) on gut microbiota using the Simulator of the Human Intestinal Microbial Ecosystem (SHIME®) in a long-term experiment. SHIME® vessels were used to investigate orange juice fermentation throughout the colon and to assess changes in microbial composition and fermentation metabolites (short-chain fatty acids, or — SCFA, and ammonium). Antioxidant activity of the SHIME® vessels and juice was also evaluated. The FOJ increased (p ≤ 0.05) Lactobacillus spp., Enterococcus spp., Bifidobacterium spp., and Clostridium spp. and reduced (p ≤ 0.05) enterobacteria. The POJ increased (p ≤ 0.05) Lactobacillus spp. and reduced (p ≤ 0.05) enterobacteria. The PCR-DGGE analysis showed a reduction in total bacteria population richness values. The FOJ and POJ increased (p ≤ 0.05) butyric, acetic, and propionic acid concentrations, whereas ammonium production was reduced. High values of antioxidant activity were observed as a result of the FOJ and POJ treatments. Principal component analysis indicated that both POJ and FOJ juices had a positive influence on gut microbiota. The FOJ and POJ were found to exhibit selective prebiotic activity, particularly in terms of gut microbiota. This finding is in agreement with increases in both SCFAs and commensal bacteria, as well as with decreases in ammonium levels, though total bacteria richness values were reduced.     

An evaluation of tobacco treatment specialist counseling performance using standardized patient interviews.

In the United States, tobacco treatment specialists are professionals from a variety of backgrounds trained to deliver moderate to intensive evidence-based tobacco treatment in a variety of settings across the country. This paper reports the results of a study that examined the extent to which specialists participating in a larger study adhered to clinical practice guidelines for tobacco dependence using standardized patient assessments. A total of 64 tobacco treatment specialists completed a survey and two audiotaped standardized patient interviews. Overall, 41% and 31% of tobacco treatment specialists demonstrated 80% or more of session content and interviewing skills assessed, respectively, when required to demonstrate the skill in both standardized patient interactions. These rates increased to 85% and 56%, respectively, when using the less stringent criteria of demonstrating the skill in at least one of the two standardized patient interactions. Tobacco treatment specialists who had attended a greater number of types of tobacco treatment training exhibited both greater coverage of session content (p<.06) and greater interviewing skills (p<.02). Those who had achieved certification as a tobacco treatment specialist exhibited greater coverage of session content (p<.02), and those perceiving more positive support from their agency for their services exhibited greater interviewing skills (p=.02). Although the tobacco treatment specialists evaluated appear to have the necessary skills to deliver guideline-based intervention, they demonstrated only moderate adherence to the guidelines when expected to do so consistently across multiple assessments. Findings suggest specific components of tobacco treatment and interviewing skills that would benefit from strengthening through training and support.     

数值模拟在热防护服装性能测评中的应用

对热防护服装性能合理的评价在公共安全领域具有重要意义。数值模拟成为继试验研究之后相关领域的重要研究手段。从模型的建立及验证2方面出发,主要对传热模型、皮肤烧伤预测模型和火场环境仿真等相关研究进行回顾,并对典型模型的发展过程、特点和不足进行归纳。根据相关技术的发展,预测了热防护服装数值模拟的发展趋势。未来将在完善热湿传递模型的基础上,发展全尺度的数值模拟,并结合人体热调节等模型对防护服进行多方位的评价。通过在优化热防护服装方面的应用,充分体现数值模拟研究的实用价值。     

Effect of high-sugar grasses on methane emissions simulated using a dynamic model

