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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Symposium review: Uncertainties in enteric methane inventories, measurement techniques, and prediction models
Hristov, A.N. ; Kebreab, Ermias ; Niu, Mutian ; Oh, J. ; Bannink, A. ; Bayat, Ali R. ; Boland, Tommy ; Brito, A.F. ; Casper, D.P. ; Crompton, Les A. ; Dijkstra, J. ; Eugène, Maguy A. ; Garnsworthy, Phil C. ; Haque, N. ; Hellwing, Anne L.F. ; Huhtanen, Pekka ; Kreuzer, Michael ; Lund, Peter ; Madsen, Jørgen ; Martin, C. ; Moate, P.J. ; Muetzel, Stefan ; Muñoz, Camila ; Peiren, Nico ; Powell, J.M. ; Reynolds, Chris ; Schwarm, Angela ; Shingfield, Kevin J. ; Storlien, Tonje M. ; Weisbjerg, Martin Riis ; Yáñez-Ruiz, D.R. ; Yu, Z. - \ 2018
Journal of Dairy Science 101 (2018)7. - ISSN 0022-0302 - p. 6655 - 6674.
Ruminant production systems are important contributors to anthropogenic methane (CH4) emissions, but there are large uncertainties in national and global livestock CH4 inventories. Sources of uncertainty in enteric CH4 emissions include animal inventories, feed dry matter intake (DMI), ingredient and chemical composition of the diets, and CH4 emission factors. There is also significant uncertainty associated with enteric CH4 measurements. The most widely used techniques are respiration chambers, the sulfur hexafluoride (SF6) tracer technique, and the automated head-chamber system (GreenFeed; C-Lock Inc., Rapid City, SD). All 3 methods have been successfully used in a large number of experiments with dairy or beef cattle in various environmental conditions, although studies that compare techniques have reported inconsistent results. Although different types of models have been developed to predict enteric CH4 emissions, relatively simple empirical (statistical) models have been commonly used for inventory purposes because of their broad applicability and ease of use compared with more detailed empirical and process-based mechanistic models. However, extant empirical models used to predict enteric CH4 emissions suffer from narrow spatial focus, limited observations, and limitations of the statistical technique used. Therefore, prediction models must be developed from robust data sets that can only be generated through collaboration of scientists across the world. To achieve high prediction accuracy, these data sets should encompass a wide range of diets and production systems within regions and globally. Overall, enteric CH4 prediction models are based on various animal or feed characteristic inputs but are dominated by DMI in one form or another. As a result, accurate prediction of DMI is essential for accurate prediction of livestock CH4 emissions. Analysis of a large data set of individual dairy cattle data showed that simplified enteric CH4 prediction models based on DMI alone or DMI and limited feed- or animal-related inputs can predict average CH4 emission with a similar accuracy to more complex empirical models. These simplified models can be reliably used for emission inventory purposes.
Comparing and combining proxies for methane emission of lactating Holstein Friesian cows
Gastelen, S. van; Hettinga, K.A. ; Dijkstra, J. - \ 2018
Are dietary strategies to mitigate enteric methane emission effective across ruminant species?
Gastelen, S. van; Dijkstra, J. ; Bannink, A. - \ 2018
Responses to incomplete essential amino acid profiles at the same metabolizable protein supply lactating dairy cows
Nichols, K.E. ; Bannink, A. ; Dijkstra, J. - \ 2018
Multi-criteria evaluation of dairy cattle feed resources and animal characteristics of nutritive and environmental impacts
Lingen, H.J. van; Fadel, J.G. ; Bannink, A. ; Dijkstra, J. ; Tricarico, J.M. ; Pacheco, D. ; Casper, D.P. ; Kebreab, Ermias - \ 2018
Multi-criteria evaluation of diary cattle feed resources and animal characteristics for nutritive and environmental impacts
Lingen, H.J. van; Fadel, J.G. ; Bannink, A. ; Dijkstra, J. ; Tricarico, J.M. ; Pacheco, D. ; Casper, D.P. ; Kebreab, E. - \ 2018
Animal (2018). - ISSN 1751-7311 - 11 p.
