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.

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    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.
    Meta-analysis of relationships between enteric methane yield and milk fatty acid profile in dairy cattle
    Lingen, H.J. van; Crompton, L.A. ; Hendriks, W.H. ; Reynolds, C.K. ; Dijkstra, J. - \ 2014
    Journal of Dairy Science 97 (2014)11. - ISSN 0022-0302 - p. 7115 - 7132.
    conjugated linoleic acids - rumen fermentation - linseed oil - nutritional regulation - extruded linseed - mammary-gland - grass-silage - odd-chain - cows - energy
    Various studies have indicated a relationship between enteric methane (CH4) production and milk fatty acid (FA) profiles of dairy cattle. However, the number of studies investigating such a relationship is limited and the direct relationships reported are mainly obtained by variation in CH4 production and milk FA concentration induced by dietary lipid supplements. The aim of this study was to perform a meta-analysis to quantify relationships between CH4 yield (per unit of feed and unit of milk) and milk FA profile in dairy cattle and to develop equations to predict CH4 yield based on milk FA profile of cows fed a wide variety of diets. Data from 8 experiments encompassing 30 different dietary treatments and 146 observations were included. Yield of CH4 measured in these experiments was 21.5 ± 2.46 g/kg of dry matter intake (DMI) and 13.9 ± 2.30 g/kg of fat- and protein-corrected milk (FPCM). Correlation coefficients were chosen as effect size of the relationship between CH4 yield and individual milk FA concentration (g/100 g of FA). Average true correlation coefficients were estimated by a random-effects model. Milk FA concentrations of C6:0, C8:0, C10:0, C16:0, and C16:0-iso were significantly or tended to be positively related to CH4 yield per unit of feed. Concentrations of trans-6+7+8+9 C18:1, trans-10+11 C18:1, cis-11 C18:1, cis-12 C18:1, cis-13 C18:1, trans-16+cis-14 C18:1, and cis-9,12 C18:2 in milk fat were significantly or tended to be negatively related to CH4 yield per unit of feed. Milk FA concentrations of C10:0, C12:0, C14:0-iso, C14:0, cis-9 C14:1, C15:0, and C16:0 were significantly or tended to be positively related to CH4 yield per unit of milk. Concentrations of C4:0, C18:0, trans-10+11 C18:1, cis-9 C18:1, cis-11 C18:1, and cis-9,12 C18:2 in milk fat were significantly or tended to be negatively related to CH4 yield per unit of milk. Mixed model multiple regression and a stepwise selection procedure of milk FA based on the Bayesian information criterion to predict CH4 yield with milk FA as input (g/100 g of FA) resulted in the following prediction equations: CH4 (g/kg of DMI) = 23.39 + 9.74 × C16:0-iso - 1.06 × trans-10+11 C18:1 - 1.75 × cis-9,12 C18:2 (R2 = 0.54), and CH4 (g/kg of FPCM) = 21.13 - 1.38 × C4:0 + 8.53 × C16:0-iso - 0.22 × cis-9 C18:1 - 0.59 × trans-10+11 C18:1 (R2 = 0.47). This indicated that milk FA profile has a moderate potential for predicting CH4 yield per unit of feed and a slightly lower potential for predicting CH4 yield per unit of milk.
    Cost-effectiveness of feeding strategies to reduce greenhouse gas emissions from dairy farming
    Middelaar, C.E. van; Dijkstra, J. ; Berentsen, P.B.M. ; Boer, I.J.M. de - \ 2014
    Journal of Dairy Science 97 (2014)4. - ISSN 0022-0302 - p. 2427 - 2439.
