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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    Stress response, peripheral serotonin and natural antibodies in feather pecking genotypes and phenotypes and their relation with coping style
    Eijk, Jerine A.J. van der; Lammers, Aart ; Kjaer, J.B. ; Rodenburg, T.B. - \ 2019
    Physiology and Behavior 199 (2019). - ISSN 0031-9384 - p. 1 - 10.
    Feather pecking - genotype - natural antibody - phenotype - serotonin - stress response

    Feather pecking (FP), a serious welfare and economic issue in the egg production industry, has been related to coping style. Proactive and reactive coping styles differ in, among others, the stress response, serotonergic activity and immune activity. Yet, it is unknown whether genetic lines divergently selected on FP (i.e. FP genotypes) or individuals differing in FP (i.e. FP phenotypes) can be categorized into coping styles. Therefore, we determined peripheral serotonin (5-HT) levels, natural antibody (NAb) titers, behavioral and corticosterone (CORT) responses to manual restraint (MR) in FP genotypes (high FP (HFP), low FP (LFP) and unselected control (CON) line) and FP phenotypes (feather pecker, feather pecker-victim, victim and neutral). We further examined the consistency of and relationships between behavioral and physiological measures. FP genotypes differed in behavioral responses to MR, 5-HT levels and NAb titers, but not in CORT levels after MR. HFP birds had less active responses at adolescent age, but more active responses at adult age compared to LFP and CON birds. The CON line had higher 5-HT levels at adolescent age, while the HFP line had lower 5-HT levels than the other lines at adult age. Overall, the HFP line had lower IgM NAb titers, while the LFP line had lower IgG NAb titers compared to the other lines. FP phenotypes differed in behavioral responses to MR and 5-HT levels, but not in CORT levels after MR or NAb titers. Within the HFP line, feather peckers tended to have less active responses compared to neutrals at adolescent age, while victims had more active responses compared to the other phenotypes at adult age. Feather peckers had higher 5-HT levels than neutrals at adult age. Behavioral and CORT responses to MR were not consistent over time, suggesting that responses to MR might not reflect coping style in this study. Furthermore, proactive behavioral responses were correlated with reactive physiological measures and vice versa. Thus, it was not possible to categorize FP genotypes or FP phenotypes into specific coping styles.

    Small intestinal targets involved in food intake regulation : 'from nutrient to satiety signal'
    Ripken, D. - \ 2016
    Wageningen University. Promotor(en): Renger Witkamp; H.F.J. Hendriks. - Wageningen : Wageningen University - ISBN 9789462576438 - 180
    obesity - preventive nutrition - small intestine - ileum - duodenum - jejunum - satiety - appetite control - food intake - safflower oil - vagus nerve - casein - stevia rebaudiana - sucrose - macronutrients - serotonin - animal models - human feeding - obesitas - preventieve voeding - dunne darm - ileum - duodenum - jejunum - verzadigdheid - eetlustcontrole - voedselopname - saffloerolie - nervus vagus - caseïne - stevia rebaudiana - sucrose - macronutriënten - serotonine - diermodellen - humane voeding

    Background and aim: The worldwide increasing prevalence of overweight and obesity raises concerns for health. There is a clear need for preventive strategies, because current preventative interventions have proven to be unsuccessful in the long term. New strategies may be developed based on targets in the small intestine by activating satiety signals. The thesis aimed to investigate small intestinal targets contributing to food intake regulation. These targets included serotonin, the vagal nerve and the intestinal brake mechanism.

    Methods: The effects of ileal stimulation with safflower oil (lipid mixture), casein (protein), sucrose (carbohydrate) and rebaudioside A (non-caloric sweetener) on GLP-1 and PYY release were investigated by applying an porcine ex vivo intestinal segment model. The same model was also used to investigate if serotonin is involved in (non-)nutritional-induced GLP-1 and PYY release.

    The contribution to satiation of GLP-1 and CCK receptors at the vagal nerve, was studied by investigating the effects of GLP-1 and CCK receptor antagonists on ad libitum food intake in a pig model of subdiaphragmatic vagotomy.

    Two placebo controlled randomized crossover studies were performed in healthy volunteers to investigate the effects of small intestinal macronutrient delivery on ad libitum food intake and satiety signals. The first study compared the effects of duodenal, jejunal and ileal casein delivery on ad libitum food intake and satiety signals. The second study investigated if ileal delivery of all three macronutrients results in activation of satiety signals and reduction in ad libitum food intake. In addition, it was investigated if ileal delivery of native casein is efficiently digested and absorbed and does not result in adverse effects. In both studies the nutrients were delivered to the small intestine by inserting a nasointestinal feeding tube in healthy volunteers.

