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

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

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

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

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

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

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

    Nutrition of pigs kept under low and high sanitary conditions : effects on animo acid and energy metabolism and damaging behaviour
    Meer, Yvonne van der - \ 2017
    Wageningen University. Promotor(en): W.J.J. Gerrits, co-promotor(en): A.J.M. Jansman; A. Lammers. - Wageningen : Wageningen University - ISBN 9789463431972 - 181
    pigs - feeds - pig feeding - animal nutrition - amino acid metabolism - animal health - energy metabolism - abnormal behaviour - behaviour disorders - immune system - nutrition physiology - varkens - voer - varkensvoeding - diervoeding - aminozuurmetabolisme - diergezondheid - energiemetabolisme - abnormaal gedrag - gedragsstoornissen - immuunsysteem - voedingsfysiologie

    It is economically and environmentally important to match the nutrient supply to the nutrient requirements in pig production. Until now, the effects of different sanitary conditions on energy and nutrient requirements are not implemented in recommendations for nutrient composition of pig diets. The current nutrient requirement data are based on studies with pigs in experimental settings, which can be regarded as rather optimal. Changes in nutrient requirements caused by differences in sanitary conditions are poorly documented. As in the pig production sector farm conditions are variable it is of major importance to determine the effects of low sanitary conditions (LSC) on requirements for amino acids and energy in growing pigs. Pigs under LSC have an increased risk of clinical and subclinical infections, resulting in a chronic stimulation of their immune system. Immune system stimulation is known to influence energy and amino acid metabolism. However, most studies in pigs evaluating the relationship between immune system stimulation and nutrient requirements often use specific experimental challenge models. Whereas such models have the obvious advantage of reproducibility and allow mechanistic insight in the effects of stimulating specific parts of the immune system, these models often induce clinical illness, rather than subclinical infections. Results obtained with such models may therefore be difficult to translate to practical situations. Therefore the objective of the present thesis was to study the effect of low and high sanitary conditions (HSC) on amino acids and energy metabolism in pigs. Also interactions between the immune system, nutrient metabolism and damaging behaviour of pigs were considered in this thesis.

    The experiment described in Chapter 2 was designed to study the effect of different dietary crude protein levels and extra amino acid supplementation on the growth performance of pigs kept under different sanitary conditions. In a 2×2×2 factorial arrangement, 68 groups of 9 pigs were allocated to either LSC or HSC, and were offered ad libitum access to two different diets, a normal crude protein concentration diet or a low crude protein concentration diet, each having either a basal dietary amino acid profile or supplemented dietary amino acid profile containing 20% more methionine, threonine, and tryptophan compared with the basal profile. The pigs were followed from 10 weeks of age until slaughter. Haptoglobin concentrations in serum and IgG antibody titers against keyhole limpet heamocyanin, collected in the starter, grower, and finisher phases, and pleuritis scores at slaughter were greater for LSC pigs compared with HSC pigs, illustrating that sanitary conditions affected health conditions. The average daily gain and gain to feed ratio were greater for HSC pigs compared with LSC pigs. A 20% increase in dietary supplementation of methionine, threonine, and tryptophan relative to lysine increased gain to feed ratio more in LSC than in HSC pigs. The results therefore illustrated that dietary requirements for methionine. threonine, and tryptophan were greater for LSC compared with HSC pigs.

    In Chapter 3 the damaging behaviour of 576 pigs from the experiment in Chapter 2 was evaluated. At 15, 18, and 24 weeks of age, prevalence of tail and ear damage, and of tail and ear wounds was scored. At 20 and 23 weeks of age, frequencies of biting behaviour and aggression were scored by behaviour sampling. The prevalence of ear damage during the finisher phase and the frequency of ear biting were increased in LSC compared with HSC pigs. The frequency of ear biting was increased in low protein fed pigs compared with normal protein fed pigs. The supplemented AA profile reduced ear biting only in LSC pigs. The prevalence of tail wounds was lower for pigs in LSC than for pigs in HSC in the grower phase. Regardless of dietary amino acid profile or sanitary status, pigs fed low protein diets showed more ear biting, tail biting, belly nosing, other oral manipulation directed at pen mates, and aggression than pigs fed normal protein diets, with no effect on ear or tail damage. In conclusion, both LSC and a reduction of dietary protein increased the occurrence of damaging behaviours in pigs and therefore may negatively impact pig welfare.

    The experiment of Chapter 4 was designed to quantify the difference in energy requirements for maintenance, and in incremental efficiencies for deposition of dietary energy and protein in the body of clinically healthy pigs kept under LSC or HSC, fed a basal diet either or not supplemented with additional methionine, threonine and tryptophan.

    In a 2 × 2 factorial arrangement, 24 groups of 6 pigs each were allocated to either a LSC or HSC, and were offered two different diets having either a basal or a dietary amino acid profile supplemented with methionine, threonine, and tryptophan. For each group of pigs, complete energy and nitrogen balances were determined during two consecutive weeks, during which feed was available ad libitum or at 70% of ad libitum. Fasting heat production was determined over a 25 h period of fasting after a period of restricted feeding. Low sanitary conditions increased fasting heat production from 696 to 750 kJ/(kg BW0.6 . d), regardless of the dietary amino acid supplementation. The incremental efficiency of ingested nitrogen for retention in the body was reduced in LSC pigs from 73 to 53%, but incremental efficiencies of digestible energy intake for fat deposition in the body were unaffected by the experimental treatments. These findings showed that the effects of continuous immune stimulation by introducing LSC, was affecting energy and nutrient efficiencies of pigs both at maintenance level and at a feeding level close to ad libitum intake.

    In Chapter 5 diurnal patterns for heat production, respiratory quotient, and carbohydrate and fat oxidation of the pigs studied in the experiment of Chapter 4 were evaluated to get more insight in the mechanisms behind the effects found in Chapter 4. The LSC pigs had reduced activity compared with HSC and a higher resting metabolic rate during the period of restricted feeding, especially during the light parts of the day. Therefore the diurnal energy expenditure pattern of LSC and HSC pigs can be considered as different. Fat and carbohydrate oxidation patterns were not different for LSC and HSC pigs, indicating that protein and fat deposition during the day was similar for LSC and HSC pigs.

    Overall, the results of this thesis indicate that both energy and AA requirements are greater in LSC pigs compared with HSC pigs. It is questionable, however, whether it is nutrient and cost effective and biologically possible to satisfy these increased nutrient requirements in LSC pigs, as the incremental efficiency of N for retained protein is low, and ADFI is reduced for LSC pigs compared with HSC pigs. The present thesis demonstrates that care should be taken in reducing dietary protein concentrations to improve protein efficiency in pigs, as it incurs a risk to increased damaging behaviours, particularly when pigs are kept under LSC.

    Interactions and functionalities of the gut revealed by computational approaches
    Benis, Nirupama - \ 2017
    Wageningen University. Promotor(en): M.A. Smits; V.A.P. Martins dos Santos, co-promotor(en): D. Schokker; M. Suarez-Diez. - Wageningen : Wageningen University - ISBN 9789463434546 - 247
    pigs - mice - digestive tract - digestive system - intestinal microorganisms - intestinal mucosa - computational science - immune system - feeds - animal nutrition - nutrition physiology - animal health - varkens - muizen - spijsverteringskanaal - spijsverteringsstelsel - darmmicro-organismen - darmslijmvlies - computational science - immuunsysteem - voer - diervoeding - voedingsfysiologie - diergezondheid

    The gastrointestinal tract is subject of much research for its role in an organism’s health owing to its role as gatekeeper. The tissue acts as a barrier to keep out harmful substances like pathogens and toxins while absorbing nutrients that arise from the digestion of dietary components in in the lumen. There is a large population of microbiota that plays an important role in the functioning of the gut. All these sub-systems of the gastrointestinal tract contribute to the normal functioning of the gut. Due to its various functionalities, the gut is able to respond to different types of stimuli and bring the system back to homeostasis after perturbations.

    The work done in this thesis uses several bioinformatic tools to improve our understanding of the functioning of the gut. This was achieved with data from model animals, mice and pigs which were subjected to changing environments before their gastrointestinal response was measured. Different types of stimuli were studied (eg, antibiotic exposure, changing diets and infection with pathogens) in order to understand the response of the gut to varying environments. This data was analysed using different data integration techniques that provide a holistic view of the gut response.

    Vertical data integration techniques look for associations between different types of ~omics data to highlight possible interactions between the measured variables. Lateral integration techniques allow the study of one type of ~omics data over several time points or several experimental conditions. Using these techniques, we show proof of interactions between different sub-systems of the gut and the functional plasticity of the gut. Of the several hypotheses generated in this thesis we have validated several using existing literature and one using an in-vitro system. Further validation of these hypotheses will increase understanding of the responses of the gut and the interactions involved.

    FeedOmics, an approach to evaluate the functional properties of protein containing feed ingredients
    Kar, Soumya K. - \ 2017
    Wageningen University. Promotor(en): M.A. Smits; J.M. Wells, co-promotor(en): A.J.M. Jansman; D. Schokker. - Wageningen : Wageningen University - ISBN 9789463434461 - 254
    compound feeds - ingredients - protein sources - proteins - functional properties - metabolism - feed formulation - protein digestion - proteomics - digestive tract - nutrition physiology - animal nutrition - livestock feeding - mengvoer - ingrediënten - eiwitbronnen - eiwitten - functionele eigenschappen - metabolisme - voersamenstelling - eiwitvertering - eiwitexpressieanalyse - spijsverteringskanaal - voedingsfysiologie - diervoeding - veevoeding

    This thesis presents FeedOmics approach as a toolkit, to evaluate (novel) protein containing feed ingredients of different origin considering both their nutritional and functional value in terms of their capacity to support or modify nutrient supply, the animal’s physiology, tissue development and functioning. Such knowledge may contribute to introduce novel and/or alternative protein containing feed ingredients in the diet of livestock, thus creating a sustainable food supply for growing human population.

