Machiel C. Blok

Machiel C. Blok
Wageningen University & Research | WUR · Department of Animal Nutrition

PhD

About

62
Publications
8,343
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1,873
Citations
Citations since 2017
12 Research Items
330 Citations
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20172018201920202021202220230102030405060
20172018201920202021202220230102030405060
20172018201920202021202220230102030405060

Publications

Publications (62)
Article
Full-text available
In equines, Cr 2 O 3 is widely accepted as an indigestible marker, but there are health concerns regarding the carcinogenic properties of Cr 2 O 3 . Recently, TiO 2 has been suggested to be an alternative digestibility marker in equines. However, a comparison between Cr 2 O 3 and TiO 2 has not been made in equines. Six Welsh pony geldings (initial...
Article
Full-text available
Exercise and physical training are known to affect gastrointestinal function and digestibility in horses and can lead to inaccurate estimates of nutrient and energy digestibility when markers are used. The effect of exercise on apparent nutrient digestibility and faecal recoveries of ADL and TiO 2 was studied in six Welsh pony geldings subjected to...
Article
Full-text available
Methodological aspects of digestibility measurements were studied in four Welsh pony geldings consuming haylage-based diets with increasing proportions of a pelleted concentrate according to a 4×4 Latin square design experiment. Ponies were fed four experimental, iso-energetic (net energy (NE) basis) diets (i.e. 22 MJ NE/day) with increasing propor...
Technical Report
Full-text available
Requirement values for apparent faecal digestible and standardised ileal digestible valine of broilers at different ages were estimated by a meta-analysis approach. This study was part of a project to estimate the apparent faecal (AFD) and standardized ileal digestible (SID) amino acid requirement values of the first limiting amino acids in both br...
Technical Report
Full-text available
Requirement values for apparent faecal digestible and standardised ileal digestible methionine+cysteine of broilers at different ages were estimated by a meta-analysis approach. This study was part of a project to estimate the apparent faecal (AFD) and standardized ileal digestible (SID) amino acid requirement values of the first limiting amino aci...
Technical Report
Full-text available
Requirement values for apparent faecal digestible and standardised ileal digestible tryptophan of broilers at different ages were estimated by a meta-analysis approach. This study was part of a project to estimate the apparent faecal (AFD) and standardized ileal digestible (SID) amino acid requirement values of the first limiting amino acids in bot...
Technical Report
Full-text available
Requirement values for apparent faecal digestible and standardised ileal digestible lysine of broilers at different ages were estimated by a meta-analysis approach. This study was part of a project to estimate the apparent faecal (AFD) and standardized ileal digestible (SID) amino acid requirement values of the first limiting amino acids in both br...
Technical Report
Full-text available
Requirement values for apparent faecal digestible and standardised ileal digestible threonine of broilers at different ages were estimated by a meta-analysis approach. This study was part of a project to estimate the apparent faecal (AFD) and standardized ileal digestible (SID) amino acid requirement values of the first limiting amino acids in both...
Technical Report
Full-text available
Requirement values for apparent faecal digestible and standardised ileal digestible arginine of broilers at different ages were estimated by a meta-analysis approach. This study was part of a project to estimate the apparent faecal (AFD) and standardized ileal digestible (SID) amino acid requirement values of the first limiting amino acids in both...
Technical Report
Full-text available
Requirement values for apparent faecal digestible and standardised ileal digestible isoleucine of broilers at different ages were estimated by a meta-analysis approach. This study was part of a project to estimate the apparent faecal (AFD) and standardized ileal digestible (SID) amino acid requirement values of the first limiting amino acids in bot...
Technical Report
Full-text available
Requirement values for apparent faecal digestible and standardised ileal digestible valine of broilers at different ages were estimated by a meta-analysis approach. This study was part of a project to estimate the apparent faecal (AFD) and standardized ileal digestible (SID) amino acid requirement values of the first limiting amino acids in both br...
Article
Full-text available
Different numbers of animals have been used in different studies to cover the variation between individual animals in in situ rumen degradation characteristics of maize and grass silages. The objective of this study was to determine whether three cows are sufficient or not to cover the variation between individual cows in in situ rumen degradation...
Article
Full-text available