    Results: All macronutrients and rebaudioside A stimulated GLP-1 and PYY release from ileal tissue segments. Protein and fat stimulated serotonin release. Inhibiting the reuptake of serotonin resulted in enhanced nutrient induced GLP-1, PYY and CCK release. Serotonin stimulated GLP-1 release from enteroendocrine cells via a serotonin receptor mediated process.

    Results of the in vivo pig study showed that antagonism of the CCK receptor increased food intake in both vagotomized and sham operated pigs. Blocking the GLP-1 receptor did not affect food intake in both groups.

    The human studies showed that ileal protein delivery inhibited food intake and activated satiety signals as compared to duodenal or jejunal protein delivery. Also, ileal delivery of small quantities (51.7 kcal) of each macronutrient decreased food intake and activated satiety signals. In addition, it was shown that ileal delivery of native casein resulted in a time and concentration depended increase in plasma concentrations of amino acids and did not result in activation of immune responses nor in gastrointestinal complaints.

    Conclusions: The data presented in this thesis show that ileal delivery of all macronutrients results in activation of satiety signals and reduction of food intake. Stimulation of the ileum resulted in the strongest activation of satiety signals and inhibition of food intake compared to duodenal and jejunal stimulation. Besides direct nutrient-receptor interaction, the ileum senses (non-)nutritional stimuli via serotonin mediated processes resulting in GLP-1 release. In conclusion, these results demonstrate that targeting the ileum with small amounts of macronutrients is safe and has potential as a weight management strategy.

    Hypothalamic regulation of food intake during cancer
    Dwarkasing, J.T. - \ 2015
    Wageningen University. Promotor(en): Renger Witkamp, co-promotor(en): Klaske van Norren; Mark Boekschoten. - Wageningen : Wageningen University - ISBN 9789462575486 - 147
    hypothalamische regulatie - anorexia - eetlustcontrole - voedselopname - cancer - chronische ziekten - diermodellen - muizen - serotonine - hypothalamic regulation - anorexia - appetite control - food intake - cancer - chronic diseases - animal models - mice - serotonin

    Appetite is often reduced in patients with chronic illness, including cancer.

    Cancer anorexia, loss of appetite, frequently co-exists with cachexia, and the combined clinical picture is known as anorexia-cachexia syndrome. In patients suffering from this syndrome, anorexia considerably contributes to the progression of cachexia, and strongly impinges on quality of life. Inflammatory processes in the hypothalamus are considered to play a crucial role in the development of disease-related anorexia.

    The main aim of this thesis was to further elucidate crucial processes involved in the pathogenesis of anorexia in cancer. To investigate mechanisms specifically involved in cancer anorexia, we used two tumour mouse models with opposing food intake behaviours: a C26-colon adenocarcinoma model with increased food intake and a Lewis lung carcinoma model with decreased food intake. In both models, tumour-induced cachexia (body wasting) was strongly present. The contrast in food intake behaviour between tumour-bearing (TB) mice in response to growth of the two different tumours was used to distinguish processes involved in cachexia from those specifically involved in anorexia.

    The hypothalamus was used for transcriptomic analysis (Affymetrix chips). We found expression of genes involved in serotonin signalling in the hypothalamus to be differentially regulated between the two tumour models. Furthermore, transcriptional activity of genes involved in serotonin signalling were inversely associated with food intake behaviour. Surprisingly, we also found a strong increase in gene expression of NPY and AgRP, potent orexigenic neuropeptides, in both models, meaning that their expression did not reflect food intake behaviour. However, NPY has also been described to regulate energy storage. Therefore, we hypothesized that this upregulation of NPY/AgRP corresponded to weight loss, which was severe in both tumour models.

