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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    National Reference Laboratories RIKILT Wageningen University & Research : annual report 2016
    Leeuwen, S.P.J. van; Mol, J.G.J. ; Lee, M.K. van der; Gerssen, A. ; Lasaroms, J.J.P. ; Sterk, S.S. ; Raamsdonk, L.W.D. van; Jong, J. de; Scholtens-Toma, I.M.J. ; Alewijn, M. ; Weesepoel, Y.J.A. ; Ginkel, L.A. van; Meijer, Nathan ; Noordam, M.Y. - \ 2017
    Wageningen : RIKILT Wageningen University & Research (RIKILT Report 2017.007) - 49
    reference standards - laboratories - food legislation - europe - annual reports - food safety - food quality - feeding standards - referentienormen - laboratoria - voedingsmiddelenwetgeving - europa - jaarverslagen - voedselveiligheid - voedselkwaliteit - voedingsnormen
    National Reference Laboratories (NRLs) are part of the system responsible for the control and enforcement of EU food and feed law. RIKILT Wageningen University & Research has been designated as the NRL for twelve subjects. The tasks of a NRL depend on its research field. This report gives an overview of the activities performed by all of RIKILT's NRLs in 2016.
    Trendanalyse van contaminanten in diervoeders : mogelijkheden en problemen bij het gebruik van historische monitoringsgegens
    Adamse, P. ; Boer, W.J. de; Nijs, W.C.M. de - \ 2014
    Wageningen : RIKILT Wageningen UR (RIKILT report 2014.007) - 53
    besmetters - diervoeding - historische verslagen - tendensen - statistische analyse - gevalsanalyse - voedselveiligheid - voedingsnormen - gegevensverwerking - analytische methoden - contaminants - animal nutrition - historical records - trends - statistical analysis - case studies - food safety - feeding standards - data processing - analytical methods
    Voor het verkrijgen van inzicht in het basisniveau van een contaminant in een diervoeder kan gebruik worden gemaakt van monitoringsgegevens. Zowel de gegevens als de te gebruiken technieken moeten wel aan bepaalde voorwaarden voldoen. In een vorig rapport (Adamse, 2014) staat beschreven hoe met redelijk eenvoudige statistische basistools analyses kunnen worden uitgevoerd. In het huidige rapport staan meer complexe statistische analyses beschreven met daarbij de mogelijkheden en potentiele problemen.
    Trendanalyse van historische gegevens : handleiding voor het gebruik van monitoringsgegevens
    Adamse, P. - \ 2014
    Wageningen : RIKILT Wageningen UR (RIKILT report 2014.001) - 22
    tendensen - historische verslagen - monitoring - analytische methoden - statistische analyse - diervoeding - besmetters - voedselveiligheid - voedingsnormen - gegevensverwerking - voederveiligheid - trends - historical records - monitoring - analytical methods - statistical analysis - animal nutrition - contaminants - food safety - feeding standards - data processing - feed safety
    Het doel van dit rapport is om aan te geven welke technieken gebruikt kunnen worden om inzicht te krijgen in het achtergrondniveau van contaminanten in diervoeders en diervoederproducten. Beschreven is tevens met welke factoren rekening gehouden moet worden bij het gebruik van historische monitoringsgegevens. Deze gegevens zijn verzameld in het kader van monitoringsprogramma’s.
    Aanbevolen hoeveelheden gebasseerd op schattingen (interview met C.P.G.M. de Groot)
    Geerts, A. ; Groot, C.P.G.M. de - \ 2010
    VoedingsMagazine 23 (2010)2. - ISSN 0922-8012 - p. 24 - 26.
    voedingsnormen - ouderen - ouderenvoeding - aanbevolen dagelijkse hoeveelheden - voedselconsumptie - voeding en gezondheid - feeding standards - elderly - elderly nutrition - recommended dietary allowances - food consumption - nutrition and health
    Eind 2009 werden de 'Vraag het de Expert'-bijeenkomsten over senioren gehouden. 'Besef dat de aanbevolen hoeveelheden voedingsmiddelen gebaseerd zijn op schattingen. Een kritische reflectie op de getallen die je hanteert is belangrijk', zei prof. dr. Lisette de Groot tegen de diëtisten in de zaal. De gebruikte voedingsnormen zijn niet zonder meer geschikt voor de beoordeling van voedselconsumptiegegevens van individuen.
    Energie- en eiwitbehoefte van schapen
    Sebek, L.B.J. ; Gosselink, J.M.J. - \ 2006
    Lelystad : Animal Sciences Group / Praktijkonderzoek (Praktijkrapport / Animal Sciences Group, Praktijkonderzoek : Schapen ) - 42
    schapen - energiebehoefte - eiwitbehoefte - schapenvoeding - voedingsnormen - sheep - power requirement - protein requirement - sheep feeding - feeding standards
    In 2004 is een literatuuronderzoek uitgevoerd om een betere onderbouwing en eventuele aanpassing van de behoeftenormen voor schapen mogelijk te maken. Op basis van deze literatuurstudie is aanpassing van de normen mogelijk. Het rapport levert echter geen ‘kant-en-klare’ voedernormen voor schapen, omdat geconstateerd is dat voor sommige onderdelen (door onvoldoende goede literatuurbronnen) de deskundigheid van een expertpanel nodig is om goed onderbouwde keuzes te maken. Samen met de bevindingen van dit expertpanel zal de inhoud van dit rapport leiden tot een CVB-documentatierapport, op basis waarvan een herziening van de voedernormen voor schapen in het CVB-Tabellenboek Veevoeding zal worden overwogen
    Voeren op de norm : scherper voeren vooral voor intensieve bedrijven financieel interessant
    Hamminga, A.J. ; Berentsen, P.B.M. - \ 2003
    Veeteelt 20 (2003)6. - ISSN 0168-7565 - p. 12 - 14.
    melkveehouderij - melkvee - rundveevoeding - voedingsnormen - kosten-batenanalyse - rendement - agrarische bedrijfsvoering - intensieve landbouw - extensieve landbouw - dairy farming - dairy cattle - cattle feeding - feeding standards - cost benefit analysis - returns - farm management - intensive farming - extensive farming
    Uitgerekend is wat de kosten en opbrengsten zijn bij het boven de norm voeren en bij verscherpt op de norm voeren, waarbij onderscheid is gemaakt in extensieve en intensieve bedrijven
    Leer uw bedrijf kennen met BBPR versie 7
    Nijssen, K. ; Boer, J.M. de; Kanis, J. - \ 2000
    Praktijkonderzoek Rundvee, Schapen en Paarden. Praktijkonderzoek 13 (2000)4. - ISSN 1386-8470 - p. 6 - 7.
    rundveeteelt - agrarische bedrijfsvoering - mineralen - boekhouding - computer software - toepassingen - rundveevoeding - voedingsnormen - cattle farming - farm management - minerals - accounting - computer software - applications - cattle feeding - feeding standards
    Begin 2000 is de nieuwe versie van BBPR gereed gekomen. BBPR versie 7 bevat belangrijke verbeteringen, bijvoorbeeld in de berekening van de voedervoorziening. Het is een hulpmiddel om uw bedrijf beter te leren kennen en het effect van veranderde bedrijfsvoering vooraf te bepalen.
    Kengetal voor energiebalans
    Vries, M.J. de; Veerkamp, R.F. - \ 1999
    Veeteelt (1999). - ISSN 0168-7565 - p. 360 - 362.
    melkveehouderij - melkvetpercentage - lactatie - agrarische bedrijfsvoering - voedingsnormen - energetische waarde - statistische gegevens - dairy farming - milk fat percentage - lactation - farm management - feeding standards - energy value - statistical data
    Op ID-DLO ging men op zoek naar een andere methode om de energiebalans in een kengetal te vatten: de verandering in het vetpercentage tijdens het begin van de lactatie blijkt een goede graadmeter. Een sterke daling van het vetgehalte duidt op een negatieve energiebalans
    Feeds and feeding strategies for Colossoma macropomum (Cuvier 1818) : fish growth as related to dietary protein
    Meer, M.B. van der - \ 1997
    Agricultural University. Promotor(en): E.A. Huisman; M.C.J. Verdegem. - S.l. : Van der Meer - ISBN 9789056510381 - 137
    visvoeding - vissen - voer - visteelt - voedingsrantsoenen - voedingsnormen - voedingswaarde - groei - metabolisme - eiwitten - characiformes - fish feeding - fishes - feeds - fish culture - feed rations - feeding standards - nutritive value - growth - metabolism - proteins - characiformes