    nitrous-oxide emissions - dietary nitrate supplementation - enteric methane mitigation - special topics-mitigation - milk-production - fat supplementation - rumen fermentation - grazing behavior - linseed oil - cows
    The objective of this paper was to evaluate the cost-effectiveness of 3 feeding strategies to reduce enteric CH4 production in dairy cows by calculating the effect on labor income at the farm level and on greenhouse gas (GHG) emissions at the chain level (i.e., from production of farm inputs to the farm gate). Strategies included were (1) dietary supplementation of an extruded linseed product (56% linseed; 1 kg/cow per day in summer and 2 kg/cow per day in winter), (2) dietary supplementation of a nitrate source (75% nitrate; 1% of dry matter intake), and (3) reducing the maturity stage of grass and grass silage (grazing at 1,400 instead of 1,700 kg of dry matter/ha and harvesting at 3,000 instead of 3,500 kg of dry matter/ha). A dairy farm linear programing model was used to define an average Dutch dairy farm on sandy soil without a predefined feeding strategy (reference situation). Subsequently, 1 of the 3 feeding strategies was implemented and the model was optimized again to determine the new economically optimal farm situation. Enteric CH4 production in the reference situation and after implementing the strategies was calculated based on a mechanistic model for enteric CH4 and empirical formulas explaining the effect of fat and nitrate supplementation on enteric CH4 production. Other GHG emissions along the chain were calculated using life cycle assessment. Total GHG emissions in the reference situation added up to 840 kg of CO2 equivalents (CO2e) per t of fat- and protein-corrected milk (FPCM) and yearly labor income of €42,605. Supplementation of the extruded linseed product reduced emissions by 9 kg of CO2e/t of FPCM and labor income by €16,041; supplementation of the dietary nitrate source reduced emissions by 32 kg of CO2e/t of FPCM and labor income by €5,463; reducing the maturity stage of grass and grass silage reduced emissions by 11 kg of CO2e/t of FPCM and labor income by €463. Of the 3 strategies, reducing grass maturity was the most cost-effective (€57/t of CO2e compared with €241/t of CO2e for nitrate supplementation and €2,594/t of CO2e for linseed supplementation) and had the greatest potential to be used in practice because the additional costs were low.
    Comparison between stearoyl-CoA desaturase expression in milk somatic cells and in mammary tissue of lactating dairy cows
    Jacobs, A.A.A. ; Dijkstra, J. ; Hendriks, W.H. ; Baal, J. van; Vuuren, A.M. van - \ 2013
    Journal of Animal Physiology and Animal Nutrition 97 (2013)2. - ISSN 0931-2439 - p. 353 - 362.
    conjugated linoleic-acid - epithelial-cells - messenger-rna - short communication - lipid-metabolism - gene-expression - linseed oil - gland - fat - cla
    Stearoyl-CoA desaturase (SCD) is an important enzyme in the bovine mammary gland, where it inserts a cis-double bond at the ¿9 position in a wide range of fatty acids. Investigating SCD expression in the bovine mammary gland generally requires invasive biopsy to obtain mammary tissue. The aim of this study was to evaluate the use of milk somatic cells as a non-invasive alternative to biopsy for measuring mammary SCD expression in dairy cows. Both milk somatic cells and mammary tissue were collected from 14 Holstein-Friesian cows and used for analysis of SCD expression by real-time PCR. The SCD5 mRNA levels in mammary tissue compared with SCD1 were low, and for several milk somatic cell samples, SCD5 expression was even below the limit of detection. A significant relationship was found between SCD1 expression in milk somatic cells and in mammary tissue. In addition, SCD1 expression in milk somatic cells was significantly related to ¿9-desaturase indices in milk, which are commonly used as an indicator of SCD1 activity within the mammary gland. Our study showed that milk somatic cells can be used as a source of mRNA to study SCD1 expression in dairy cows, offering a non-invasive alternative to mammary tissue samples obtained by biopsy.
    Effects of different fat sources, technological forms and characteristics of the basal diet on milk fatty acid profile in lactating dairy cows - a meta-analysis
    Sterk, A.R. ; Vuuren, A.M. van; Hendriks, W.H. ; Dijkstra, J. - \ 2012
    The Journal of Agricultural Science 150 (2012)04. - ISSN 0021-8596 - p. 495 - 517.
