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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    Short communication: Genetic correlations between methane and milk production, conformation, and functional traits
    Pszczola, M. ; Calus, M.P.L. ; Strabel, T. - \ 2019
    Journal of Dairy Science 102 (2019)6. - ISSN 0022-0302 - p. 5342 - 5346.
    genetic correlations - methane production - sniffer

    Livestock produce CH 4 , therefore contributing to the global warming effect. One of the currently investigated solutions to reduce CH 4 production is selective breeding. The goal of this study was to estimate the genetic correlations between CH 4 and milk production, conformation, and functional traits used in the selection index for Polish-Holstein cows. In total, 34,429 daily CH 4 production observations collected from 483 cows were available, out of which 281 cows were genotyped. The CH 4 was measured using a so-called sniffer device installed in an automated milking system. Breeding values for CH 4 were estimated with the use of single-step genomic BLUP, and breeding values for remaining traits were obtained from the Polish national genomic evaluation. Genetic correlations between CH 4 production and remaining traits were estimated using bivariate analyses. The estimated genetic correlations were in general low. The highest values were estimated for fat yield (0.21), milk yield (0.15), chest width (0.15), size (0.15), dairy strength (0.11), and somatic cell count (0.11). These estimates, as opposed to estimates for the remaining traits, were significantly different from zero.

    Predicting methane emission of dairy cows using milk composition
    Gastelen, Sanne van - \ 2017
    Wageningen University. Promotor(en): W.H. Hendriks, co-promotor(en): J. Dijkstra; K.A. Hettinga. - Wageningen : Wageningen University - ISBN 9789463437097 - 266
    dairy cows - dairy cattle - methane production - emission - milk composition - fatty acids - cattle feeding - fermentation - nutrition physiology - animal nutrition - pollution - melkkoeien - melkvee - methaanproductie - emissie - melksamenstelling - vetzuren - rundveevoeding - fermentatie - voedingsfysiologie - diervoeding - verontreiniging

    Enteric methane (CH4) is produced as a result of microbial fermentation of feed components in the gastrointestinal tract of ruminant livestock. Methane has no nutritional value for the animal and is predominately released into the environment through eructation and breath. Therefore, CH4 not only represents a greenhouse gas contributing to global warming, but also an energy loss, making enteric CH4 production one of the main targets of greenhouse gas mitigation practices for the dairy industry. Obviously, reduction of CH4 emission could be achieved by simply reducing livestock numbers. However, the global demand for dairy products has been growing rapidly and is expected to further grow in the future. Therefore, it is critical to minimize environmental impact to produce high-quality dairy products. The overall aim of this PhD research was, therefore, to develop a proxy for CH4 emission that can be measured in milk of dairy cows.

    There are currently a number of potentially effective dietary CH4 mitigation practices available for the livestock sector. The results of Chapter 3 show that replacing fiber-rich grass silage with starch-rich corn silage in a common forage-based diet for dairy cattle offers an effective strategy to decrease enteric CH4 production without negatively affecting dairy cow performance, although a critical level of starch in the diet seems to be needed. Little is known whether host genetics may influence the CH4 emission response to changes in diet. Therefore, the interaction between host DGAT1 K232A polymorphism with dietary linseed oil supplementation was evaluated in Chapter 7. The results of Chapter 7 indicate that DGAT1 K232A polymorphism is associated with changes in milk composition, milk N efficiency, and diet metabolizability, but does not affect digestibility and enteric CH4 emission, whereas linseed oil reduces CH4 emission independent of the DGAT1 K232A polymorphism.

    Accurate and repeatable measurements of CH4 emission from individual dairy cows are required to assess the efficacy of possible mitigation strategies. There are several techniques to estimate or measure enteric CH4 production of dairy cows, including climate respiration chambers, but none of these techniques are suitable for large scale precise and accurate measurements. Therefore, the potential of various metabolites in milk, including milk fatty acids (MFA), as a proxy (i.e., indicators or animal traits that are correlated with enteric CH4 production) for CH4 emission of dairy cows gained interest. Until recently, gas chromatography was the principal method used to determine the MFA profile, but this technique is unsuitable for routine analysis. This has led to the application of Fourier-transform infrared spectroscopy (FTIR) for determination of the MFA profile. Chapter 2 provides an overview of the recent research that relates MFA with CH4 emission, and discusses the opportunities and limitations of using FTIR to estimate, indirectly via MFA or directly, CH4 emission of dairy cattle. The recent literature on the relationship between MFA and CH4 emission gives inconsistent results. Where some studies found a clear and strong relation, other studies consider MFA to be unreliable predictors for CH4 emitted by dairy cows. Even the studies that do find a clear relation between MFA and CH4 emissions do not describe similar prediction models using the same MFA. These discrepancies can be the result of many factors, including dietary composition and lactation stage. Additionally, literature showed that the major advantages of using FTIR to predict CH4 emission include its simplicity and potential practical application on a large scale. Disadvantages include the inability to predict important MFA for the prediction of CH4 emission, and the moderate power of FTIR to directly predict CH4 emission. The latter was also demonstrated in Chapter 9, in which the CH4 prediction potential of MFA was compared with that of FTIR using data from 9 experiments (n = 218 individual cow observations) covering a broad range of roughage-based diets. The results indicate that MFA have a greater potential than FTIR spectra to estimate CH4 emissions, and that both techniques have potential to predict CH4 emission of dairy cows, but also limited current applicability in practice. Much focus has been placed on the relationship between MFA and CH4 emission, but milk also contains other metabolites, such as volatile and non-volatile metabolites. Currently, milk volatile metabolites have been used for tracing animal feeding systems and milk non-volatile metabolites were shown to be related to the health status of cows. In Chapter 4, the relationship between CH4 emission and both volatile and non-volatile metabolites was investigated, using data and milk samples obtained in the study described in Chapter 3. In general, the non-volatile metabolites were more closely related to CH4 emissions than the volatile metabolites. More specifically, the results indicate that CH4 intensity (g/kg fat- and protein-corrected milk; FPCM) may be related to lactose synthesis and energy metabolism in the mammary gland, as reflected by the milk non-volatile metabolites uridine diphosphate-hexose B and citrate. Methane yield (g/kg dry matter intake) on the other hand, may be related to glucogenic nutrient supply, as reflected by the milk non-volatile acetone. Based on the metabolic interpretations of these relationships, it was hypothesized that the addition of both volatile and non-volatile metabolites in a prediction model with only MFA would enhance its predictive power and, thus, leads to a better proxy in milk for enteric CH4 production of dairy cows. This was investigated in Chapter 5, again using data and milk samples described in Chapter 3. The results indicate that MFA alone have moderate to good potential to estimate CH4 emission. Furthermore, including volatile metabolites (CH4 intensity only) and non-volatile metabolites increases the CH4 emission prediction potential.

    The work presented in Chapters 3, 4 and 5, was based upon a small range of diets (i.e., four roughage-based diets in which grass silage was replaced partly or fully by corn silage) of one experiment. Therefore, in Chapter 6, the relationship between CH4 emission and the milk metabolome in dairy cattle was further quantified. Data (n = 123 individual cow observations) were used encompassing a large of roughage-based diets, with different qualities and proportions of grass, grass silage and corn silage. The results show that changes in individual milk metabolite concentrations can be related to the ruminal CH4 production pathways. These relationships are most likely the result from changes in dietary composition that affect not only enteric CH4 production, but also the profile of volatile and non-volatile metabolites in milk. Overall, the results indicate that both volatile and non-volatile metabolites in milk might provide useful information and increase our understanding of CH4 emission of dairy cows. However, the development of CH4 prediction models revealed that both volatile and non-volatile metabolites in milk hold little potential to predict CH4 emissions despite the significant relationships found between individual non-volatile metabolites and CH4 emissions. Additionally, combining MFA with milk volatile metabolites and non-volatile metabolites does not improve the CH4 prediction potential relative to MFA alone. Hence, it is concluded that it is not worthwhile to determine the volatile and non-volatile metabolites in milk in order to estimate CH4 emission of dairy cows.