The chemical composition and the energy and protein value of five batches of condensed distillers solubles (CDS) originating from wheat were determined. The net energy for lactation (NEL) was derived from digestion coefficients obtained with sheep. The true protein digested in the small intestine (DVE) and the rumen degradable protein balance (OEB)...
Article
Methodological aspects of digestibility measurements of feedstuffs for equines were studied in four Welsh pony geldings consuming four grass-hay diets in a 4 × 4 Latin square design. Diets contained either a low (L), medium (M), high (H), or very high (VH) ADF content (264, 314, 375, or 396 g·kg DM, respectively). Diets were supplemented with miner...
Article
Methodological aspects of digestibility measurements of feedstuffs for equines were studied in four Welsh pony geldings consuming four grass-hay diets in a 4 × 4 Latin square design. Diets contained either a low (L), medium (M), high (H), or very high (VH) ADF content (264, 314, 375, or 396 g·kg-1 DM, respectively). Diets were supplemented with min...
Article
In in situ nylon bag technique, many feed evaluation systems use a washing machine method (WMM) to determine the washout (W) fraction and to wash the rumen incubated nylon bags. As this method has some disadvantages, an alternate modified method (MM) was recently introduced. The aim of this study was to determine and compare the W and non-washout (...
Technical Report
Full-text available
Dit rapport geeft een update van de behoefte aan aminozuren (lysine, methionine+cysteine, threonine en tryptofaan) van leghennen, zowel op basis van schijnbaar fecaal verteerbare als gestandaardiseerd ileaal verteerbare aminozuurgehalten van het voer. Hiervoor is een meta-analyse uitgevoerd op peer reviewed dosis-response studies. Studies moesten v...
Article
Full-text available
The DVE/OEB2010 system in the Netherlands uses a large database of in situ rumen incubations with grass silage and grass hay samples to derive prediction formulas to estimate the rumen degradation characteristics of a number of feed value parameters. These in situ rumen incubations were not performed for this specific purpose and the data were gene...
Article
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 mi...
Article
Full-text available
The chemical composition inclusive amino acids (AAs) and the energy and protein value of three wheat, three maize and seven blend (mainly wheat) dried distillers grains and solubles (DDGS) were determined. The net energy for lactation (NEL) was derived from digestion coefficients obtained with sheep. The digestible protein in the intestines (DVE) a...
Article
The Dutch feed evaluation system for ruminants uses assumptions and regression equations to estimate the intestinal digestibility of crude protein (CP), neutral detergent fibre (NDF) and starch. These assumptions and equations are based on many different studies, obtained over a very long period. The objective of this study was to develop a unique...
Article
In deze publicatie wordt beschreven hoe de in CVB verband tot stand gekomen voedernormen voor deze voedingsstoffen tot stand zijn gekomen. De publicatie is het resultaat van een deskstudie waarbij allereerst de Duitse DLG normen en de Amerikaanse NRC normen zijn geëvalueerd. Daar waar nodig is gericht gekeken of er nieuwe studies beschikbaar zijn,...
Article
In the current Dutch protein evaluation system (the DVE/OEB 1991 system), two characteristics are calculated for each feed: true protein digested in the intestine (DVE) and the rumen degradable protein balance (OEB). Of these, DVE represents the protein value of a feed, while OEB is the difference between the potential microbial protein synthesis (...
Conference Paper
The DVE/OEB2010 system (Van Duinkerken et al., 2011) for protein evaluation in ruminants is an update of the DVE/OEB1994 system (Tamminga et al,., 1994). In the DVE/OEB2010 system more detail and differentiation is included concerning representation of chemical components in feed, rumen degradation characteristics of these components, efficiency of...
Article
In this study, a modified version of the gas production technique was used to determine protein fermentation characteristics in rumen fluid of 19 feedstuffs. Performing the incubations in a N-free environment, and with an excess of rapidly fermentable carbohydrates, made N the limiting factor to microbial growth, and so gas production profiles refl...
Article
In vitro and in situ studies were conducted to evaluate the influence of different mathematical models, used to fit gas production profiles of 15 feedstuffs, on estimates of nylon bag organic matter (OM) degradation kinetics. The gas production data were fitted to Exponential, Logistic, Gompertz and a Sigmoidal model. Using only gas production para...
Article
Een penssynchronisatiesysteem heeft als doel energie en stikstof gelijktijdig en in de juiste verhouding beschikbaar te laten komen voor de micro-organismen in de pens. Penssynchronisatie blijkt in vivo minder belangrijk dan theoretisch wordt aangenomen. Met het verschijnen van dit rapport en de overige publicaties uit het project “Penssynchronisat...
Article