High-sugar grass varieties have received considerable attention for their potential ability to decrease N excretion in cattle. However, feeding high-sugar grasses alters the pattern of rumen fermentation, and no in vivo studies to date have examined this strategy with respect to another environmental pollutant: methane (CH(4)). Modeling allows us to examine potential outcomes of feeding strategies under controlled conditions, and can provide a useful framework for the development of future experiments. The purpose of the present study was to use a modeling approach to evaluate the effect of high-sugar grasses on simulated CH(4) emissions in dairy cattle. An extant dynamic, mechanistic model of enteric fermentation and intestinal digestion was used for this evaluation. A simulation database was constructed and analysis of model behavior was undertaken to simulate the effect of (1) level of water-soluble carbohydrate (WSC) increase in dietary dry matter, (2) change in crude protein (CP) and neutral detergent fiber (NDF) content of the plant with an increased WSC content, (3) level of N fertilization, and (4) presence or absence of grain feeding. Simulated CH(4) emissions tended to increase with increased WSC content when CH(4) was expressed as megajoules per day or percent of gross energy intake, but when CH(4) was expressed in terms of grams per kilogram of milk, results were much more variable due to the potential increase in milk yield. As a result, under certain conditions, CH(4) (g/kg of milk) decreased. The largest increases in CH(4) emissions (MJ/d or % gross energy intake) were generally seen when WSC increased at the expense of CP in the diet and this can largely be explained by the representation in the model of the type of volatile fatty acid produced. Effects were lower when WSC increased at the expense of NDF, and intermediary when WSC increased at the expense of a mixture of CP and NDF. When WSC increased at the expense of NDF, simulated milk yield increased and, therefore, CH(4) (g/kg of milk) tended to decrease. Diminished increases of CH(4) (% gross energy intake or g/kg of milk) were simulated when DMI was increased with elevated WSC content. Simulation results suggest that high WSC grass, as a strategy to mitigate N emission, may increase CH(4) emissions, but that results depend on the grass composition, DMI, and the units chosen to express CH(4). Overall, this project demonstrates the usefulness of modeling for hypothesis testing in the absence of observed experimental results.     

Prediction of dry matter intake throughout lactation in a dynamic model of dairy cow performance

In the dynamic modeling of dairy cow performance over a full lactation, the difference between net energy intake and net energy used for maintenance, growth, and output in milk accumulates in body reserves. A simple dynamic model of net energy balance was constructed to select, out of some common dry matter intake (DMI) prediction equations, the one that resulted in a minimum cumulative bias in body energy deposition. Dry matter intake was predicted using the Cornell Net Carbohydrate and Protein System, Agricultural Research Council, or National Research Council (NRC) DMI equations from body weight (BW) and predicted fat-corrected milk yield. The instantaneous BW of cows at progressive weeks of lactation was simulated as the numerical integral of the BW change obtained from the predicted net energy balance. Predicted DMI and BW from each DMI equation, using either of 2 equations to describe maintenance energy expenditures, were compared statistically against observed data from 21 herd average published full lactation data sets. All DMI equations underpredicted BW and DMI, but the NRC DMI equation resulted in the minimum cumulative error in predicted BW and DMI. As a general solution to prevent predicted BW from deviating substantially over time from the observed BW, a lipostatic feedback mechanism was integrated into the NRC DMI equation as a 2-parameter linear function of the relative size of simulated body reserves and week of lactation. Residual sum of squares was reduced on average by 52% for BW predictions and by 41% for DMI predictions by inclusion of the negative feedback with parameters taken from the average of all 21 least squares fits. Similarly, root mean square prediction error (%) was reduced by 30% on average for BW predictions and by 23% for DMI predictions. Inclusion of a feedback of energy reserves onto predicted DMI, simulating lipostatic regulation of BW, solved the problem of final BW deviation within a dynamic model and improved its DMI prediction to a satisfactory level.     

Investigating arsenic speciation and mobilization in sediments with DGT and DET: a mesocosm evaluation of oxic-anoxic transitions

Mobilization of arsenic from freshwater and estuarine sediments during the transition from oxic to anoxic conditions was investigated using recently developed diffusive sampling techniques. Arsenic speciation and Fe(II) concentrations were measured at high resolution (1-3 mm) with in situ diffusive gradients in thin films (DGT) and diffusive equilibration in thin films (DET) techniques. Water column anoxia induced Fe(II) and As(III) fluxes from the sediment. A correlation between water column Fe(II) and As(III) concentrations was observed in both freshwater (r(s) = 0.896, p < 0.001) and estuarine (r(s) = 0.557, p < 0.001) mesocosms. Porewater sampling by DGT and DET techniques confirmed that arsenic mobilization was associated with the reductive dissolution of Fe(III) (hydr)oxides in the suboxic zone of the sediment; a relationship that was visible because of the ability to measure the coincident profiles of these species using combined DGT and DET samplers. The selective measurement of As(III) and total inorganic arsenic by separate DGT samplers indicated that As(III) was the primary species mobilized from the solid phase to the porewater. This measurement approach effectively ruled out substantial As(V) mobilization from the freshwater and estuarine sediments in this experiment. This study demonstrates the capabilities of the DGT and DET techniques for investigating arsenic speciation and mobilization over a range of sediment conditions.     