    Colossoma macropomum is an indigenous fish species from the Amazon region. The amino acid profile of its body protein proved to be similar to that of other fish species. Soya meal and fish meal have, based on their amino acid profiles, a comparable protein quality. This hypothesis was confirmed in a feeding trial. As soya meal is less palatable than fish meal, more soya in the diet tends to decrease feed uptake and growth rate, but increases protein utilization efficiency. Growth of C. macropomum is fast and requires a dietary protein content of approximately 43%. Fish growing at maximal speed displayed a protein utilization efficiency of only 50% of the maximal possible efficiency. In ad libitum fed C macropomum 20 - 30% of the feed remains uneaten. In spite of this wasted feed, the feed uptake/weight gain ratio ranged between 0.57 and 0.71 with a high quality feed. Increasing the feeding frequency from one to five meals per day increased feed uptake and growth. Fish displayed a clear daily bio-rhythm with maximal feed uptake in the late afternoon. Lipid addition to the diet increased the protein utilization efficiency less than reported for salmon. An increased dietary protein content increased the body protein content and decreased the body lipid content. Adaptation of the size of the internal organs to the characteristics of the diet is possibly the cause that diet composition affects the body composition of fish. Accumulated data were analyzed by an empirical and an explanatory model. Both methods identified protein ration as the major variable determining fish growth. In describing the data, the average errors of both methods were similar. However, the empirical model produced more outlying values. It was concluded that the explanatory model with some minor improvements can be turned into a useful tool for research and practical management. Fast growth and a flexible body composition make C. macropomum a suitable study object for the development of improved fish growth models.

