Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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Delaying investments in sensor technology : The rationality of dairy farmers' investment decisions illustrated within the framework of real options theory
Rutten, C.J. ; Steeneveld, W. ; Oude Lansink, A.G.J.M. ; Hogeveen, H. - \ 2018
Journal of Dairy Science (2018). - ISSN 0022-0302
adoption - dairy - economics - investment - sensor

The adoption rate of sensors on dairy farms varies widely. Whereas some sensors are hardly adopted, others are adopted by many farmers. A potential rational explanation for the difference in adoption may be the expected future technological progress in the sensor technology and expected future improved decision support possibilities. For some sensors not much progress can be expected because the technology has already made enormous progress in recent years, whereas for sensors that have only recently been introduced on the market, much progress can be expected. The adoption of sensors may thus be partly explained by uncertainty about the investment decision, in which uncertainty lays in the future performance of the sensors and uncertainty about whether improved informed decision support will become available. The overall aim was to offer a plausible example of why a sensor may not be adopted now. To explain this, the role of uncertainty about technological progress in the investment decision was illustrated for highly adopted sensors (automated estrus detection) and hardly adopted sensors (automated body condition score). This theoretical illustration uses the real options theory, which accounts for the role of uncertainty in the timing of investment decisions. A discrete event model, simulating a farm of 100 dairy cows, was developed to estimate the net present value (NPV) of investing now and investing in 5 yr in both sensor systems. The results show that investing now in automated estrus detection resulted in a higher NPV than investing 5 yr from now, whereas for the automated body condition score postponing the investment resulted in a higher NPV compared with investing now. These results are in line with the observation that farmers postpone investments in sensors. Also, the current high adoption of automated estrus detection sensors can be explained because the NPV of investing now is higher than the NPV of investing in 5 yr. The results confirm that uncertainty about future sensor performance and uncertainty about whether improved decision support will become available play a role in investment decisions.

Analysing trade-offs between milk, feed and manure production on Dutch dairy farms
Samson, Sabrina ; Gardebroek, C. ; Jongeneel, R.A. - \ 2017
European Review of Agricultural Economics 44 (2017)3. - ISSN 0165-1587 - p. 475 - 498.
manure surplus - dairy - milk quota abolition - panel data - the Netherlands - Q12 - D22 - Q52
The abolition of milk quota fuels environmental concerns in the Netherlands. A microeconomic model is developed to analyse the technical relations between milk, roughage and manure production. Production functions for milk, feed and roughage are estimated based on milk quota and manure constraints. Together with an equation for manure production these are used to calculate the costs and benefits of dairy livestock expansion. It turns out that at the margin and at prevailing input and output prices and manure processing costs, it will be attractive for dairy farms to expand production, unless regulatory constraints prevent them from doing so.
The value of pathogen information in treating clinical mastitis
Cha, Elva ; Smith, Rebecca L. ; Kristensen, Anders R. ; Hertl, Julia A. ; Schukken, Ynte H. ; Tauer, Loren W. ; Welcome, Frank L. ; Gröhn, Yrjö T. - \ 2016
Journal of Dairy Research 83 (2016)4. - ISSN 0022-0299 - p. 456 - 463.
dairy - mastitis - Value of information

The objective of this study was to determine the economic value of obtaining timely and more accurate clinical mastitis (CM) test results for optimal treatment of cows. Typically CM is first identified when the farmer observes recognisable outward signs. Further information of whether the pathogen causing CM is Gram-positive, Gram-negative or other (including no growth) can be determined by using on-farm culture methods. The most detailed level of information for mastitis diagnostics is obtainable by sending milk samples for culture to an external laboratory. Knowing the exact pathogen permits the treatment method to be specifically targeted to the causation pathogen, resulting in less discarded milk. The disadvantages are the additional waiting time to receive test results, which delays treating cows, and the cost of the culture test. Net returns per year (NR) for various levels of information were estimated using a dynamic programming model. The Value of Information (VOI) was then calculated as the difference in NR using a specific level of information as compared to more detailed information on the CM causative agent. The highest VOI was observed where the farmer assumed the pathogen causing CM was the one with the highest incidence in the herd and no pathogen specific CM information was obtained. The VOI of pathogen specific information, compared with non-optimal treatment of Staphylococcus aureus where recurrence and spread occurred due to lack of treatment efficacy, was $20.43 when the same incorrect treatment was applied to recurrent cases, and $30.52 when recurrent cases were assumed to be the next highest incidence pathogen and treated accordingly. This indicates that negative consequences associated with choosing the wrong CM treatment can make additional information cost-effective if pathogen identification is assessed at the generic information level and if the pathogen can spread to other cows if not treated appropriately.