    Using hypothalamic cell lines we further explored how serotonin might act on food intake regulatory pathways. We showed that serotonin was able to inhibit neuronal NPY secretion, while not affecting gene expression. Inflammatory markers IL-6 and TNFα were also measured in plasma and it was found that C26 TB mice had a lower inflammatory response than LL TB mice. These differences in inflammatory response could be implicated in the differences in feeding behaviour and serotonin signalling between C26 and LL TB mice. We therefore investigated the direct influence of inflammation on hypothalamic serotonin turnover and its contribution to the development of anorexia. To this end, different doses of TNF and IL-6 were administered by injection to healthy mice, inducing an acute inflammatory response. The injected cytokine doses were estimated from their corresponding plasma levels measured in tumour bearing (TB) mice. Also in this cytokine induced-anorexia model, where anorexia was exclusively induced by an inflammatory response, serotonin metabolism in the hypothalamus was affected. Both TNF and IL-6 increased hypothalamic serotonin turnover while also inducing anorectic behaviour. Furthermore, the effect of cytokines on increasing serotonin turnover was supported by in vitro experiments with hypothalamic neuronal cell lines.

    In conclusion, we identified hypothalamic serotonin signalling to play a major role in the decrease in food intake during cancer. Serotonin signalling itself is modulated by inflammatory mediators. Therefore, hypothalamic inflammation is an important trigger in the failure of hypothalamic food-intake regulation, probably by affecting serotonergic signalling, which acts as an upstream modulator of various orexigenic and anorexigenic systems.