    OEB in rantsoen vleesstieren
    Heeres-van der Tol, J.J. ; Plomp, M. - \ 1996
    Lelystad : Praktijkonderzoek Rundvee, Schapen en Paarden (Publicatie / Praktijkonderzoek Rundvee, Schapen en Paarden (PR) 119) - 17
    voer - eiwitten - diervoedering - voedingswaarde - voedingsnormen - groei - ontwikkeling - vleesvee - stieren (bulls) - vleesproductie - feeds - proteins - animal feeding - nutritive value - feeding standards - growth - development - beef cattle - bulls - meat production
    Op grond van de proefresultaten wordt voor vleesstieren voorlopig een rantsoen met een positieve OEB geadviseerd.
    Control of individual daily growth in group-housed pigs using feeding stations
    Ramaekers, P.J.L. - \ 1996
    Agricultural University. Promotor(en): M.W.A. Verstegen; L.A. den Hartog; J.W.G.M. Swinkels. - S.l. : Ramaekers - ISBN 9789054856054 - 133
    varkens - groei - ontwikkeling - voedingsnormen - voedersystemen - pigs - growth - development - feeding standards - feeding systems
    In this thesis, it was examined whether it is possible to control individual daily growth and carcass composition in group-housed pigs using feeding stations. A forelegs weighing system to estimate the daily individual body weight (BW) of group-housed pigs was developed and validated. In two experiments, BW dependent feeding strategies in the finishing period were examined in relation to performance and carcass traits. In Exp. 1, the daily energy allowance of barrows was restricted to 18 MJ ME per day above maintenance. In Exp. 2, barrows were restricted to a feeding level at which their growth was similar to the mean growth of a group of ad libitum fed gilts. In Exp. 1, feed restriction improved lean meat tissue percentage with 2.6 units. In Exp. 2, feed restriction resulted in a similar growth as the ad libitum fed gilts, but gave no improvement of the lean meat tissue percentage. In both experiments, feed restriction decreased the between animal variance in energy intake, but not in energy conversion ratio, growth or lean meat tissue percentage. In addition to energy intake, carryover effects from the growing period and number of meals per day of ad libitum fed pigs explained part of the variance in lean meat tissue percentage. In conclusion, feeding stations and forelegs weighing devices can be used to control individual daily growth and carcass traits of group-housed pigs. However, the variance in performance and carcass traits was not only related to the variance in energy intake.
    Nieuwe versie Normen Voor de Voedervoorziening
    Boer, J.A. de; Vellinga, Th.V. - \ 1995
    Praktijkonderzoek / Praktijkonderzoek Rundvee, Schapen en Paarden (PR), Waiboerhoeve 8 (1995)4. - ISSN 0921-8874 - p. 9 - 11.
    diervoedering - rundvee - landbouwbedrijven - voedingsnormen - voer - bedrijfsinformatiesystemen - animal feeding - cattle - farms - feeding standards - feeds - management information systems
    In dit artikel worden de belangrijkste uitbreidingen en aanpassingen toegelicht.
    Towards a physiological feeding strategy for protein in broilers
    Doeschate, R.A.H.M. ten - \ 1995
    Agricultural University. Promotor(en): M.W.A. Verstegen, co-promotor(en): V.V.A.M. Schreurs. - S.l. : Ten Doeschate - ISBN 9789054854098 - 227
    voer - eiwitten - vleeskuikens - voedingsnormen - feeds - proteins - broilers - feeding standards