    fed fish-oil - in-vitro - ruminal biohydrogenation - extruded soybeans - prostaglandin secretion - rumen biohydrogenation - linoleic acids - sunflower oil - linseed oil - forage type
    A meta-analysis was conducted to study milk fatty acid (FA) profile in dairy cows in response to changes in dietary nutrient composition in relation to supplementation of fat sources, their technological form, addition of fish oil and main forage type in the basal diet. Data comprised 151 treatment means from 50 experiments, which were included in the database when diet composition, nutrient composition, FA composition, dry matter (DM) intake, milk yield, milk composition and milk FA profile were reported. Mixed model regression analysis including a random experiment effect and unequal variances among experiments was used. Least squares means were obtained for the different fat sources (unsupplemented, rapeseed, soybean+sunflower, linseed, or fish oil), technological form including addition of fish oil (oil, seed, protected and added fish oil), and main forage type (lucerne silage, barley silage, maize silage, grass silage, maize silage combined with haylage, or haylage) in the basal diet. Results showed that the technological form of supplemental rapeseed, soybean, sunflower, or linseed significantly influenced the effect of dietary nutrient composition on milk fat content and milk FA profile resulting in significant differences between technological forms within the different fat sources. Protected rapeseed and linseed increased C18:2n6 and C18:3n3 proportions in milk fat, respectively, whereas soybean and sunflower seed increased transfer efficiencies for C18:2n6 and C18:3n3 and their proportions in milk fat. Soybean, sunflower, or linseed supplied as oil increased trans-11-C18:1 proportions in milk fat, whereas the addition of fish oil to a diet containing soybean or sunflower decreased C18:0 and cis-9-C18:1 proportions in milk fat. The main forage type in the diet also significantly influenced the effect of dietary nutrient composition on milk fat content and milk FA profile, resulting in significant differences between main forage types in the diet within the different fat sources. Maize silage as the main forage type increased trans-11-C18:1 in unsupplemented diets or diets supplemented with a source of soybean or sunflower. For rapeseed supplemented diets, barley silage increased transfer efficiency and milk fat proportion of C18:2n6, whereas grass silage increased proportion of C18:3n3 in milk fat. For soybean or sunflower supplemented diets, haylage increased proportions of saturated FA, cis-9-C18:1 and C18:2n6, whereas the combination of maize silage and haylage increased transfer efficiency and milk fat proportion of C18:3n3. For linseed supplemented diets, grass silage as the main forage type resulted in the highest C18:3n3 proportion, whereas cis-9-C18:1 proportion was comparable for grass silage, lucerne silage and maize silage as the main forage type. This meta-analysis confirmed that the effect of dietary nutrient composition on several milk FA proportions depends on the type and form of fat supplementation, addition of fish oil, and main forage type in the basal diet.
    Effect of corn silage harvest maturity and concentrate type on milk fatty acid composition of dairy cows
    Khan, N.A. ; Tewoldebrhan, T.A. ; Zom, R.L.G. ; Cone, J.W. ; Hendriks, W.H. - \ 2012
    Journal of Dairy Science 95 (2012)3. - ISSN 0022-0302 - p. 1472 - 1483.
    conjugated linoleic acids - trans octadecenoic acid - replacing grass-silage - maize silage - rumen fermentation - detergent fiber - sunflower oil - duodenal flow - linseed oil - fish-oil
    The variation in maturity at harvest during grain filling has a major effect on the carbohydrate composition (starch:NDF ratio) and fatty acid (FA) content of corn silages, and can alter the FA composition of milk fat in dairy cows. This study evaluated the effect of silage corn (cv. Atrium) harvested and ensiled at targeted DM contents of 300, 340, 380, and 420g/kg of fresh weight and fed to dairy cows in combination with a highly degradable carbohydrate (HC) or low-degradable carbohydrate concentrate, on the nutrient intake, milk yield, and composition of milk and milk fat. Sixty-four multiparous Holstein-Friesian dairy cows in their first week of lactation were assigned to the 8 dietary treatments according to a randomized complete block design. The 8 dietary treatments consisted of a factorial combination of the 4 corn silages and the 2 concentrates. Corn silages were offered ad libitum as part of a basal forage mixture, whereas the concentrates were given at the rate of 8.5kg of DM/cow per day during the 15-wk experimental period. Dry matter, crude protein, and energy intakes did not differ across the corn silages. However, the intake of starch increased, and those of NDF and C18:3n-3 decreased with increasing maturation. Milk yield and composition were not different across the corn silages. Yield (kg/d) of milk, protein, and lactose was higher for low-degradable carbohydrate compared with HC concentrate-fed groups. Increasing maturity of corn silages decreased the content of C18:3n-3 and total n-3 and increased the n-6:n-3 ratio in milk fat. Concentrate type significantly altered the composition of all trans FA, except C18:2 trans-9,12. Inclusion of the HC concentrate in the diets increased the contents of all C18:1 trans isomers, C18:2 cis-9,trans-11, and C18:2 trans-10,cis-12 conjugated linoleic acid in milk fat. Milk fat composition was strongly influenced by the stage of lactation (wk 3 to 10). The content of all even short- and medium-chain FA changed with lactation, except C8:0 and C10:0. The content of C12:0, C14:0, and C16:0 and total saturated FA increased and the content of C18:0, C18:1 cis total, and total cis monounsaturated FA decreased with lactation. Maturity of the corn silages at harvest did not affect the production performance of dairy cows, but resulted in a decreased content of C18:3n-3, total n-3, and an increased n-6:n-3 ratio in the milk fat of dairy cows.