    The olfactory receptor OR51E1 is present along the gastrointestinal tract of pigs and is modulated by intestinal microbiota
    Priori, D. ; Clavenzani, P. ; Jansman, A.J.M. ; Lalles, J.P. ; Trivisil, P. ; Bosi, P. - \ 2015
    PLoS ONE 10 (2015)6. - ISSN 1932-6203 - 17 p.
    enterotoxigenic escherichia-coli - butyrate-producing bacteria - fatty-acid receptor - net absorption - weaned pigs - odorant receptor - taste receptors - gene-expression - gut microbiota - serotonin
    The relevance of the butyrate-sensing olfactory receptor OR51E1 for gastrointestinal (GIT) functioning has not been considered so far. We investigated in young pigs the distribution of OR51E1 along the GIT, its relation with some endocrine markers, its variation with age and after interventions affecting the gut environment and intestinal microbiota. Immuno-reactive cells for OR51E1 and chromogranin A (CgA) were counted in cardial (CA), fundic (FU), pyloric (PL) duodenal (DU), jejunal (JE), ileal (IL), cecal (CE), colonic (CO) and rectal (RE) mucosae. OR51E1 co-localization with serotonin (5HT) and peptide YY (PYY) were evaluated in PL and CO respectively. FU and PL tissues were also sampled from 84 piglets reared from sows receiving either or not oral antibiotics (amoxicillin) around parturition, and sacrificed at days 14, 21, 28 (weaning) and 42 of age. JE samples were also obtained from 12 caesarean-derived piglets that were orally associated with simple (SA) or complex (CA) microbiota in the postnatal phase, and of which on days 26–37 of age jejunal loops were perfused for 8 h with enterotoxigenic Escherichia coli F4 (ETEC), Lactobacillus amylovorus or saline (CTRL). Tissue densities of OR51E1+ cells were in decreasing order: PL=DU>FU=CA>JE=IL=CE=CO=RE. OR51E1+ cells showed an enteroendocrine nature containing gastrointestinal hormones such as PYY or 5HT. OR51E1 gene expression in PL and FU increased during and after the suckling period (p
    Indirect Genetic Effects for Growth Rate in Domestic Pigs Alter Aggressive and Manipulative Biting Behaviour
    Camerlink, I. ; Ursinus, W.W. ; Bijma, P. ; Kemp, B. ; Bolhuis, J.E. - \ 2015
    Behavior Genetics 45 (2015)1. - ISSN 0001-8244 - p. 117 - 126.
    social breeding values - multilevel selection - environment interactions - interacting phenotypes - housing systems - traits - performance - chickens - populations - serotonin
    Indirect genetic effects (IGEs) are heritable effects of an individual on phenotypic values of others, and may result from social interactions. We determined the behavioural consequences of selection for IGEs for growth (IGEg) in pigs in a G × E treatment design. Pigs (n = 480) were selected for high versus low IGEg with a contrast of 14 g average daily gain and were housed in either barren or straw-enriched pens (n = 80). High IGEg pigs showed from 8 to 23 weeks age 40 % less aggressive biting (P = 0.006), 27 % less ear biting (P = 0.03), and 40 % less biting on enrichment material (P = 0.005). High IGEg pigs had a lower tail damage score (high 2.0; low 2.2; P = 0.004), and consumed 30 % less jute sacks (P = 0.002). Selection on high IGEg reduced biting behaviours additive to the, generally much larger, effects of straw-bedding (P <0.01), with no G × E interactions. These results show opportunities to reduce harmful biting behaviours in pigs.
    Feather pecking and monoamines - a behavioral and neurobiological approach
    Kops, M.S. - \ 2014
    Wageningen University; Utrecht University. Promotor(en): B. Olivier; O. Güntürkün, co-promotor(en): S.M. Korte; Liesbeth Bolhuis. - Utrecht, The Netherlands : Utrecht University - ISBN 9789039361283 - 172
    pluimveehouderij - hennen - verenpikken - diergedrag - dierenwelzijn - pluimvee - diergezondheid - dierlijke productie - serotonine - dopamine - fenotypen - genotypen - neurotransmitters - invloeden - poultry farming - hens - feather pecking - animal behaviour - animal welfare - poultry - animal health - animal production - serotonin - dopamine - phenotypes - genotypes - neurotransmitters - influences
    Severe feather pecking (SFP) remains one of the major welfare issues in laying hens. SFP is the pecking at and pulling out of feathers, inflicting damage to the plumage and skin of the recipient. The neurobiological profile determining the vulnerability of individual hens to develop into a severe feather pecker is unknown, although brain monoamines such as serotonin (5-HT) and dopamine (DA) seem to play a role. Previous studies related lower 5-HT and DA turnover ratios to an increased risk to develop SFP.In this thesis, monoamine levels in brain areas involved in emotional regulation and motor control were compared between phenotypically and genetically selected high and low feather peckers at different ages. It was found that adult high feather peckers had higher monoaminergic activity (lower metabolite levels and/or turnover ratios) in comparison to low feather peckers, which is in contrast with results on young hens. Differences were seen in several brain areas, namely the dorsal thalamus, medial striatum, amygdala, caudocentral nidopallium, and the somatomotor arcopallium, but to a lesser extend or not in the caudolateral nidopallium and the hippocampus. To investigate the exact neurobiological mechanism behind severe feather pecking further extracellular levels of 5-HT and DA and their metabolites were measured by in vivo microdialysis. Up till now, microdialysis has only been executed in young chickens, but this thesis describes the first microdialysis study performed in adult laying hens. It was found that adult severe feather peckers had a higher baseline release of 5-HT in the caudal nidopallium, a large associative area in the chicken’s forebrain. This result could not be explained by the amount of 5-HT presynaptically stored, as both high and low SFP lines displayed a similar 5-HT release after d-fenfluramine administration. This confirms that genetic selection on SFP has altered the serotonergic system in feather pecking-phenotypes. With