    The present thesis describes the development of a physiological feeding strategy for protein in broilers. This project was initiated to improve the efficiency of deposition of dietary nitrogen into animal product in order to reduce nitrogen excretion to the environment. The physiological feeding strategy was based on the consideration that feeding the birds according to their requirements based on physiological status would result in the highest efficiency. At the start of the project, requirement data for amino acids were considered not adequate. For this reason the amino acid pattern required was estimated based on a factorial approach. Generally in a factorial approach requirements are divided in a requirement for production and a requirement for non- productive purposes. The required amino acid pattern for production was based on the amino acid pattern of body accretion. Due to the high growth rate of broiler chicks and high N-efficiency the largest part of dietary amino acids is used for nett protein deposition. This implies that the required dietary amino acid pattern is mainly determined by the amino acid pattern of body accretion.

    In the first chapter whole body amino acid composition of broiler chicks was studied with the aim to provide this basis amino acid pattern for diet formulation. Three genotypes were studied; a commercial broiler hybrid (Corn) and two experimental lines: one selected for high growth rate (GL) and one selected for efficient feed conversion (FC). Male and female Corn chicks were compared. Change of whole body amino acid composition with age was studied in male Corn chicks by weekly analysis.

    Whole body amino acid composition at the consecutive sampling moments showed several small, but statistically significant (P<0.001), differences. The differences in the amino acid pattern of body accretion in 0-21 and 22-49 days of age leads to the proposal to compose different dietary formulations in these age- periods.

    The three genotypes differed in relative amino acid composition. Analysis of growth pattern revealed no differences between Corn and GL genotype, the FC genotype however had a clearly different growth pattern. Similar growth patterns did not result in similar whole body amino acid composition.

    Compared to male Corn birds, whole body of female Corn birds contained relative less essential amino acids (cys, met, val, tyr, phe and his) and more non-essential (glu, asp) amino acids. It is suggested that the amino acid pattern of whole body accretion in male Corn chicks can be used as a basis for diet formulation for broiler chicks of different genotypes and sexes.

    When formulating diets based on the required amino acid pattern it is essential to know the nett availability of nutrients from the diet. For this reason in chapter 2 a digestibility study is included in this thesis. The influences of genotype, age and sex on droppings digestibility coefficients of a compound food were studied using male and female broiler chickens of three different genotypes at 2, 4 and 6 weeks of age. Because the traditional method of determination of droppings digestibility coefficients of nitrogen may lead to systematic errors in estimating the feeding value of foodstuffs, a method is proposed to determine the ileal digestibility coefficients. The ileal method is compared with the droppings method for a mixed food and for two foodstuffs: wheat and solvent-extracted soyabean meal.

