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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    Applying a mechanistic fermentation and digestion model for dairy cows with emission and nutrient cycling inventory and accounting methodology
    Bannink, A. ; Zom, R.L.G. ; Groenestein, K.C. ; Dijkstra, J. ; Sebek, L.B.J. - \ 2020
    Animal 14 (2020)S2. - ISSN 1751-7311 - p. 406 - 416.
    digestibility - enteric methane - farm accounting - nitrogen - Tier 3

    In mitigating greenhouse gas (GHG) emissions and reducing the carbon footprint of dairy milk, the use of generic estimates in inventory and accounting methodology at farm level largely ignores variation of on-farm GHG emissions. The present study aimed to implement results of an extant dynamic, mechanistic Tier 3 model for enteric methane (CH4) (applied in Dutch national GHG inventory) in order to capture variation in enteric CH4 emission, and in faecal N and organic matter (OM) digestibility, ultimately required to predict manure CH4 and ammonia emission. Tier 3 model predictions were translated into calculation rules that could easily be implemented in an annual nutrient cycling assessment tool including GHG emissions, which is currently used by Dutch dairy farmers. Calculations focussed on (1) enteric CH4 emission, (2) apparent faecal OM digestibility and (3) apparent faecal N digestibility. Enteric CH4 was expressed in CH4 yield indicated with the term emission factor (EF; g CH4/kg DM) for individual dietary components and feedstuffs. Factors investigated to cover predicted variation in EF value included the level of feed intake, the type of roughage fed (proportions of grass silage and maize silage) and the quality of roughage fed. A minimum number of three classes of roughage type (i.e. 0. 40% and 80% maize silage in roughage DM) appeared necessary to obtain correspondence between interpolated EF values from EF lists and Tier 3 model predictions. A linear decline in EF value with 1% per kg increase in DM intake is adopted based on model simulations. The quality of roughage was represented by the effect of maturity of harvested grass or of the whole plant maize at cutting, based on a survey of modelling as well as experimental work. Also, predictions were assembled for apparent faecal OM digestibility which could be used in national inventory and in farm accounting. Apparent faecal N digestibility (as a major determinant of predicted urinary N excretion) was predicted, to support current Dutch national ammonia emission inventory and to correct the level of N digestibility in farm accounting. Compared to generic values or values retrieved from the Dutch feeding tables, predicted OM and N digestibility and enteric CH4 are better rooted in physiological principles and better reflect observed variation under experimental conditions. The present results apply for conditions with fairly intensive grassland management in temperate regions.

    Carbohydrate utilisation by tilapia: a meta-analytical approach
    Maas, Roel M. ; Verdegem, Marc C.J. ; Wiegertjes, Geert F. ; Schrama, Johan W. - \ 2020
    Reviews in Aquaculture (2020). - ISSN 1753-5123
    digestibility - meta-analysis - non-starch polysaccharides - Oreochromis niloticus - starch

    Currently, studies reporting the digestibility of carbohydrates, starch and especially non-starch polysaccharides (NSP) in fish are scarce. Carbohydrate digestibility in the diet is largely dependent upon carbohydrate composition (starch vs. NSP). NSP are often considered to be indigestible and thus of no nutritional value. The present study reviews carbohydrates in fish feed, distinguishing between total carbohydrate, starch and NSP. Besides a qualitative approach, a meta-analysis was performed, compiling available data from digestibility studies on tilapia. Our meta-analysis confirms the negative effect of NSP on performance (FCR) and nutrient digestibility (crude protein, fat and energy). However, an average NSP digestibility of 24.3% was calculated in 95 cases. Out of these 95 cases, 88% of them showed a positive NSP digestibility. NSP digestibility was shown to contribute to energy digestibility. The digestion of NSP in fish is associated with fermentation in the gut, producing beneficial volatile fatty acids that are rapidly absorbed by the colonic lumen. Therefore, in diet formulation, digestibility and thus energy originating from NSP should be taken into consideration because NSP contribute to the energy needs of fish, here tilapia. Besides being an energy source, specific types of NSP may have immune-modulating and prebiotic effects and may be increasingly added to fish feed as modulators of fish health. We suggest that NSP is potentially (partly) digested by a wide range of fish species, especially by warm-water species with a long gut adapted to feeding on plant matter, as these factors favour gut fermentation.

    Cell wall disruption: An effective strategy to improve the nutritive quality of microalgae in African catfish (Clarias gariepinus)
    Agboola, Jeleel O. ; Teuling, Emma ; Wierenga, Peter A. ; Gruppen, Harry ; Schrama, Johan W. - \ 2019
    Aquaculture Nutrition 25 (2019)4. - ISSN 1353-5773 - p. 783 - 797.
    accessibility - algae - digestibility - disruption treatments - nutrient utilization - rigid cell wall

    The rigid cell walls of microalgae may hinder their utilization in fish feeds. The current experiment assessed the correlation between the accessibility of microalgae nutrients and their in vivo digestibility in African catfish. Nannochloropsis gaditana biomass was subjected to physical or mechanical treatments to weaken its cell wall; untreated—no disruption treatment (UNT), pasteurization (PAS), freezing (FRO), freeze-drying (FRD), cold pasteurization (L40) and bead milling (BEM). Six experimental diets formulated from differently treated and untreated microalgae (at 30% diet inclusion level) were tested on growth performance and apparent nutrient digestibility (ADCs) in juvenile African catfish. A basal diet (REF) containing no microalgae was used as reference diet. Results showed that biomass gain and feed conversion ratio of fish fed L40 and BEM diets increased by 13% and 11%, respectively, relative to the UNT diet. Additionally, FRD, FRO, L40 and BEM cell wall disruption treatments improved protein digestibility by 0.5%, 5.9%, 8.4% and 16.3%, respectively, compared to the UNT treatment. There was a positive correlation between accessibility of microalgal nutrients and their digestibility in African catfish. Nutrient digestibility of microalgae was dependent on extent of cell disruption. Also, the impact of cell disruption on nutrient digestibility of microalgae differs between African catfish and Nile tilapia.