Fate of PBDEs in juvenile lake trout estimated using a dynamic multichemical fish model

Biotransformation half-lives (HL) and gut absorption efficiencies (GAE) of PBDE congeners in fish are poorly known and challenging to quantify experimentally. These values are needed in order to accurately assess their food web dynamics, and in turn, for policy development We recently developed a multichemical aquatic food web model, which was used to estimate HL of four PBDE congeners in a simple Arctic food web. However, an application of this model to more complex food webs would dramatically increase the uncertainties in the results due to the large number of unknowns that would need to be considered simultaneously. As such, an in-depth analysis of possible HL and GAE of additional PBDE congeners at the scale of individual fish species would facilitate model application to more complex food webs. For this purpose, we developed a fugacity-based dynamic multichemical fish model and applied it to previously published experimental laboratory data. The model was calibrated by maximizing correspondence between the modeled and observed concentrations for each of the thirteen congeners at two dietary concentrations in juvenile lake trout (Salvelinus namaycush) during uptake and depuration phases mainly by varying HL and GAE. A robust parametrization and calibration procedure gave us confidence in our back-calculated congener-specific HL of 42-420 days and GAE of 20-45%. These values can be used as a starting point for model applications to natural fish populations. The fate/transport results suggest that not only loss of PBDE congeners via degradation, but also input through biotransformation of higher brominated congeners, should be accounted for in order to accurately portray dynamics of PBDEs in fish.     

Genetic evaluation of fertility traits of dairy cattle using a multiple-trait animal model

A genetic evaluation system was developed for 5 fertility traits of dairy cattle: interval from first to successful insemination and nonreturn rate to 56 d of heifers, and interval from calving to first insemination, nonreturn rate to 56 d, and interval first to successful insemination of cows. Using the 2 interval traits of cows as components, breeding values for days open were derived. A multiple-trait animal model was applied to evaluate these fertility traits. Fertility traits of later lactations of cows were treated as repeated measurements. Genetic parameters were estimated by REML. Mixed model equations of the genetic evaluation model were solved with preconditioned conjugate gradients or the Gauss-Seidel algorithm and iteration on data techniques. Reliabilities of estimated breeding values were approximated with a multi-trait effective daughter contribution method. Daughter yield deviations and associated effective daughter contributions were calculated with a multiple trait approach. The genetic evaluation software was applied to the insemination data of dairy cattle breeds in Germany, Austria, and Luxembourg, and it was validated with various statistical methods. Genetic trends were validated. Small heritability estimates were obtained for all the fertility traits, ranging from 1% for nonreturn rate of heifers to 4% for interval calving to first insemination. Genetic and environmental correlations were low to moderate among the traits. Notably, unfavorable genetic trends were obtained in all the fertility traits. Moderate to high correlations were found between daughter yield-deviations and estimated breeding values (EBV) for Holstein bulls. Because of much lower heritabilities of the fertility traits, the correlations of daughter yield deviations with EBV were significantly lower than those from production traits and lower than the correlations from type traits and longevity. Fertility EBV were correlated unfavorably with EBV of milk production traits but favorably with udder health and longevity. Integrating fertility traits into a total merit selection index can halt or reverse the decline of fertility and improve the longevity of dairy cattle.     

A static model for estimating energy content of compound feeds in a dynamic feed evaluation system

The objective of the study was to develop a static empirical model for the estimation of net energy content of compound feeds in a dynamic feeding system using net energy for lactation at 20 kg of dry matter intake/d (NEL20) values calculated by the Nordic Feed Evaluation System (NorFor) model. In the NorFor system, NEL20 is a standardized value used to describe net energy content of feeds. The static model would allow prediction of the net energy value of compound feeds without access to the input data needed for the dynamic models. Our hypothesis was that NEL20 values of compound feeds can be predicted using organic matter digestibility (in vitro) and chemical components of the compound feeds as input variables. For this, 75 compound feeds and their 108 associated ingredients were collected across Scandinavia for model development. The proposed best model for prediction of compound feed NEL20 included crude fat, neutral detergent fiber, digestible organic matter measured in vitro, and crude protein (urea corrected) as independent variables. Lack of additivity of chemical components between values analyzed directly in the compound feed and values calculated by the weighted sum of ingredients was detected as the main source of error in the model, emphasizing the importance of accurate chemical analysis and sampling practices. Results from practical use of the model show that it may be a valuable tool that could be used by several actors in the feeding sector using the NorFor system. Feed manufacturers could use it to monitor the net energy content in their final product, and farmers could use it to check the net energy content of the purchased compound feed. However, validation of this model against an independent set of samples is lacking in this study and its prediction performance should be further evaluated. The model will need recalibration if the feed parameters used in the dynamic model for the estimation of reference values change, as this would not be reflected in the predicted values of the created model.     