    Birds selected for efficient food conversion showed distinctly higher digestibility coefficients for all nutrients than birds selected for high growth potential or birds from a commercial strain. The influence of age on digestibility coefficients was not consistent. Female birds showed digestibility coefficients which were, in general, 3% higher than those of male chickens. Interactions of genotype and sex and between genotype and age for energy metabolisability were the only interactions observed for digestibility measurements.

    The method of determination influenced the amino acid digestibility coefficients of the mixed food and the relative feeding values of wheat and soyabean meal.

    It is important to use well defined animals (genotype, sex, age) in evaluating foodstuffs. The preferred method for determination of digestibility coefficients of nitrogen and amino acids is based on ileal sampling, although the differences in amino acid digestibility coefficients were small between methods.

    After amino acids are made available from the diet, the metabolic utilisation of the amino acids determines whether they are used for either protein synthesis or for non- productive purposes. The utilisation of amino acids for non-productive purposes was studied with 14CO 2 breath test measurements. In these measurements a tracer quantitiy of a [ 14C]amino acid is injected in a bird with a defined physiological status and exhaled 14CO 2 is collected during 4½ hours after injection. 14CO 2 recovery is a measure for oxidation of the amino acid.

    In chapter 3 the effect of nutritional status (dietary lysine content, time of injection relative to the meal) on 14CO 2 recovery from intraperitoneal hp) injected [U- 14C] lysine was studied in broiler chicks.

    It was found that ip injection of [ 14C] labelled amino acids ([U- 14C] lysine) sometimes resulted in unrealistic high recovery values in 14CO 2 breath test measurements. The most probable explanation is that with ip-injection in some cases label is injected in an abdominal air sac. In this case part of the substrate is not converted to 14CO 2 but is straight excreted as an aerosol. For this reason ip-injection of tracer amino acids is considered to be risky in chickens and therefore subcutaneous injection is used in further experiments.

    When only the realistic, lower, range of 14CO 2 recoveries from ([U- 14C] lysine were considered, lysine content of the diet caused a response in 14CO 2 recovery while time of injection did not give a detectable effect. Low lysine diet resulted in lower 14CO 2 recovery, indicating a restriction of lysine oxidation.

    In birds conditioned on a lighting regime of 1L:2D, 14CO 2 recovery from subcutaneous injected [1- 14C]leucine or [1- 14C]valine was studied within one cycle of the lighting regime with injections at 30, 60, 120 or 180 minutes after onset of a half-hour meal.

    For both [1- 14C] leucine and [1- 14C]valine 14CO 2 recovery was higher when injection at 30 or 60 min after onset of a half hour meal is compared to injection at 120 or 180 min. This can be interpreted as that a 14CO 2 breath test measurement should be started at 30 or 60 minutes after onset of a meal when amino acid utilisation in fed animals is to be investigated.

    In chapter 4 the effect of dietary amino acid content and of length of adaptation period on 14CO 2 , recovery from [ 14C]amino acids was studied in broiler chick breath test measurements.

    A lower (70% of normal) dietary lysine level increased 14CO 2 recovery from [1- 14C]leucine as well as from [1- 14C]valine during the first growth phase (5-22 d of age). In older chicks this effect was less pronounced. A reduced vs increased dietary methionine level (67 vs 133 % of normal) increased 14CO 2 recovery from [1- 14C]leucine only at about 4 weeks of age. At a low dietary lysine level 14CO 2 recovery from [U- 14C]lysine was lower than at a normal lysine level. Length of adaptation period to a low lysine diet (1, 2, 3 or 5 d) had no statistically significant effect on 14CO 2 2 recovery from [1- 14C]leucine

    The utilization of leucine and valine for protein synthesis, as indicated by the complement of the 14CO 2 recovery from [ 14C]amino acids, is affected by dietary limiting amino acid level. The age-dependent effect of dietary methionine level suggests that the method is especially suited for assessment of specific requirements during specific stages of development. The absence of influence of length of adaptation period to a low lysine diet on 14CO 2 recovery from [ 14C] leucine suggests that adaptation is either rapid (< 1 day) or not measured with this approach. It is concluded that 14CO 2 recovery from [ 14C ]amino acids indicates amino acid adequacy of the diet fed immediately preceeding (20h period) the breath test measurement.