    Effect of supplementing sheep diets with macroalgae species on in vivo nutrient digestibility, rumen fermentation and blood amino acid profile
    Özkan Gülzari, S. ; Lind, V. ; Aasen, I.M. ; Steinshamn, H. - \ 2019
    Animal (2019). - ISSN 1751-7311
    digestibility - in vivo - Porphyra spp - ruminant - Saccharina latissima

    In this study, a brown macroalgae species, Saccharina latissima, processed to increase its protein concentration, and a red macroalgae species, Porphyra spp., were used to evaluate their in vivo digestibility, rumen fermentation and blood amino acid concentrations. Four castrated rams were used, whose diets were supplemented with a protein-rich fraction of S. latissima, a commercial Porphyra spp. and soybean meal (SBM). Our results show that the protein digestibility of a diet with S. latissima extract was lower (0.55) than those with Porphyra spp. (0.64) and SBM (0.66). In spite of the higher nitrogen (N) intake of diets containing Porphyra spp. and SBM (20.9 and 19.8 g N/day, respectively) than that with S. latissima (18.6 g N/day), the ratio of N excreted in faeces to total N intake was significantly higher in the diet with S. latissima than those with Porphyra spp. and SBM. This reflects that the utilization of protein in S. latissima was impaired, possibly due to reduced microbial activity. The latter statement is corroborated by lower volatile fatty acid composition (25.6, 54.8 and 100 mmol/l for S. latissima, Porphyra spp. and SBM, respectively) and a non-significant tendency for lower ammonia concentration observed in diets with S. latissima and Porphyra spp. compared to SBM. It is important to note that the S. latissima used in this trial was rinsed during processing to remove salt. This process potentially also removes other water-soluble compounds, such as free amino acids, and may have increased the relative fraction of protein resistant to rumen degradation and intestinal absorption. Furthermore, the phlorotannins present in macroalgae may have formed complexes with protein and fibre, further limiting their degradability in rumen and absorption in small intestines. We recommend that further studies explore the extent to which processing of macroalgae affects its nutritive properties and rumen degradability, in addition to studies to measure the intestinal absorption of these macroalgae species.

    Effects of feed ingredients on nutrient digestibility, nitrogen/energy balance and morphology changes in the intestine of Nile tilapia (Oreochromis niloticus)
    Tran-Ngoc, Kim T. ; Haidar, Mahmoud N. ; Roem, Arjen J. ; Sendão, João ; Verreth, Johan A.J. ; Schrama, Johan W. - \ 2019
    Aquaculture Research 50 (2019)9. - ISSN 1355-557X - p. 2577 - 2590.
    digestibility - feed ingredient - intestinal morphology - nitrogen and energy balance

    The present study assessed the effect of different feed ingredients on nutrient apparent digestibility coefficients (ADC), nitrogen/energy balance and morphology changes in the intestine of Nile tilapia; using a control diet and six test diets, in which the following six ingredients were included at 30%: hydrolysed feather meal (HFM), soybean meal (SBM), rice bran (RB), rapeseed meal (RM), sunflower meal (SFM) and dried distillers grains with solubles (DDGS). The proximal, middle and distal intestine was processed for quantitative histology counting the number of goblet cells (GC), and measuring the thickness of lamina propria (LP) and submucosa (SM). The study showed that the ADC of protein in raw materials were highest in SBM (92.2%), followed by SFM (90.2%), DDGS (89.2%), RM (87.8%), HFM (86.9%) and RB (84.0%). The nutrient ADCs had no correlation with intestinal morphology changes. Only the SBM diet caused noticeable changes in intestinal morphology such as an increase the thickness of SM and LP and the number of GC. The diet composition, however, altered the protein efficiency and the maintenance energy requirement. Protein retention efficiency was the lowest in fish fed HFM and the highest in RB. The highest maintenance energy requirements were observed in HFM and SBM treatments.