    Assessing methane emission from dairy cows : modeling and experimental approaches on rumen microbial metabolism
    Lingen, Henk J. - \ 2017
    Wageningen University. Promotor(en): W.H. Hendriks, co-promotor(en): J. Dijkstra; A. Bannink; C.M. Plugge. - Wageningen : Wageningen University - ISBN 9789463431590 - 207
    dairy cows - methane - emission - microbial degradation - rumen metabolism - rumen fermentation - models - fatty acids - biochemical pathways - animal nutrition - nutrition physiology - melkkoeien - methaan - emissie - microbiële afbraak - pensmetabolisme - pensfermentatie - modellen - vetzuren - biochemische omzettingen - diervoeding - voedingsfysiologie

    Methane (CH4) is a greenhouse gas (GHG) with a global warming potential of 28 CO2 equivalents. The livestock sector was estimated to emit 7.1 gigatonnes of CO2 equivalents, which is approximately 14.5% of total global anthropogenic GHG emissions. Enteric CH4 production is the main source of GHG emissions from dairy cattle, representing 46% of the global GHG emissions in dairy supply chains. Dairy production has great value in view of the ability of ruminants to effectively turn human inedible biomass into human edible food and to produce food from non-arable land. Consequently, there is an urgent need to develop strategies to decrease dairy cattle enteric CH4 emission. Evaluation of these strategies requires meticulous quantification and increased understanding of anaerobic fermentation and methanogenesis in the rumen ecosystem. The overall aim of this PhD research was, therefore, to quantitatively evaluate enteric CH4 emission from dairy cows as affected by feeding and rumen microbial metabolism.

    A meta-analysis was performed to quantify relationships between enteric 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. Various milk FA concentrations were significantly or tended to be positively or negatively related to CH4 yield per unit of feed or milk. Mixed model multiple regression resulted in various milk FA included in optimal equations to predict CH4 yield per unit of feed and per unit of milk. These regression equations indicated a moderate potential for using milk FA profile to predict CH4 yield.

    For the development of a mechanistic model of CH4 production in the rumen, the thermodynamic control of pH2 on reaction rates of specific fermentation pathways, NADH oxidation and methanogenesis was theoretically explored. This control was determined using the thermodynamic potential factor (FT), which is a dimensionless factor that corrects a predicted kinetic reaction rate for the thermodynamic control exerted. The thermodynamic feasibility of these microbial conversions showed that the control of pH2 on individual VFA produced and associated yield of H2 and CH4 cannot be explained without considering NADH oxidation, with a considerable effect of pH.

    For obtaining experimental support of the conclusions drawn from the theoretical exploration, diurnal patterns of gaseous and dissolved metabolite concentrations in the bovine rumen, H2 and CH4 emitted, and the rumen microbiota were monitored. In addition, the effect of dietary inclusion of linseed oil on these patterns was assessed. An in vivo experiment with rumen cannulated dairy cows was performed to study the anaerobic metabolism and the microbiota composition in the rumen. A 100-fold increase in pH2 in the rumen headspace was observed at 0.5 h after feeding, followed by a decline. Qualitatively similar patterns after feeding were observed for H2 and CH4 emission, ethanol and lactate concentrations, and propionate molar proportion, whereas an opposite pattern was seen for acetate molar proportion. Associated with these patterns, a temporal biphasic change in the microbial composition was observed as based on 16S ribosomal RNA with certain taxa specifically associated with each phase. Bacterial concentrations were affected by time and increased by linseed oil supplementation. Archaeal concentrations tended to be affected by time and were not affected by diet, despite linseed oil supplementation tending to decrease the partial pressure and emission of CH4 and tending to increase propionate molar proportion. The various diurnal profiles that were monitored support the key role of the NAD+ to NADH ratio in rumen fermentation and the importance of diurnal dynamics when understanding VFA, H2 and CH4 production.

    A dynamic mechanistic model was developed, in which the thermodynamic control of pH2 on VFA fermentation pathways, and methanogenesis in the bovine rumen are incorporated. The model represents substrate degradation, microbial fermentation and methanogenesis in the rumen, with the type of VFA formed to be controlled by the NAD+ to NADH ratio, which in turn is controlled by pH2. Feed composition and feed intake rate representing a twice daily feeding regime were used as model input. The model predicted a marked peak in pH2 after feeding that rapidly declined in time. This peak in pH2 caused a decrease in NAD+ to NADH ratio followed by an increased propionate molar proportion at the expense of acetate molar proportion. In response to feeding, the model predicted a sudden increase and a steady decrease in CH4 production in time. The pattern of CH4 emission rate followed the patterns of pH2 and H2 emission rate, but its magnitude of increase in response to feeding was less pronounced. A global sensitivity analysis indicated the parameter that determines the NADH oxidation rate to explain the most substantial part of the variation of predicted daily CH4 emission. The modeling effort provides the integration of more detailed knowledge than accomplished in previous rumen fermentation models and enables assessment of diurnal dynamics of rumen metabolic pathways yielding VFA, H2 and CH4.

    For assessing the general value of the research reported in this thesis, the potential for predicting enteric CH4 emission from dairy cattle based on milk FA profile was discussed in the light of published studies and compared with empirical modeling of enteric CH4 based on feed input. Moreover, the concept of NAD-controlled fermentation was considered in a more general perspective by comparing the rumen ecosystem with bioreactor systems. Furthermore, the feasibility of the developed models as an alternative for IPCC tiered approaches was explored. In conclusion, the research reported in this thesis contributes to an increased understanding of rumen fermentation and microbial metabolism, and has provides a basis to further improve prediction models of enteric CH4 emissions from dairy cattle.

    First week nutrition for broiler chickens : effects on growth, metabolic status, organ development, and carcass composition
    Lamot, David - \ 2017
    Wageningen University. Promotor(en): Bas Kemp, co-promotor(en): Henry van den Brand; Peter Wijtten. - Wageningen : Wageningen University - ISBN 9789463430777 - 187
    broilers - animal nutrition - poultry feeding - feeds - growth - metabolism - carcass composition - nutrition physiology - vleeskuikens - diervoeding - pluimveevoeding - voer - groei - metabolisme - karkassamenstelling - voedingsfysiologie

    During the first week of life, broiler chickens undergo various developmental changes that are already initiated during incubation. Ongoing development of organs such as the gastro- intestinal tract and the immune system may affect the nutritional requirements during this age period. Despite the residual yolk that is available at hatch and that may provide nutritional support during the first days after hatch, the growth performance may be affected by the time in between hatch and first feed intake. Furthermore, it remains largely unknown to what extend nutritional composition of a pre-starter diet, as well as feed availability directly after hatch have an effect on physiological development directly after hatch, but also at later age. The aim of this thesis was to determine the impact of feed availability and feed composition provided during the first week of life on short-term physiological development, as well as potential long-term effects on growth performance of broiler chickens. Especially early hatched chickens were suggested to benefit more from direct feed access compared to midterm and late hatched chickens, as they tended to have a higher body weight gain during the first week after hatch. A delay in feed access for 48 h resulted in lowered body weight gain and feed intake when compared to direct feed access, but so did a short (13 to 26 h) delay in feed access after hatch. In the latter case, delayed feed access resulted in a lower weight to length ratio of the jejunum and ileum at 4 d of age compared with chickens with direct feed access. Although delayed feed access after hatch resulted in lower body weight gain during the first week after hatch and thereafter, it can be discussed whether this is truly an impairment of long-term growth or just a delayed onset of growth. With respect to feed composition, the inclusion of fish oil and medium chain fatty acids in a pre-starter diet had minor effects on humoral immune function. Inclusion of medium chain fatty acids did result in higher body weight gain and lowered feed efficiency during the first week of life, but only during the period it was provided. Feeding increased diet densities during the first week of life, obtained by formulating diets with different dietary fat levels, resulted in an increased gain to feed ratio, whereas body weight gain and feed intake decreased. Despite the shift in dietary energy supply from carbohydrates to fat and the perceived lower fat digestibility in young broiler chickens, nitrogen metabolizability and fat digestibility were not affected in the current study by feeding increased diet densities. The relative crop, liver and pancreas weights decreased when feeding increased diet densities, whereas the length of the entire intestinal tract increased. This suggests that broiler chickens repartition visceral organ development in response to feeding more concentrated diets during the first week of life. Interestingly, protein and fat accretion were not affected. Continued feeding of increased diet densities after 7 d of age resulted in increased BW gain, G:F ratio and metabolizable energy intake, but mainly during the periods that these diets were provided. In summary, even short durations of delayed feed access already impact intestinal development of young broiler chickens. However, a delayed feed access up to 48 h after hatch does not result in impaired growth, but only a delayed onset of growth. Even though digestibility of fats and oils may be suboptimal in young broiler chickens, feeding of these diets does not have to result in lowered performance per se. Young broiler chickens appear to adapt themselves towards high density diets with high fat inclusion levels in the first week of life, enabling them to digest and metabolize these diet types despite a suboptimal capacity for fat digestion. High density diets result in higher growth performance, but only for the period these diets are provided and thus carry-over effects at later age appear to be limited.