    Overall, in comparison with FTIR, volatile and non-volatile metabolites, the MFA are the most accurate and precise proxy in milk for CH4 emission of dairy cows. However, most of MFA-based models to predict CH4 emission tend to be accurate only for the production system and the environmental conditions under which they were developed. In Chapter 8 it was demonstrated that previously developed MFA-based prediction equations did not predict CH4 emission satisfactory of dairy cows with different DGAT1 genotypes or fed diets with or without linseed oil. Therefore, the greatest shortcoming today of MFA-based CH4 prediction models is their lack of robustness. Additionally, MFA have restricted practical application, meaning that most MFA retained in the current CH4 prediction models cannot be determined routinely because of the use of gas chromatography. The MFA that can be determined with the use of infrared spectroscopy are however no promising predictors for CH4 emission. Furthermore, MFA have only a moderate CH4 prediction potential. This together suggests that it might not be the best option to focus in the future on MFA alone as a proxy for CH4 emission of dairy cows.

    The FTIR technique has a low to moderate CH4 prediction potential. However, FTIR has a great potential for practical high throughput application, facilitating repeated measurements of the same cow potentially reducing random noise. Results of this thesis also demonstrated that FTIR spectra do not have the potential to detect differences in CH4 emission between diets which are, in terms of forage level and quality, commonly fed in practice. Moreover, the robustness of FTIR spectra is currently unknown. Hence, it remains to be investigated whether FTIR spectra can predict CH4 emissions from dairy cows housed under different conditions from those under which the FTIR-based prediction equations were developed. It is therefore concluded that the accuracy and precision to predict CH4 emission using FTIR needs to increase, and the capacity of FTIR to evaluate the differences in CH4 emission between dairy cows and different types of diets needs to improve, in order to actually be a valuable proxy for CH4 emission of dairy cows.

    Genetic improvement of feed intake and methane emissions of cattle
    Manzanilla Pech, Coralia I.V. - \ 2017
    Wageningen University. Promotor(en): Roel Veerkamp, co-promotor(en): Yvette de Haas. - Wageningen : Wageningen University - ISBN 9789463430692 - 199
    cattle - feed intake - methane production - genetic improvement - genetic parameters - conformation - breeding value - animal genetics - rundvee - voeropname - methaanproductie - genetische verbetering - genetische parameters - bouw (dier) - fokwaarde - diergenetica

    Feed costs represent half of the total costs of dairy production. One way to increase profitability of dairy production is to reduce feed costs by improving feed efficiency. As DMI is a trait that varies significantly during and across lactations, it is imperative to understand the underlying genetic architecture of DMI across lactation. Moreover, phenotypes of DMI are scarce, due to the difficulty of recording them (expensive and labor-intensive). Some predictor traits have been suggested to predict DMI. Examples of these predictor traits are those related to production (milk yield (MY) or milk content) or to the maintenance of the cow (body weight (BW) or conformation traits). The ability to determine when predictor traits ideally should be measured in order to achieve an accurate prediction of DMI throughout the whole lactation period is thus important. Recently, with the use of information of single nucleotide polymorphism (SNP) markers, together with phenotypic data and pedigree, genomically estimated breeding values (GEBV) of scarcely recorded traits, such as DMI, have become easier to accurately predict. This approach, combined with predictor traits, could contribute to an increased accuracy of predictions of GEBV of DMI. Methane (CH4) is the second important greenhouse gas, and enteric CH4 is the largest source of anthropogenic CH4, representing 17% of global CH4 emissions. Furthermore, methane emissions represent 2-12% of feed energy losses. Selecting for lower CH4 emitting animals and more feed-efficient animals would aid in mitigating global CH4 emissions. To identify the impact on CH4 emissions of selecting for lower DMI animals, it is important to determine the correlations between DMI and CH4 and to identify whether the same genes that control DMI affect CH4. Therefore, the general objectives of this thesis were to (1) explore the genetic architecture of DMI during lactation, (2) study the relationship of DMI to conformation, production and other related traits, (3) investigate the correlations between DMI and methane traits, and determine the SNP in common between DMI and CH4 through a genome-wide association study (GWAS), and (4) investigate the accuracy of predictions of DMI using predictor traits combined with genomic data.

    Low Emission Feed : using feed additives to decrease methane production in dairy cows
    Klop, G. - \ 2016
    Wageningen University. Promotor(en): Wouter Hendriks, co-promotor(en): Jan Dijkstra; Andre Bannink. - Wageningen : Wageningen University - ISBN 9789462578944 - 168
    feeds - emission - feed additives - dairy cows - methane production - nitrates - docosahexaenoic acid - milk composition - voer - emissie - voedertoevoegingen - melkkoeien - methaanproductie - nitraten - docosahexaeenzuur - melksamenstelling

    Research into manipulating methane (CH4) production as a result of enteric fermentation in ruminants currently receives global interest. Using feed additives may be a feasible strategy to mitigate CH4 as they are supplied in such amounts that the basal diet composition will not be largely affected. The latter is relevant because ruminants have the capacity to convert human inedible feedstuffs into human edible energy and protein. However, the application of CH4 mitigation feed additives may be hampered by several negative side effects including trade-offs with other environmental impacts, negative effects on animal performance, and lack of persistency of the mitigating effect. The research described in this thesis addresses both the mitigating effect of feed additives as well as its persistency. The main focus was on investigating additivity of the CH4 mitigating effect of feed additives, on the adaptation of rumen microbes to long term feeding of feed additives, and on exploring the potential of rotational feeding of additives to avoid (or reduce) microbial adaptation.

    In an experiment with lactating dairy cows in climate respiration chambers to study potential interactions between the effects of feeding nitrate and docosahexaenoic acid (DHA; C22:6 n-3) on enteric CH4 production, the effects of nitrate and DHA on CH4 yield [g/kg dry matter intake (DMI)] and CH4 intensity [g/kg fat- and protein- corrected milk (FPCM)], were additive (Chapter 2). Nitrate decreased CH4 irrespective of the unit in which it was expressed, and the average decline in CH4 emission corresponds to 85% of the stoichiometric potential of nitrate to decrease CH4. Feeding DHA had no effect on CH4 yield, but resulted in a higher CH4 intensity, because of milk fat depression. The interaction effect between nitrate and DHA on fiber digestibility indicated that negative effects of nitrate on apparent total tract digestibility of nutrients were alleviated by DHA, probably due to an altered feed intake pattern.

    Using an isotope measurement protocol in the same study, it was demonstrated that effects of nitrate as a CH4 mitigating feed additive on fiber degradation in the rumen can be detected by evaluating diurnal patterns of 13C enrichment of exhaled CO2 (Chapter 3). Feeding nitrate, but not DHA, resulted in a pronounced increase in 13C enrichment of CO2 in the first 3 to 4 h after feeding only. Results support the hypothesis that effects of a feed additive on the rate of fiber degradation in the rumen can be detected by evaluating diurnal patterns of 13C enrichment of CO2. A prerequisite for this detection method is that the main ration components differ in natural 13C enrichment (e.g., C3 and C4 plants), and in content of the nutrients that are expected to be involved in a shift in fermentation (e.g., starch and fiber) or in degradability of a nutrient.