    Environmental conditions alter the effect of organic acid salts on digestibility and intestinal morphology in Nile tilapia (Oreochromis niloticus)
    Tran-Ngoc, Kim T. ; Huynh, Son T. ; Sendão, João ; Nguyen, Thinh H. ; Roem, Arjen J. ; Verreth, Johan A.J. ; Schrama, Johan W. - \ 2019
    Aquaculture Nutrition 25 (2019)1. - ISSN 1353-5773 - p. 134 - 144.
    digestibility - hypoxia - intestinal morphology - normoxia - organic acid - soybean meal diet

    The impact of two dietary organic acids (OAs) on nutrient digestibility and intestinal morphology was determined in Nile tilapia under conditions of dissolved oxygen in the water: normoxia and hypoxia. Four diets designated as control (0 g/kg organic acid salt), KDF (2 g/kg potassium diformate), CAB (2 g/kg calcium butyrate) and their combination (4 g/kg of a mixture of KDF and CAB, ration 1:1) were formulated with 520 g/kg of soybean meal in order to produce soybean meal enteritis-like symptoms. The four diets were tested first under normoxic conditions (6 mg/L) for a period of 5 weeks, followed by a test period under hypoxic conditions (3 mg/L). The results showed that OAs were unable to significantly improve growth and nutrient digestibility under normoxic conditions but under hypoxic conditions, there was a significant enhancement of the growth and nutrient digestibility. Fish fed OA-supplemented diets showed improvements in the intestinal morphology under the normoxic conditions, and these effects were more pronounced under the hypoxic conditions. Experimental findings suggest that OAs can improve the nutrient digestibility and intestinal morphology under hypoxic conditions. A synergistic effect by the combination of formic and butyric acid on growth, digestibility and intestinal morphology was not found.

    Review: Selecting for improved feed efficiency and reduced methane emissions in dairy cattle
    Løvendahl, P. ; Difford, G.F. ; Li, B. ; Chagunda, M.G.G. ; Huhtanen, P. ; Lidauer, M.H. ; Lassen, J. ; Lund, P. - \ 2018
    Animal 12 (2018)s2. - ISSN 1751-7311 - p. s336 - s349.
    digestibility - genetics - holobiont - microbiome - ranking

    It may be possible for dairy farms to improve profitability and reduce environmental impacts by selecting for higher feed efficiency and lower methane (CH4) emission traits. It remains to be clarified how CH4 emission and feed efficiency traits are related to each other, which will require direct and accurate measurements of both of these traits in large numbers of animals under the conditions in which they are expected to perform. The ranking of animals for feed efficiency and CH4 emission traits can differ depending upon the type and duration of measurement used, the trait definitions and calculations used, the period in lactation examined and the production system, as well as interactions among these factors. Because the correlation values obtained between feed efficiency and CH4 emission data are likely to be biased when either or both are expressed as ratios, therefore researchers would be well advised to maintain weighted components of the ratios in the selection index. Nutrition studies indicate that selecting low emitting animals may result in reduced efficiency of cell wall digestion, that is NDF, a key ruminant characteristic in human food production. Moreover, many interacting biological factors that are not measured directly, including digestion rate, passage rate, the rumen microbiome and rumen fermentation, may influence feed efficiency and CH4 emission. Elucidating these mechanisms may improve dairy farmers ability to select for feed efficiency and reduced CH4 emission.

    Smullen van beschimmeld stro
    Hendriks, W.H. ; Cone, J.W. - \ 2018
    biobased economy - animal nutrition - biomass - fibres - enzymes - digestibility - straw
    Delicious mouldy straw : animal nutrition
    Hendriks, W.H. ; Cone, J.W. - \ 2018
    biobased economy - animal nutrition - biomass - fibres - enzymes - digestibility - straw
    Feed and nitrogen efficiency are affected differently but milk lactose production is stimulated equally when isoenergetic protein and fat is supplemented in lactating dairy cow diets
    Nichols, K. ; Bannink, A. ; Pacheco, S. ; Valenberg, H.J. van; Dijkstra, J. ; Laar, H. van - \ 2018
    Journal of Dairy Science 101 (2018)9. - ISSN 0022-0302 - p. 7857 - 7870.
    digestibility - hydrogenated palm fatty acid - milk lactose - rumen-protected protein