    Protein quality of pig diets : processing effects on amino acid digestibility and post-absorptive utilization
    Hulshof, Tetske - \ 2016
    Wageningen University. Promotor(en): Wouter Hendriks, co-promotor(en): Paul Bikker; Thomas van der Poel. - Wageningen : Wageningen University - ISBN 9789462579026 - 175
    pigs - protein quality - pig feeding - feeds - feed processing - amino acids - protein digestibility - digestive absorption - protein utilization - nutrition physiology - animal nutrition - varkens - eiwitkwaliteit - varkensvoeding - voer - voedermiddelbewerking - aminozuren - eiwitverteerbaarheid - verteringsabsorptie - eiwitgebruik - voedingsfysiologie - diervoeding

    The increasing world population and per capita income imposes a risk for protein scarcity. It is, therefore, necessary to use current ingredients more efficiently which includes the accurate assessment of protein quality before inclusion in animal diets. Protein quality is defined in this thesis as the capacity of a dietary protein to meet a pig’s requirement for nitrogen (N) and amino acids (AA) to meet a particular production target. Protein quality is influenced by processing applied to feed ingredients which may lead to the formation of Maillard reaction products (MRP) or cross-link products. The Maillard and cross-link reactions mainly involve lysine (Ly)s and their products may decrease ileal crude protein (CP) digestibility. During the acid hydrolysis step used to analyze AA, part of the early MRP revert back to Lys. This reverted Lys is not bioavailable for animals. Therefore, methods that specifically analyze Lys with a free ε-amino group (that is, not bound to other nutrients) have been developed. The guanidination reaction with O-methylisourea (OMIU) is one such method. The initial aim of this thesis was to evaluate the ileal digestible reactive Lys assay as a more accurate measure for protein quality of processed protein sources than the ileal digestible total Lys assay. Soybean meal (SBM) and rapeseed meal (RSM) were used as sole protein sources throughout this thesis. Processing of SBM and RSM by toasting at 95°C for 30 min in the presence of a sugar-rich lignosulfonate was used as model for over-processed protein sources.

    Digestibility, post-absorptive utilization, and pig growth performance

    In Chapter 2, protein quality in processed protein sources was determined using the content of AA, OMIU-reactive Lys, MRP, and lysinoalanine (LAL; as cross-link product), the standardized ileal digestibility (SID) of AA and OMIU-reactive Lys and pig growth performance. The SBM and RSM diets contained furosine and carboxymethyllysine (CML) as MRP, and LAL indicating that the Maillard and cross-link reactions had taken place in SBM and RSM, presumably during the oil extraction/desolventizing process. The amounts of furosine, CML, and LAL were elevated in the pSBM and pRSM diets due to further processing. Processing resulted in a reduction in total and OMIU-reactive Lys contents, a decreased pig growth performance as determined by the gain to feed ratio (G:F), and the SID of CP, AA, and OMIU-reactive Lys. The SID AA contents of the protein sources from Chapter 2 were used to formulate the diets of the main in vivo experiment (Chapters 3 and 4). In this experiment, six experimental diets were used of which four contained either SBM, pSBM, RSM, or pRSM as sole protein source. The remaining two experimental diets contained pSBM or pRSM and were supplemented with crystalline AA to the same SID AA levels as the SBM or RSM diet. These supplemented diets were used to verify that processing affected AA digestibility rather than post-absorptive AA utilization. The effects of processing on CP digestibility and N solubilization along the small intestine, metabolic load as assessed by organ weight, and nutrient composition of the empty body of growing pigs are described in Chapter 3. The small intestine was divided in three segments of similar length and digesta was collected from the last 100 cm of each segment. The amount of insoluble N as a fraction of N in digesta at each small intestinal segment was not affected by processing. Thus, the reduced SID of CP and AA reported in Chapter 2 was not caused by a reduced N solubility but by a general increase of N in digesta. Processing reduced the SID of CP, CP content in the empty body, and G:F. Supplementing crystalline AA to diets containing pSBM or pRSM increased the CP content and G:F to the level of the SBM and RSM diets. Processing also reduced the weight of several organs and supplementing crystalline AA restored organ weight. The effects of processing on whole body AA composition, nutrient retention, and post-absorptive utilization of AA in growing pigs are described in Chapter 4. Post-absorptive AA utilization was calculated as percentage of SID AA intake used for AA retention. Processing affected the AA composition of protein in the organ fraction (that is, empty organs and blood), carcass, and empty body. The Lys concentration in body protein was mainly reduced by processing. Supplementing crystalline AA restored the AA composition of body protein for SBM and RSM. Processing reduced AA retention and again supplementing crystalline AA restored AA retention for both SBM and RSM. Since crystalline AA were supplemented on an SID AA basis, the results indicated that processing affected AA digestibility but not post-absorptive AA utilization. Thus, correcting AA retention for SID AA intake would result in a similar post-absorptive AA utilization which was found for most AA for the RSM diets. However, the post-absorptive AA utilization was lower for the pSBM diet than for the SBM diet which might be related to an imbalanced AA supply after absorption in the first diet.

    The assessment of ileal digestibility and utilization is expensive and laborious. Therefore, two alternative in vitro methods for determining protein digestibility for processed protein sources were evaluated (Chapter 5). The protein digestibility determined using the pH-STAT method and a 2-step enzymatic method was compared with the in vivo SID of CP reported in Chapter 2. Initial pH and the degree of hydrolysis assessed in the pH-STAT method were positively correlated to SID of CP. Protein digestibility determined with the 2-step enzymatic method, simulating digestion in the stomach and small intestine, tended to correlate to SID of CP. Both the 2-step enzymatic method and pH-STAT method were suitable alternatives for the assessment of SID of CP. However, only four ingredients were tested. The suitability of the methods should be further studied using multiple (processed) feed ingredients before they can be used as alternatives for in vivo assays.

    Reactive Lys analysis

    O-methylisourea was reported to bind specifically to the ε-amino group of Lys. The results of Chapter 2, however, cast doubt on the specificity of OMIU to react only with the ε-amino group of Lys. A series of experiments was conducted to study this specificity (Chapter 6). Incubating crystalline L-Lys with OMIU under standard conditions (OMIU pH of 10.6, OMIU to AA ratio of 1000:1, and reaction time of 7 d) resulted in a low homoarginine (that is, Lys with OMIU bound to its ε-amino group) recovery. The reaction of OMIU with the α-amino group of Lys was confirmed by mass spectrometry analysis with double derivatized Lys being identified. Several reaction conditions (OMIU pH, OMIU to Lys ratio, and reaction time) were studied but none of these resulted in 100% recovery of homoarginine. Binding of OMIU to the α-amino group of Lys could result in an underestimation of the reactive Lys content when significant levels of Lys with a free α-amino group (that is, crystalline L-Lys (HCl), free and N-terminal Lys) are present in food/feed ingredients, diets, and ileal digesta. The free Lys content in food/feed ingredients was on average 1.3% of total Lys. The free Lys content can be substantial in certain diets and was reported to be 13% of total Lys in ileal digesta. The latter might result in an overestimation of the OMIU-reactive Lys digestibility. The reaction of OMIU with α-amino groups may necessitate analysis of free Lys to accurately quantify reactive lysine in samples containing a large proportion of Lys with a free α-amino group.

    The results presented in this thesis indicate that the effects of processing on SID of CP and AA, body composition, nutrient retention, post-absorptive AA utilization, and growth performance could be substantial. These effects should, therefore, be taken into account when using processed feed ingredients in diets for growing pigs. The extent of protein damage in feed ingredients can be assessed by the analysis of OMIU-reactive and total Lys, MRP, and cross-link products. However, OMIU-reactive Lys only provides accurate results when samples contain small levels of Lys with a free α-amino group (that is, crystalline L-Lys (HCl), free and N-terminal Lys). When samples contain significant levels of Lys with a free α-amino group, it is recommended to use standard guanidination conditions (OMIU pH of 10.6, OMIU to AA ratio of 1000:1, and reaction time of 7 d) to convert protein-bound Lys to homoarginine and to separately analyze such samples for free Lys.

    Are all eggs equal? : embryonic development and nutrient metabolism in chicken eggs of different origins
    Nangsuay, A. - \ 2016
    Wageningen University. Promotor(en): Bas Kemp, co-promotor(en): Henry van den Brand; R. Meijerhof. - Wageningen : Wageningen University - ISBN 9789462577749 - 213
    eggs - hens - broilers - characteristics - strains - embryonic development - nutrients - metabolism - hatcheries - poultry - nutrition physiology - eieren - hennen - vleeskuikens - karakteristieken - stammen (biologisch) - embryonale ontwikkeling - voedingsstoffen - metabolisme - broedinstallaties - pluimvee - voedingsfysiologie

    Hatching eggs, supplied to hatcheries are originating from different origins varying in breed, strain, and breeder age. These hatching eggs can be different in size, composition and eggshell properties, which might influence nutrient and O2 availability and consequently could affect embryonic development and nutrient metabolism. The aim of this thesis was therefore 1) to investigate effects of egg origin on nutrient and O2 availability, 2) to investigate effects of egg origins on nutrient metabolism and embryonic development and 3) to investigate consequences of different egg origins on the incubation process and hatching characteristics. In five studies, effects of different egg origins on nutrient and O2 availability, nutrient metabolism, embryo development and hatching characteristics were investigated. The first and second study focused on breeder age and egg size. The third study on breed; broilers and layers. The fourth study on broiler strain and the fifth study on breeder age, strain and eggshell temperature (EST). The overall findings in this thesis suggest that hatching eggs from different origins are not equal in availability of nutrients and O2. Nutrient availability is altered through variation in yolk size, especially by the effects of breeder age and breed. O2 availability is altered by differences in eggshell properties, which is influenced by especially breed and broiler strain. The availability of both nutrients and O2 plays a role on nutrient metabolism measured as embryonic heat production (HP) and consequently on embryonic development. Between incubation day (E) E7 and E14, both nutrient and O2 availability might affect nutrient metabolism as shown in the results of the broiler and layer comparison. Between E14 and hatching, the availability of O2 becomes the most determinant factor for nutrient metabolism and consequently for embryonic development. An increase in EST from 37.8 to 38.9°C from E7 onward resulted in an acceleration of nutrient metabolism and embryonic development until E16, but thereafter a high EST resulted in reduced yolk free body mass development. Embryos with an accelerated metabolic speed at an early stage of incubation, caused by an increased EST, might reach limited O2 availability at a higher magnitude than the embryos at a normal EST. As a result, nutrient metabolism is restricted and embryonic development is depressed. It can be concluded that not only the HP, but also the availability of O2 is crucial to be taken into account for developing incubator temperature. The principle is to obtain an optimal EST, which could maintain the balance between O2 requirement (driven by nutrient metabolism) and O2 availability for a continuing optimal nutrient metabolism to generate sufficient energy for embryonic development throughout incubation.