    In a combined in vivo and in vitro trial, the adaptation to CH4 mitigating feed additives, viz. an essential oil blend or lauric acid (C12:0), compared with a control diet was first investigated using the in vitro gas production technique during the period that lactating cows were adapting to certain feed additives (Chapter 4). Rumen fluid was collected from each cow at several days relative to the introduction of the additives in the diets and used as inoculum for the gas production experiment with each of the three different substrates that reflected the treatment diets offered to the cows. The feed additives in the donor cow diet had a stronger effect on in vitro gas and CH4 production than the same additives in the incubation substrate. From day 4 onwards, the C12:0 diet persistently reduced gas and CH4 production, total volatile fatty acid concentration, acetate molar proportion and in vitro organic matter degradation, and increased propionate molar proportion. In contrast, in vitro CH4 production was reduced by the essential oils diet on day 8, but not on days 15 and 22. In line with these findings, the molar proportion of propionate in fermentation fluid was higher, and that of acetate smaller, for the essential oils diet than for the control diet on day 8, but not on days 15 and 22. Overall, the data indicate a transient effect of the essential oils on CH4 production, which may indicate microbial adaptation, whereas the CH4 mitigating effect of C12:0 persisted. It is recommended that this phenomenon is considered in the planning of future studies on the mitigation potential of feed additives in vitro.

    In a follow-up in vivo study, it was investigated whether the alternate feeding of two CH4 mitigating feed additives with a different mode of action (viz. C12:0 and a blend of essential oils) would result in a persistently lower CH4 production compared to feeding a single additive over a period of 10 weeks. The experiment comprised a pre-treatment period and three two-week measurement periods, with two periods of 2 weeks in between in which CH4 emission was not measured. Cows received either continuously the essential oil blend, or both the essential oil blend and C12:0 following a weekly rotation schedule (Chapter 5). Both CH4 yield and CH4 intensity changed over time, but were not affected by treatment. Methane yield and intensity were significantly lower (12 and 11%, respectively) in period 1 compared with the pre-treatment period, but no significant difference relative to the pre-treatment period was observed in period 3 (numerically 9 and 7% lower, respectively) and in period 5 (numerically 8 and 4% lower, respectively). These results indicate a transient decrease in CH4 yield and intensity in time, but no improvement in extent or persistency of CH4 reduction due to rotational feeding of essential oils and C12:0 in lactating dairy cows. However, there were indications that the concept of rotation may be effective and warrants further investigation.

    The additives and concepts tested in this thesis are applied under specific experimental conditions. More mechanistic understanding is required to predict the response of the same additives when supplemented to other basal diets or cows in a different physiological state. Trade-offs in environmental impact, and effects on cow health and performance, and on milk processing parameters and food safety are important aspects to consider in future research on the application of feed additives as CH4 mitigation strategy.

    Sainfoin (Onobrychis viciifolia) : a forgotten crop for dairy cows with future potential
    Huyen, Nguyen Thi - \ 2016
    Wageningen University. Promotor(en): Wouter Hendriks, co-promotor(en): Wilbert Pellikaan; Martin Verstegen. - Wageningen : Wageningen University - ISBN 9789462577268 - 160
    onobrychis viciifolia - dairy cows - fodder legumes - fodder crops - legume silage - rumen digestion - nutrition physiology - methane production - milk yield - dairy performance - animal nutrition - onobrychis viciifolia - melkkoeien - voederpeulvruchten - voedergewassen - peulvruchtenkuilvoer - pensvertering - voedingsfysiologie - methaanproductie - melkopbrengst - melkresultaten - diervoeding

    Sainfoin (Onobrychis viciifolia): a forgotten crop for dairy cows with future potential

    SUMMARY

    The world population growth and rising incomes are expected to increase the consumption of animal-derived foods such as meat, eggs and milk. However, livestock production should not only be directed towards increasing productivity but should also incorporate environmental, food safety and animal welfare aspects. Therefore, farm businesses have to respond to the high environment impact of their activities, by using low-input systems including the use of forage legumes. Recent studies have demonstrated that forage legumes with moderate levels of condensed tannins (CT) are beneficial for animal nutrition and animal health. Sainfoin (Onobrychis viciifolia Scop.) is a tanniniferous forage legume containing CT that has potential nutritional and health benefits, i.e. preventing bloating, reducing nematode larval establishment, improving nitrogen (N) utilization and reducing greenhouse gas and N emissions (Chapter 1). However, the use of sainfoin as a fodder crop in dairy cow rations in northwestern Europe is still rather unknown. This thesis investigated the potential of sainfoin in the dairy cow diets and the effect of CT structural properties on rumen fermentation and biohydrogenation (BH).

    Chapter 2 reports a study where the effect of sainfoin silage on nutrient digestibility, animal performance, energy and N utilization and methane (CH4) production in dairy cows was investigated. Six rumen cannulated, lactating dairy cows were randomly assigned to either a control (CON) or sainfoin based (SAIN) diet. The CON diet was a mixture of grass silage, corn silage, concentrate and linseed. In the SAIN diet, 50% of the grass silage DM in the CON diet was exchanged by sainfoin silage. Total daily dry matter (DM), organic matter (OM) and neutral detergent fiber (NDF) intake did not differ between the two diets. The apparent digestibility of DM, OM, NDF and acid detergent fiber (ADF) were respectively, 5.7, 4.0, 15.7 and 14.8% lower for the SAIN diet. Methane production per kg DM intake was lowest for the SAIN diet and CH4 production as a percentage of gross energy intakes tended to be lower while milk yield was greater for the SAIN diet. Nitrogen intake, N retention and energy retained in body protein were greater for the SAIN than the CON diet. Nitrogen retention as a percentage of N intake tended to be greater for the SAIN diet. These results showed that inclusion of sainfoin silage at the expense of grass silage in dairy cow rations reduced CH4 per kg DM intake. Although nutrient digestibility was decreased, sainfoin silage improved milk production and redirected metabolism towards body protein accretion at the expense of body fat.

    In Chapter 3, reticular fatty acid (FA) flow and ruminal BH of C18:3n-3 is reported using the reticular sampling technique (Cr-EDTA and Yb-acetate as digesta flow markers) in the lactating cows fed the SAIN and CON diet in Chapter 2. The reticular flows of DM, OM and N were not affected by dietary treatment. However, NDF flow was higher (1.87 vs. 1.40 kg/d) where the cows were fed the SAIN diet. A higher mono-unsaturated FA flow was caused by the higher trans-9-C18:1 and cis-9-C18:1 flow for the SAIN compared to the CON fed cows. The flows of trans-9,trans-12-C18:2 and cis-12,trans-10 C18:2 were higher in the SAIN diet fed cows, but total poly-unsaturated FA flow was not affected by the different diet treatments. The SAIN diet fed cows had a significant lower ruminal BH of cis-9-C18:1 and C18:3n-3, compared to the CON fed cows and tended to a lower ruminal BH in case of cis-9,cis-12-C18:2. These results show that inclusion of sainfoin silage at the expense of grass silage in dairy cow rations reduces ruminal BH of dietary cis-9-C18:1 and C18:3n-3.