clear phenotypic and genotypic differences in brain areas related to emotional regulation and motor control, it can be assumed that brain deficits at a young age increase an individual’s vulnerability to stressful environmental changes, which is associated with the prevalence of SFP later in life. The cause of the inversion of neurochemical patterns in young and adult high and low feather pecking hens remains to be elucidated. Perhaps this inversion is caused by development itself. On the other hand, higher behavioral patterns (SFP and other types of allopecking) observed in the high feather pecking chickens might have influenced the monoaminergic activity since the brain influences behavior and vice versa. Altogether, this thesis demonstrates the importance of considering the impact of genetic selection and also environmental conditions on brain neurotransmission and with that, on the vulnerability of individual chickens to develop SFP. Both the serotonergic and dopaminergic systems are involved in the development of SFP. With SFP being a multifactorial problem both genotype and phenotype have to be taken into account. Furthermore, in vivo microdialysis is a valuable approach to investigate why individual laying hens start SFP. This will lead to further understanding and ultimately in the reduction of SFP.
    Bloed vertelt over persoonlijkheid varken : zoeken naar voorspeller(s) voor staartbijten
    Ursinus, W.W. - \ 2013
    V-focus 10 (2013)4. - ISSN 1574-1575 - p. 28 - 29.
    varkenshouderij - staartbijten - diergedrag - varkens - dierenwelzijn - serotonine - dierlijke productie - pig farming - tail biting - animal behaviour - pigs - animal welfare - serotonin - animal production
    Wageningen UR heeft de handen ineen geslagen in de zoektocht naar oplossingen tegen staartbijten bij varkens. Eén optie is staartbijten in te perken nadat het ontstaan is, een tweede optie is staartbijten te voorspellen en al vóórdat het ontstaat, tegen te gaan. Het meten van bloedwaardes en deze waardes relateren aan het gedrag van het varken, lijkt daarvoor kansen te bieden.
    Effects of genetic origin and social environment on behavioral response to manual restraint and monoamine functioning in laying hens
    Uitdehaag, K.A. ; Rodenburg, T.B. ; Reenen, C.G. van; Koopmanschap, R.E. ; Vries Reilingh, G. de; Engel, B. ; Buist, W.G. ; Komen, J. ; Bolhuis, J.E. - \ 2011
    Poultry Science 90 (2011)8. - ISSN 0032-5791 - p. 1629 - 1636.
    feather pecking behavior - open-field - dopamine turnover - tonic immobility - group selection - serotonin - chicks - corticosterone - platelets - lines
    Purebred laying hen lines of White Leghorn (WL) origin have been found to be more flighty and to show more feather pecking than lines of Rhode Island Red (RIR) origin. It has been found, however, that when RIR birds were housed together with WL birds, RIR birds became more flighty and those mixed groups developed more feather damage than pure-line cage-housed groups. It is unknown, however, whether this effect of social environment is accompanied by changes in stress-related behavior and neurophysiological activity, which are assumed to be associated with increased feather damage. The objective of this study was therefore to investigate the effects of genetic origin (WL or RIR) and social environment (mixed or pure groups) on behavioral response to manual restraint and monoamine functioning. Monoamine functioning was measured by brain serotonin (5-HT) and dopamine turnover. Furthermore, correlations between 5-HT turnover in the brain and peripheral measures of 5-HT in the blood were calculated. Experimental birds, housed either with other birds from the same genetic origin (pure groups) or with both RIR and WL birds (mixed groups) from hatching onward, were subjected to a manual restraint test at 47 wk of age. The WL birds struggled less during restraint and had higher dopamine and 5-HT turnover levels after restraint than did RIR birds. The WL birds also showed higher levels of platelet 5-HT uptake than did RIR birds. No effects of social environment were found. Blood and brain 5-HT measures were found to be correlated, with correlations ranging from 0.34 to 0.57, which seems to offer opportunities for less invasive peripheral indicators of 5-HT activity. In conclusion, genetic origin, but not social environment, affected the behavioral response to manual restraint and monoamine functioning in laying hens
    Across-Line SNP Association Study for Direct and Associative Effects on Feather Damage in Laying Hens
    Biscarini, F. ; Bovenhuis, H. ; Poel, J.J. van der; Parmentier, H.K. ; Jungerius, B.J. ; Arendonk, J.A.M. van - \ 2010
    Behavior Genetics 40 (2010)5. - ISSN 0001-8244 - p. 715 - 727.
    quantitative trait loci - open-field response - 2 different ages - pecking behavior - multilevel selection - genetic-parameters - domestic chicks - serotonin - young - cannibalism
    An association study between SNP markers and feather condition score on the back, rump and belly of laying hens was performed. Feather condition score is a measure of feather damage, which has been shown to be closely related to feather pecking behaviour in hens housed in groups. A population of 662 hens was genotyped for 1536 SNPs of which 1022 could be used for the association study. The analysis was conducted across 9 different lines of White Leghorn and Rhode Island Red origin. Across lines linkage disequilibrium is conserved at shorter distances than within lines; therefore, SNPs significantly associated with feather condition score across lines are expected to be closer to the functional mutations. The SNPs that had a significant across-line effect but did not show significant SNP-by-line interaction were identified, to test that the association was consistent across lines. Both the direct effect of the individual’s genotype on its plumage condition, and the associative effect of the genotype of the cage mates on the individual’s plumage condition were analysed. The direct genetic effect can be considered as the susceptibility to be pecked at, whereas the associative genetic effect can be interpreted as the propensity to perform feather pecking. Finally, 11 significant associations between SNPs and behavioural traits were detected in the direct model, and 81 in the associative model. A role of the gene for the serotonin receptor 2C (HTR2C) on chromosome 4 was found. This supports existing evidence of a prominent involvement of the serotonergic system in the modulation of this behavioural disorder in laying hens. The genes for IL9, IL4, CCL4 and NFKB were found to be associated to plumage condition, revealing relationships between the immune system and behaviour.