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

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


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

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

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

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

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

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

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

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

    Influence of pectin supplementation on feed fermentation characteristics in rats and pigs
    Tian, L. - \ 2016
    Wageningen University. Promotor(en): Harry Gruppen; Henk Schols. - Wageningen : Wageningen University - ISBN 9789462577282 - 142
    pigs - rats - pectins - feed supplements - dietary fibres - digestion - digestive tract - carbohydrates - microbial flora - nutrition physiology - animal nutrition - food chemistry - varkens - ratten - pectinen - voedersupplementen - voedingsvezels - spijsvertering - spijsverteringskanaal - koolhydraten - microbiële flora - voedingsfysiologie - diervoeding - voedselchemie

    The physiological effects of dietary fiber (DFs) depend on several factors including structural features of the DFs, composition and activity of colonic microbiota, and products formed during fermentation. In this thesis, the influence of pectin supplementation to feed fermentation characteristics in rats and pigs was studied. The non-starch polysaccharides (NSP) present in the selected feed ingredient oats were characterized. Distinct populations of arabinoxylans (AXs) were observed in oats, compared to those reported for other cereals like wheat and barley. The fate of cereal AXs and soybean pectin during fermentation and the consequent effects on appetite regulation and fat accumulation were studied in rats as a model. Oat AXs were fermented less rapidly than wheat AXs in the caecum of rats. Soy pectin was fermented more early and efficiently than cereal AXs. A significant inverse correlation between rat retroperitoneal fat-pad weight and concentration and relative SCFA proportion of butyrate was observed. In a following in vivo rat experiment, commercial soy pectin together with three other soluble pectins originating from citrus and sugar beet and differing in their methyl esterification were individually supplemented to the diets. Their effects on the utilization of the different DFs present in the feed and the consequent effect on the microbial community in the colon of rats was studied. All pectins were fermented rapidly and consequently shifted fermentation of other consumed DFs (e.g. cereal AXs) to more distal part of colon, although low-methyl esterified pectin was more efficiently fermented by the microbiota than high-methyl esterified pectin. Results suggested that pectins can confer beneficial health effects through modulation of the gut microbiota. In a last in vivo experiment, citrus pectins together with a hydrothermal treated soybean meal were supplemented to pig diets to study their effect on the digestion and fermentation of carbohydrates in both the small and large intestine. Pectins, and more particularly low-methyl esterified pectin, decreased the ileal digestibility of digestible starch resulting in more starch to be fermentated in the proximal colon of pigs. Consequently, also the fermentation patterns of DFs and the microbiota composition was affected. All pectins tested shaped the colonic microbiota from a Lactobacillus-dominated microbiota to a Prevotella-dominated community, with potential health-promoting effects.

    Fungal treatment of lignocellulosic biomass
    Kuijk, S.J.A. van - \ 2016
    Wageningen University. Promotor(en): Wouter Hendriks, co-promotor(en): John Cone; Anton Sonnenberg. - Wageningen : Wageningen University - ISBN 9789462576544 - 191
    lignocellulosic wastes - fungi - treatment - ruminant feeding - rumen digestion - wheat straw - wood chips - livestock feeding - nutrition physiology - animal nutrition - lignocellulosehoudend afval - schimmels - behandeling - herkauwersvoeding - pensvertering - tarwestro - houtspaanders - veevoeding - voedingsfysiologie - diervoeding

    Summary PhD thesis Sandra J.A. van Kuijk

    Carbohydrates in plant cell walls are highly fermentable and could be used as a source for ruminant nutrition or biofuel production. The presence of lignin in cell walls hampers the utilization of these carbohydrates and should thus be removed. In this thesis, the possibilities of a fungal treatment of lignocellulosic biomass are investigated.

    A review of the scientific literature focusing on the potential of fungal treatments to increase the utilization of lignocellulosic biomass in ruminants feed ingredients is presented in Chapter 2. A prerequisite to the effective use of high lignocellulose feed ingredients is lignin removal, since lignin is negatively correlated to in vitro rumen degradability. Selective lignin degrading fungi have proven to increase in vitro rumen degradability with Ceriporiopsis subvermispora and Pleurotus eryngii showing the greatest potential. The effectiveness of fungal treatment is not only dependent on the choice of fungal strain, but also on the choice of substrate and culture conditions.

    Based on the literature review, four different edible fungal species, i.e. Ganoderma lucidum, Lentinula edodes, P. eryngii and P. ostreatus were chosen to treat four different substrates, i.e. miscanthus, rice straw, wheat straw and wood chips. The results of these fungal-substrate combinations are described in Chapter 3 and confirm that fungal species, substrate and incubation time are important factors in fungal treatment. The most promising fungus-substrate combinations are L. edodes treatment of wheat straw and L. edodes treatment of wood chips. These two fungus-substrate combinations were used in a more detailed characterization of changes in lignin upon fungal treatment.

    In Chapter 4, a study is described where L. edodes treated wheat straw and wood chips are analyzed by pyrolysis coupled to gas chromatography and mass spectrometry (Py-GC/MS) confirming the selective lignin degradation as determined with the detergent fiber analysis. Structural changes in lignin were observed with preferential degradation of syringyl (S) lignin units over guaiacyl (G) lignin units by L. edodes. Upon fungal delignification, a number of degradation products of lignin were observed. The building blocks in the original lignin consist of phenolic groups with 3 C-atoms in the side chain, while degradation products consist of phenolic groups with 0 to 2 C-atoms in the side chain. The ratio between side chain degradation products and original compounds was increasing in both wheat straw and wood chips upon L. edodes treatment. Besides side chain degradation, L. edodes modified the Cα-atom of the side chain by oxidation. Although correlations were found, a clear relationship between lignin composition and in vitro rumen degradability could not be demonstrated.

    The safety of a fungal treatment of ruminant feed ingredients requires the used fungus to have a Generally Regarded As Safe (GRAS) status. The literature data compiled in Chapter 2 indicates C. subvermispora, which does not have a GRAS status, as one of the most promising fungi for fungal treatment. For this reason this fungus was included in the remaining chapters. This fungus was researched in Chapter 5 with the substrates wheat straw and wood chips and compared to L. edodes. Both fungi selectively degraded lignin and improved in vitro rumen degradability and the amount of sugar released upon enzymatic saccharification. L. edodes continuously grew on wheat straw and wood chips while degrading lignin and hemicellulose at the same time. C. subvermispora colonized the wheat straw within the first week of treatment and starts degrading lignin and hemicellulose thereafter. Growth continued again after 5 weeks, which was accompanied by cellulose degradation. On wood chips, C. subvermispora stopped growing after the first week of treatment, while lignin degradation continued until 4 weeks of treatment. From 5 weeks onwards, no chemical changes were observed in wood chips. One of the explanations for this lack of change is the dense structure of the wood as observed with light microscopy. Both fungi degraded hemicellulose simultaneously with lignin. The loss of carbohydrates during fungal treatment and the long treatment times of up to 8 weeks represent a major disadvantage of fungal treatment of lignocellulosic biomass.

    In Chapter 6, the incubation of C. subvermispora and L. edodes with wheat straw and wood chips were supplemented with urea to stimulate growth, and manganese and linoleic acid to stimulate lignin degradation via the enzyme manganese peroxidase produced by the fungi. Addition of manganese increased the selectivity of C. subvermispora treatment of wheat straw within the first 4 weeks of treatment. Addition of 150 µg manganese per g substrate improved lignin degradation and in vitro rumen degradability the most. A combination of manganese and linoleic acid did not show synergistic effects.

    In Chapter 7 the particle size of wheat straw and wood chips, and the amount of C. subvermispora or L. edodes at the start of the treatment was varied. The amount of fungus added at the start of the treatment did not have an effect on colonization rate, lignin degradation or in vitro rumen degradability. L. edodes treatment of wheat straw chopped to 2 cm particles resulted in a higher lignin degradation and in vitro rumen degradability compared to L. edodes treatment of wheat straw chopped to a length of 0.5 cm. The particle size of wood chips did not have an effect on C. subvermispora treatment. In C. subvermispora treated wheat straw and L. edodes treated wood chips, a reduced growth was observed, which was unexpected based on results from previous experiments. A toxic compound to fungi (fungicide) was identified.

    This thesis describes the potential of fungal treatment to increase utilization of lignocellulosic biomass. Fungal treatment resulted in an increased in vitro rumen degradability, and thus an increased cellulose accessibility. The same theory applies for biofuel production in which fungal treatment results in an increased accessibility of cellulose for enzymes. The major disadvantages of this low cost, relatively simple and environmentally-friendly biotechnological treatment are the loss of carbohydrates during the relatively long process of fungal incubation. Future studies should focus on optimization of the fungal treatment to enable large scale application.