Allocation choices strongly affect technology evaluation in dairy processing
Helmes, Roel ; Ponsioen, Tommie ; Robbemond, R.M. - \ 2016
In: Putting LCA into practice: 10th International Conference on Life Cycle Assessment of Food 2016. - UCD - p. 80 - 86.
Mozzarella - whey - dairy - global warming potential - multifunctionality
Failure and preventive costs of mastitis on Dutch dairy farms
Soest, Felix J.S. van; Santman-Berends, Inge M.G.A. ; Lam, Theo J.G.M. ; Hogeveen, Henk - \ 2016
Journal of Dairy Science 99 (2016)10. - ISSN 0022-0302 - p. 8365 - 8374.
dairy - economics - management - mastitis

Mastitis is an important disease from an economic perspective, but most cost assessments of mastitis include only the direct costs associated with the disease (e.g., production losses, culling, and treatment), which we call failure costs (FC). However, farmers also invest time and money in controlling mastitis, and these preventive costs (PC) also need to be taken into account. To estimate the total costs of mastitis, we estimated both FC and PC. We combined multiple test-day milk records from 108 Dutch dairy farms with information on applied mastitis prevention measures and farmers’ registration of clinical mastitis for individual dairy cows. The aim was to estimate the total costs of mastitis and to give insight into variations between farms. We estimated the average total costs of mastitis to be 240/lactating cow per year, in which FC contributed 120/lactating cow per year and PC contributed another 120/lactating cow per year. Milk production losses, discarded milk, and culling were the main contributors to FC, at 32, 20, and 20/lactating cow per year, respectively. Labor costs were the main contributor to PC, next to consumables and investments, at 82, 34, and 4/lactating cow per year, respectively. The variation between farmers was substantial, and some farmers faced both high FC and PC. This variation may have been due to structural differences between farms, different mastitis-causing pathogens, the time at which preventive action is initiated, stockmanship, or missing measures in PC estimates. We estimated the minimum FC to be 34 per lactating cow per yr. All farmers initiated some preventive action to control or reduce mastitis, indicating that farmers will always have mastitis-related costs, because mastitis will never be fully eradicated from a farm. Insights into both the PC and FC of a specific farm will allow veterinary advisors and farmers to assess whether current udder health strategies are appropriate or whether there is room for improvement from an economic perspective.

Consumption of dairy foods and diabetes incidence: a dose-response meta-analysis of observational studies
Gijsbers, L. ; Ding, E.L. ; Malik, Vasanti ; Goede, J. de; Geleijnse, J.M. ; Soedamah-Muthu, S.S. - \ 2016
American Journal of Clinical Nutrition 103 (2016)4. - ISSN 0002-9165 - p. 1111 - 1124.