On-farm nutrition and management interventions to reduce enteric CH4 (eCH4) emission, the most abundant greenhouse gas from cattle, may also affect volatile solids and N excretion. The objective was to jointly quantify eCH4 emissions, digestible volatile solids (dVS) excretion and N excretion from dairy cattle, based on dietary variables and animal characteristics, and to evaluate relationships between these emissions and excreta. Univariate and Bayesian multivariate mixed-effects models fitted to 520 individual North American dairy cow records indicated dry matter (DM) intake and dietary ADF and CP to be the main predictors for production of eCH4 emissions and dVS and N excreta (g/day). Yields (g/kg DM intake) of eCH4 emissions and dVS and N excreta were best predicted by dietary ADF, dietary CP, milk yield and milk fat content. Intensities (g/kg fat- and protein-corrected milk) of eCH4, dVS and N excreta were best predicted by dietary ADF, dietary CP, days in milk and BW. A K-fold cross-validation indicated that eCH4 and urinary N variables had larger root mean square prediction error (RMSPE; % of observed mean) than dVS, fecal N and total N production (on average 24.3% and 26.5% v. 16.7%, 15.5% and 16.2%, respectively), whereas intensity variables had larger RMSPE than production and yields (29.4%, 14.7% and 14.6%, respectively). Univariate and multivariate equations performed relatively similar (18.8% v. 19.3% RMSPE). Mutual correlations indicated a trade-off for eCH4v. dVS yield. The multivariate model indicated a trade-off between eCH4 and dVS v. total N production, yield and intensity induced by dietary CP content.
Short communication: Antimethanogenic effects of 3-nitrooxypropanol depend on supplementation dose, dietary fiber content, and cattle type
Dijkstra, J. ; Bannink, A. ; France, J. ; Kebreab, E. ; Gastelen, S. van - \ 2018
Journal of Dairy Science 101 (2018)10. - ISSN 0022-0302 - p. 9041 - 9047.
3-nitrooxypropanol - cattle - methane

3-Nitrooxypropanol (NOP) is a promising methane (CH4) inhibitor. Recent studies have shown major reductions in CH4 emissions from beef and dairy cattle when using NOP but with large variation in response. The objective of this study was to quantitatively evaluate the factors that explain heterogeneity in response to NOP using meta-analytical approaches. Data from 11 experiments and 38 treatment means were used. Factors considered were cattle type (dairy or beef), measurement technique (GreenFeed technique, C-Lock Inc., Rapid City, SD; sulfur hexafluoride tracer technique; and respiration chamber technique), dry matter (DM) intake, body weight, NOP dose, roughage proportion, dietary crude protein content, and dietary neutral detergent fiber (NDF) content. The mean difference (MD) in CH4 production (g/d) and CH4 yield (g/kg of DM intake) was calculated by subtracting the mean of CH4 emission for the control group from that of the NOP-supplemented group. Forest plots of standardized MD indicated variable effect sizes of NOP across studies. Compared with beef cattle, dairy cattle had a much larger feed intake (22.3 ± 4.13 vs. 7.3 ± 0.97 kg of DM/d; mean ± standard deviation) and CH4 production (351 ± 94.1 vs. 124 ± 44.8 g/d). Therefore, in further analyses across dairy and beef cattle studies, MD was expressed as a proportion (%) of observed control mean. The final mixed-effect model for relative MD in CH4 production included cattle type, NOP dose, and NDF content. When adjusted for NOP dose and NDF content, the CH4-mitigating effect of NOP was less in beef cattle (−22.2 ± 3.33%) than in dairy cattle (−39.0 ± 5.40%). An increase of 10 mg/kg of DM in NOP dose from its mean (123 mg/kg of DM) enhanced the NOP effect on CH4 production decline by 2.56 ± 0.550%. However, a greater dietary NDF content impaired the NOP effect on CH4 production by 1.64 ± 0.330% per 10 g/kg DM increase in NDF content from its mean (331 g of NDF/kg of DM). The factors included in the final mixed-effect model for CH4 yield were −17.1 ± 4.23% (beef cattle) and −38.8 ± 5.49% (dairy cattle), −2.48 ± 0.734% per 10 mg/kg DM increase in NOP dose from its mean, and 1.52 ± 0.406% per 10 g/kg DM increase in NDF content from its mean. In conclusion, the present meta-analysis indicates that a greater NOP dose enhances the NOP effect on CH4 emission, whereas an increased dietary fiber content decreases its effect. 3-Nitrooxypropanol has stronger antimethanogenic effects in dairy cattle than in beef cattle.