    Characterization of milk fatty acids based on genetic and herd parameters
    Heck, J.M.L. ; Valenberg, H.J.F. van; Bovenhuis, H. ; Dijkstra, J. ; Hooijdonk, A.C.M. van - \ 2012
    Journal of Dairy Research 79 (2012)1. - ISSN 0022-0299 - p. 39 - 46.
    bovine-milk - dairy-cows - mammary-gland - methane production - lactation stage - linseed oil - odd-chain - concentrate - diet - supplementation
    The objective of this study was to characterize the fatty acids (FA) in milk based on genetic and herd parameters to investigate the origin of the different FA in milk. Milk samples of 1912 Dutch Holstein-Friesian cows were analysed for 39 different FA including odd and branched-chain fatty acids. The proportion of variation caused by genetic and herd effects was calculated. In addition, genetic and herd correlations among the fatty acids were estimated and a clustering technique was used to visualise these correlations. The results indicated that in Dutch milk C12:0 is not completely synthesised de novo but also partly blood derived. It was suggested that C20:0 in milk is formed from the action of elongase enzymes on C18:0 and that the odd-chain FA C5:0-C13:0 and a part of C15:0 and C17:0 are synthesised de novo while the other part of C15:0 and C17:0 is blood derived. Furthermore, this work gives an overview of the opportunities to change the concentration of individual FA both by breeding and feeding. It is clearly shown that the extent to which the individual FA can be changed varies greatly and is dependent on the origin of the different FA in milk.
    Greenhouse gas mitigation in animal production: towards an integrated life cycle sustainability assessment.
    Boer, I.J.M. de; Cederberg, C. ; Eady, S. ; Gollnow, S. ; Kristensen, T. ; Macleod, M. ; Meul, M. ; Nemecek, T. ; Phong, L.T. ; Thoma, G. ; Werf, H.M.G. ; Williams, A.G. ; Zonderland-Thomassen, M.A. - \ 2011
    Current Opinion in Environmental Sustainability 3 (2011)5. - ISSN 1877-3435 - p. 423 - 431.
    nitrous-oxide emissions - dairy-cows - production systems - ruminal microorganisms - environmental-impact - carbon sequestration - livestock production - agricultural soils - milk-production - linseed oil
    The animal food chain contributes significantly to emission of greenhouse gases (GHGs). We explored studies that addressed options to mitigate GHG emissions in the animal production chain and concluded that most studies focused on production systems in developed countries and on a single GHG. They did not account for the complex interrelated effects on other GHGs or their relation with other aspects of sustainability, such as eutrophication, animal welfare, land use or food security. Current decisions on GHG mitigation in animal production, therefore, are hindered by the complexity and uncertainty of the combined effect of GHG mitigation options on climate change and their relation with other aspects of sustainability. There is an urgent need to integrate simulation models at animal, crop and farm level with a consequential life cycle sustainability assessment to gain insight into the multidimensional and sometimes conflicting consequences of GHG mitigation options. Highlights ¿ Most studies that address options to mitigate greenhouse gas (GHG) emissions in the animal production focus on systems in developed countries and on a single GHG. ¿ Current decisions on GHG mitigation in animal production are hindered by the complexity and uncertainty of the combined effect of GHG mitigation options on climate change and their relation with other aspects of sustainability. ¿ There is an urgent need to integrate simulation models at animal, crop and farm level with a consequential life cycle sustainability assessment to gain insight into the multidimensional and sometimes conflicting consequences of GHG mitigation options.
    Effects of a combination of feed additives on methane production, diet digestibility, and animal performance in lactating dairy cows
    Zijderveld, S.M. van; Fonken, B.C.J. ; Dijkstra, J. ; Gerrits, W.J.J. ; Perdok, H.B. ; Fokkink, W.B. ; Newbold, J.R. - \ 2011
    Journal of Dairy Science 94 (2011)3. - ISSN 0022-0302 - p. 1445 - 1454.