    Replacing lactose from calf milk replacers : effects on digestion and post-absorptive metabolism
    Gilbert, M.S. - \ 2015
    Wageningen University. Promotor(en): Wouter Hendriks, co-promotor(en): Walter Gerrits; Henk Schols. - Wageningen : Wageningen University - ISBN 9789462576032 - 171
    vleeskalveren - lactose - kunstmelk - polysacchariden - glucose - fructose - glycerol - zetmeelvertering - metabolisme - fermentatie - kalvervoeding - diervoeding - voedingsfysiologie - veal calves - lactose - filled milk - polysaccharides - glucose - fructose - glycerol - starch digestion - metabolism - fermentation - calf feeding - animal nutrition - nutrition physiology

    Summary PhD thesis Myrthe S. Gilbert

    Replacing lactose from calf milk replacers – Effects on digestion and post-absorptive metabolism

    Veal calves are fed milk replacer (MR) and solid feed. The largest part of the energy provided to veal calves originates from the MR. Calf MR contains 40 to 50% lactose, originating from whey, a by-product from cheese production. High and strongly fluctuating dairy prices are a major economic incentive to replace lactose from the calf MR by alternative energy sources. The objective of this thesis was to study the effects of replacing lactose from calf MR on nutrient digestion and fermentation and post-absorptive metabolism.

    In Chapter 2 and 3, four starch products (SP) were evaluated for replacing lactose. The four SP differed in size and branching, and consequently required different ratios of starch-degrading enzymes for their complete hydrolysis to glucose. Gelatinized starch required α-amylase and (iso)maltase; maltodextrin required (iso)maltase and α-amylase; maltodextrin with α-1,6-branching required isomaltase, maltase and α-amylase and maltose required maltase. In Chapter 2, adaptation to these SP was assessed during 14 weeks, using a within-animal titration study. Forty male Holstein-Friesian calves (n = 8 per treatment) were assigned to either a lactose control MR or one of four titration strategies, each testing the stepwise exchange of lactose for one of the SP. For control calves, fecal dry matter (DM) content and fecal pH did not change over time. The response in fecal DM content and fecal pH in time did not differ between SP treatments and decreased linearly with 0.57% and 0.32 per week, respectively, where one week corresponded to an increase in SP inclusion of 3%. This indicates that the capacity for starch digestion was already exceeded at low inclusion levels, resulting in SP fermentation. All SP required maltase to achieve complete hydrolysis to glucose and it was, therefore, suggested that maltase is the rate-limiting enzyme in starch digestion in milk-fed calves.

    Following the titration, a fixed inclusion level of 18% of the SP in the MR was applied. Effects on starch-degrading enzyme activity, nutrient disappearance, SP fermentation and jugular glucose appearance were measured (Chapter 3). Lactase activity in the brush border was high in the proximal small intestine of all calves, resulting in a high apparent ileal disappearance of lactose (≥ 99% of intake). Maltase and isomaltase activities in the brush border were not increased for any of the SP treatments. Luminal α-amylase activity was lower in the proximal small intestine but greater in the distal small intestine of SP-fed calves compared to control calves. This amylase activity in the distal small intestine of SP-fed calves might have been of microbial origin. Apparent SP disappearance did not differ between SP treatments. The difference between apparent ileal (62%) and total tract (99%) SP disappearance indicated substantial SP fermentation in the large intestine (37% of intake). In addition, total tract SP fermentation was quantified using fecal 13C excretion which originated from the naturally 13C-enriched corn SP. Total tract SP fermentation averaged 89% of intake, regardless of SP treatment. MR leaking into the reticulorumen was measured as the recovery of Cr in the reticulorumen at slaughter after feeding MR pulse-dosed with Cr 4h prior to slaughter. MR leaking into the reticulorumen averaged 11% for SP-fed calves. By difference, this leaves 41% of the SP intake fermented in the small intestine. This coincided with increased fecal nitrogen (N) and DM losses for SP-fed calves. However, apparent total tract crude fat disappearance tended to increase when replacing lactose with SP. The substantial SP fermentation indicates that only 10% of the SP intake was enzymatically hydrolyzed and absorbed as glucose. This was in agreement with the marginal increase in 13C enrichment in peripheral plasma glucose after feeding naturally 13C-enriched gelatinized starch and maltose, compared to a clear increase after feeding naturally 13C-enriched lactose to control calves. It was concluded that fermentation, rather than enzymatic digestion, is the main reason for small intestinal starch disappearance in milk-fed calves. The expected decrease in growth performance with such extensive SP fermentation is partially compensated by the greater crude fat digestion and possibly by a reduced urinary glucose excretion when replacing lactose with SP.

    Glucose, fructose and glycerol do not require enzymatic hydrolysis and can be absorbed directly from the small intestine. However, these lactose replacers might differentially affect glucose and insulin metabolism and with that energy partitioning. The effects of partly replacing lactose with glucose, fructose or glycerol on energy and N partitioning and glucose homeostasis and insulin sensitivity were, therefore, studied in Chapter 4 and 5. Forty male Holstein-Friesian calves either received a lactose control MR or a MR in which one third of the lactose was replaced with glucose, fructose or glycerol (n = 10 per treatment). Energy and N retention were not affected by MR composition. Fructose absorption from the small intestine was incomplete resulting in fructose fermentation. This resulted in fecal losses of DM, energy and N and the lowest numerical energy and N retention for fructose-fed calves. Postprandial plasma concentrations of glucose exceeded the renal threshold for glucose in glucose-fed calves and control calves, which resulted in urinary glucose excretion. Glycerol was likely excreted with the urine of glycerol-fed calves. Oxidation of glucose, fructose and glycerol was quantified by feeding a single dose of [U-13C]glucose, [U-13C]fructose or [U-13C]glycerol with the MR and subsequently measuring 13CO2 production. Oxidation of lactose replacers did not differ between lactose replacers and averaged 72% of intake. However, the time at which the maximum rate of oxidation was reached was delayed for fructose-fed compared to glucose-fed and glycerol-fed calves, indicating that fructose was converted into other substrates before being oxidized. Conversion of fructose and glycerol into glucose was confirmed by an increase in 13C enrichment of peripheral plasma glucose after feeding [U-13C]fructose and [U-13C]glycerol, respectively. Insulin sensitivity did not differ between MR treatments, but was already low at the start of the experiment at 15 weeks of age and remained low throughout the experiment. It was concluded that glucose and glycerol can replace one third of the lactose from the calf MR, but that inclusion of fructose should be lower to prevent incomplete absorption from the small intestine.

    In literature and the studies in this thesis, high inter-individual variation in growth performance was found in veal calves. The experiment described in Chapter 6 was, therefore, designed to assess the predictability of later life growth performance by charactering calves in early life. In addition, it was examined whether the ability of calves to cope with MR in which lactose is partially replaced by alternative energy sources can be predicted. From 2 to 11 weeks of age, male Holstein-Friesian calves were fed a lactose control MR and solid feed according to a practical feeding scheme and were characterized individually using targeted challenges related to feeding motivation, digestion, post-absorptive metabolism, immunology, behavior and stress. Based on the results in Chapter 4, a combination of glucose, fructose and glycerol in a 2:1:2 ratio was used to replace half of the lactose from the MR (GFG). From 11 to 27 weeks of age, calves received a lactose control MR or the GFG MR (n = 65 per treatment). Growth performance from 11 to 27 weeks of age tended to be lower for GFG-fed than for control calves (-25 g/d). Measurements in early life explained 12% of the variation in growth performance in later life. However, this was mainly related to variation in solid feed refusals. When growth performance was adjusted to equal solid feed intake, only 4% of the variation in standardized growth performance in later life, reflecting feed efficiency, could be explained by early life measurements. This indicates that > 95% of the variation in feed efficiency in later life could not be explained by early life characterization. It is hypothesized that variation in health status explains substantial variation in feed efficiency in veal calves. Significant relations between fasting plasma glucose concentrations, fecal dry matter and fecal pH in early life and feed efficiency in later life depended on MR composition. These measurements are, therefore, potential tools for screening calves in early life on their ability to cope with a MR in which half of the lactose is replaced by glucose, fructose and glycerol (in a 2:1:2 ratio).

    The studies reported in this thesis demonstrate that glycerol, glucose and a combination of glucose, fructose and glycerol in a 2:1:2 ratio are promising lactose replacers. The effects of replacing lactose by other carbohydrate or energy sources described in this thesis are required to evaluate the potential of lactose replacers for inclusion in calf milk replacers and provide input for feed evaluation for calves and ruminants.