dairy - milk - yoghurt - type 2 diabetes - cheese
BACKGROUND: A growing number of cohort studies suggest a potential role of dairy consumption in type 2 diabetes (T2D) prevention. The strength of this association and the amount of dairy needed is not clear. OBJECTIVE: We performed a meta-analysis to quantify the associations of incident T2D with dairy foods at different levels of intake. DESIGN: A systematic literature search of the PubMed, Scopus, and Embase databases (from inception to 14 April 2015) was supplemented by hand searches of reference lists and correspondence with authors of prior studies. Included were prospective cohort studies that examined the association between dairy and incident T2D in healthy adults. Data were extracted with the use of a predefined protocol, with double data-entry and study quality assessments. Random-effects meta-analyses with summarized dose-response data were performed for total, low-fat, and high-fat dairy, (types of) milk, (types of) fermented dairy, cream, ice cream, and sherbet. Nonlinear associations were investigated, with data modeled with the use of spline knots and visualized via spaghetti plots. RESULTS: The analysis included 22 cohort studies comprised of 579,832 individuals and 43,118 T2D cases. Total dairy was inversely associated with T2D risk (RR: 0.97 per 200-g/d increment; 95% CI: 0.95, 1.00; P = 0.04; I2 = 66%), with a suggestive but similar linear inverse association noted for low-fat dairy (RR: 0.96 per 200 g/d; 95% CI: 0.92, 1.00; P = 0.072; I2 = 68%). Nonlinear inverse associations were found for yogurt intake (at 80 g/d, RR: 0.86 compared with 0 g/d; 95% CI: 0.83, 0.90; P < 0.001; I2 = 73%) and ice cream intake (at ∼10 g/d, RR: 0.81; 95% CI: 0.78, 0.85; P < 0.001; I2 = 86%), but no added incremental benefits were found at a higher intake. Other dairy types were not associated with T2D risk. CONCLUSION: This dose-response meta-analysis of observational studies suggests a possible role for dairy foods, particularly yogurt, in the prevention of T2D. Results should be considered in the context of the observed heterogeneity.
Functional implications of the microbial community structure of undefined mesophilic starter cultures
Smid, E.J. ; Erkus, O. ; Spus, M. ; Wolkers-Rooijackers, J.C.M. ; Alexeeva, S.V. ; Kleerebezem, M. - \ 2014
Microbial Cell Factories 13 (2014)suppl. 1. - ISSN 1475-2859
lactic-acid bacteria - lactococcus-lactis - subsp lactis - listeria-monocytogenes - biovar diacetylactis - metabolic models - cheddar cheese - diversity - cremoris - dairy
This review describes the recent advances made in the studies of the microbial community of complex and undefined cheese starter cultures. We report on work related to the composition of the cultures at the level of genetic lineages, on the presence and activity of bacteriophages and on the population dynamics during cheese making and during starter culture propagation. Furthermore, the link between starter composition and starter functionality will be discussed. Finally, recent advances in predictive metabolic modelling of the multi-strain cultures will be discussed in the context of microbe-microbe interactions.
Expected utility of voluntary vaccination in the middel of an emergent Bluetongue virus serotype 8 epidemic: A decision analysis parameterized for Dutch circumtances
Sok, J. ; Hogeveen, H. ; Elbers, A.R.W. ; Velthuis, A.G.J. ; Oude Lansink, A.G.J.M. - \ 2014
Preventive Veterinary Medicine 115 (2014)3-4. - ISSN 0167-5877 - p. 75 - 87.
field observations - health - dairy - netherlands - economics - farmers - cattle - incentives - management - insurance
In order to put a halt to the Bluetongue virus serotype 8 (BTV-8) epidemic in 2008, the European Commission promoted vaccination at a transnational level as a new measure to combat BTV-8. Most European member states opted for a mandatory vaccination campaign, whereas the Netherlands, amongst others, opted for a voluntary campaign. For the latter to be effective, the farmer's willingness to vaccinate should be high enough to reach satisfactory vaccination coverage to stop the spread of the disease. This study looked at a farmer's expected utility of vaccination, which is expected to have a positive impact on the willingness to vaccinate. Decision analysis was used to structure the vaccination decision problem into decisions, events and payoffs, and to define the relationships among these elements. Two scenarios were formulated to distinguish farmers’ mindsets, based on differences in dairy heifer management. For each of the scenarios, a decision tree was run for two years to study vaccination behaviour over time. The analysis was done based on the expected utility criterion. This allows to account for the effect of a farmer's risk preference on the vaccination decision. Probabilities were estimated by experts, payoffs were based on an earlier published study. According to the results of the simulation, the farmer decided initially to vaccinate against BTV-8 as the net expected utility of vaccination was positive. Re-vaccination was uncertain due to less expected costs of a continued outbreak. A risk averse farmer in this respect is more likely to re-vaccinate. When heifers were retained for export on the farm, the net expected utility of vaccination was found to be generally larger and thus was re-vaccination more likely to happen. For future animal health programmes that rely on a voluntary approach, results show that the provision of financial incentives can be adjusted to the farmers’ willingness to vaccinate over time. Important in this respect are the decision moment and the characteristics of the disease. Farmers’ perceptions of the disease risk and about the efficacy of available control options cannot be neglected.