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

    Apparent ileal digestibility of Maillard reaction products in growing pigs
    Salazar Villanea, S. - \ 2018
    digestibility - Maillard reaction - pigs
    Data used for the calculation of apparent digestibility values of Maillard reaction products for each experimental unit
    Effect of exercise on apparent total tract digestibility of nutrients and faecal recovery of ADL and TiO2 in ponies
    Schaafstra, F.J.W.C. ; Doorn, D.A. van; Schonewille, J.T. ; Roelfsema, E. ; Westermann, C.M. ; Dansen, O. ; Jacobs, M. ; Lee, J.Y. ; Spronck, E.A. ; Blok, M.C. ; Hendriks, W.H. - \ 2018
    Animal 12 (2018)12. - ISSN 1751-7311 - p. 2505 - 2510.
    digestibility - equines - exercise - markers - total faeces collection
    Exercise and physical training are known to affect gastrointestinal function and digestibility in horses and can lead to inaccurate estimates of nutrient and energy digestibility when markers are used. The effect of exercise on apparent nutrient digestibility and faecal recoveries of ADL and TiO2 was studied in six Welsh pony geldings subjected to either a low- (LI) or high-intensity (HI) exercise regime according to a cross-over design. Ponies performing LI exercise were walked once per day for 45 min in a horse walker (5 km/h) for 47 consecutive days. Ponies submitted to HI exercise were gradually trained for the same 47 days according a standardized protocol. Throughout the experiment, the ponies received a fixed level of feed and the daily rations consisted of 4.7 kg DM of grass hay and 0.95 kg DM of concentrate. The diet was supplemented with minerals, vitamins and TiO2 (3.0 g Ti/day). Total tract digestibility of DM, organic matter (OM), CP, crude fat, NDF, ADF, starch, sugar and energy was determined with the total faeces collection (TFC) method. In addition, DM and OM digestibility was estimated using internal ADL and the externally supplemented Ti as markers. Urine was collected on the final 2 days of each experimental period. Exercise did not affect apparent digestibility of CP, crude fat, starch and sugar. Digestibility of DM (DMD), OM (OMD), ADF and NDF tended to be lower and DE was decreased when ponies received the HI exercise regime. For all treatments combined, mean faecal recoveries of ADL and Ti were 87.8±1.7% and 99.3±1.7%, respectively. Ti was not detected in the urine, indicating that intestinal integrity was maintained with exercise. Dry matter digestibility estimated with the TFC, ADL and Ti for ponies subjected to LI exercise were 66.3%, 60.3% and 64.8%, respectively, while DMD for HI ponies were 64.2%, 60.3% and 65.2%, respectively. In conclusion, physical exercise has an influence on the GE digestibility of the feed in ponies provided with equivalent levels of feed intake. In addition, the two markers used for estimating apparent DMD and OMD indicate that externally supplemented Ti is a suitable marker to determine digestibility of nutrients in horses performing exercise unlike dietary ADL.
    Butyrate presence in distinct gastrointestinal tract segments modifies differentially digestive processes and amino acid bioavailability in young broiler chickens
    Moquet, P.C.A. ; Salami, S.A. ; Onrust, L. ; Hendriks, W.H. ; Kwakkel, R.P. - \ 2018
    Poultry Science 97 (2018)1. - ISSN 0032-5791 - p. 167 - 176.
    Butyrate - broiler - digestibility - digesta retention time - location effect
    The hypothesis was tested that butyrate presence in the digesta of distinct gastrointestinal tract (GIT) segments of broilers leads to differential effects on digesta retention time, gut morphology, and proteolytic enzymatic activities, ultimately resulting in differences in protein digestibility. A total of 320 male day-old Ross 308 broilers were randomly assigned to 5 dietary treatments: 1) control (no butyrate), 2) unprotected butyrate (main activity in the crop and gastric regions), 3) tributyrin (main activity in the small intestine), 4) fat-coated butyrate (activity in the whole GIT) and 5) unprotected butyrate combined with tributyrin, each replicated 8 times. Rapeseed meal was used in combination with a fine dietary particle size in order to challenge the digestive capacity of young broilers. Birds were dissected at 22, 23, and 24 d of age and samples of digesta at various GIT locations as well as tissues were collected. Butyrate concentration varied significantly across GIT segments depending on treatment, indicating that the dietary contrasts were successful. The apparent ileal digestibility of methionine tended to increase when butyrate and/or propionate was present in colonic and cecal contents, possibly due to modifications of GIT development and digesta transit time. Butyrate presence in the digesta of the crop, proventriculus and gizzard, on the contrary, decreased the apparent ileal digestibility of several amino acids (AA). In addition, butyrate presence beyond the gizzard elicited anorexic effect that might be attributable to changes in intestinal enteroendocrine L-cells secretory activities. The present study demonstrates that, in broilers, effects of butyrate on digestive processes are conditioned by the GIT segment wherein the molecule is present and indicates its influence on digestive function and bioavailability of AA.
    Effects of animal type (wild vs. domestic) and diet alfalfa level on intake and digestibility of European adult rabbits (Oryctolagus cuniculus)
    Pinheiro, Victor ; Outor-Monteiro, D. ; Mourão, J.L. ; Cone, J.W. ; Guimaraes Dias Lourenco, Ana - \ 2018
    Journal of Animal Physiology and Animal Nutrition 102 (2018)1. - ISSN 0931-2439 - p. e460 - e467.
    alfalfa level - digestibility - domestic - intake - rabbit - wild
    The aim of this study was to evaluate the effect of the level of alfalfa in the diet on feed intake and digestibility of two types of rabbits, wild (Oryctolagus cuniculus algirus) vs. domestic (O. cuniculus cuniculus). Ten wild (W; mean LW = 927 g) and 10 domestic (D; mean LW = 4,645 g) adult rabbit does were fed ad libitum two pelleted diets: a control diet (C) with 15% of dehydrated alfalfa hay (as feed basis) and a test diet (A) with 36% of dehydrated alfalfa hay (as feed basis), according to a change-over design. Wild does dry matter (DM) intake per kg live weight (BW) was 55% higher (p < .001) than the intake of the D ones (58 g vs. 37 g DM per kg BW respectively). However, no difference (p > .05) was found when intake was expressed per kg0.75 BW (ca. 56 g DM) and tended to be higher (p = .07) in D does when expressed per kg0.67 BW (62 g vs. 55 g DM). Domestic does showed a higher (p < .05) DM, organic matter, crude energy and neutral detergent fibre digestibility (3; 2; 3; 3 percentage points respectively) than W does. The amount of nutrients and energy digested by D does was lower per kg BW (p < .001), similar per kg0.75 BW (p > .05) and tended to be higher per kg0.67 BW (p < .1) than in W does. The diet content of alfalfa did not affect (p > .05) the feed intake nor the diet digestibility. This study suggests that W rabbits exhibit a higher intake per kg BW and a lower digestibility than their D counterparts, which results in similar digestible nutrient and energy intake per kg BW powered to 0.75. The nutritive value of dehydrated alfalfa for rabbits, evaluated through intake and digestibility, seems to be equivalent to their base diets (forage plus concentrate).
    Pelleting and extrusion can ameliorate negative effects of toasting of rapeseed meal on protein digestibility in growing pigs
    Salazar-Villanea, S. ; Bruininx, E.M.A.M. ; Gruppen, H. ; Hendriks, W.H. ; Carré, P. ; Quinsac, A. ; Poel, A.F.B. van der - \ 2018
    Animal 12 (2018)5. - ISSN 1751-7311 - p. 950 - 958.
    digestibility - extrusion - growing pigs - pelleting - rapeseed meal
    Toasting time (TT) of rapeseed meal (RSM), the diet processing (DP) method and the interaction between both on the apparent CP digestion along the gastrointestinal tract and the apparent ileal digestibility (AID) of amino acids of growing pigs were investigated. The experiment consisted of a 3×3 factorial design of TT of RSM (0, 60 and 120 min) and DP method (mash, pelleting and extrusion). In total, 81 boars with a starting BW of 20 kg were euthanized 4 h after their last feeding. The gastrointestinal tract was dissected and the small intestine divided in three sections of similar length. Samples were collected from the stomach, 1.5 m from the ends of each of the three sections of the small intestine, and the rectum. The apparent digestibility (AD) of CP for each of the small intestine sections was used to calculate the rate of CP digestion. Increasing the TT of RSM resulted in lower protein solubility, lower lysine/reactive lysine contents and higher protein denaturation, indicative of the occurrence of protein aggregation and Maillard reactions. There were significant effects (P⩽0.01) of TT on the AD of CP in the different sections of the gastrointestinal tract. The rate of CP digestion of the 0 min toasted RSM diets was 23% and 35% higher than that of the 60 and 120 min toasted RSM diets, respectively. There was a significant interaction (P=0.04) between TT and DP for the AID of CP. Although pelleting of the 0 and 60 min toasted RSM diets did not change the AID of CP with respect to the mash diets, pelleting of the 120 min toasted RSM diet increased the AID of CP by 9.3% units. Extrusion increased the AID of CP of the 0 and 60 min toasted RSM diets by 3.4% and 4.3% units with respect to the mash diets, whereas extrusion of the 120 min toasted RSM diet increased the AID of CP by 6.9% units. Similar positive effects of pelleting and extrusion were obtained for the AID of lysine and reactive lysine, especially in the diets with higher TT. In conclusion, processing (pelleting and extrusion) of RSM containing diets can ameliorate the negative effects of RSM toasting on protein and amino acid digestibility; these effects were larger for the RSM toasted for longer times.
    Feeds, water quality, gut morphology and digestion in Nile tilapia (Oreochromis niloticus)
    Trần Ngọc Thiên Kim, Kim - \ 2017
    Wageningen University. Promotor(en): J.A.J. Verreth, co-promotor(en): J.W. Schrama; Arjen J. Roem. - Wageningen : Wageningen University - ISBN 9789463431484 - 127
    tilapia - oreochromis niloticus - feeds - fish feeding - water quality - digestion - digestibility - intestines - morphology - fish culture - aquaculture - tilapia - oreochromis niloticus - voer - visvoeding - waterkwaliteit - spijsvertering - verteerbaarheid - darmen - morfologie - visteelt - aquacultuur