服装动态热阻测定及预测模型的研究进展

为探究风和人体运动对服装动态热阻的影响,基于对人体和环境间热对流的分析,结合实际研究数据,阐明风和人体运动对服装动态热阻存在显著影响。总结了风和人体运动作用下动态热阻的测试方法。动态热阻变化规律的定性分析表明,动态热阻值在风和人体运动作用下呈现下降趋势,且二者对动态热阻的影响程度随着风速和步行速度的增加逐渐下降。分类对正常工作服、冬季防寒服和轻质服装动态热阻具体数值的预测研究进行了概括和总结。研究认为,服装动态热阻预测模型未来的研究重点是动态热阻修正公式的优化和局部动态热阻变化规律2方向。     

Assessing economic consequences of foot disorders in dairy cattle using a dynamic stochastic simulation model

Foot disorders are an important health problem in dairy cattle, in terms of economics and animal welfare. The incidence, severity, and duration of foot disorders account for their importance. Prevalence of both subclinical and clinical foot disorders is high. More insight into the economic consequences could increase awareness among dairy farmers and could be an incentive for them to take action on this problem of animal welfare. The objective of this research was to estimate the economic consequences of different types of foot disorders, both clinical and subclinical. A dynamic stochastic Monte Carlo simulation model was used, taking into account the different types of foot disorders. The economic consequences of the foot disorders modeled were costs due to milk production losses, culling, prolonged calving interval, labor of the dairy farmer and the foot trimmer, visits of a veterinarian, treatment, and discarded milk. Under the milk quota system in the Netherlands, costs due to foot disorders for a default farm with 65 cows averaged $4,899 per year (ranging from $3,217 to $7,001), an annual loss of $75 per cow. This calculation implies that the costs due to foot disorders are more substantial than farmers might think. The costs of subclinical foot disorders account for 32% of all costs due to foot disorders. The costs due to foot disorders that are present without treatment or detection by the farmer are considerable. This finding implies that farmers might underestimate the benefits of taking action earlier and more thoroughly. A clinical foot disorder costs, on average, $95, and a subclinical foot disorder $18. The highest costs classified by foot disorder were those due to digital dermatitis, which has a high incidence and relatively high clinical prevalence. The highest costs classified by cost factor were those due to milk production losses and culling. Sensitivity analysis showed that variables regarding milk production were important for economic costs due to foot disorders. Furthermore, the probability of getting a foot disorder and probability of cure were important for estimating the costs due to foot disorders. Farmer awareness concerning dairy cow foot health and taking action more thoroughly, therefore, could reduce the economic consequences and improve welfare simultaneously.     

Genetic evaluation of stillbirth in United States Holsteins using a sire-maternal grandsire threshold model

A sire-maternal grandsire threshold model was used for genetic evaluation of stillbirth in US Holsteins. Calving ease and stillbirth records for herds reporting at least 10 dead calves were extracted from the Animal Improvement Programs Laboratory database. About half of the 14 million calving ease records in the database had a known livability score, mostly from herds processed by Dairy Records Management Systems (Raleigh, NC). Calf livability scores of 2 and 3, representing calves born dead and calves that died within 48 h of parturition, respectively, were combined into a single category. The model included effects of herd-year, year-season, parity-sex, sire, birth year group of sire, maternal grandsire (MGS), and birth year group of MGS. Herd-year, sire, and MGS were random effects. Mean predicted transmitting abilities, expressed as the expected percentage of stillbirths, were 7.9 and 8.6 for direct and maternal stillbirths, respectively. Mean reliabilities for both the direct and maternal effects were 45%. Correlations among domestic and Interbull stillbirth solutions on the underlying scale for bulls with at least 90% reliability ranged from 0.63 to 0.90 across countries for direct stillbirths and from 0.69 to 0.96 for maternal stillbirths, indicating that results were generally consistent with those from other countries. There was no evidence of a genetic trend for either trait. More complete recording of stillbirth scores would improve reliabilities and could allow for evaluations of other breeds.     