    Hoe kan je je eetlust remmen?
    Witkamp, R.F. - \ 2015
    Universiteit van Nederland
    eetlust - eetlustremmers - cannabis - voeding en gezondheid - voedingsfysiologie - fysiologie - voedselonderzoek - appetite - anorexiants - cannabis - nutrition and health - nutrition physiology - physiology - food research
    Denk je bij cannabis aan het krijgen van een vreetkick? Na dit college van Renger Witkamp (Wageningen UR) snap je wat het verband tussen die twee is en hoe we die kennis kunnen gebruiken om je eetlust te remmen. Klinkt goed, toch? Er is alleen één groot probleem. Welk? Dat hoor je in dit college.
    Rumen by-pass copper = Koper voorbij de Pens
    Goselink, R.M.A. - \ 2015
    Wageningen : Wageningen UR Livestock Research (Livestock Research rapport 905) - 22
    herkauwers - koper - verteringsabsorptie - pens - pensfermentatie - spijsvertering - voedingsfysiologie - diervoeding - ruminants - copper - digestive absorption - rumen - rumen fermentation - digestion - nutrition physiology - animal nutrition
    De absorptie van koper (Cu) bij herkauwers is relatief laag vanwege de interacties tussen Cu en andere bestanddelen van het rantsoen, waardoor onoplosbare complexen gevormd worden die niet worden geabsorbeerd in de dunne darm. Dit kan mogelijk verbeterd worden door pensbestendige Cu bronnen aan te bieden, waardoor de Cu uitscheiding via de mest naar het milieu verminderd kan worden. Het doel van dit project was het evalueren van het effect van pensbestendige Cu bronnen op de Cu absorptie bij herkauwers. Dit is onderzocht met behulp van een in vitro model waarbij verschillende Cu bronnen zijn geïncubeerd om de fermentatie- en verteringsprocessen in het maagdarmkanaal te simuleren. Daarna is een proef uitgevoerd met 18 vleeskalveren waarbij twee pensbestendige Cu bronnen zijn vergeleken met kopersulfaat als controle. Het verschil in Cu absorptie tussen pensbestendige Cu bronnen en kopersulfaat was echter onvoldoende om in deze beperkte proefopzet aangetoond te kunnen worden.
    Snelle meettechnieken voor nutriëntenbenutting bij landbouwhuisdieren
    Vrolijk, M. ; Goselink, R.M.A. ; Veldkamp, T. - \ 2015
    Wageningen : Wageningen UR Livestock Research (Livestock Research rapport 902) - 43
    vee - veevoeding - nutriëntengebruiksefficiëntie - voedingsstoffenopname (mens en dier) - meettechnieken - voedingsfysiologie - livestock - livestock feeding - nutrient use efficiency - nutrient intake - measurement techniques - nutrition physiology
    Efficient feeding of animals in livestock production deserves constant attention. Feed is input for milk, meat and egg production. It is a challenge to use nutrients as efficiently as possible, and produce ‘more with less’. Feeding the animals at their requirements can be improved if the effects of nutrient intake can be measured within a short time. This project made an overview of possible ‘rapid measuring techniques’ to be used in the near future. Each technique was scored for relevance, technical feasibility, practical application and the investment needed for development (time and money). From an expert workshop, measuring by means of sensor boluses or fluorescent markers as well as manure analysis, were defined as most promising for future research and practice.
    What happens in the bag? : development and evaluation of a modified in situ protocol to estimate degradation of nitrogen and starch in the rumen
    Jonge, L.H. de - \ 2015
    Wageningen University. Promotor(en): Wouter Hendriks, co-promotor(en): Jan Dijkstra; H. van Laar. - Wageningen : Wageningen University - ISBN 9789462574519 - 175
    herkauwers - pensfermentatie - stikstof - zetmeelvertering - pensvertering - protocollen - evaluatie - methodologie - schatting - voedingsfysiologie - ruminants - rumen fermentation - nitrogen - starch digestion - rumen digestion - protocols - evaluation - methodology - estimation - nutrition physiology

    The most widely used method to estimate the rumen degradation of dietary components in feedstuffs is the in situ or in sacco method. This method is based on rumen incubation of substrate (feed) in nylon or dacron bags followed by rinsing and analysis of the residue. Small pores in the bag allow microbes to enter the bag whilst a variable portion of the feed is retained in the bag. The results are used to estimate the ruminal effective degradation (ED) that is used in several protein evaluation systems. The weaknesses of the in situ method are its low precision, the lack of standardization, and its inaccuracy. The accuracy can be divided in a bias with respect to the in situ method itself, and the difference between the in situ and in vivo degradation. The bias of the in situ method itself is related to several assumptions regarding the size and degradation rate of the washable fraction, secondary particle loss, and microbial contamination. The aim of this thesis was to examine possibilities to reduce this bias by modification of the in situ methodology.

    The bias related to the assumptions regarding the washout fraction was successfully reduced by developing and using a modified rinsing method that involves less vigorously shaking conditions and a solvent which mimics the rumen pH and osmolality. This modified rinsing method markedly reduced the soluble (S) fraction of N, especially for legume seeds, and the non-soluble washout (W-S) fraction, especially for starch, compared to the conventional method. Consequently, the estimation of the ED became less dependent on the assumptions regarding the degradation of the S and W-S fraction. In vitro results did not support the assumption of a much faster degradation of the W-S fraction of starch than that of the non-washout fraction of starch. The modified rinsing method also allowed measuring the in situ degradation of products that contain mainly small particles such as wheat yeast concentrates.

    The bias related to the breakdown of particles was also successfully reduced by development and application of a combination of the modified rinsing method and an in vitro method that simulates particulate matter loss during incubation. This in vitro method was based on in situ results obtained with an inert marker (i.e., silica gel) which showed that particulate matter loss during incubation was moderate and limited to particles smaller than approximately 40 μm. Correction for these losses decreased the estimated ED of feed ingredients used. This study also showed that the fractional degradation rate of starch in grains was strongly affected by the process of secondary particulate loss when using the conventional method, and applying the modified rinsing method markedly reduced the error due to secondary particulate loss.

    In comparison to the conventional method, the modified method resulted in an increase of the bias related to microbial contamination of the residues. The ratio between diaminopimelic acid (DAPA), a marker for bacterial protein, and N in the residues was higher when using the modified method than that in the conventional method. The results obtained for the modified method also indicated lysis of bacterial cells during rinsing. This bias led to a lower ED when using the modified method with the impact greatly depending on the degree of lysis of bacterial cells.

    In summary, the modified method increased the non-washout fraction of N and starch of various feed ingredients, which offers the possibility to use it for a larger range of feed ingredients, and reduced the bias related to assumptions on the washout fraction and the breakdown of particles compared to the conventional method. On the other hand, the modified method increased the bias related to microbial contamination and enlarged the difference between the in situ and in vivo degradation.

    Unveiling causes for growth retardation in piglets
    Paredes Escobar, S. - \ 2014
    Wageningen University. Promotor(en): Leonard den Hartog, co-promotor(en): Martin Verstegen; Walter Gerrits. - Wageningen : Wageningen University - ISBN 9789462571204 - 168
    biggen - groei - mestresultaten - geboortegewicht - speengewicht - voer - groeivertraging - inslineresistentie - varkensvoeding - diervoeding - voedingsfysiologie - piglets - growth - fattening performance - birth weight - weaning weight - feeds - growth retardation - insulin resistance - pig feeding - animal nutrition - nutrition physiology

    The evolution of hyper‐prolific sow breeds has led to a higher number of piglets born per sow per year. This increase in litter size has enlarged the number of light weight (or growth retarded) piglets, increased pre‐weaning mortality and heterogeneity at the end of the nursery phase (ten weeks of age). These poorly performing piglets represent a challenge to the swine industry as their presence in the herd has economic and welfare implications.

    Reducing the heterogeneity at the end of the nursery phase is relevant, as it influences the efficiency of use of the grower and finisher facilities, and/or it reduces penalties for delivering underweight piglets to the slaughterhouse. The focus of this thesis was the end of the nursery phase, as this is the time point where piglets are transferred to the grower and finisher facilities.

    The aim of this thesis was to identify and describe the causes of growth retardation in the nursery phase to provide a basis to look for alternative nutrition or management solutions.

    The database analysis described in Chapter 2 provides a phenotypic definition of growth retardation based on the risk factor analysis approach, and describes season of birth, body weight at birth, at weaning and at six weeks of age as the main factors to predict piglet BW at the end of the nursery phase.

    Based on the algorithm developed to predict piglets’ BW at the end of the nursery phase, our target population was defined as piglets with a birth weight above the mean ‐2 times the SD from the total population and a predicted BW at the end of the nursery phase below the mean ‐1 time the SD from the mean of the total population, considered Low Performing

    piglets LP). We aimed to characterize differences between LP piglets and their heavier counterpart (piglets with a predicted BW at the end of the nursery phase above the mean +1 time the SD from the mean of the total population HP).

    Compared to the HP, the LP piglets grew slower, ate less and were lighter but have an equal gain:feed ratio at ten weeks of age. The LP piglets tended to take more time to touch a novel object and spent more time eating. The LP and HP piglets have an equal macronutrient digestibility, with the exception of NSP. When fed a high fibre diet, both groups have a lower starch and fat apparent total tract digestibility. Yet, the LP piglets have a reduced fermentative capacity, which might place them in disadvantage. Also LP piglets are unable to engage into compensatory gain or compensatory feed intake, as efficiency of nutrient utilization and feed intake per kg BW0.75 was unaffected. In terms of skeletal muscle development, the LP piglets have a low muscularity (total fiber number and fiber cross sectional area), which might be of disadvantage for lean mass accretion in further life and for meat quality. The LP piglets exhibit insulin resistance and a lower pancreatic amylase activity, which might be related to the lower performance. Lastly, in the general discussion a comparison of the main findings with literature characterizing growth retarded piglets is presented. Also based on modelled data, the economic impact of growth retarded piglets is estimated from 10 weeks of age until slaughter weight (110 kg BW).

    The studies reported in this thesis describe a novel method for selecting growth retarded piglets in the nursery phase and provide insight into possible mechanism for growth retardation in the piglet phase.