    Diet composition, ingredient and nutrients, are important to consider for maintaining intestinal functions. Studies on both positive (using feed additives) and negative effects (using high inclusion of plant ingredients) of fish feeds are numerous, however, between studies results are often highly variable, both in type of response and in significance. The central hypothesis of this study was that adverse environmental conditions may aggravate negative effects of plant ingredients on the intestinal functions to the extent that mild effects become severe and perceptible. To do so, dietary factors and environmental conditions were evaluated and the interaction between diet composition and environmental conditions were studied in Nile tilapia.

    In Chapter 2, six common raw materials including hydrolysed feather meal (HFM), soybean meal (SBM), rice bran (RB), rapeseed meal (RM), sunflower meal (SFM) and dried distiller grains with solubles (DDGS) were chosen to determine the effect of nutrient digestibility, nitrogen/energy balance and changes in intestinal morphology. The study demonstrated that feed ingredients do have an impact on the alteration in intestinal parameters, but also on the nutrient digestibility and the nitrogen/energy balance. Although being well digested, soybean meal caused the most obvious alteration in the intestinal morphology. These alterations were not related to the nutrient digestibility nor to nitrogen/energy balance parameters. Soybean meal, causing the most alterations in the intestinal morphology, was further used in all subsequent chapters of this thesis.