Energy use and greenhouse gas emissions in organic and conventional farming systems in the Netherlands
Bos, J.F.F.P. ; Haan, J.J. de; Sukkel, W. ; Schils, R.L.M. - \ 2014
NJAS Wageningen Journal of Life Sciences 68 (2014). - ISSN 1573-5214 - p. 61 - 70.
life-cycle assessment - southern germany - dairy - agriculture - efficiency - biodiversity - balances - impacts - model - milk
Organic agriculture is often considered to contribute to reducing energy use and greenhouse gas (GHG) emissions, also on a per unit product basis. For energy, this is supported by a large number of studies, but the body of evidence for GHGs is smaller. Dutch agriculture is characterized by relatively intensive land use in both organic and conventional farming, which may affect their performance in terms of energy use and GHG emissions. This paper presents results of a model study on energy use and GHG emissions in Dutch organic and conventional farming systems. Energy use per unit milk in organic dairy is approximately 25% lower than in conventional dairy, while GHG emissions are 5-10% lower. Contrary to dairy farming, energy use and GHG emissions in organic crop production are higher than in conventional crop production. Energy use in organic arable farming is 10-30% and in organic vegetable farming 40-50% higher than in their respective conventional counterparts. GHG emissions in organic arable and vegetable farming are 0-15% and 35-40% higher, respectively. Our results correspond with other studies for dairy farming, but not for crop production. The most likely cause for higher energy use and GHG emissions in Dutch organic crop production is its high intensity level, which is expressed in crop rotations with a large share of high-value crops, relatively high fertiliser inputs and frequent field operations related to weeding
Genetic parameters for calving and conformation traits in Charolais x Montbéliard and Charolais x Holstein crossbred calves.
Vallee, A.A.A. ; Arendonk, J.A.M. van; Bovenhuis, H. - \ 2013
Journal of Animal Science 91 (2013)12. - ISSN 0021-8812 - p. 5582 - 5588.
beef-cattle - livestock auctions - postnatal-growth - birth-weight - body-weight - model - difficulty - dairy - selection - parities
Charolais sires can be mated to Montbéliard or Holstein dairy cows to produce crossbred calves sold for meat production. Heritabilities and correlations between traits can differ when they are calculated within Charolais × Montbéliard or within Charolais × Holstein population. Moreover, the genetic correlation between the same trait measured on Charolais × Montbéliard and on Charolais × Holstein crossbred calves is not necessarily unity. The first objective of this study was to estimate heritability and genetic correlation between traits within Charolais × Montbéliard and within Charolais × Holstein population. The second objective was to investigate if those traits are genetically identical between crossbred populations. Traits studied were calving difficulty, birth weight, height, bone thinness, and muscular development. Data included 22,852 Charolais × Montbéliard and 16,012 Charolais × Holstein crossbred calves from 391 Charolais sires. Heritabilities estimated separately within each crossbred population were similar. Stronger genetic correlations were observed in Charolais × Holstein population compared with Charolais × Montbéliard between calving difficulty and height (0.67 vs. 0.54), calving difficulty and bone thinness (0.42 vs. 0.27), birth weight and bone thinness (0.52 vs. 0.20), and birth weight and muscular development (0.41 vs. 0.18). Bivariate analysis considering observations on Charolais × Montbéliard and on Charolais × Holstein as different traits showed that genetic variances and heritabilities were similar for all traits except height. Birth weight and muscular development were genetically identical traits in each crossbred populations, with genetic correlations of 0.96 and 0.99. Genetic correlations were 0.91 for calving difficulty, 0.80 for height, and 0.70 for bone thinness and log-likelihood ratio tests indicated that they were significantly different from 1 (P = 0.01). Results show evidence for reranking of Charolais sires for calving difficulty, height, and bone thinness depending on whether they are mated to Montbéliard or Holstein cows.