    The effects of replacing grass silage by sainfoin silage in a TMR on milk production and FA in milk fat of the dairy cows in Chapter 2 is reported in Chapter 4. Milk yield reported in Chapter 4 was highest for the SAIN diet with every kg of OM digested of the SAIN diet resulting, on average, in 0.2 kg more milk production. The SAIN diet fed cows had a higher C18:3n-3 and cis-9,cis-12-C18:2 proportion in milk fat compared to the CON diet fed cows. A higher proportion of total trans-C18:1 was found in the cows fed the SAIN diet. There were no differences in proportion of total saturated and unsaturated FA in milk fat between the two diets. Our results showed that replacing grass silage by sainfoin silage improved milk yield and milk FA profile of dairy cows.

    Effects of the structural properties of CT, i.e. average polymer size (or mean degree of polymerization, mDP); percentage of cis flavan-3-ols (%cis) and percentage of prodelphinidins (%PD) in CT extracts on CH4 production and fermentation characteristics of rumen fluid using an in vitro gas production technique was investigated in Chapter 5. Extracts of CT from eight plants; black currant leaves, goat willow leaves, goat willow twigs, pine bark, red currant leaves, sainfoin plants, weeping willow catkins and white clover flowers were extracted, in order to obtain CT with a wide range in mDP, %PD and %cis. All CT extracts reduced CH4 concentration, decreased the maximum rate of fermentation for CH4 production and rate of substrate degradation. The correlation between CT structure on the one hand and CH4 production and fermentation characteristics on the other hand showed that the %PD within CT had the largest effect on fermentation characteristics, followed by mDP and %cis.

    Chapter 6 reports results of an in vitro study to investigate the effects of the structural properties CT (mDP, %cis and %PD) on rumen fermentation and BH end-products. The total volatile FA (VFA), ammonia concentration and the proportion of branched chain VFA was reduced in all CT extracts, compared to the control. The proportion of cis-9-C18:1; cis-9,cis-12-C18:2; cis-9,cis-12,cis-15-C18:3 were numerically higher in all CT sources, while the proportion of C18:0 and fractional rate of BH of C18:3n-3 were numerically lower in all CT sources, compared to the control. The correlation between CT structural properties on the one hand and fermentation and BH end-products on the other hand showed that the CT with a high %PD and smaller mDP had the largest effect on fermentation end-products. However, mDP was found to be the most important factor affecting rumen BH.

    Chapter 7 provides a general synthesis on the major findings of the studies presented in the preceding chapters. In addition, results are reported of a further in vitro as well as an in situ study in which I investigated the mechanisms of CT action in the rumen, in the post-rumen compartments and digestive tract. In the in situ study, fresh sainfoin (Esparcette) was incubated in the rumen and in the abomasum before digested during passage through the digestive tract. For the in vitro study, sainfoin (Ambra) was incubated with rumen fluid buffer for 1, 2, 4, 8, 12, 24 hours. After incubation in situ and in vitro, the incubated material was analyzed for tannin content by butanol-HCl assay. The results showed that the soluble CT dramatically reduced upon introduction in the digestive tract. Additional analyses showed that CT had bound to the fiber and protein (diet and microbes) fractions in the digestive tract.

    The present work showed that sainfoin silage can be used in dairy cow rations to improve milk production and N utilization and reduce CH4 emissions per kg DM intake. Moreover, sainfoin silage, when replacing part of the grass silage in a TMR of dairy cows, increases ruminal unsaturated FA flow into the reticulum and reduces ruminal BH of dietary cis-9-C18:1 and C18:3n-3. Cows fed sainfoin silage at the expense of grass silage in a TMR increase the proportion of unsaturated FA in milk fat. In terms of condensed tannin structure, mDP and %PD appear to be the most important properties of CT that affect fermentation and BH end-products. Condensed tannins with a mDP ranging from 5 to 10 monomeric units and a %PD > 70.0% seem to have the highest biological activity in the rumen.

    Measurement methods to assess methane production of individual dairy cows in a barn
    Wu, L. - \ 2016
    Wageningen University. Promotor(en): Peter Groot Koerkamp, co-promotor(en): Nico Ogink. - Wageningen : Wageningen University - ISBN 9789462577312 - 190
    dairy cows - cows - methane production - barns - measurement techniques - modeling - breath - uncertainty analysis - greenhouse gases - cubicles - melkkoeien - koeien - methaanproductie - landbouwschuren - meettechnieken - modelleren - adem - onzekerheidsanalyse - broeikasgassen - ligboxen

    Mitigation of methane production from dairy cows is critical to reduce the dairy industry’s contribution to the production of greenhouse gases. None of current used methane measurement methods are flawless and application of the methods is limited to assess the effects of methane mitigation methods under practical conditions. The main objective of this thesis is to design, test, and validate methods to determine or rank the methane production of individual dairy cows at farm house level.

    As a start, I evaluated merits and drawbacks of existing methane measurement methods and discussed against 14 requirements of methane measurement methods to assess methane mitigation strategies. This review study revealed that none of existing methods meet all requirements, and pointed out that sampling of breath air during the lying period of cows in cubicles could be a practical direction to measure methane production of individual cows under farm conditions. Therefore, we first assessed methane concentration levels and variations in time, and around cubicles, explored effects of barn and management factors on them, and assessed the effect of the variation of the background methane concentrations on assessing methane production of individual dairy cows in cubicles. Then, we designed and constructed an artificial reference cow (ARC) that mimics the methane production of real cows with known pre-set methane production rates and dynamics of eructations. With the acquired background information and the developed ARC, we assessed the uncertainty of a breath methane concentration (BMC) method in a feeder and developed a cubicle hood sampler (CHS) that measures methane fluxes from lying cows in cubicles. The observed uncertainty related to random errors of the BMC method can be overcome by sufficient numbers of repetitions. However identified uncertainty with a systematic nature, related to inconsistent relation between concentration and production rate, cannot be compensated by repeated measurements and requires further investigation into the widely used BMC method before it can be used with confidence. Compared to the BMC method, the developed CHS is not subject to such systematic effects and allows prolonged measurement periods. Performance test under field conditions showed that the designed CHS accurately measured methane fluxes provided by the ARC.

    Overall, in this thesis I assessed the measurement error of current three methane measurement principles (flux, breath concentration & tracer gas), provided information to limit the measurement variation, and assessed the availability to determine or rank the methane production of individual dairy cows at farm house level. The newly developed ARC can be used as a known reference source to calibrate and develop practical methane measurement methods, and the CHS is sufficiently accurate to measure methane production of individual cows at farm house level.