Feed and nitrogen efficiency are affected differently but milk lactose production is stimulated equally when isoenergetic protein and fat is supplemented in lactating dairy cow diets
Nichols, K. ; Bannink, A. ; Pacheco, S. ; Valenberg, H.J. van; Dijkstra, J. ; Laar, H. van - \ 2018
Journal of Dairy Science 101 (2018)9. - ISSN 0022-0302 - p. 7857 - 7870.
digestibility - hydrogenated palm fatty acid - milk lactose - rumen-protected protein

Fifty-six Holstein-Friesian cows were used in a randomized complete block design to test the effects of supplemental energy from protein (PT) and fat (FT) on lactation performance and nutrient digestibility in a 2 × 2 factorial arrangement. During the control period, cows were adapted for 28 d to a basal total mixed ration consisting of 34% grass silage, 33% corn silage, 5% grass hay, and 28% concentrate on a dry matter (DM) basis. Experimental rations were fed for 28 d immediately following the control period and consisted of (1) low protein, low fat (LP/LF), (2) high protein, low fat (HP/LF), (3) low protein, high fat (LP/HF), or (4) high protein and high fat (HP/HF). To obtain the HP and HF diets, intake of the basal ration was restricted and supplemented isoenergetically (net energy basis) with 2.0 kg/d of rumen-protected protein (soybean + rapeseed, 50:50 mixture on DM basis) and 0.68 kg/d of hydrogenated palm fatty acids (FA) on a DM basis. Milk production and composition, nutrient intake, and apparent digestibility were measured during the final 7 d of the control and experimental periods. No interaction was found between PT and FT on milk production and composition. Yields of milk, fat- and protein-corrected milk, and lactose increased in response to PT and FT and lactose concentration was unaffected by treatment. Milk protein concentration and yield increased in response to PT, and protein yield tended to increase in response to FT. Milk fat concentration and yield increased in response to FT and were unaffected by PT. Milk urea concentration increased and nitrogen efficiency decreased in response to PT. Feed and nitrogen efficiency were highest on the LP/HF diet and both parameters increased in response to FT, whereas milk urea concentration was not affected by FT. Energy from fat increased the concentration and yield of ≥16-carbon FA in milk and decreased the concentration of FA synthesized de novo, but had no effect on their yield. Concentration and yield of de novo-synthesized FA increased in response to PT. Concentration and yield of polyunsaturated FA increased and decreased in response to PT and FT, respectively. Apparent total-tract digestibility of crude fat decreased in response to PT, and FT increased crude protein digestibility. Energy supplementation through rumen-inert hydrogenated palm FA appears to be an efficient feeding strategy to stimulate milk production with regard to feed and nitrogen efficiency compared with supplementing an isoenergetic level of rumen-protected protein.

Technische Briefing Kringlooplandbouw; Notitie opgesteld op verzoek van de Tweede Kamer Commissie LNV : Wat mogen we verwachten van een circulaire voedselproductie gebaseerd op een kringlooplandbouw, in het perspectief van klimaat- en biodiversiteitdoelen?
Scholten, M.C.T. ; Bianchi, F.J.J.A. ; Boer, I.J.M. de; Conijn, J.G. ; Dijkstra, J. ; Doorn, A.M. van; Ende, J.E. van den; Fresco, L.O. ; Jongschaap, R.E.E. ; Kernebeek, H.R.J. van; Lesschen, J.P. ; Olde, E.M. de; Schulte, Rogier ; Termeer, C.J.A.M. ; Vorst, J.G.A.J. van der; Vos, J.A. de; Woltjer, G.B. - \ 2018
Wageningen University and Research - 14 p.
Prediction of enteric methane production, yield, and intensity in dairy cattle using an intercontinental database
Niu, Mutian ; Kebreab, Ermias ; Hristov, Alexander N. ; Oh, Joonpyo ; Arndt, Claudia ; Bannink, André ; Bayat, Ali R. ; Brito, André F. ; Boland, Tommy ; Casper, David ; Crompton, Les A. ; Dijkstra, Jan ; Eugène, Maguy A. ; Garnsworthy, Phil C. ; Haque, Md Najmul ; Hellwing, Anne L.F. ; Huhtanen, Pekka ; Kreuzer, Michael ; Kuhla, Bjoern ; Lund, Peter ; Madsen, Jørgen ; Martin, Cécile ; Mcclelland, Shelby C. ; Mcgee, Mark ; Moate, Peter J. ; Muetzel, Stefan ; Muñoz, Camila ; O'Kiely, Padraig ; Peiren, Nico ; Reynolds, Christopher K. ; Schwarm, Angela ; Shingfield, Kevin J. ; Storlien, Tonje M. ; Weisbjerg, Martin R. ; Yáñez-Ruiz, David R. ; Yu, Zhongtang - \ 2018
Global Change Biology (2018). - ISSN 1354-1013 - p. 3368 - 3389.