Dietary nitrate supplementation reduces methane emission in beef cattle fed sugarcane-based diets
Hulshof, R.B.A. ; Berndt, A. ; Gerrits, W.J.J. ; Dijkstra, J. ; Zijderveld, S.M. van; Newbold, J.R. ; Perdok, H.B. - \ 2012
Journal of Animal Science 90 (2012)7. - ISSN 0021-8812 - p. 2317 - 2323.
rumen fermentation - sheep - methanogenesis - manipulation - mitigation - livestock - nitrite - dairy - urea - wall
The objective of this study was to determine the effect of dietary nitrate on methane emission and rumen fermentation parameters in Nellore × Guzera (Bos indicus) beef cattle fed a sugarcane based diet. The experiment was conducted with 16 steers weighing 283 ± 49 kg (mean ± SD), 6 rumen cannulated and 10 intact steers, in a cross-over design. The animals were blocked according to BW and presence or absence of rumen cannula and randomly allocated to either the nitrate diet (22 g nitrate/kg DM) or the control diet made isonitrogenous by the addition of urea. The diets consisted of freshly chopped sugarcane and concentrate (60:40 on DM basis), fed as a mixed ration. A 16-d adaptation period was used to allow the rumen microbes to adapt to dietary nitrate. Methane emission was measured using the sulfur hexafluoride tracer technique. Dry matter intake (P = 0.09) tended to be less when nitrate was present in the diet compared with the control, 6.60 and 7.05 kg/d DMI, respectively. The daily methane production was reduced (P <0.01) by 32% when steers were fed the nitrate diet (85 g/d) compared with the urea diet (125 g/d). Methane emission per kilogram DMI was 27% less (P <0.01) on the nitrate diet (13.3 g methane/kg DMI) than on the control diet (18.2 g methane/kg DMI). Methane losses as a fraction of gross energy intake (GEI) were less (P <0.01) on the nitrate diet (4.2% of GEI) than on the control diet (5.9% of GEI). Nitrate mitigated enteric methane production by 87% of the theoretical potential. The rumen fluid ammonia-nitrogen (NH3-N) concentration was significantly greater (P <0.05) for the nitrate diet. The total concentration of VFA was not affected (P = 0.61) by nitrate in the diet, while the proportion of acetic acid tended to be greater (P = 0.09), propionic acid less (P = 0.06) and acetate/propionate ratio tended to be greater (P = 0.06) for the nitrate diet. Dietary nitrate reduced enteric methane emission in beef cattle fed sugarcane based diet.
Semi-quantitative study to evaluate the performance of a HACCP-based food safety management system in Japanese milk processing plants
Sampers, I. ; Toyofuku, H. ; Luning, P.A. ; Uyttendaele, M. ; Jacxsens, L. - \ 2012
Food Control 23 (2012)1. - ISSN 0956-7135 - p. 227 - 233.
critical control point - quality-assurance - hazard analysis - industry - businesses - dairy - size
This study aimed to gain an insight in the performance of Hazard Analysis and Critical Control Points (HACCP)-based food safety management systems (FSMS) implemented in Japanese milk processing plants. Since 1995, Japan has a comprehensive approval system for food manufacturing establishments by evaluating the development and implementation of GHP and HACCP by the food manufacturing companies/operators. An FSMS-diagnostic instrument was applied to assess the level of the core control and assurance activities in the FSMS and to judge the risk level of the context wherein the companies operate. The data were collected in 13 dairy companies (mostly located around Tokyo area) and involved in-depth interviews performed (by the National Institute of Public Health) with responsible quality assurance persons of respective companies. The results revealed that the microbial food safety output was higher for companies with national HACCP approval. They have more advanced FSMS in combination with a less risky context. All Japanese companies scored high on technology-dependent activities (i.e. preventive measures and intervention processes), but less in managerial activities as monitoring and typical quality assurance activities as validation and verification of the FSMS. Japan has a detailed vertical legislation, leading to a “hazard-based” and ”legislation-based” FSMS compared to a “science- or risk-based” FSMS common in Europe.