    Emissies naar lucht uit de landbouw, 1990-2013 : berekeningen van ammoniak, stikstofoxide, lachgas,methaan en fijn stof met het model NEMA
    Bruggen, C. van; Bannink, A. ; Groenestein, C.M. ; Huijsmans, J.F.M. ; Luesink, H.H. ; Sluis, S.M. ; Velthof, G.L. ; Vonk, J. - \ 2015
    Wettelijke Onderzoekstaken Natuur & Milieu (WOt-technical report 46) - 160
    luchtverontreiniging - ammoniakemissie - methaanproductie - dierlijke meststoffen - stikstof - intensieve veehouderij - fijn stof - begrazing - air pollution - ammonia emission - methane production - animal manures - nitrogen - intensive livestock farming - particulate matter - grazing
    Landbouwkundige activiteiten zijn een belangrijke bron van ammoniak (NH3), stikstofoxiden (NO), lachgas (N2O), methaan
    (CH4) en fijn stof (PM10 en PM2,5) in Nederland. De emissies voor de periode 1990-2013 zijn berekend met het National Emission
    Model for Agriculture (NEMA) met toepassing van nieuwe wetenschappelijke inzichten rond emissiefactoren voor ammoniak uit
    stallen en op basis van de nieuwe 2006 IPCC Guidelines. De rekenmethodiek gaat bij de berekening van de ammoniakemissie
    uit van de hoeveelheid totaal ammoniakaal stikstof (TAN) in de mest. De ammoniakemissie uit dierlijke mest, kunstmest en
    overige bronnen bedroeg in 2013 120 miljoen kg NH3, 1,5 miljoen kg minder dan in 2012, voornamelijk door meer emissiearme
    huisvesting bij varkens en pluimvee. De N2O-emissie bedroeg zowel in 2012 als in 2013 ruim 19 miljoen kg. De NO-emissie
    nam licht toe van 16,7 naar 16,9 miljoen kg. De methaanemissie nam toe van 487 tot 499 miljoen kg. De emissie van fijn stof
    nam licht toe van 6,4 miljoen kg PM10 in 2012 tot 6,5 miljoen kg in 2013 door een toename van het aantal leghennen. De
    emissie van PM2,5 bedroeg in beide jaren 0,6 miljoen kg. Sinds 1990 is de ammoniakemissie uit dierlijke mest en kunstmest
    met bijna 70% gedaald, vooral door een lagere stikstof-uitscheiding door landbouwhuisdieren en emissiearme mesttoedieningstechnieken.
    Lachgas en stikstofoxiden daalden in dezelfde periode eveneens, maar minder scherp (ca. 40%) vanwege hogere
    emissies door het ondergronds aanwenden van mest (N2O) en door de omschakeling van stalsystemen met dunne naar vaste
    mest bij pluimvee (N2O en NO). Tussen 1990 en 2013 daalde de emissie van methaan met 17%, wat vrijwel geheel verklaard
    kan worden door een afname in de dieraantallen
    Graskwaliteit beïnvloedt methaanuitstoot flink : Jong en hoog bemest gras zorgt voor minste methaanuitstoot per kg meetmelk
    Bannink, A. ; Dijkstra, J. - \ 2015
    Veeteelt Maart 1 (2015). - ISSN 0168-7565 - p. 30 - 30.
    dairy farming - fodder grasses - crop quality - emission reduction - methane production - grassland management - melkveehouderij - voedergrassen - gewaskwaliteit - emissiereductie - methaanproductie - graslandbeheer
    Het rantsoen heeft een grote invloed op de methaanuitstoot.
    Omdat gras een belangr k onderdeel is van het rantsoen, keken
    Wageningse onderzoekers naar de gevolgen van graskwaliteit op
    de methaanuitstoot. Een van de conclusies is dat een lichte maaisnede
    minder methaanuitstoot geeft per kilogram meetmelk.
    Low emission feed : opportunities to mitigate enteric methane production of dairy cows
    Hatew, B. - \ 2015
    Wageningen University. Promotor(en): Wouter Hendriks, co-promotor(en): Jan Dijkstra; Andre Bannink; Wilbert Pellikaan. - Wageningen : Wageningen University - ISBN 9789462574458 - 228
    melkkoeien - rundveevoeding - methaanproductie - milieueffect - pensfermentatie - voer - zetmeel - maïskuilvoer - graskuilvoer - diervoeding - dairy cows - cattle feeding - methane production - environmental impact - rumen fermentation - feeds - starch - maize silage - grass silage - animal nutrition

    As global demand for high-quality food originating from animal production is expected to rise due to an increasing human population and consumer income level, the expected role of ruminants in meeting this demand brings multiple challenges. Ruminant production needs to adapt to environmental changes and, at the same time, reduce its impact on the environment. Ruminants production systems have a major impact on the environment through the emission of greenhouse gases such as methane (CH4), nitrous oxide and carbon dioxide. Microbial fermentation of feeds in the gastrointestinal tract, known as enteric fermentation, is the main source of CH4 emissions from dairy production. Enteric CH4 emission is strongly related to the amount of feed fermented in the rumen, which depends on feed intake, feed composition and rumen fermentation conditions associated to the intrinsic characteristics of these feeds and the characteristics of the whole diet. Important gaps in knowledge remain however. The prime aim of this thesis was to investigate the effects of various feeding strategies to mitigate enteric CH4 emissions of dairy cows.

    First experiment was conducted to investigate the effects of type and level of starch in the concentrate. Inclusion of a high level (53%) of starch in the concentrate that accounted for 40% of the total mixed ration dry matter (DM) produced lower CH4 per unit of estimated rumen fermentable organic matter (eRFOM) than a low level (27% of DM) of starch (43.1 vs. 46.9 g/kg of eRFOM). Methane production per kg of eRFOM also was lower for diets based on rapidly fermentable starch (gelatinized maize grain) compared to diets based on slowly fermentable starch (native maize grain) (42.6 vs. 47.4 g/kg of eRFOM). However, inclusion of 53% of starch in the concentrate from both types of starch did not affect CH4 emission intensity (CH4 Ei) (CH4 emission per kg of fat- and protein-corrected milk; FPCM). In a subsequent experiment, maize silage was prepared from whole-plant maize harvested at a very early (25% DM), early (28% DM), medium (32% DM) and late (40% DM) stage of maturity and fed to dairy cows as an alternative to concentrate as starch source. Diet consisted of (on DM basis) 75% maize silage, 20% concentrate and 5% wheat straw. Increasing harvest maturity of maize silage linearly decreased CH4 yield (21.7, 23.0, 21.0 and 20.1 g/kg of DM intake) and CH4 emission as a fraction of gross energy intake (6.3, 6.7, 6.3 and 6.0%). Methane Ei tended to decrease linearly with maturity (13.0, 13.4, 13.2 and 12.1 g/kg FPCM). In another experiment grass silage as roughage source was tested. This experiment was designed to investigate the effects of N fertilisation of grassland and maturity of grass at cutting on CH4 emission in dairy cows. Two N fertilisation rates (65 vs. 150 kg of N/ha) were examined in combination with three stages of grass maturity (early, 28 days of regrowth; mid, 41 days of regrowth; and late, 62 days of regrowth). Diet contained 80:20 ratio (on DM basis) of grass silage (mainly ryegrass) and concentrate. Dry matter intake decreased with N fertilisation and maturity, and FPCM decreased with maturity but was unaffected by N fertilisation. Methane Ei (mean 15.0 g/kg of FPCM) increased by 31% and CH4 per unit digestible OM intake (mean 33.1 g/kg of DOMI) increased by 15% with increasing maturity. Methane yield (mean 23.5 g/kg of DM intake) and CH4 as a fraction of gross energy intake (mean 7%) increased by 7 and 9% with maturity, respectively, which implies an increased loss of dietary energy with progressing grass maturity. Rate of N fertilisation had no effect on CH4 Ei and CH4 yield.