Dairy cows - Dry matter intake - Enteric methane emissions - Methane intensity - Methane yield - Prediction models
Enteric methane (CH4) production from cattle contributes to global greenhouse gas emissions. Measurement of enteric CH4 is complex, expensive, and impractical at large scales; therefore, models are commonly used to predict CH4 production. However, building robust prediction models requires extensive data from animals under different management systems worldwide. The objectives of this study were to (1) collate a global database of enteric CH4 production from individual lactating dairy cattle; (2) determine the availability of key variables for predicting enteric CH4 production (g/day per cow), yield [g/kg dry matter intake (DMI)], and intensity (g/kg energy corrected milk) and their respective relationships; (3) develop intercontinental and regional models and cross-validate their performance; and (4) assess the trade-off between availability of on-farm inputs and CH4 prediction accuracy. The intercontinental database covered Europe (EU), the United States (US), and Australia (AU). A sequential approach was taken by incrementally adding key variables to develop models with increasing complexity. Methane emissions were predicted by fitting linear mixed models. Within model categories, an intercontinental model with the most available independent variables performed best with root mean square prediction error (RMSPE) as a percentage of mean observed value of 16.6%, 14.7%, and 19.8% for intercontinental, EU, and United States regions, respectively. Less complex models requiring only DMI had predictive ability comparable to complex models. Enteric CH4 production, yield, and intensity prediction models developed on an intercontinental basis had similar performance across regions, however, intercepts and slopes were different with implications for prediction. Revised CH4 emission conversion factors for specific regions are required to improve CH4 production estimates in national inventories. In conclusion, information on DMI is required for good prediction, and other factors such as dietary neutral detergent fiber (NDF) concentration, improve the prediction. For enteric CH4 yield and intensity prediction, information on milk yield and composition is required for better estimation.
Dynamics of volatile fatty acids, hydrogen, and methane in dairy cattle: A model of rumen metabolic pathways
Lingen, H.J. van; Fadel, J.G. ; Moraes, L.E. ; Kebreab, Ermias ; Bannink, A. ; Dijkstra, J. - \ 2018
On the stability and finite-size effects of a columnar phase in single-component systems of hard-rod-like particles
Dussi, Simone ; Chiappini, Massimiliano ; Dijkstra, Marjolein - \ 2018
Molecular Physics 116 (2018)21-22. - ISSN 0026-8976 - p. 2792 - 2805.
columnar phase - entropy - hard particles - Liquid crystals - Monte Carlo simulations

Colloidal rod-like particles self-assemble into a variety of liquid crystal phases. In contrast to the formation of the nematic and smectic phases for which it is well understood that it can be driven by entropy, the stabilisation mechanism of a prolate columnar phase ((Formula presented.)), observed for example in fd-virus suspensions, is still unclear. Here, we investigate whether or not a (Formula presented.) phase can exist in a purely entropy-driven single-component system. We perform computer simulations of hard particles with different shapes: spherocylinders, top-shaped rods, cuboidal particles, and crooked rods. We show that the (Formula presented.) phases observed in previous simulation studies are mere artefacts due to either finite-size effects or simulation boxes that are incommensurate with the stable thermodynamic phase. In particular, we observe that the characteristic layering of the stable smectic or crystal phase disappears when the dimension of the simulation box along the direction of the layers is too small. Such a system-size effect depends both on particle shape and the competing phases, and appears to be more pronounced for less anisotropic particles.

Letter to the Editor: Recovery test results as a prerequisite for publication of gaseous exchange measurements
Gerrits, W.J.J. ; Labussiere, Etienne ; Reynolds, Chris ; Metges, Cornelia ; Kuhla, Björn ; Lund, Peter ; Weisbjerg, Martin Riis ; Dijkstra, J. - \ 2018
Journal of Dairy Science 101 (2018)6. - ISSN 0022-0302 - p. 4703 - 4704.