A quantitative risk assessment for bovine spongiform encephalopathy in Japan
Kadohira, M. ; Stevenson, M.A. ; Hogasen, H.R. ; Koeijer, A.A. de - \ 2012
Risk Analysis 32 (2012)12. - ISSN 0272-4332 - p. 2198 - 2208.
sensitivity analysis techniques - meat-and-bone - computer-models - bse epidemic - united-kingdom - cattle - dairy - prevalence - infection - surveillance
A predictive case-cohort model was applied to Japanese data to analyze the interaction between challenge and stability factors for bovine spongiform encephalopathy (BSE) for the period 1985–2020. BSE risk in cattle was estimated as the expected number of detectable cases per year. The model was comprised of a stochastic spreadsheet calculation model with the following inputs: (1) the origin and quantity of live cattle and meat and bone meal imported into Japan, (2) the age distribution of native cattle, and (3) the estimated annual basic reproduction ratio (R0) for BSE. The estimated probability of having zero detectable cases in Japan in 2015 was 0.90 (95% CI 0.83–0.95). The corresponding value for 2020 was 0.99 (95% CI 0.98–0.99). The model predicted that detectable cases may occur in Japan beyond 2015 because of the assumption that continued transmission was permitted to occur (albeit at a very low level) after the 2001 ban on the importation and domestic use of all processed animal proteins for the production of animal feed and for fertilizer. These results reinforce the need for animal health authorities to monitor the efficacy of control measures so that the future course of the BSE epidemic in Japan can be predicted with greater certainty
Supplementary dietary calcium stimulates faecal fat and bile acid excretion, but does not protect against obesity and insulin resistance in C57BL/6J mice
Wit, N.J.W. de; Bosch-Vermeulen, H. ; Oosterink, E. ; Müller, M.R. ; Meer, R. van der - \ 2011
British Journal of Nutrition 105 (2011)7. - ISSN 0007-1145 - p. 1005 - 1011.
metabolism-related proteins - body-weight - lipid-metabolism - energy-expenditure - rna expression - dairy - milk - gain - rats - adiposity
There is increased interest in the potential protective role of dietary Ca in the development of metabolic disorders related to the metabolic syndrome. Ca-induced intestinal precipitation of fatty acids and bile acids as well as systemic metabolic effects of Ca on adipose tissue is proposed to play a causal role. In this experiment, we have studied all these aspects to validate the suggested protective effect of Ca supplementation, independent of other dietary changes, on the development of diet-induced obesity and insulin resistance. In our diet intervention study, C57BL/6J mice were fed high-fat diets differing in Ca concentrations (50 v. 150 mmol/kg). Faecal excretion analyses showed an elevated precipitation of intestinal fatty acids (2.3-fold; P
Ex situ conservation of Holstein-Friesian cattle: Comparing the Dutch, French, and US germplasm collections
Danchin-Burge, C. ; Hiemstra, S.J. ; Blackburn, H. - \ 2011
Journal of Dairy Science 94 (2011)8. - ISSN 0022-0302 - p. 4100 - 4108.
genetic-variability - pedigree analysis - population - breeds - resources - selection - sizes - dairy
Holstein-Friesian (HF) gene bank collections were established in France, the Netherlands, and the United States to conserve genetic diversity for this breed. Genetic diversity of HF collections within and between countries was assessed and compared with active male HF populations in each country by using pedigree data. Measures of genetic diversity such as probability of gene origin inbreeding and kinship were calculated. The cryobanks have captured substantial amounts of genetic diversity for the HF compared with the current populations. A substantial part of the US, French, and Dutch collections seems to be genetically similar. On the other hand, the US collection in particular represents an interesting reservoir of HF genes of the past. Gene banks can play an important role in conserving genetic diversity within livestock breeds over time, and may support industry in the future when needed.