    Despite the importance of in vitro gas production technique for evaluating feeds, in vitro study as a stand-alone approach was considered inadequate to fully evaluate the potential effect of feeds and rumen fermentation modifiers on CH4 production, because in vitro studies are frequently performed separately rather than in parallel with in vivo studies. To test this hypothesis, both in vitro and in vivo CH4 measurements were measured simultaneously using cows in the first experiment that were fed (and adapted to) the same dietary material used as a substrate for in vitro incubation, as donor for microbial inoculum. It was found that 24-h in vitro CH4 (mL/g of incubated organic matter) correlated well with in vivo CH4 when expressed per unit of eRFOM (R2 = 0.54), but not when expressed per unit of organic matter ingested (R2 = 0.04). In the same experiment, results showed that incubation of the same substrate with rumen inocula obtained from donor cows adapted to different diets produced a variable amount of CH4 suggesting that it is important to consider the diet of the donor animal when collecting rumen inocula for in vitro incubation. Even though the in vitro technique has limitations to represent in vivo conditions, it is useful for screening of large sets of animal feeds or feed additives to be used as a CH4 mitigation strategy. In this thesis, two in vitro experiments were conducted to examine the effects of variation in structural composition of condensed tannins (CT) in sainfoin accessions collected from across the world on CH4 production, and CT extracts obtained from a selected sainfoin accessions on CH4 production. Results revealed substantial variation among CT in their effect on in vitro CH4 production and this variation was attributed to differences in chemical structure of CT. Condensed tannins evaluated in this thesis showed to have potential to reduce in vitro CH4 production, but require further investigations to fully evaluate their in vivo effects.

    In conclusion, results from the research work conducted in this thesis show that changes in the basal diet of dairy cows and in roughage production management can substantially reduce the amount of enteric CH4 produced and thereby influence the impact of dairy production on the environment.

    Methaanproductie van dikke mestfracties: met en zonder voorbehandeling
    Timmerman, M. ; Buisonjé, F.E. de - \ 2015
    Wageningen : Wageningen UR Livestock Research (Livestock Research rapport 838) - 33
    methaanproductie - dierlijke meststoffen - voorbehandeling - mestvergisting - biogas - co-vergisting - landbouw en milieu - gasproductie - biobased economy - methane production - animal manures - pretreatment - manure fermentation - biogas - co-fermentation - agriculture and environment - gas production - biobased economy
    This report presents the international knowledge about the methane yields of solid manure fractions and the possibilities to increase the methane yields by pre-treatment. The methane yields of solids fractions in batch tests were globally in the range of 40 to 60 m3 per tonne. Promising pre-treatment technologies to increase the methane yield are: thermal treatment, two-stage digestion, steam explosion and thermochemical pre-treatment. Most research of pre-treatment technologies only looked at the increase in methane yield, but not at the increased consumption of electricity and chemicals nor at the economic return.
    Optimizing the performance of a reactor by reducing the retention time and addition of glycerin for anaerobically digesting manure
    Timmerman, M. ; Schuman, E. ; Eekert, M. ; Riel, J.W. van - \ 2015
    Environmental Technology 36 (2015)10. - ISSN 0959-3330 - p. 1223 - 1236.
    co-digestion - methane production - crude glycerin - cattle manure - biogas - waste - biogasification - inhibition - ammonia
    Anaerobic digestion of manure is a widely accepted technology for energy production. However, only a minimal portion of the manure production in the EU is anaerobically digested and occurs predominantly in codigestion plants. There is substantial potential for biogas plants that primarily operate on manure (>90%); however, the methane yields of manure are less compared to coproducts, which is one of the reasons for manure-based biogas plants often being economically non-viable. Therefore, it is essential to begin increasing the efficiency of these biogas plants. This study investigated the effect of decreasing retention time and introducing a moderate amount of glycerin on the biogas production as methods to improve efficiency. An experiment has been conducted with two different manure types in four biogas reactors. The results of the study demonstrated that, first, it was possible to decrease the retention time to 10–15 days; however, the effect on biogas production varied per manure type. Secondly, the biogas production almost triples at a retention time of 15.6 days with an addition of 4% glycerin. The relative production-enhancing effect of glycerin did not vary significantly with both manure types. However, the absolute production-enhancing effect of glycerin differed per manure type since the biogas production per gram VS differed per manure type. Thirdly, the positive effect of the glycerin input declines with shorter retention times. Therefore, the effect of glycerin addition depends on the manure type and retention time.
    Impact of crop-manure ratios on energy production and fertilizing characteristics of liquid and solid digestate during codigestion
    Pabon Pereira, C.P. ; Vries, J.W. de; Slingerland, M.A. ; Zeeman, G. ; Lier, J.B. van - \ 2014
    Environmental Technology 35 (2014)19. - ISSN 0959-3330 - p. 2427 - 2434.
    anaerobic co-digestion - methane production - biogas production - cattle manure - grass-silage - pig manure - maize - residues - sludge - slurry
    The influence of maize silage-manure ratios on energy output and digestate characteristics was studied using batch experiments. The methane production, nutrients availability (N and P) and heavy metals' content were followed in multiflask experiments at digestion times 7, 14, 20, 30 and 60 days. In addition, the available nutrient content in the liquid and solid parts of the digestate was evaluated. Aanaerobic digestion favoured the availability of nutrients to plants, after 61 days 20-26% increase in NH4+ and 0-36% increase in PO43- were found in relation to initial concentrations. Digestion time and maize addition increased the availability of PO43-. Inorganic nutrients were found to be mainly available in the liquid part of the digestate, i.e. 80-92% NH4+ and 65-74% PO43-. Manure had a positive effect on the methane production rate, whereas maize silage increased the total methane production per unit volatile solids in all treatments.
    Methaanemissie op het melkveebedrijf : impactanalyse voor reductiemaatregelen en doorrekening daarvan in de Kringloopwijzer
    Šebek, L.B. ; Haan, M.H.A. de; Bannink, A. - \ 2014
    Wageningen : Wageningen UR Livestock Research (Rapport / Wageningen UR Livestock Research 796) - 38
    melkveebedrijven - methaanproductie - methaanremmers - broeikasgassen - koolstofcyclus - melkvee - mest - voer - diervoedering - melkveehouderij - emissiereductie - dairy farms - methane production - methane inhibitors - greenhouse gases - carbon cycle - dairy cattle - manures - feeds - animal feeding - dairy farming - emission reduction
    Voor u ligt het rapport ‘Methaanemissie op het melkveebedrijf: Impactanalyse voor reductiemaatregelen en doorrekening daarvan in de KringloopWijzer’. Het rapport geeft antwoord op de vraag van het Nederlandse diervoederbedrijfsleven om inzicht te geven in de relevantie en mogelijkheden voor aanpassing van de rekenregels in de KringloopWijzer. Het betreft de rekenregels voor methaanemissie uit de veestapel met als doel het effect van sturen op voerfactoren volledig in te rekenen. Door volledig inrekenen van voerfactoren wordt, met betrekking tot de vermindering van de methaanemissie, het handelingsperspectief duidelijk van zowel diervoederbedrijfsleven als (melk)veehouder.
    Long-term acclimation of anaerobic sludges for high-rate methanogenesis from LCFA
    Silva, S.A. ; Cavaleiro, A.J. ; Pereira, M.A. ; Stams, A.J.M. ; Alves, M.M. ; Sousa, D.Z. - \ 2014
    Biomass and Bioenergy 67 (2014). - ISSN 0961-9534 - p. 297 - 303.
    chain fatty-acids - oleic-acid - oxidizing bacteria - methane production - waste-water - digestion - lipids - quantification - hybridization - accumulation
    Inhibition of methanogens by long chain fatty acids (LCFA) and the low numbers of LCFA-degrading bacteria are limitations to exploit biogas production from fat-rich wastewaters. Generally reactors fail due to excessive LCFA accumulation onto the sludge. Here, long-term acclimation and bioaugmentation with a LCFA-degrading coculture were hypothesized as strategies to enhance methanogenic conversion of these compounds. Anaerobic sludges previously exposed to LCFA for more than 100 days converted a specific biomass-associated substrate of (3.2 ± 0.1) kg·kg-1 with very short lag phases (
    Bioelectrochemical methane production from CO2
    Eerten-Jansen, M.C.A.A. van - \ 2014
    Wageningen University. Promotor(en): Cees Buisman, co-promotor(en): Annemiek ter Heijne. - Wageningen : Wageningen University - ISBN 9789462570061 - 189
    methaanproductie - hernieuwbare energie - kooldioxide - elektrochemie - technieken - methane production - renewable energy - carbon dioxide - electrochemistry - techniques