    Chapter 3 and 4 described the interaction between diet composition and environmental conditions on the intestinal functions. This was studied with two different environmental conditions, dissolved oxygen (Chapter 3) and salinity (Chapter 4). These two chapters evaluated whether suboptimal environmental conditions (low dissolved oxygen or elevated salinity in water) may interact with a soybean meal based diet in nutrient digestion and intestinal morphology of tilapia. The study demonstrated that environmental stressors can aggravate/reveal the negative intestinal morphology changes induced by a soybean meal based diet. However, these effects of adverse environmental conditions on the intestinal functions were not homogenously dispersed over the whole intestinal length. The effect of salinity on the intestinal morphology occurred predominantly in the distal intestine, whereas the effect of low oxygen concentration was more visible at the proximal intestine. Alterations in the intestinal morphology, as found in this study, have wider effects on the performance of the affected fish. In Chapter 3, the protein digestibility decreased under hypoxic conditions at week 8, which parallels with the time related alteration in intestinal morphology. Chapter 4 showed that when fish were raised at 15 ‰ salinity, nutrient digestibility increased; however, this positive effect decreased when the intestinal morphology changed. The study also found that the combined effect of a soybean meal based diet and hypoxia was stronger compared to the combination with elevated salinity. Therefore, the combination with hypoxia was further used in the next study of this thesis.

    In Chapter 5, the combination of hypoxic condition and a soybean meal based diet was chosen to test the hypothesis that only under stressful conditions, the effects of feed additives can be noticed. The impact of two dietary organic acids, formic acid and butyric acid, on nutrient digestibility and intestinal morphology was determined under optimal (normoxia) and suboptimal conditions (hypoxia). The results showed that although organic acids did not significantly improve growth performance and nutrient digestibility under normoxic condition, they did so under hypoxic conditions. Fish fed organic acid supplemented diets all showed improvements in the morphology of intestine under normoxic conditions, and these effects were more enhanced under hypoxic conditions. This indicates that environmental conditions can alter the effect of organic acid on nutrient digestibility and intestinal morphology in tilapia.

    Finally, Chapter 6 provided a synthesis of the main findings, and a reflection on the methodologies used in Chapters 2-5 as well as a discussion on the relevance of this study to aquaculture. It is concluded that although being well digested, soybean meal caused the most obvious alteration in intestinal morphology. The adverse environmental conditions aggravated negative effects of soybean meal based diets on the intestinal functions to the extent that mild effects become severe and visible. The negative effect on intestinal morphology of soybean meal in the diet is enhanced at low oxygen level and at elevated salinity. The effect of salinity on the intestinal morphology occurs predominantly in the distal intestine, whereas the effect of low oxygen concentration is more visible at the proximal intestine. The thesis indicated that the impact of organic acids on intestinal functions is dependent on environmental conditions, being more pronounced under challenging conditions (e.g. hypoxia). Therefore, studies on both positive (using feed additives) and negative effects (using high inclusion of plant ingredients) of dietary factors should be done under suboptimal conditions.

    Evaluation of methodological aspects of digestibility measurements in ponies fed different haylage to concentrate ratios
    Schaafstra, F.J.W.C. ; Doorn, D.A. van; Schonewille, J.T. ; Riet, M.M.J. van; Visser, P. ; Blok, M.C. ; Hendriks, W.H. - \ 2017
    Animal 11 (2017)11. - ISSN 1751-7311 - p. 1922 - 1929.
    dietary markers - digestibility - equines - recovery - total faeces collection

    Methodological aspects of digestibility measurements were studied in four Welsh pony geldings consuming haylage-based diets with increasing proportions of a pelleted concentrate according to a 4×4 Latin square design experiment. Ponies were fed four experimental, iso-energetic (net energy (NE) basis) diets (i.e. 22 MJ NE/day) with increasing proportions of a pelleted concentrate (C) in relation to haylage (H). The absolute amounts of diet dry matter fed per day were 4.48 kg of H (100H), 3.36 and 0.73 kg of H and C (75H25C), 2.24 and 1.45 kg of H and C (50H50C) and 1.12 and 2.17 kg of H and C (25H75C). Diets were supplemented with minerals, vitamins and TiO2 (3.7 g Ti/day). Voluntary voided faeces were quantitatively collected daily during 10 consecutive days and analysed for moisture, ash, ADL, acid-insoluble ash (AIA) and Ti. A minimum faeces collection period of 6 consecutive days, along with a 14-day period to adapt the animals to the diets and become accustomed to the collection procedure, is recommended to obtain accurate estimations on dry matter digestibility and organic matter digestibility (OMD) in equids fed haylage-based diets supplemented with concentrate. In addition, the recovery of AIA, ADL and Ti was determined and evaluated. Mean faecal recovery over 10 consecutive days across diets for AIA, ADL and Ti was 124.9% (SEM 2.9), 108.7% (SEM 2.0) and 97.5% (SEM 0.9), respectively. Cumulative faecal recovery of AIA significantly differed between treatments, indicating that AIA is inadequate to estimate the OMD in equines. In addition, evaluation of the CV of mean cumulative faecal recoveries obtained by AIA, ADL and Ti showed greater variations in faecal excretion of AIA (9.1) and ADL (7.4) than Ti (3.7). The accuracy of prediction of OMD was higher with the use of Ti than ADL. The use of Ti is preferred as a marker in digestibility trials in equines fed haylage-based diets supplemented with increasing amounts of pelleted concentrate.