How has the EU milk quota affected patterns of herd-size change?
Huettel, S. ; Jongeneel, R. - \ 2011
European Review of Agricultural Economics 38 (2011)4. - ISSN 0165-1587 - p. 497 - 527.
farm size - structural-change - dairy - impacts - growth - policy
This paper analyses the impact of milk quotas on the size structure of dairy herds in two major EU milk-producing member states, Germany and the Netherlands, using Markov chain models. Four mobility indicators characterising structural change are developed and calculated. Structural change in the dairy sector as measured by the mobility measures is found to be affected by the milk quota scheme. In the quota period, mobility out of dairying is lower, but the overall and upward mobility increase. This effect is stronger in the Netherlands than in West Germany.
High-resolution amplified fragment length polymorphism typing of Lactococcus lactis strains enables identification of genetic markers for subspecies-related phenotypes
Erkus Kütahya, O. ; Starrenburg, M.J.C. ; Rademaker, J.L.W. ; Klaassen, C.H.W. ; Hylckama Vlieg, J.E.T. van; Smid, E.J. ; Kleerebezem, M. - \ 2011
Applied and Environmental Microbiology 77 (2011)15. - ISSN 0099-2240 - p. 5192 - 5198.
complete genome sequence - acid bacteria - streptococcus-lactis - genus lactococcus - cremoris - aflp - diversity - dairy - nov
A high-resolution amplified fragment length polymorphism (AFLP) methodology was developed to achieve the delineation of closely related Lactococcus lactis strains. The differentiation depth of 24 enzyme-primer-nucleotide combinations was experimentally evaluated to maximize the number of polymorphisms. The resolution depth was confirmed by performing diversity analysis on 82 L. lactis strains, including both closely and distantly related strains with dairy and nondairy origins. Strains clustered into two main genomic lineages of L. lactis subsp. lactis and L. lactis subsp. cremoris type-strain-like genotypes and a third novel genomic lineage rooted from the L. lactis subsp. lactis genomic lineage. Cluster differentiation was highly correlated with small-subunit rRNA homology and multilocus sequence analysis (MLSA) studies. Additionally, the selected enzyme-primer combination generated L. lactis subsp. cremoris phenotype-specific fragments irrespective of the genotype. These phenotype-specific markers allowed the differentiation of L. lactis subsp. lactis phenotype from L. lactis subsp. cremoris phenotype strains within the same L. lactis subsp. cremoris type-strain-like genomic lineage, illustrating the potential of AFLP for the generation of phenotype-linked genetic markers.
Perceived risk and strategy efficacy as motivators of risk management strategy adoption to prevent animal diseases in pig farming
Valeeva, N.I. ; Asseldonk, M.A.P.M. van; Backus, G.B.C. - \ 2011
Preventive Veterinary Medicine 102 (2011)4. - ISSN 0167-5877 - p. 284 - 295.
mouth-disease - biosecurity - farmers - perceptions - dairy - hazard - herds - model
For Dutch fattening pig farms, this study explored (1) farmers’ perceptions towards animal disease risks and animal health risk management; (2) factors underlying farmers’ adoption of the two risk management strategies, namely, biosecurity measures and animal health programs. The risks included endemic and epidemic diseases. Data were obtained through a questionnaire (n = 164). A behavioral model was developed using the Health Belief Model and tested using structural equation modeling. Endemic and epidemic diseases were regarded as an operational and catastrophic risk, respectively. Farmers considered severity of epidemics as slightly more important, compared to endemics. For both disease categories, farmers valued biosecurity measures as a more effective strategy than animal health programs. In the behavioral model, perceived benefits in terms of strategy efficacy was the strongest direct predictor of strategy adoption. Other behavioral components had a minor indirect effect, namely, via perceived benefits, and only in case of biosecurity measures. The indirect effect path did, however, vary per disease category. For endemics, such a path captured the effect of perceived susceptibility on perceived benefits mediated by perceived severity. For epidemics, it only captured the effect of perceived severity on perceived benefits. The results also revealed the importance of innate risk characteristics of farmers in their adoption decisions. In particular, general self-protection behavior directly contributed to decisions to adopt a certain strategy. The obtained knowledge highlights possible ways of improvement of programs aimed at promoting effective risk management strategies.