In the last decade, various applications of gaseous exchange measurements have been developed to quantify the production or consumption of particular gases by animals. Notably, booming research into methane emissions has led to an expansion of the number of facilities in which such measurements are made. Results of a ring test calibration of respiration chambers in the UK by Gardiner et al. (2015) confirmed our concern that not all research groups comply with the same standards of chamber operation.
Hard Competition : Stabilizing the Elusive Biaxial Nematic Phase in Suspensions of Colloidal Particles with Extreme Lengths
Dussi, Simone ; Tasios, Nikos ; Drwenski, Tara ; Roij, René Van; Dijkstra, Marjolein - \ 2018
Physical Review Letters 120 (2018)17. - ISSN 0031-9007

We use computer simulations to study the existence and stability of a biaxial nematic Nb phase in systems of hard polyhedral cuboids, triangular prisms, and rhombic platelets, characterized by a long (L), medium (M), and short (S) particle axis. For all three shape families, we find stable Nb states provided the shape is not only close to the so-called dual shape with M=LS but also sufficiently anisotropic with L/S>9,11,14,23 for rhombi, (two types of) triangular prisms, and cuboids, respectively, corresponding to anisotropies not considered before. Surprisingly, a direct isotropic-Nb transition does not occur in these systems due to a destabilization of Nb by a smectic (for cuboids and prisms) or a columnar (for platelets) phase at small L/S or by an intervening uniaxial nematic phase at large L/S. Our results are confirmed by a density functional theory provided the third virial coefficient is included and a continuous rather than a discrete (Zwanzig) set of particle orientations is taken into account.

Atmosphere-vegetation-soil interactions in a climate change context; Impact of changing conditions on engineered transport infrastructure slopes in Europe
Tang, A.M. ; Hughes, P.N. ; Dijkstra, T.A. ; Askarinejad, A. ; Brenčič, M. ; Cui, Y.J. ; Diez, J.J. ; Firgi, T. ; Gajewska, B. ; Gentile, F. ; Grossi, G. ; Jommi, C. ; Kehagia, F. ; Koda, E. ; Maat, H.W. Ter; Lenart, S. ; Lourenco, S. ; Oliveira, M. ; Osinski, P. ; Springman, S.M. ; Stirling, R. ; Toll, D.G. ; Beek, V. Van - \ 2018
Quarterly Journal of Engineering Geology and Hydrogeology 51 (2018)2. - ISSN 1470-9236 - p. 156 - 168.

In assessing the impact of climate change on infrastructure, it is essential to consider the interactions between the atmosphere, vegetation and the near-surface soil. This paper presents an overview of these processes, focusing on recent advances from the literature and those made by members of COST Action TU1202 - Impacts of climate change on engineered slopes for infrastructure. Climate- and vegetation-driven processes (suction generation, erosion, desiccation cracking, freeze- thaw effects) are expected to change in incidence and severity, which will affect the stability of new and existing infrastructure slopes. This paper identifies the climate- and vegetation-driven processes that are of greatest concern, the suite of known unknowns that require further research, and lists key aspect that should be considered for the design of engineered transport infrastructure slopes in the context of climate change.

Gluren naar vetzuren
Dijkstra, Jan - \ 2018
Site-specific aftercare completion criteria for sustainable landfilling in the Netherlands : Geochemical modelling and sensitivity analysis
Dijkstra, Joris J. ; Zomeren, André van; Brand, Ellen ; Comans, Rob N.J. - \ 2018
Waste Management 75 (2018). - ISSN 0956-053X - p. 407 - 414.
Aftercare completion - Environmental protection criteria - Geochemical modelling - Risk assessment - Sensitivity analysis - Sustainable landfill management
A novel, regulatory accepted approach is developed that enables competent authorities to decide whether landfill aftercare can be reduced or terminated. Our previous paper (Brand et al., Waste Management 2016, 56, 255–261, https://doi.org//10.1016/j.wasman.2016.07.038) outlines the general approach, that consists of a 10-year treatment phase (e.g., aeration, leachate recirculation), in combination with site-specific Environmental Protection Criteria (EPC) for contaminant concentrations in the landfill leachate after treatment. The current paper presents the unique modelling approach by which the site-specific EPC are derived. The modelling approach is based on the use of mechanistic multi-surface geochemical models covering the main sorption processes in soils underneath the landfills, and is composed of widely-accepted surface complexation models in combination with published “generic” parameter sets. This approach enables the consideration of the main site-specific soil properties that influence the attenuation of emitted contaminants. In addition, the sensitivity of the EPC is shown for variation of the main physicochemical-assumptions and policy-based decisions. Site-specific soil properties have been found to substantially determine the EPC and include soil-pH, dissolved organic matter, and iron-(hydr)oxide content. Apart from the sorption capacity of the local soil, EPC also depend strongly on the assumed dilution with local groundwater in the saturated zone. An important policy-related decision that influences the calculated EPC is the assessment period during which the groundwater is protected. The transparent setup of the approach using geochemical modelling, the explicit consideration of site-specific properties and the achieved regulatory acceptance may also stimulate application to landfills in other countries.