    chain fatty-acids - ruminal methanogenesis - fumaric-acid - beef-cattle - coconut oil - linseed oil - extruded linseed - detergent fiber - myristic acid - crude linseed
    Two experiments were conducted to assess the effects of a mixture of dietary additives on enteric methane production, rumen fermentation, diet digestibility, energy balance, and animal performance in lactating dairy cows. Identical diets were fed in both experiments. The mixture of feed additives investigated contained lauric acid, myristic acid, linseed oil, and calcium fumarate. These additives were included at 0.4, 1.2, 1.5, and 0.7% of dietary dry matter, respectively (treatment ADD). Experimental fat sources were exchanged for a rumen inert source of fat in the control diet (treatment CON) to maintain isolipidic rations. Cows (experiment 1, n = 20; experiment 2, n = 12) were fed restricted amounts of feed to avoid confounding effects of dry matter intake on methane production. In experiment 1, methane production and energy balance were studied using open-circuit indirect calorimetry. In experiment 2, 10 rumen-fistulated animals were used to measure rumen fermentation characteristics. In both experiments animal performance was monitored. The inclusion of dietary additives decreased methane emissions (g/d) by 10%. Milk yield and milk fat content tended to be lower for ADD in experiment 1. In experiment 2, milk production was not affected by ADD, but milk fat content was lower. Fat- and protein-corrected milk was lower for ADD in both experiments. Milk urea nitrogen content was lowered by ADD in experiment 1 and tended to be lower in experiment 2. Apparent total tract digestibility of fat, but not that of starch or neutral detergent fiber, was higher for ADD. Energy retention did not differ between treatments. The decrease in methane production (g/d) was not evident when methane emission was expressed per kilogram of milk produced. Feeding ADD resulted in increases of C12:0 and C14:0 and the intermediates of linseed oil biohydrogenation in milk in both experiments. In experiment 2, ADD-fed cows tended to have a decreased number of protozoa in rumen fluid when compared with that in control cows. Total volatile fatty acid concentrations were lower for ADD, whereas molar proportions of propionate increased at the expense of acetate and butyrate
    Effect of in vitro docosahexaenoic acid supplementation to marine algae-adapted and unadapted rumen inoculum on the biohydrogenation of unsaturated fatty acids infreeze-dried grass
    Vlaeminck, B. ; Mengistu, G. ; Fievez, V. ; Jonge, L.H. de; Dijkstra, J. - \ 2008
    Journal of Dairy Science 91 (2008)3. - ISSN 0022-0302 - p. 1122 - 1132.
    conjugated linoleic-acid - fish-oil - sunflower oil - linseed oil - dairy-cows - butyrivibrio-fibrisolvens - milk - diet - chain - cla
    The objective of this study was to examine the ruminal biohydrogenation of linoleic (18:2n-6) and linolenic (18:3n-3) acid during in vitro incubations with rumen inoculum from dairy cattle adapted or not to marine algae and with or without additional in vitro docosahexaenoic acid (DHA, 22:6n-3) supplementation. Treatments were incubated in 100-mL flasks containing 400 mg of freeze-dried grass, 5 mL of strained ruminal fluid, and 20 mL of phosphate buffer. Ruminal fluid was collected just before the morning feeding from 3 cows receiving a control diet (49% ryegrass silage, 39% corn silage, 1% straw, and 11% concentrate, fresh-weight basis) supplemented with marine algae for 21 d (adapted rumen fluid, aRF) or from the same cows receiving the control diet only for 14 d after marine algae supplementation was stopped (unadapted rumen fluid, uRF). In half of the incubation flasks, pure DHA (5 mg) was added as an oil-ethanol solution (100 mL). Incubations were carried out during 0, 0.5, 1, 2, 4, 6, and 24 h. After 24 h, in vitro addition of DHA resulted in greater amounts (mg/incubation) of 18:3n-3 (0.23, 0.43, 0.26, and 0.34 for aRF, aRF+DHA, uRF, and uRF+DHA), 18:2n-6 (0.14, 0.22, 0.15, and 0.20 for aRF, aRF+DHA, uRF, and uRF+DHA) and trans-11, cis-15-18:2 (0.27, 2.40, 0.06, and 2.21 for aRF, aRF+DHA, uRF, and uRF+DHA), whereas no effect of inoculum source was observed. Trans-11-18:1 accumulated after 24 h when aRF was incubated irrespective of in vitro DHA supplementation, whereas in incubations with uRF, accumulation of trans-11-18:1 only occurred when DHA was added (6.40, 4.35, 1.06, and 3.91 for aRF, aRF+DHA, uRF, and uRF+DHA). The increased amounts of trans-11-18:1 were due to the strong inhibition of the reduction to 18:0 because no 18:0 was formed when trans-11-18:1 accumulated after 24 h. The results of the current experiment shows hydrogenation of trans-11, cis-15-18:2 occurred in the absence of in vitro DHA only, whereas substantial hydrogenation of trans-11-18:1 to 18:0 only took place in incubations without DHA and with unadapted rumen inoculum, confirming the higher sensitivity of the latter process to DHA.