    Nowadays, most of our energy and fuels are produced from fossil resources. Fossil resources are, however, finite and their use results in emissions that affect the environment and human health. For reasons of energy security and environmental sustainability, there is therefore a need to produce energy and fuels from renewable resources. However, currently several challenges need to be overcome before renewable resources can be implemented on a large scale for the production of renewable energy and fuels. At the moment, all the renewable resources can be converted into electricity. However, renewable electricity is often produced intermittently. Therefore, excess renewable electricity, when supply does not meet demand, needs to be stored not to get lost. On the other hand, fuels can currently only be produced directly from biomass. There are, however, discussions about whether sufficient biomass can be produced in a sustainable way to cover the global demand.

    A methane-producing Bioelectrochemical system (BES) is a novel technology to store excess renewable electricity in the form of methane, independent of biomass. Key principle of the methane-producing BES is the use of microorganisms as catalysts for the reduction of CO2 and electricity into methane. At the start of this thesis, the methane-producing BES was at its infancy, and for implementation of the technology a more thorough understanding of the technology was needed. Therefore, the aim of this thesis was to investigate the principles and perspectives of bioelectrochemical methane production from CO2. Focus was on the main bottlenecks limiting system’s performance.

    In Chapter 2, the performance of a flat-plate methane-producing BES that was operated for 188 days was studied. The methane production rate and energy efficiency were investigated with time to elucidate the main bottlenecks limiting system’s performance. Using water as electron donor at the anode, methane production rate was 0.12 mL CH4/m2 cathode per day and overall energy efficiency was 3.1% at -0.55 V vs. Normal Hydrogen Electrode (NHE) cathode potential during continuous operation. Analysis of the internal resistance showed that in the short term, cathode and anode losses were dominant, but with time also pH gradient and transport losses became important.

    Since the cathode energy losses were dominant, in Chapter 3, the microbial community that catalyses the reduction of CO2 into methane was studied. The microbial community was dominated by three phylotypes of methanogenic archaea, being closely related to Methanobacterium palustre and Methanobacterium aarhusense, and six phylotypes of bacteria. Besides methanogenic archaea, the bacteria seemed to be associated with methane production, producing hydrogen as intermediate. Biomass density varied greatly with part of the electrode being covered by a thick biofilm, whereas only clusters of biomass were found on other parts of the electrode.

    Based on the microbial community it seemed that methane was produced indirectly using hydrogen as electron donor. Therefore, the electron transfer mechanisms of bioelectrochemical methane production were investigated in Chapter 4. Understanding the electron transfer mechanisms could give insight in methods to steer the process towards higher rate. A mixed culture methane-producing biocathode was developed that produced 5.2 L methane/m2 cathode per day at -0.7 V vs. NHE cathode potential. To elucidate the formation of intermediates, methanogenic archaea in the biocathode were inhibited with 2-bromethanesulfonate. Methane was primarily produced indirectly using hydrogen and acetate as electron donor, whereas methane production via direct electron transfer hardly occurred.

    Besides producing methane, a BES could also be used to produce higher value organics, such as medium chain fatty acids. Currently, medium chain fatty acids are produced by fermenting (low-grade) organic biomass using an external electron donor, such as hydrogen and/or ethanol. A BES could provide the electrons in-situ, either as the electrode directly or indirectly via hydrogen. In Chapter 5, medium chain fatty acids production in a BES at -0.9 V vs. NHE cathode potential was demonstrated, without addition of an external electron mediator. Caproate (six carbon atoms), butyrate (four carbon atoms), and smaller fractions of caprylate (eight carbon atoms) were the main products formed from acetate (two carbon atoms). In-situ produced hydrogen was likely electron donor for the reduction of acetate. Electron and carbon balances revealed that 45% of the electrons in electric current and acetate, and 31% of the carbon in acetate were recovered in the formed products.

    In Chapter 6, the present performance of methane-producing BESs was evaluated. Analysis of the performances reported in literature did not reveal an increase with time. Based on the main bottlenecks that limit system’s performance as found in this thesis, methods to increase performance were discussed. Besides, we showed that our envisioned first application is to upgrade CO2 in biogas of anaerobic digestion to additional methane. Finally, the feasibility of production of higher-value organics, such as medium chain fatty acids, in BES was discussed.

    Role of protein-protein interactions on protein aggregation and emulsion flocculation
    Delahaije, R.J.B.M. - \ 2014
    Wageningen University. Promotor(en): Harry Gruppen, co-promotor(en): Peter Wierenga. - Wageningen : Wageningen University - ISBN 9789462570054 - 158
    methaanproductie - elektrochemie - kooldioxide - elektrolyse - microbiële brandstofcellen - duurzame energie - methane production - electrochemistry - carbon dioxide - electrolysis - microbial fuel cells - sustainable energy

    In this thesis, the effect of molecular properties on the aggregation and flocculation behaviour is studied. The aggregation behaviour was thought to be mainly affected by the structural stability of the protein. A decreased structural stability results in unfolded proteins which are more prone to aggregation. The flocculation behaviour was shown to be affected by the adsorbed amount at saturation and the adsorption rate. These parameters have been combined in a surface coverage model, which describes the stabilization of emulsions away from the iso‑electric point (pI) to be affected by excess protein in the continuous phase. In addition, a model was proposed for the prediction of the adsorbed amount at saturation. This is influenced by the protein charge and radius and system conditions (i.e. pH and ionic strength). The adsorption rate, which is a measure for the affinity of the protein towards the adsorption to the interface, was shown to increase with increasing relative exposed hydrophobicity and a decrease of the electrostatic repulsion (i.e. decrease of ionic strength or the protein charge). Close to the pI, the applicability of protein-stabilized emulsions is limited. Hence, a steric interaction was introduced to stabilize the emulsion. It was shown that glycation of the protein with a trisaccharide was sufficient to sterically stabilize the emulsions against pH-induced flocculation.