Om meer inzicht te krijgen in de waterbehoefte van guste en drachtige zeugen en in factoren die de waterbehoefte beïnvloeden is door het ID-DLO en het Praktijkonderzoek Varkenshouderij gezamenlijk onderzoek hiernaar gedaan. Op het ID-DLO is nagegaan wat het effect is van verschillende water-/voerverhoudingen en verschillende eiwitgehalten in het vo...
Article
Full-text available
In 1991 a new protein evaluation system replaced the Digestible Crude Protein (DCP) system in the Netherlands: the DVE/OEB-system. The system was mainly developed with the aim to prevent avoidable losses of nitrogen, by feeding according to more exactly defined requirements of dairy cows. A second aim was to predict milk protein production more acc...
Article
Bacteriorhodopsin vesicles were associated with cellulose-nitrate filters impregnated with a solution of phospholipids in hexadecane. The generation of (photo)potentials upon illumination of the filter was studied in the absence and presence of ionophores, phospholipase A2, EDTA or polyene antibiotics. From these experiments the following conclusio...
Article
31P NMR has been used to measure light-induced pH changes inside bacteriorhodopsin vesicles containing entrapped sodium glucose-6-phosphate. Reversible light-induced pH changes were observed at various pH values. The results indicate that our vesicle preparations were not homogeneous with respect to the generation of pH gradients.
Article
The non-electrolyte permeability of liposomal membranes has been investigated according to the concepts of irreversible thermodynamics. A strong interaction between the permeation of solute and water was observed. This solute-solvent interaction can be fully described by assuming that a number of water molecules will copermeate with each molecule o...
Article
1. The reflection coefficient for the permeation of thiourea through bilayers of phosphatidylcholine is a function of the fatty-acid composition of the lipid molecules. By means of these reflection coefficients an index for membrane fluidity has been given to each of those lipids, relative to that of egg phosphatidylcholine. 2. The maximum number o...
Article
A photopotential is generated upon illumination of a phospholipid-impregnated Millipore filter to which are bound phospholipid vesicles, containing bacteriorhodopsin isolated from Halobacterium halobium. In this study, experiments are described that show how the bacteriorhodopsin-dependent photo effect is influenced by factors that have an affect o...
Article
The permeation of water through liposomal membranes composed of phosphatidylcholine plus varying amounts of cholesterol was studied as a function of temperature. 1. Increasing amounts of cholesterol caused a gradual disappearance of the abrupt change in the rate of water permeation near the gel to liquid-crystalline phase transition temperature of...
Chapter
Because the barrier properties of biological membranes are provided by a lipid bilayer, it has been useful to establish correlations between membrane characteristics and the chemical and physical properties of their constituent lipids by comparative studies on permeability properties of liposomes. Studies on liposomes demonstrated that the bilayer...
Article
In this paper experimental conditions are described to measure the three irreversible thermodynamic parameters for the nonelectrolyte permeatiion through liposomes.The values for the reflection coefficient σ, measured by this method, differ significantly from those found previously.
Article
Aspects of osmotic properties of liposomes, prepared from synthetic lecithin, above, at and below the gel to liquid crystalline phase transition temperature are described. The experiments show that liposomal membranes with their lipids in the gel state are still permeable to water. The rate of water permeation changes drastically on passing the tra...
Article
This paper describes experiments showing the importance of the fatty acid chain length on the barrier properties of liposomal bilayers, prepared from saturated lecithins, under conditions of lateral phase separation. 1. Above the gel to liquid crystalline phase transition temperature, liposomes prepared from saturated lecithins with 14 or more carb...
Article
The kinetics of the valinomycin-induced K+ leak from egg lecithin liposomes with KCNS enclosed were studied by measuring the initial increase of the leak following the addition of the ionophore. Variation of liposome and valinomycin concentrations enabled a discrimination between the affinity of the ionophore for the lipid bilayer and the turnover...
Article
Experiments dealing with the valinomycin-induced K+ leak from egg lecithin liposomes have demonstrated the importance of the enclosed anion. Except when lipophilic anions are enclosed, the addition of both valinomycin and a uncoupler, e.g. carbonylcyanide p-trifluoromethoxyphenylhydrazone, is necessary to induce a significant increase of the K+ lea...
Article
1.1. Sixty minutes after injection of 32P-labelled phosphate into rats, the specific activities of phosphatidylcholine and phosphatidylethanolamine were determined in mitochondria, outer and inner mitochondrial membranes, and microsomes. The phospholipid specific activities of the outer membrane were lower than those of the microsomes and 3 to 4 ti...

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