    Milk Odd- and Branched-Chain Fatty Acids in Relation to the Rumen Fermentation Pattern
    Vlaeminck, B. ; Fievez, V. ; Tamminga, S. ; Dewhurst, R.J. ; Vuuren, A.M. van; Brabander, D. de; Demeyer, D. - \ 2006
    Journal of Dairy Science 89 (2006)10. - ISSN 0022-0302 - p. 3954 - 3964.
    lactating dairy-cows - in-vitro - fish-oil - linseed oil - bacteria - concentrate - digestion - forage - diets - metabolism
    The objectives of this study were 1) to determine whether a relationship exists between molar proportions of volatile fatty acids in the rumen and milk odd-and branched-chain fatty acid concentrations (i.e., iso C13:0, anteiso C13:0, iso C14:0, C15:0, iso C15:0, anteiso C15:0, iso C16:0, C17:0, iso C17:0, anteiso C17:0, and cis-9 C17:1); and 2) to evaluate the accuracy of prediction of the latter equations using an independent data set. For development of the regression equations, individual cow data from 10 feeding experiments with rumen-fistulated dairy cows were used, resulting in a data set of 148 observations. Milk odd- and branched-chain fatty acids were closely related to the molar proportions of acetate (SE = 15.3 mmol/mol), propionate (SE = 14.7 mmol/mol), and butyrate (SE = 9.2 mmol/mol). These regression equations were further validated using data from the literature (n = 14). Evaluation of these prediction equations using the independent data set resulted in a root mean square prediction error of 3.0, 9.0, and 8.9% of the observed mean for acetate, propionate, and butyrate, respectively. In addition, less then 5% of the mean square prediction error was due to line bias. This suggests that the currently developed prediction equations based on milk odd- and branched-chain fatty acids show potential to predict molar proportions of individual volatile fatty acids in the rumen
    Oxidation and oligomerization of ethyl linoleate under the influence of the combination of ascorbic acid 6-palmitate/iron-2-ethylhexanoate
    Micciche, F. ; Haveren, J. van; Oostveen, E.A. ; Ming, W. ; Linde, R. van der - \ 2006
    Applied Catalysis A-General 297 (2006)2. - ISSN 0926-860X - p. 174 - 181.
    unsaturated fatty-acids - metal-catalyzed autoxidation - lipid-peroxidation - mass-spectrometry - alkyd resins - linseed oil - cross-linking - paints - drier - iron(iii)
    In this paper we report the oxidation and oligomerization of ethyl linoleate (EL), a model compound for alkyd resins, under the influence of iron-2-ethylhexanoate (Fe-eh) in combination with ascorbic acid 6-palmitate (AsA6p) at different AsA6p/Fe-eh molar ratios (0/1¿4/1). Reactions were studied in time by FT-IR, NMR, size exclusion chromatography (SEC) and peroxide amount determination. The oxidation and oligomerization of EL were accelerated by the combination of AsA6p and Fe-eh, and the catalytic properties of the catalysts were strongly dependent on the molar ratio AsA6p/Fe-eh. The molar ratio of 2/1 appeared to be optimal, at which both the oxidation and oligomerization of EL were the fastest. At molar ratio smaller than 2/1, or only in the presence of Fe-eh, the EL oxidation showed a time lag of up to 100 h; above the ratio 2/1 the rates of both EL oxidation and oligomerization decreased. Results are explained in terms of the multi-facet role played by AsA6p: its pro-oxidant or anti-oxidant properties, depending on the ratio of AsA6p/Fe-eh, and its effect on the Fe-eh complex.
    De bepaling van totaal oliegehalte in lijnzaad met NIRS
    Frankhuizen, R. ; Tusveld, M.A.H. - \ 1988
    Wageningen : RIKILT (Rapport / Rijkskwaliteitsinstituut voor Land- en Tuinbouwprodukten 88.77) - 17
    linum usitatissimum - vlas - infraroodspectroscopie - lijnolie - linum usitatissimum - flax - infrared spectroscopy - linseed oil
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