    Genomic selection for feed efficiency in dairy cattle
    Pryce, J.E. ; Wales, W.J. ; Haas, Y. de; Veerkamp, R.F. ; Hayes, B.J. - \ 2014
    Animal 8 (2014)01. - ISSN 1751-7311 - p. 1 - 10.
    body condition score - dry-matter intake - 1st 3 lactations - genetic-parameters - beef-cattle - methane production - production traits - energy-balance - live weight - random regression
    Feed is a major component of variable costs associated with dairy systems and is therefore an important consideration for breeding objectives. As a result, measures of feed efficiency are becoming popular traits for genetic analyses. Already, several countries account for feed efficiency in their breeding objectives by approximating the amount of energy required for milk production, maintenance, etc. However, variation in actual feed intake is currently not captured in dairy selection objectives, although this could be possible by evaluating traits such as residual feed intake (RFI), defined as the difference between actual and predicted feed (or energy) intake. As feed intake is expensive to accurately measure on large numbers of cows, phenotypes derived from it are obvious candidates for genomic selection provided that: (1) the trait is heritable; (2) the reliability of genomic predictions are acceptable to those using the breeding values; and (3) if breeding values are estimated for heifers, rather than cows then the heifer and cow traits need to be correlated. The accuracy of genomic prediction of dry matter intake (DMI) and RFI has been estimated to be around 0.4 in beef and dairy cattle studies. There are opportunities to increase the accuracy of prediction, for example, pooling data from three research herds (in Australia and Europe) has been shown to increase the accuracy of genomic prediction of DMI from 0.33 within country to 0.35 using a three-country reference population. Before including RFI as a selection objective, genetic correlations with other traits need to be estimated. Weak unfavourable genetic correlations between RFI and fertility have been published. This could be because RFI is mathematically similar to the calculation of energy balance and failure to account for mobilisation of body reserves correctly may result in selection for a trait that is similar to selecting for reduced (or negative) energy balance. So, if RFI is to become a selection objective, then including it in an overall multi-trait selection index where the breeding objective is net profit is sensible, as this would allow genetic correlations with other traits to be properly accounted for. If genetic parameters are accurately estimated then RFI is a logical breeding objective. If there is uncertainty in these, then DMI may be preferable.
    Emissies naar lucht uit de landbouw in 2012 : berekeningen van ammoniak, stikstofoxide, lachgas, methaan en fijn stof met het model NEMA
    Bruggen, C. van; Bannink, A. ; Groenestein, C.M. ; Haan, B.J. de; Huijsmans, J.F.M. ; Luesink, H.H. ; Sluis, S.M. ; Velthof, G.L. ; Vonk, J. - \ 2014
    Wageningen : Wettelijke Onderzoekstaken Natuur & Milieu (WOt-technical report 3) - 79
    luchtverontreiniging - ammoniakemissie - methaanproductie - dierlijke meststoffen - emissie - stikstof - intensieve veehouderij - fijn stof - landbouw - nederland - modellen - air pollution - ammonia emission - methane production - animal manures - emission - nitrogen - intensive livestock farming - particulate matter - agriculture - netherlands - models
    Landbouwkundige activiteiten zijn een belangrijke bron van ammoniak (NH3), stikstofoxide (NO), lachgas (N2O), methaan (CH4) en fijn stof in Nederland. De emissies voor de periode 1990-2012 zijn berekend met NEMA. In 2013 is NEMA uitgebreid met modules voor N2O, NO, CH4 en fijn stof. De rekenmethodiek gaat bij de berekening van de ammoniakemissie uit van de hoeveelheid totaal ammoniakaal stikstof (TAN) in de mest. De ammoniakemissie uit dierlijke mest en kunstmest bedroeg in 2012 ruim 108 miljoen kg NH3, 5 miljoen kg minder dan in 2011, voornamelijk door een lagere stikstofuitscheiding in dierlijke mest en een toename van de mestexport. In lijn hiermee nam de N2O-emissie af van 22,4 tot 21,7 miljoen kg. De NO-emissie nam af van 19,9 naar 19,1 miljoen kg. Sinds 1990 is de ammoniakemissie uit dierlijke mest en kunstmest met bijna 70% gedaald, vooral door een lagere stikstofuitscheiding door landbouwhuisdieren en emissiearme toedieningstechnieken. Lachgas en stikstofoxiden daalden in dezelfde periode eveneens, maar minder scherp (ca. 40%) vanwege hogere emissies door ondergronds aanwenden van mest (N2O) en door de omschakeling van stalsystemen met dunne naar droge mest bij pluimvee (N2O en NO). De totale emissie van methaan veranderde tussen 2011 en 2012 nauwelijks, en komt uit op 437,3 miljoen kg. Tussen 1990 en 2012 daalde de emissie met 14%, wat vrijwel geheel verklaard kan worden door een afname in de dieraantallen. Fijn stof ten slotte, daalde van 6,6 naar 6,4 miljoen kg PM10 als gevolg van het toenemende aandeel stallen met luchtwasser. Hiervan is 0,6 miljoen kg PM2,5.
    Variation in phosphorus content of milk from dairy cattle as affected by differences in milk composition
    Klop, G. ; Ellis, J.L. ; Blok, M.C. ; Brandsma, G.G. ; Bannink, A. ; Dijkstra, J. - \ 2014
    The Journal of Agricultural Science 152 (2014)5. - ISSN 0021-8596 - p. 860 - 869.
    environmental-impact - methane production - blood-plasma - beef-cattle - cows - excretion - prediction - magnesium - calcium
    In view of environmental concerns with regard to phosphorus (P) pollution and the expected global P scarcity, there is increasing interest in improving P utilization in dairy cattle. In high-producing dairy cows, P requirements for milk production comprise a significant fraction of total dietary P requirements. Although variation in P content of milk can affect the efficiency of P utilization for milk production (i.e. the fraction of ingested P that is incorporated in milk), this variation is poorly understood. It was hypothesized that the P content of milk is related to both milk protein and milk lactose content, but not necessarily to milk fat content. Three existing experiments comprising individual animal data on milk yield and fat, protein, lactose and P content of milk (in total 278 observations from 121 cows) were analysed to evaluate this hypothesis using a mixed model analysis. The models including the effects of both protein and lactose content of milk yielded better prediction of milk P content in terms of root-mean-square prediction error (RMSPE) and concordance correlation coefficient (CCC) statistics than models with only protein included as prediction variable; however, estimates of effect sizes varied between studies. The inclusion of milk fat content in equations already including protein and lactose did not further improve prediction of milk P content. Equations developed to describe the relationship between milk protein and lactose contents (g/kg) and milk P content (g/kg) were: (Expt 1) P in milk=-0·44(±0·179)+0·0253(±0·00300)×milk protein+0·0133(±0·00382)×milk lactose (RMSPE: 5·2%; CCC: 0·71); (Expt 2) P in milk=-0·26 (±0·347)+0·0174(±0·00328)×milk protein+0·0143 (±0·00611)×milk lactose (RMSPE: 6·3%; CCC: 0·40); and (Expt 3) P in milk=-0·36(±0·255)+0·0131(±0·00230)×milk protein+0·0193(±0·00490)×milk lactose (RMSPE: 6·5%; CCC: 0·55). Analysis of the three experiments combined, treating study as a random effect, resulted in the following equation to describe the same relationship as in the individual study equations: P in milk=-0·64(±0·168)+0·0223(±0·00236)×milk protein+0·0191(±0·00316)×milk lactose (RMSPE: 6·2%; CCC: 0·61). Although significant relationships between milk protein, milk lactose and milk P were found, a considerable portion of the observed variation remained unexplained, implying that factors other than milk composition may affect the P content of milk. The equations developed may be used to replace current fixed milk P contents assumed in P requirement systems for cattle.
    Autogenerative high pressure digestion : biogass production and upgrading in a single step
    Lindeboom, R.E.F. - \ 2014
    Wageningen University. Promotor(en): Jules van Lier, co-promotor(en): Jan Weijma; Caroline Plugge. - Wageningen : Wageningen University - ISBN 9789461738608 - 208
    biogas - spijsvertering - druk - methaanproductie - kooldioxide - zetmeel - hydrolyse - biogas - digestion - pressure - methane production - carbon dioxide - starch - hydrolysis
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