Effects of rumen-undegradable protein on intake, performance, and mammary gland development in prepubertal and pubertal dairy heifers
Silva, A.L. ; Detmann, E. ; Dijkstra, J. ; Pedroso, A.M. ; Silva, L.H.P. ; Machado, A.F. ; Sousa, F.C. ; Santos, G.B. dos; Marcondes, M.I. - \ 2018
Journal of Dairy Science 101 (2018)7. - ISSN 0022-0302 - p. 5991 - 6001.
growth - mammary gland ultrasound - nitrogen retention
The objective of this study was to evaluate the influence of different amounts of rumen-undegradable protein (RUP) on intake, N balance, performance, mammary gland development, carcass traits, and hormonal status of Holstein heifers at different physiological stages (PS). Sixteen prepubertal (PRE) heifers (initial BW = 106 ± 7.6 kg; age = 4.3 ± 0.46 mo) and 16 pubertal (PUB) heifers (initial BW = 224 ± 7.9 kg; age = 12.6 ± 0.45 mo) were used in an experiment over a period of 84 d. Four diets with increasing RUP contents (38, 44, 51, and 57% of dietary crude protein) and heifers at 2 PS (PRE or PUB) were used in a 4 × 2 factorial arrangement of treatments in a completely randomized design. Throughout the experiment, 2 digestibility trials were performed over 5 consecutive days (starting at d 36 and 78) involving feed and ort sampling and spot collections of feces and urine. At d 0 and 83, body ultrasound images were obtained for real-time carcass trait evaluation. The mammary gland was ultrasonically scanned at d 0 and every 3 wk during the experiment. Blood samples were taken at d 0 and 84 to determine serum concentrations of progesterone, estrogen, insulin-like growth factor I (IGF-I), and insulin. No interaction between PS and the level of RUP was found for any trait. Apparent digestibility of dry matter, organic matter, and neutral detergent fiber corrected for ash and protein was not affected by RUP level but was lower for PRE compared with PUB heifers. Sorting against neutral detergent fiber corrected for ash and protein (tendency only) and for crude protein was greater for PUB than PRE heifers. Pubertal heifers had greater average daily gain (905 vs. 505 g/d) and N retention (25.9 vs. 12.5 g/d) than PRE heifers. In addition, average daily gain and N retention were greatest at 51% RUP of dietary protein. Mammary ultrasonography indicated no effects of RUP amounts on mammary gland composition, whereas PRE heifers had greater pixel values than PUB, indicating higher contents of fat rather than protein in the mammary glands of PRE heifers. Serum progesterone and IGF-I concentration was affected only by PS, and PRE heifers had greater values of progesterone and IGF-I concentrations than PUB heifers. Serum insulin concentration was unaffected by PS but tended to be higher at 51% of RUP. In conclusion, an RUP level of 51% increases body weight, average daily gain, feed efficiency, and N retention in heifers regardless of the PS. In addition, PRE heifers have a lower sorting ability and reduced intake, total-tract digestibility, and N retention. They also have higher amounts of fat in their mammary glands, even at moderate growth rates.
Short communication: The effect of linseed oil and DGAT1 K232A polymorphism on the methane emission prediction potential of milk fatty acids
Gastelen, S. van; Antunes-Fernandes, E.C. ; Hettinga, K.A. ; Dijkstra, J. - \ 2018
Journal of Dairy Science 101 (2018)6. - ISSN 0022-0302 - p. 5599 - 5604.