    Physiology and genetics of root growth, resource capture and resource use efficiency in lettuce (Lactuca sativa L.)
    Kerbiriou, P.J. - \ 2014
    Wageningen University. Promotor(en): Edith Lammerts van Bueren; Paul Struik, co-promotor(en): Tjeerd-Jan Stomph. - Wageningen : Wageningen University - ISBN 9789462570863 - 179
    lactuca sativa - slasoorten - cultivars - groei - wortels - scheuten - plantenontwikkeling - nutriëntengebruiksefficiëntie - voedingsfysiologie - watergebruiksrendement - genetische variatie - droogteresistentie - tolerantie van variëteiten - genotype-milieu interactie - biologische plantenveredeling - lactuca sativa - lettuces - cultivars - growth - roots - shoots - plant development - nutrient use efficiency - nutrition physiology - water use efficiency - genetic variation - drought resistance - varietal tolerance - genotype environment interaction - organic plant breeding
    Improving performance of broilers fed lower digestible protein diets
    Qaisrani, S.N. - \ 2014
    Wageningen University. Promotor(en): Wouter Hendriks, co-promotor(en): Rene Kwakkel; Marinus van Krimpen. - Wageningen : Wageningen University - ISBN 9789462570313 - 182
    vleeskuikens - eiwitverteerbaarheid - vleeskuikenresultaten - fermentatie - einddarm - boterzuur - voer - voedingsfysiologie - pluimveevoeding - diervoeding - broilers - protein digestibility - broiler performance - fermentation - hindgut - butyric acid - feeds - nutrition physiology - poultry feeding - animal nutrition

    Background and Problem Statement

    There is a great interest in recent years to replace soybean meal by cost effective protein sources such as rapeseed meal and maize gluten in animal feed. In poultry, this replacement, however, may result in a poorer performance due to among others its low ileal digestibility, which may lead to hindgut protein fermentation. This hindgut protein fermentation can result in the production of harmful compounds such as ammonia, branched chain fatty acids, biogenic amines and different sulfur containing compounds such as skatole, indole and phenolic compounds. This can negatively affect the cost of broiler meat production. When digestibility is low gut health may be compromised. Also feed to gain ratios will be high and overall performance will be low. Apart from the economic losses, good digestible protein sources may be preferably used for human consumption. Thus, the challenge is to provide the basis for the development of a new feeding strategy that meets the nutrient requirements of modern-day broilers, especially when they are fed a low ileal digestible protein source, i.e. rapeseed meal and maize gluten, thereby minimizing the interruption of their production performance.

    Objectives of the Study

    The aim of the study was to find ways to improve protein digestibility of poor ileal digestible resources, to reduce potential hindgut protein fermentation by developing appropriate dietary strategies such as an adequate diet structure, the supplementation of organic acids and/or fermentable energy that improve nutrient availability at ileal level and gut health in broilers.

    The specific objectives of the present study were to:

    Review various factors that influence hindgut protein fermentation in broilers and nutritional strategies that may reduce hindgut protein fermentation (Chapter 2). Determine the effects of protein source, differing in fermentation characteristics, and of digestible dietary protein content on performance, gut morphology and cecal fermentation characteristics in broiler (Chapter 3). Investigate the effects of diet structure combined with different levels of indigestible dietary protein source on performance and gut morphology in broilers (Chapter 4). Study the main and interactive effects of protein source, diet structure, butyric acid and fermentable energy supplementations on performance, gut morphology and cecal fermentation characteristics (Chapter 5). Analyze the effects of protein source, diet structure, butyric acid and fermentable energy supplementation on cecal microbiota population and composition (Chapter 6).

    Major Findings of the Thesis

    This thesis provides a literature review and describes the results of three experiments in which different nutritional strategies were tested. All experiments were carried out with Ross-308 broilers.

    Chapter 2 reviews the literature on hindgut fermentation in broilers with special attention to protein fermentation, its detrimental effects on performance, gut health and on gut microbiota population. A wide range of harmful products such as ammonia, branched chain fatty acids, biogenic amines and different sulfur containing compounds such as skatole, indole and phenols are produced as a result of protein fermentation. Greater concentrations of biogenic amines, branched chain fatty acids, hydrogen sulfide, ammonia, indole, phenols, cresol and skatole in the cecal indicate more proteolytic fermentation. Low concentrations of some of the protein fermentation products including biogenic amines are necessary for a normal gut development. This may result in distinct differences in protein digestibility when measured at the ileum and the total digestive tract. It was concluded that nutritional strategies, such as a reduction in dietary CP, supplementation of pre- and probiotics and organic acids, or feeding diets with coarse particles may increase ileal CP digestibility, thereby reducing the amount of substrate available for fermentation. These nutritional interventions can potentially enhance protein digestion in the upper gastrointestinal tract and, therefore, reduce the chances of protein fermentation in the hindgut.

    In Chapter 3, effects of three major protein sources, soybean meal, rapeseed meal and maize gluten at two different digestible CP levels (15.8 and 17.2%) were studied to test the hypothesis that broilers fed a diet with high levels of indigestible protein, will result in a reduced growth performance, lower villus heights, deeper crypts, and more protein fermentation products in cecal digesta. In total, 288 one-day-old male broilers were used for this study. Broilers fed soybean meal diet showed a better performance compared with those fed rapeseed meal and maize gluten diets due its greater ileal digestibility compared with the other two protein sources. High digestible CP (17.2%) diet fed broilers showed better performance compared with those on low digestible CP (15.8%) diet. No significant effects of protein source as well as digestible CP level were found on gastrointestinal tract development, cecal ammonia and volatile fatty acid concentrations. Broilers fed soybean meal had improved duodenal morphology compared with those fed the rapeseed meal and maize gluten diets. A lower cecal pH and greater branched chain fatty acids concentrations in the cecal digesta were observed in broilers fed the rapeseed meal diet compared with those fed the soybean meal and maize gluten diets, indicating more proteolytic fermentation. In conclusion, protein source as well as digestible CP level affected growth performance, gut morphology and protein fermentation characteristics in broilers.

    In Chapter 4, a hypothesis that a coarse diet improves performance of broilers fed a poorly digestible protein source was tested by using 210 one-day-old broilers. A highly digestible protein diet based on soybean meal was gradually replaced by a low digestible protein diet based on rapeseed meal (RSM) in five steps (RSM-0%, RSM-25%, RSM-50%, RSM-75% and RSM-100%) with two diet structures (fine vs. coarse). An increase in indigestible dietary protein decreased the performance of broilers. Total cecal volatile fatty acid concentrations decreased from 209 to 126 mmol/kg DM digesta in broilers with increasing rapeseed meal in diets. Increase in the indigestible protein level, from RSM-0% to RSM-100%, decreased villus heights (1782 vs. 1574 µm), whereas crypt depths increased (237 vs. 274 µm). A coarse diet improved the performance with a 15% heavier empty gizzard weight and changed gut morphology. Coarseness of the diet reduced the empty weights of the crop, proventriculus and jejunum, and reduced gizzard pH by 16%. Protein fermentation indices such as branched chain fatty acids and biogenic amines were reduced by 24 and 12%, respectively, in the cecal digesta of broilers fed coarse diets compared with those fed fine diets. In conclusion, feeding coarse particles improved the performance of broilers even with a poorly digestible protein source. Hindgut protein fermentation was reduced in broilers fed diets with a low CP digestibility by coarse grinding of the diet.

    In Chapter 5, the effects of protein source, diet structure and supplementation of butyric acid and fermentable energy on growth performance and cecal digesta characteristics were investigated to test the hypothesis that a coarse diet supplemented with butyric acid and fermentable energy improves growth performance of broilers fed a poorly digestible protein source. The interaction effects of diet structure (fine vs. coarse), fermentable energy (with vs. without) and butyric acid supplementation (with vs. without) in a poorly digestible diet based on rapeseed meal were evaluated. Coarseness of the diet positively affected performance and improved relative empty gizzard weights by on average 14%. The relative empty weights of the crop, duodenum, jejunum and ileum, were reduced in coarse diets fed broilers compared with those fed fine diets. Broilers fed coarse diet showed a 6% greater ileal protein digestibility, 20% lower gizzard pH, improved gut morphology, and 23% reduced cecal branched chain fatty acids compared with those fed the fine diets. Broilers fed butyric acid supplemented diets had improved performance and gut morphology compared with those fed the diets without butyric acid. Fermentable energy supplementation did not influence growth performance nor gut development and contents of total branched chain fatty acids and total biogenic amines in the cecal digesta. Supplementation with fermentable energy, however, decreased the concentration of spermine by approximately 31%. In conclusion, feeding a coarse diet supplemented with butyric acid improves growth performance of broilers even if they are fed a diet containing a poorly digestible protein source. The negative effects of a low digestible protein source can thus be partly counterbalanced by coarse grinding and butyric acid supplementation in the diet.

    In Chapter 6, the effects of protein source, diet structure, butyric acid and fermentable energy supplementations on cecal microbiota population and composition in broilers were evaluated. Cecal digesta samples collected in experiments 1, 2 and 3 were therefore, analysed for some microbiota. The results indicated that cecal microbial diversity was suppressed by dietary coarseness. Similarly, butyric acid and fermentable energy supplementation also resulted in a lower microbial diversity. Soybean meal promoted the average relative contribution of health beneficial L. paracasei and C. lactifermentans spp. compared with those fed rapeseed meal. Dietary coarseness reduced the average relative contribution of E. coli. Butyric acid supplementation promoted the average relative contribution of C. lactifermentans and R. bromii, and suppressed the pathogenic C. perfringens in the cecal digesta. Fermentable energy, in contrast, promoted C. perfringens. In conclusion, feeding a poorly digestible protein source, with coarse grinding and supplemented with butyric acid may be an effective strategy to promote health beneficial and suppress pathogenic microbiota in the cecal digesta.