    Phytate degradation in broilers
    Krimpen, M.M. van; Emous, R.A. van; Spek, J.W. ; Kwakernaak, C. - \ 2016
    Wageningen : Wageningen Livestock Research (Wageningen Livestock Research report 978) - 50
    broilers - phytic acid - digestibility - poultry feeding - vleeskuikens - fytinezuur - verteerbaarheid - pluimveevoeding
    The nutritive value of condensed wheat distillers solubles for cattle
    Boever, J.L. De; Blok, M.C. ; Millet, S. ; Vanacker, J. ; Campeneere, S. De - \ 2016
    Animal 10 (2016)12. - ISSN 1751-7311 - p. 1955 - 1964.
    condensed wheat distillers solubles - digestibility - protein value - ruminants - solubility

    The chemical composition and the energy and protein value of five batches of condensed distillers solubles (CDS) originating from wheat were determined. The net energy for lactation (NEL) was derived from digestion coefficients obtained with sheep. The true protein digested in the small intestine (DVE) and the rumen degradable protein balance (OEB) were based on the rumen degradation rate (kd D), the rumen undegradable fraction (U) and intestinal digestibility of undegraded protein (%DVBE) predicted by regression equations derived from a data set of 28 protein feeds with kd D, U and %DVBE determined in situ. The CDS is a by-product with a high, but very variable CP content (238 to 495 g/kg DM). The CP contained on average 81% amino acids, with glutamine as main component (on average 21.8% of CP) and a relatively good lysine proportion (3.0%). Further, CDS contains quite a lot of crude fat (mean±SD: 71±14 g/kg DM), glycerol (95±52 g/kg DM) and sugars (123±24 g/kg DM) resulting in a high organic matter digestibility (88.6±3.0%) and high NEL content (8.3±0.4 MJ/kg DM). The protein value showed a large variation, with DVE ranging from 122 to 244 g/kg DM and OEB from 50 to 204 g/kg DM. Wheat CDS is a rich source of minerals and trace elements with exception of calcium.

    Maillard reaction products in pet foods
    Rooijen, C. van - \ 2015
    Wageningen University. Promotor(en): Wouter Hendriks, co-promotor(en): Guido Bosch; Peter Wierenga. - Wageningen : Wageningen University - ISBN 9789462575523 - 182
    gezelschapsdieren - huisdierenvoer - maillard-reactie - voedselverwerking - voedingswaarde - diergezondheid - lysine - stoom - omhullen - verteerbaarheid - voedselchemie - voedertechnologie - pets - pet foods - maillard reaction - food processing - nutritive value - animal health - lysine - steam - pelleting - digestibility - food chemistry - feed technology

    Pet dogs and cats around the world are commonly fed processed commercial foods throughout their lives. Often heat treatments are used during the processing of these foods to improve nutrient digestibility, shelf life, and food safety. Processing is known to induce the Maillard reaction, in which a reducing sugar binds to a free reactive amino group of an amino acid. In intact proteins, the ε-amino group of lysine is the most abundant free amino group. The reaction reduces the bioavailability of lysine and results in the formation of advanced Maillard reaction products. The aim of this thesis was to determine the occurrence and progression of the Maillard reaction during the manufacturing of pet foods, the subsequent impact on nutritive value of the food, and the bioavailability of Maillard reaction products in cats.

    In Chapter 2, the scientific literature was reviewed to investigate the current state of knowledge on the Maillard reaction and its potential effect on the nutritive value of pet foods and on pet health. Determination of the difference between total and reactive lysine by chemical methods provides an indication of the Maillard reaction in pet foods. Studies reported that the proportion of reactive lysine is on average 73% (range 39 – 100%) of total lysine, and that foods for growing dogs may be at risk of supplying less lysine than the animals require. The endogenous analogues of Maillard reaction products, advanced glycation end-products, have been associated with age-related diseases in humans, such as diabetes and impaired renal function. In dogs, data indicate higher advanced glycation end-product contents in plasma from dogs suffering from canine diabetes mellitus compared with healthy control animals. In addition, elevated levels of advanced glycation end-products in tissue proteins in dogs were observed for a number of diseases. To date it was unknown to what extent Maillard reaction products were present in pet foods, and whether dietary Maillard reaction products can be associated with the development of diseases such as diabetes and impaired renal function in pet animals. As the Maillard reaction is induced by processing, changing processing conditions should have an influence on the severity of the reaction. However, effects of processing conditions on the difference in total and reactive lysine contents in pet foods were inconsistent and did not always correspond to model systems. Processing temperature was reported to be the most important factor followed by moisture level. In addition, differences between total and reactive lysine were observed in several ingredients commonly used in pet foods. Reviewing the literature indicates that it is unknown to which extent the Maillard reaction occurs and whether Maillard reaction products are present in pet foods. There might be a risk for certain foods not meeting minimal lysine requirements. It is also unknown what the exact effect of processing on the Maillard reaction is in pet foods.

    The experiment described in Chapter 3 was designed to evaluate whether commercial pet foods meet minimal lysine requirements. Sixty-seven extruded, canned and pelleted commercially available dog and cat foods formulated for growth and maintenance were analysed using conventional amino acid analysis and O-methylisourea as reagent for reactive lysine. Sixty out of the 67 foods in this study, regardless of the type of processing technology used, contained a lower reactive lysine than total lysine content. On average, pelleted and extruded foods contain lower reactive to total lysine ratios compared to canned foods (0.85, 0.89, and 0.93, respectively). All cat foods and foods for adult dogs met minimal lysine requirements. However, eight dry foods for growing dogs contained reactive lysine contents between 96 and 138% of the minimal lysine requirement, indicating that reactive lysine has to be between 62 and 104% digestible to meet minimal requirement. Considering the variability in reactive lysine digestibility, these foods could be at risk of not meeting minimal lysine requirements for growing dogs.