DGAT1 K232 polymorphism - enteric methane production - linseed oil - milk fatty acid
Several in vivo CH4 measurement techniques have been developed but are not suitable for precise and accurate large-scale measurements; hence, proxies for CH4 emissions in dairy cattle have been proposed, including the milk fatty acid (MFA) profile. The aim of the present study was to determine whether recently developed MFA-based prediction equations for CH4 emission are applicable to dairy cows with different diacylglycerol o-acyltransferase 1 (DGAT1) K232A polymorphism and fed diets with and without linseed oil. Data from a crossover design experiment were used, encompassing 2 dietary treatments (i.e., a control diet and a linseed oil diet, with a difference in dietary fat content of 22 g/kg of dry matter) and 24 lactating Holstein-Friesian cows (i.e., 12 cows with DGAT1 KK genotype and 12 cows with DGAT1 AA genotype). Enteric CH4 production was measured in climate respiration chambers and the MFA profile was analyzed using gas chromatography. Observed CH4 emissions were compared with CH4 emissions predicted by previously developed MFA-based CH4 prediction equations. The results indicate that different types of diets (i.e., with or without linseed oil), but not the DGAT1 K232A polymorphism, affect the ability of previously derived prediction equations to predict CH4 emission. However, the concordance correlation coefficient was smaller than or equal to 0.30 for both dietary treatments separately, both DGAT1 genotypes separately, and the complete data set. We therefore concluded that previously derived MFA-based CH4 prediction equations can neither accurately nor precisely predict CH4 emissions of dairy cows managed under strategies differing from those under which the original prediction equations were developed.
Predicting enteric methane emission of dairy cows with milk Fourier-transform infrared spectra and gas chromatography–based milk fatty acid profiles
Gastelen, S. van; Mollenhorst, H. ; Antunes-Fernandes, E.C. ; Hettinga, K.A. ; Burgsteden, G.G. van; Dijkstra, J. ; Rademaker, J.L.W. - \ 2018
Journal of Dairy Science 101 (2018)6. - ISSN 0022-0302 - p. 5582 - 5598.
dairy cow - enteric methane production - milk fatty acid concentration - milk Fourier-transform infrared spectroscopy

The objective of the present study was to compare the prediction potential of milk Fourier-transform infrared spectroscopy (FTIR) for CH4 emissions of dairy cows with that of gas chromatography (GC)–based milk fatty acids (MFA). Data from 9 experiments with lactating Holstein-Friesian cows, with a total of 30 dietary treatments and 218 observations, were used. Methane emissions were measured for 3 consecutive days in climate respiration chambers and expressed as production (g/d), yield (g/kg of dry matter intake; DMI), and intensity (g/kg of fat- and protein-corrected milk; FPCM). Dry matter intake was 16.3 ± 2.18 kg/d (mean ± standard deviation), FPCM yield was 25.9 ± 5.06 kg/d, CH4 production was 366 ± 53.9 g/d, CH4 yield was 22.5 ± 2.10 g/kg of DMI, and CH4 intensity was 14.4 ± 2.58 g/kg of FPCM. Milk was sampled during the same days and analyzed by GC and by FTIR. Multivariate GC-determined MFA–based and FTIR-based CH4 prediction models were developed, and subsequently, the final CH4 prediction models were evaluated with root mean squared error of prediction and concordance correlation coefficient analysis. Further, we performed a random 10-fold cross validation to calculate the performance parameters of the models (e.g., the coefficient of determination of cross validation). The final GC-determined MFA–based CH4 prediction models estimate CH4 production, yield, and intensity with a root mean squared error of prediction of 35.7 g/d, 1.6 g/kg of DMI, and 1.6 g/kg of FPCM and with a concordance correlation coefficient of 0.72, 0.59, and 0.77, respectively. The final FTIR-based CH4 prediction models estimate CH4 production, yield, and intensity with a root mean squared error of prediction of 43.2 g/d, 1.9 g/kg of DMI, and 1.7 g/kg of FPCM and with a concordance correlation coefficient of 0.52, 0.40, and 0.72, respectively. The GC-determined MFA–based prediction models described a greater part of the observed variation in CH4 emission than did the FTIR-based models. The cross validation results indicate that all CH4 prediction models (both GC-determined MFA–based and FTIR-based models) are robust; the difference between the coefficient of determination and the coefficient of determination of cross validation ranged from 0.01 to 0.07. The results indicate that GC-determined MFA have a greater potential than FTIR spectra to estimate CH4 production, yield, and intensity. Both techniques hold potential but may not yet be ready to predict CH4 emission of dairy cows in practice. Additional CH4 measurements are needed to improve the accuracy and robustness of GC-determined MFA and FTIR spectra for CH4 prediction.

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