    In chapter 5, nitrogen efficiency was studied in birds fed diets based on the amino acid pattern of body accretion at three levels of proteinlenergy (P/E) ratio, supplemented with Met, Arg, Glu and Gly, individually, as a group or not. This study was performed to see whether the amino acid pattern of body accretion could be used as a basis for diet formulation or that specific alterations in the pattern were required. The level of protein/energy (P/E) ratio may affect N-efficiency Furthermore, there may be an interaction between dietary composition and genotype. Growth performance and nitrogen efficiency were measured in male and female chicks of two different genotypes, fed diets differing in amino acid composition and in P/E ratio. There were twelve diets. Three diets, of which the amino acid pattern was similar to the amino acid pattern of body accretion, differed only in P/E ratio (High: 17.8 and 19.3 g CP/MJ AME during 0-21 d of age and 22 d-slaughter age, respectively; Medium and Low: 94 % and 87 % of High). Six other diets were based on the medium P/E ratio but were supplemented with either Met, Arg, Glu, Gly, Glu + Gly or all four amino acids together. Two more diets were based on the low or high P/E ratio and supplemented with all four amino acids. Diet 12 was a control diet with a semi-practical composition. Male chicks of a commercial broiler hybrid (Corn) were fed all diets. Male chicks from a population selected for low feed conversion ratio (FC) were fed the three diets differing in P/E ratio plus the medium P/E diet supplemented with all four amino acids. This latter diet and the unsupplemented medium P/E diet were fed to female chicks of both genotypes.

    It was shown that no amino acid supplementation improved N-efficiency; Metsupplementation improved growth rate at similar N-efficiency while other supplementations negatively affected N-efficiency. Both genotypes reacted similar to differences in dietary composition. This supports the hypothesis that the amino acid pattern of body accretion is a good reference for dietary amino acid pattern. Female chicks also reacted similar to differences in dietary composition as male chicks but attained a much lower N-efficiency. Growth performance was lower at low P/E ratio while N-efficiency was lower at high P/E ratio. This shows that maximal growth performance and maximal N-efficiency can not be attained simultaneously. It is calculated that, compared to male Com chicks fed the control diet, feeding the diet with highest N- efficiency (low P/E ratio) will result in a reduction of N-excretion of 11 %. When this diet is fed to male FC chicks, N-excretion will be only 67 % of that of male Com chicks fed the control diet. It is concluded that dietary as well as genetic improvement will result in lower N-excretion.

    Based on the previous studies it was hypothesized that nitrogen efficiency could be further increased by a decrease in dietary supply of specific non-essential amino acids (Glu + Asp + Ala, NEAA) since these amino acids are synthesized as a result of the degradation of essential amino acids. Normally these amino acids function to transport amino acid nitrogen from the sites of amino acid degradation to the site of where they are combined with glycine to synthesize uric acid which is subsequently excreted. If the excretion of uric acid is increased by extra dietary non-essential amino acid nitrogen this will result in a extra demand for glycine since glycine, contrary to the other amino acids contributing nitrogen to uric acid, is completely incorporated. Since glycine can be synthesized from threonine an increase in dietary NEAA level might result in an increased non-productive threonine requirement.