    In Chapter 4, the foods from Chapter 3 were used to quantitate the Maillard reaction products fructoselysine (FL), carboxymethyllysine (CML), hydroxymethylfurfural (HMF), and the cross-linked amino acid lysinoalanine (LAL) using UPLC-MS. In all foods, Maillard reaction products and LAL were found but in highly variable amounts. Type of processing seems to be a key factor for the concentration of FL, CML and HMF, with on average higher amounts in canned foods than pelleted and extruded foods (on a dry matter basis). The contents of CML and HMF found in commercial pet foods are, on average, within the range reported in processed human food products. Average daily intake (mg/kg body weight0.75) of HMF was 122 times higher for dogs and 38 times higher for cats than the calculated average intake for adult humans. Average daily intake of CML was comparable to the intake of adult humans.

    As Chapters 3 and 4 indicated that pelleted foods contain more Maillard reaction products than extruded foods, despite the less severe production process, an experiment was designed to gain insight in the effect of steam pelleting on the Maillard reaction in a dog food (Chapter 5). The aim was to examine the effect of conditioning temperature (65 and 90°C) and die hole length (ø 5 × 45, 65, and 80 mm) during pelleting processing of a standard dry dog food on selected indicators of the Maillard reaction (total lysine, reactive lysine, FL, CML, HMF, LAL), browning development and CIE-Lab colour. Steam pelleting did not cause a significant loss of reactive lysine and change of absorbance values. This indicates that the effect of steam pelleting on the nutritive value of the foods is low. However, steam pelleting did increase the content of Maillard reaction products. The formation of the Maillard reaction products was associated with an increase in temperature and die hole length during the steam pelleting process. The unprocessed ingredient mix already contained a larger difference between reactive and total lysine, and contents of Maillard reaction products than was induced during steam pelleting. Therefore, the choice of the ingredients used in this study mainly determines reactive lysine content and Maillard reaction products in the pet food formulation.

    As it is unknown to which extent extrusion processing influences the Maillard reaction in pet foods, the effect of extrusion processing on selected indicators of the Maillard reaction was determined (Chapter 6). The extrusion parameters temperature (140 and 165°C), moisture content (200 and 300 g/kg) and screw speed (100 and 200 rpm) were applied to two dry dog foods formulated using either intact or hydrolysed proteins. Extrusion processing in general results in a decrease in total and reactive lysine and an increase in FL, CML, HMF and LAL content. However, this effect appeared more pronounced in the diet containing hydrolysed protein. Decreasing temperature and moisture content led to higher total and reactive lysine contents, and less Maillard reaction products in the dog foods. Increasing screw speed had a positive influence on total and reactive lysine, but a negative influence on Maillard reaction products. As was found in Chapter 5, the unprocessed ingredient mixtures in this experiment contained already more Maillard reaction products than was induced during extrusion processing.

    Whether the Maillard reaction products reported in pet foods are physiologically relevant in pet animals depends on the bioavailability of these components. Therefore, urinary excretion was studied in adult cats fed commercial moist and dry foods containing varying amounts of FL, CML and the amino acid LAL (Chapter 7). A pilot study was first conducted to determine the adaptation time required for stable urinary excretion of the Maillard reaction products when changing diets with contrasting contents of Maillard reaction products. An adaptation time of 1 d was deemed sufficient in adult cats. The short adaptation time indicates an effective urinary excretion of Maillard reaction products. In the main study, six commercially processed dry and six moist diets were fed to 12 adult female cats in two parallel randomized, 36-day, balanced Latin square designs. Urine was collected quantitatively and FL, CML and LAL were analysed in foods and collected urine using HPLC-MS. Daily urinary excretion of FL and CML showed a positive relationship with daily intake in the dry and moist foods. For LAL, no significant relationship was observed. The observed increase in urinary excretion with increasing dietary intake indicates that dietary Maillard reaction products are absorbed from the gastro-intestinal tract of cats and excreted in the urine. Minimum apparent absorption based on urinary excretion (assuming 100% of the excreted component originates from the diet) of FL, CML and LAL was found to range between 8 to 23%, 25 to 73% and 6 to 19%, respectively. Urinary recovery (% ingested) showed a negative relationship with daily intake for FL, CML and LAL in the dry foods and for CML and LAL in the moist foods. The observed decrease in urinary recovery with increasing intake suggests a limiting factor in digestion, absorption, metabolism or urinary excretion.

    The studies reported in this thesis are one of the first to determine Maillard reaction products in pet foods and the bioavailability of FL, CML and LAL in cats. In addition, the results highlight the importance of reactive lysine measurement in foods for growing dogs used as weaning diets. Contribution of the absorption of dietary Maillard reaction products to the pathogenesis of various health conditions requires further study, as well as the potential role of restriction of dietary Maillard reaction products in prevention and treatment of long-term health implications. Extrusion and pelleting processing do increase the Maillard reaction, however, choice of ingredients appears to have a larger effect on the content of Maillard reaction products and can, therefore, be a useful strategy for pet food manufacturers that want to decrease the content of Maillard reaction products in their pet foods.

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