Process audits versus product quality monitoring of bulk milk
Velthuis, A.G.J. ; Asseldonk, M.A.P.M. van - \ 2011
Journal of Dairy Science 94 (2011)7. - ISSN 0022-0302 - p. 235 - 249.
butyric-acid bacteria - somatic-cell count - farm tank milk - assurance program - bacteriological quality - management-practices - recall costs - risk-factors - dairy - spores
The aim was to investigate whether on-line somatic cell count (SCC) assessment, when combined with electrical conductivity (EC), should be implemented at the udder quarter or at the cow level. Data were collected from 3 farms with automatic milking systems, resulting in 3,191 quarter milkings used in the analyses. Visual observations of foremilk and quarter milk samples for laboratory SCC analysis were used to define 2 gold standards. One was based on visual observation only and the other was based on a combination of visual observation and SCC (using a reference value of 500,000 cells/mL), which means that a quarter milking must have visually abnormal milk as well as an increased SCC to be categorized positive. On-line SCC assessment took place at the quarter level during the first part of the milking. Composite cow level samples were used for laboratory SCC analysis and to compare the performance of SCC assessment at quarter and cow levels. The EC at the quarter level was measured by in-line sensors of the automatic milking system. Alerts for SCC indicators were calculated based on straightforward reference values. Alerts for EC were based on straightforward reference values, or on interquarter ratios. The latter was calculated by dividing the value of a given quarter by the average value of the 2 lowest quarters of that milking. The EC and SCC indicators were combined with either a Boolean “and” or “or” function. Receiver operating characteristic curves were used to visually present results using different threshold values. Sensitivity, specificity, and success rate at the quarter level and false alert rate per 1,000 cow milkings were used to compare indicators at given sensitivity or specificity levels. Quarter level SCC assessment was superior to cow level assessment (transformed partial area under the curve = 0.70 vs. 0.62) when combined with EC measurement at quarter level. When aiming for the same sensitivity level (e.g., 50%) with all visual abnormal milk as the gold standard, more false alerts were generated with cow level assessment (137 per 1,000 cow milkings) compared with quarter level SCC assessment (75 per 1,000 cow milkings). As a comparison, using EC alone resulted in 292 false alerts per 1,000 cow milkings in the same situation. Therefore, it is concluded that quarter level SCC assessment was superior to cow level assessment when combined with EC measurement at quarter level. Key words: abnormal milk; detection; on-line assessment; somatic cell count
Genome-Scale Model of Streptococcus thermophilus LMG18311 for Metabolic Comparison of Lactic Acid Bacteria
Pastink, M.I. ; Teusink, B. ; Hols, P. ; Visser, S. ; Vos, W.M. de; Hugenholtz, J. - \ 2009
Applied and Environmental Microbiology 75 (2009)11. - ISSN 0099-2240 - p. 3627 - 3633.
lactobacillus-plantarum wcfs1 - lactococcus-lactis - amino-acids - acetaldehyde production - exponential-growth - natural diversity - cheese flavor - sequence - cremoris - dairy
In this report we describe amino acid-metabolism and amino acid-dependency of the dairy bacterium Streptococcus thermophilus LMG18311 and compare that with two other characterized lactic acid bacteria, Lactococcus lactis and Lactobacillus plantarum. Through the construction of a genome-scale metabolic model of S. thermophilus, the metabolic differences between the three bacteria were visualized by direct projection on a metabolic map. The comparative analysis revealed the minimal amino acid auxotrophy (only histidine and methionine or cysteine) of S. thermophilus LMG18311 and the broad variety of volatiles produced from amino acids compared to the other two bacteria. It also revealed the limited number of pyruvate branches, forcing this strain to use the homofermentative metabolism for growth optimization. In addition, some industrially-relevant features could be identified in S. thermophilus such as the unique pathway for acetaldehyde (yoghurt flavour) production and the absence of a complete pentose phosphate pathway
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