    In chapters 6 and 7 three experiments are described in which responses of birds fed several different diets are compared. Chapter 6 describes technical performance such as growth rate, feed conversion ratio (FCR) and nitrogen efficiency whereas chapter 7 describes weight and yield percentages of edible and other portions after slaughter. In the first experiment described in chapters 6 and 7 a comparison is made between a practical diet and experimental diets based on either data from the literature or the amino acid pattern of body accretion plus some adaptations of both these patterns. It was shown that the amino acid pattern of body accretion can be used as basis for calculation of amino acid requirements. There were no differences in response between a diet based on literature or a diet based on the amino acid pattern of body accretion. The practical diet resulted in a lower N-efficiency, higher growth rate and lower FCR. In the second growth phase (15-35 d of age) there was a positive effect of extra methionine (relative to the pattern of body accretion) on growth and FCR without negative effect on N-efficiency. This implies that in this growth phase dietary methionine level should be higher than that based on the level of body accretion.

    It was shown that absolute meat production was only slightly affected by dietary amino acid pattern while for relative yields several significant but minor differences were found. Breast meat percentage was highest in birds fed a diet with extra Met and lowest in birds fed a diet with extra Glu. It is concluded that within three proposed dietary amino acid patterns variation in dietary amino acid pattern had only minor influence on slaughter efficiency.

    In the second experiment described in chapters 6 and 7 it was tested whether it was possible to promote utilisation of non-essential amino acids formed in the obligatory breakdown of essential amino acids for nett protein synthesis by lowering the dietary non-essential amino acid level. Nine diets with varying levels of glutamic acid + aspartic acid + alanine (NEAA) were fed to male broiler chicks. It was shown that with lower NEAA levels growth rate was lowered, FCR was higher, but N-efficiency was higher. Maximal growth rate and maximal N-efficiency can thus not be reached simultaneously.

    It was shown that variation in dietary NEAA level had no effect on yields of body parts as percentage of live weight. Total production was related to live weight and was decreased with decreasing dietary NEAA level.

    The third experiment described in chapters 6 and 7 was based on the theory that high NEAA excess will lead to extra uric acid production which will lead to an increase in glycine requirement. Since glycine can be formed from threonine, threonine requirement might be affected by NEAA level. In an experiment with three threonine and three NEAA levels it was shown that at high NEAA level the effect of low threonine level was more severe than at low NEAA level. A distinct interaction between dietary Thr and NEAA level on yields was observed. This supports the hypothesis that the requirement of threonine is determined not only by the requirement for body accretion but also by a requirement for glycine production to excrete excess nitrogen.

    In general it can be concluded that the developed physiological feeding strategy can improve nitrogen efficiency. However, the limits to practical application may depend on an economic evaluation. Moreover, an improved knowledge concerning utilisation of non-essential amino acids for uric acid and protein synthesis may result in further improvement in the physiological feeding strategy.