A stochastic dynamic model of a dairy farm to evaluate the technical and economic performance under different scenarios

Dairy farms need to improve their competitiveness through decisions that are often difficult to evaluate because they are highly dependent on many economic and technical factors. The objective of this project was to develop a stochastic and dynamic mathematical model to simulate the functioning of a dairy farm to evaluate the effect of changes in technical or economic factors on performance and profitability. Submodels were developed for reproduction, feeding, diseases, heifers, environmental factors, facilities, management, and economics. All these submodels were simulated on an animal-by-animal and day-by-day basis. Default values for all variables are provided, but the user can change them. The outcome provides a list of technical and economic indicators essential for the decision-making process. Performance of the program was verified by evaluating the effects and sensitivity analysis of different scenarios in 20 different dairy farms. As an example, a case study of a dairy farm with 300 cows producing 40 L/d and a 12% pregnancy rate (PR) was used. The effect of using a time-fixed artificial insemination (TFAI) protocol in the first insemination at 77 d in milk, with 45 and 40% conception rates for first-lactation and older cows, respectively, and a cost of €13 was explored. During the 5-yr simulation, the TFAI increased PR (12 to 17%) and milk yield per milking cow (39.8 to 41.2 L/d) and reduced days to first AI (93 to 74), days open (143 to 116), and the proportion of problem cows (24.3 to 15.9%). In the TFAI, cows were dried 30 d earlier, resulting in more dry cows, and a smaller difference in milk yield by present cows (35.5 vs 36.0 L/d for control and TFAI, respectively). A longer productive life (2.56 vs. 2.79 yr) with shorter lactations in TFIA resulted in less first-lactation cows (42 vs 36%), 32 more calvings per year, and, therefore, more cases of postpartum diseases. Total (32.5 to 29.9%) and reproductive (10.5 vs 6.8%) culling rates decreased in TFIA. Overall, the net margin was €245 and €309/cow per year in control and TFIA, respectively. The net margin of applying TFAI decreased as PR of the farm increased, with limited benefit of TFAI at a PR of 30%. The model provides a powerful web-based tool to explore the short- and medium-term consequences of technical and economic decisions on the economic sustainability of dairy farms.     

An agent-based model evaluation of economic control strategies for paratuberculosis in a dairy herd

This paper uses an agent-based simulation model to estimate the costs associated with Mycobacterium avium ssp. paratuberculosis (MAP), or Johne's disease, in a milking herd, and to determine the net benefits of implementing various control strategies. The net present value (NPV) of a 1,000-cow milking herd is calculated over 20 yr, parametrized to a representative US commercial herd. The revenues of the herd are generated from sales of milk and culled animals. The costs include all variable and fixed costs necessary to operate a representative 1,000-cow milking herd. We estimate the NPV of the herd with no MAP infection, under an expected endemic infection distribution with no controls, and under an expected endemic infection distribution with various controls. The initial number of cows in a herd with an endemic MAP infection is distributed as 75% susceptible, 13% latent, 9% low MAP shedding, and 3% high MAP shedding. Control strategies include testing using ELISA and fecal culture tests and culling of cows that test positive, and culling based on observable milk production decrease. Results show that culling cows based on test results does not increase the herd's NPV and in most cases decreases NPV due to test costs as well as false positives and negatives with their associated costs (e.g., culling healthy cows and keeping infected cows). Culling consistently low producing cows when MAP is believed to be present in the herd produces higher NPV over the strategy of testing and culling MAP infected animals, and over the case of no MAP control.     

The performance evaluation of a continuous vegetable cooker

Summary A continuous vegetable cooker was evaluated and shown to produce improved quality-cooked vegetables under more hygienic conditions as compared to batch type conventional cooking. The operating parameters for 85  ±  3% degree of cooking as optimal were determined for green peas, carrot, kohlrabi, and radish. The final product was evaluated in comparison to conventional cooking in terms of the degree of cooking and product quality (retention of chlorophyll, vitamin C and carotenoids; microbial analysis). The thermal efficiency of the cooker and specific energy consumption were compared with published data for steam blanchers.