    The main conclusion of the study is that rapeseed meal diets reduce performance and gut health, but these negative effects can be partially counterbalanced by coarse grinding and butyric acid supplementation. Some specific conclusions based on the results of the studies described in this thesis are:

    Rapeseed meal is a poorly digestible protein source for broilers and results in reduced growth performance and gut morphology (Chapter 3). Coarse diet feeding enhances the development of the foregut, specially the gizzard, and it increases villus heights and reduces crypts depths in the duodenum (Chapters 4 and 5). The negative effects of moderate inclusion of indigestible protein can be counterbalanced to some extent by feeding a coarse diet (Chapters 4 and 5). The improved foregut development and villus height in the duodenum is associated with an enhanced ileal digestibility of protein, thereby allowing less protein available for fermentation in the hindgut (Chapter 5). Butyric acid supplementation improves growth performance and gut morphology (Chapter 5). Both soybean meal and dietary coarseness suppress cecal microbial diversity and promotes health beneficial microbiota (Chapter 6). Dietary coarseness suppresses pathogenic bacteria and promotes health beneficial microbiota in the ceca (Chapter 6). Coarsely ground diet with a moderate inclusion of poorly digestible protein source, supplements with butyric acid, is a good strategy to improve the ileal digestibility of protein and thus growth performance of broilers (Chapters 4 and 5).

    Practical Implementations

    This study might have some practical conclusions. Rapeseed meal can be used as a protein source in a broiler ration. Coarsely ground rapeseed meal, supplemented with butyric acid (approximately €2.1/100 broilers), can potentially replace soybean meal. It will not only provide a cheaper protein source but will also reduce the cost of feed production by reducing the steps in grinding the feed ingredients or using a roller mill instead of a hammer mill. These coarse particles will improve gut morphology and growth performance of broilers as well as increase the profitability of broiler feed producers and also broiler farmers (approximately €6/100 broilers). The most perspective feeding strategy to enhance the growth performance of broilers fed a poorly digestible protein source is the use of coarsely ground supplemented with butyric acid.

    Fiber fermentation in pigs and poultry : sense and nonsense of its manipulation
    Vries, S. de - \ 2014
    Wageningen University. Promotor(en): Wouter Hendriks, co-promotor(en): Walter Gerrits; Mirjam Kabel. - Wageningen : Wageningen UR - ISBN 9789461739513 - 180
    varkens - pluimvee - vezels - fermentatie - spijsvertering - voer - diervoeding - voedingsfysiologie - pigs - poultry - fibres - fermentation - digestion - feeds - animal nutrition - nutrition physiology

    The increased use of fiber-rich feedstuffs in pig and poultry diets requires an optimal utilization of these feed ingredients. Hence, the animal feed industry explores opportunities to improve degradability of these feedstuffs and maximize their inclusion levels in pig and poultry diets. Processing and enzyme technologies can modify the physicochemical characteristics of fiber fractions from feed ingredients, thereby affecting their degradability. In this way, fermentability of non-starch polysaccharides (NSP) and thus their potential energetic utilization might be enhanced. In addition, technologies can be aimed at alleviation of adverse effects on digestion and absorption of other nutrients, which might be particularly of interest for young pigs and poultry. However, to understand modifications that occur during processing detailed information on the composition of fiber structures is required.

    This thesis aimed at identifying limiting factors in the degradability of fiber fractions in pigs and poultry and at development of technologies to improve their degradation. Focus was on recalcitrant fiber structures as found in in maize dried distillers grain with solubles (DDGS) and rapeseed meal (RSM). Fiber degradation in growing pigs and broilers was studied in detail and limiting structures in the degradation of NSP were identified (Chapter 5 to 7). Effects of processing and enzyme technologies on fiber-rich feedstuffs were evaluated based on literature and in vitro and in vivo studies in growing pigs and broilers (Chapter 2 to 7). In addition, marker methods to study digestibility of fiber-rich diets in broilers were discussed (Chapter 8). Furthermore, interactive effects between specific fermentable fiber sources and the digestive utilization of the diet were investigated (Chapter 9). In the final chapter, results of the thesis were summarized and synthesized. Methods to analyze fiber components and evaluate fiber degradation in vitro and in vivo were discussed, suggestions for future research were given, and implications of the results for feed formulation were addressed (Chapter 10).

    Recalcitrant fiber fractions in DDGS and RSM

    The fiber fraction of maize DDGS was found to consist of complex, highly substituted glucuronoarabinoxylans (GAX) that are cross-linked to or associated with cellulose and lignin within the cell wall matrix. In pigs, total tract degradation of non-glucosyl polysaccharides (NGP) from DDGS was between 51 and 62 %. Coumaric acid and ferulic acid associated (ester)-linkages were found to contribute to the recalcitrance of DDGS fiber to fermentation in the pig.The fiber fraction of RSM consists of pectic polysaccharides, xyloglucan, and cellulose that are linked via ester-linkages or H-bonds, forming a rigid cell wall matrix. This rigid matrix was found to hinder the complete degradation of NSP from RSM. In pigs, total tract degradation of NSP from RSM was ~70 %. Nearly 50 % of the unfermented carbohydrate structures in feces were tightly bound pectins (e.g. rhamnogalacturonan and arabinan), xyloglucan, and cellulose. The other half consisted of smaller uronyl-rich carbohydrates, presumably ester-linked or H-bound. In broilers, total tract degradation of NSP from RSM was ~24 %.

    Processing and enzyme technologies

    Common feed processing technologies may improve degradability of easily solubilizable NSP, but are not sufficient to affect rather recalcitrant fiber fractions, such as those found in DDGS and RSM. Particle size reduction, hydrothermal treatment with or without shear, acid hydrolysis, and cell wall degrading enzymes improved in vitro degradability barley (13-43 % units, P < 0.01), whereas only severe hydrothermal acid treatment increased in vitro degradability of fiber fractions from DDGS (30-60 % units,P < 0.01). In pigs, however, hydrothermal acid treatment did not improve degradability of NSP from DDGS, despite the increased solubility of the fiber fraction. Acid treatment shifted fermentation to more proximal gastrointestinal segments, but total extent of NSP degradation was not affected.Apparently, acid-extrusion accelerated degradation of NSP structures that are not resistant to degradation by microbial enzymes in the pigs’ gastrointestinal tract, whereas the most recalcitrant NSP structures were still not affected.Furthermore, acid treatment reduced feed intake, digestibility of crude protein (CP; 3 % units, P = 0.06) and starch (1 % unit, P = 0.10), and tended to reduce digestibility of crude fat (0.4 % units, P < 0.10). Degradability of NGP from rapeseed meal was found to be successfully improved by addition of pectolytic enzymes (9-20 % units, P < 0.01), due to increased degradation of branched water-soluble arabinans. This coincided with an increased NGP concentration in the ceca (4-7 g/g cobalt, P < 0.01), indicating that more NGP were solubilized such that they could enter the ceca and become available for fermentation. Particle size reduction, through wet milling and extrusion, facilitated solubilization of NSP, but solubilized structures could still not be degraded by the cecal microbiota. No interaction between processing technologies and enzyme addition was found. Apparently, the processing technologies studied were not facilitating accessibility of NSP to pectolytic enzymes added to the feed in vivo.

    In conclusion, both processing and enzyme technologies can be effective in solubilizing NSP from DDGS and RSM, but in vivo research demonstrated the limited potential to improve the degradation, and thus feeding value, of recalcitrant fiber fractions. Future research should aim at targeted degradation of recalcitrant NSP structures only, while minimizing the effects on relatively easy degradable NSP and other nutrients. Enzyme technologies, targeting specific structures, seem to provide more perspective than more rigorous processing technologies.In DDGS and RSM, ester-linkages or H-bonds seem to be involved in the recalcitrance of the fiber fraction to degradation in the animal, presumably due to anchorage of NSP in the rigid cellulose-lignin matrix. Hence, technologies that degrade such linkages, as alkali treatments and especially esterases could be of interest for future research.

    Marker methods

    Digestibility measurements are a crucial tool in the evaluation of the nutritive value of feedstuffs. The marker method, where digestibility is estimated from the ratio between an indigestible marker and the nutrient of interest in feed and digesta or excreta, is commonly used as alternative for the laborious total collection method. In broilers, separation of marker and specific digesta fractions occurs, and especially when degradation of fiber fractions is the matter of interest, the marker method has limitations. When estimating apparent ileal digestibility (AID), separation of marker and digesta resulted in unrealistic high estimates for the digestibility of non-glucosyl polysaccharides (54-66 %), exceeding ATTD values by 16-42 % units. Moreover, the effect of pectolytic enzyme addition on the AID of non-glucosyl polysaccharides was in opposite direction when compared with total collection.These data illustrate that fractionation of digesta, particularly in high-fiber diets, complicates accurate ileal digestibility measurements in broilers, regardless the choice of markers used. It is recommended to add a soluble marker when fiber degradation is of interest, even though it does not allow quantifying fermentative degradation of nutrients.

    Interactions between fiber and digestive utilization of the diet

    In current feed formulation systems interactions between feed ingredients are assumed to be absent. This assumption can be challenged as interactions between specific feed components, such as various types of fiber, and the digestive utilization of the diet exist. Although the effects of fiber inclusion on the digestive utilization of the diet are complex, specific properties can be ascribed to certain fiber types. β-Glucan, a rapidly fermentable, viscous, fiber source, enhanced the degradation of xyloglucan from RSM (ATTD of NGP increased by 6 % units, P < 0.001) but did not seem to affect the recalcitrant fiber fraction of DDGS. Furthermore, β-glucan decreased enzymatic digestion of CP and starch in the small intestine. In contrast, resistant starch (RS), a more slowly, but-well fermentable fiber, decreased degradation of fiber-fractions from DDGS as well as RSM (> 10 % units, P < 0.01). These results clearly show the interactive effects between specific fiber fractions in the diet and the degradation of NSP and other nutrients. It is suggested to include effects of individual feed ingredients on the physicochemical properties of the chyme, such as viscosity and water binding capacity, and retention times in various segments of the gastro-intestinal tract in feed formulation, to more accurately predict the nutritive value of diets.

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