    Nieuwe versie Normen Voor de Voedervoorziening sluit beter aan op de praktijk
    Boer, J.A. de; Vellinqa, Th.V. - \ 1994
    Praktijkonderzoek / Praktijkonderzoek Rundvee, Schapen en Paarden (PR), Waiboerhoeve 7 (1994)6. - ISSN 0921-8874 - p. 3 - 6.
    toepassingen - computer software - concentraten - melkvee - melkveehouderij - voedingsnormen - ruwvoer (roughage) - applications - computer software - concentrates - dairy cattle - dairy farming - feeding standards - roughage
    Bij de ontwikkeling van deze nieuwe versie is ook getracht het programma beter aan te laten sluiten op praktijksituaties. In dit artikel worden enkele belangrijke verschillen met de oude versie toegelicht.
    Hoe nemen MDM-bedrijven beslissingen over de veevoeding?
    Bakker, J.J. ; Wien, J.F. ; Zaalmink, B.W. - \ 1994
    Praktijkonderzoek / Praktijkonderzoek Rundvee, Schapen en Paarden (PR), Waiboerhoeve 7 (1994)1. - ISSN 0921-8874 - p. 25 - 28.
    diervoedering - computers - concentraten - melkvee - melkveehouderij - gegevensverwerking - voedingsnormen - voer - bedrijfsvoering - microcomputers - minicomputers - natuurlijke hulpbronnen - bescherming - herstel - hulpbronnengebruik - statistische gegevens - duurzaamheid (sustainability) - machines - animal feeding - computers - concentrates - dairy cattle - dairy farming - data processing - feeding standards - feeds - management - microcomputers - minicomputers - natural resources - protection - rehabilitation - resource utilization - statistical data - sustainability - machines
    Het project Management op Duurzame Melkveebedrijven omvat het volgen en demonstreren van bedrijven die een voorbeeldfunctie vervullen voor 'duurzame melkveehouderij'.
    Nieuwe DVE-normen voor melkvee
    Subnel, A. ; Meijer, R. - \ 1993
    Lelystad : Proefstation voor de Rundveehouderij, Schapenhouderij enPaardenhouderij (Publikatie / Proefstation voor de Rundveehouderij, Schapenhouderij en Paardenhouderij 78) - 22
    dierlijke producten - melkvee - melkveehouderij - voedingsnormen - voer - melkkwaliteit - melkopbrengst - eiwitgehalte - eiwitten - jonge dieren - animal products - dairy cattle - dairy farming - feeding standards - feeds - milk quality - milk yield - protein content - proteins - young animals
    Het PR heeft 8 proeven gedaan om de DVE-nor-men voor melkvee te toetsen. Er zijn 5 proeven uitgevoerd met nieuwmelkte koeien en 3 proeven met oudmelkte koeien. Uit de resultaten van het onderzoek blijkt dat naast de verhouding tussen eiwit en energie in het rantsoen ook het lactatiestadium en productieniveau van invloed zijn op de efficiëntie waarmee DVE wordt omgezet in melkeiwit en dus op de DVE-behoefte.
    Normen voor de Voedervoorziening
    Alem, G.A.A. van; Holshof, G. ; Mandersloot, F. ; Meulen, M.A. van der; Mooij, M. ; Nijssen, J.M.A. ; Vellinga, Th.V. ; Teenstra, E.D. ; Wever, C.J.G. - \ 1991
    Lelystad : Proefstation voor de Rundveehouderij, Schapenhouderij enPaardenhouderij (Publikatie / Proefstation voor de Rundveehouderij, Schapenhouderij en Paardenhouderij 70) - 63
    diervoedering - voer - rundvee - voedingsnormen - computer software - toepassingen - animal feeding - feeds - cattle - feeding standards - computer software - applications
    In deze publicatie is een beschrijving gegeven van het systeem Normen Voor de Voedervoorziening (NVV). Doel van NVV is het berekenen van een voor elk bedrijf specifieke, taakstellende norm voor de aankoop van krachtvoer en de aan- of verkoop van ruwvoer. Deze norm wordt gebruikt voor begrotingen voor en analyse van melkveebedrijven.
    Amino acid requirements of pigs. 3. Requirement for apparent digestible threonine of pigs in different stages of growth.
    Lenis, N.P. ; Diepen, J.T.M. van - \ 1990
    Netherlands Journal of Agricultural Science 38 (1990)3B. - ISSN 0028-2928 - p. 609 - 622.
    amino acids - feeding standards - feeds - growth - pigs - proteins
    Amino acid requirements of pigs. 1. Requirements for methionine + cystine, threonine and tryptophan of fast-growing boars and gilts, fed ad libitum.
    Lenis, N.P. ; Diepen, J.T.M. van; Goedhart, P.W. - \ 1990
    Netherlands Journal of Agricultural Science 38 (1990)3B. - ISSN 0028-2928 - p. 577 - 595.
    amino acids - digestibility - feeding standards - feeds - pigs - proteins
    Effect van sorteren en aantal voerplekken op groei en spreiding van groei bij aal (Anguilla anguilla)
    Heul, J.W. van der - \ 1989
    IJmuiden : R.I.V.O. (Rapport / Rijksinstituut voor Visserijonderzoek AQ 89-05) - 13
    palingen - voedingsrantsoenen - voedingsnormen - visteelt - vissen - eels - feed rations - feeding standards - fish culture - fishes
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