    Breeding amiable animals? Improving farm animal welfare by including social effects in breeding programmes
    Rodenburg, T.B. ; Bijma, P. ; Ellen, E.D. ; Bergsma, R. ; Vries, S. de; Bolhuis, J.E. ; Kemp, B. ; Arendonk, J.A.M. van - \ 2010
    Animal Welfare 19 (2010)Suppl. 1. - ISSN 0962-7286 - p. 77 - 82.
    different coping characteristics - open-field response - laying hens - feather pecking - multilevel selection - behavioral-development - genetic-parameters - pigs - serotonin - lines
    Social interactions between individuals, such as co-operation and competition, are key factors in evolution by natural selection. As a consequence, evolutionary biologists have developed extensive theories to understand the consequences of social interactions for response to natural selection. Current genetic improvement programmes in animal husbandry, in contrast, largely ignore the implications of social interactions for the design of breeding programmes. Recently, we have developed theoretical and empirical tools to quantify the magnitude of heritable social effects, ie the heritable effects that animals have on their group mates' traits, in livestock populations, and to utilise those effects in genetic improvement programmes. Results in commercial populations of pigs and laying hens indicate large heritable social effects, and the potential to substantially increase responses to selection in traits affected by social interactions. In pigs, including social effects into the breeding programme affected aggressive behaviour, both at mixing and in stable groups, indicating changes in the way dominance relationships are established and in aggressiveness. In laying hens, we applied selection between kin-groups to reduce mortality due to cannibalistic pecking. This resulted in a considerable difference in mortality between the low mortality line and the unselected control line in the first generation (20 vs 30%). Furthermore, changes in behavioural and neurobiological responses to stress were detected in the low mortality line, pointing to reduced fearfulness and stress sensitivity. These first results indicate that including social effects into breeding programmes is a promising way to reduce negative social interactions in farm animals, and possibly to also increase positive social interactions, by breeding animals with better social skills
    Dietary tryptophan supplementation in privately owned mildly anxious dogs
    Bosch, G. ; Beerda, B. ; Beynen, A.C. ; Borg, J.A.M. van der; Poel, A.F.B. van der; Hendriks, W.H. - \ 2009
    Applied Animal Behaviour Science 121 (2009)3-4. - ISSN 0168-1591 - p. 197 - 205.
    separation anxiety - saliva cortisol - amino-acids - food-intake - serotonin - stress - behavior - plasma - brain - responses
    Food composition has been reported to influence mood and behaviour in humans and animals and it could help to reduce unwanted behaviour in dogs. Anxiety-related behaviour is associated with the functioning of the central serotonergic system and here it was investigated if dietary supplementation with the serotonin precursor tryptophan (Trp) affects behaviour in privately owned dogs. For 8 weeks, privately owned dogs were fed a control diet (n = 66) or a diet containing 2.6-fold more Trp than the control diet (n = 72), using a randomised double-blinded, placebo-controlled approach. A third diet fortified with Trp, beet pulp, salmon oil, soy lecithin, and green tea extract was studied for its potential in 69 dogs. Owners reported on their dogs’ behaviour in the home-situation by filling out a web-based questionnaire before the onset of dietary treatment and after 4 and 8 weeks of feeding the diets. Thirty-four dogs fed the control diet and 39 dogs fed the Trp diet were subjected to behaviour tests before and after 8 weeks of dietary treatment. The tests included open-field situations and owner-separation procedures and were set up to measure anxiousness. Blood was collected after 8 weeks from dogs in the control (15 dogs) and Trp (15) groups for evaluation of plasma amino acid concentrations. Dietary effects on behaviour were investigated for significance by means of testing interactions between diet and time, using Residual Maximum Likelihood. Intake of the Trp supplemented diet significantly increased plasma Trp concentrations by 37.4% and its ratio with large neutral amino acids by 31.2% compared to the control diet but owners did not report on behavioural changes that could be attributed to a specific dietary treatment. Also, the dogs’ responses in the behavioural tests, including those in saliva cortisol, were unaffected after 8 weeks of consuming the Trp supplemented food. A number of significant changes in both owner-reported assessments and behavioural responses did occur over time, possibly mirroring a placebo-effect and/or influences of a new diet regardless of its specific composition. It is concluded that intake of diets supplemented solely with Trp or in combination with beet pulp, salmon oil, soy lecithin, and green tea extract does not change (anxiety-related) behaviour in privately owned dogs that do not show clear signs of abnormal behaviour. The influence of dietary Trp intake on behaviour of pathological anxious or chronically stressed dogs remains to be established
    Surplus dietary tryptophan inhibits stress hormone kinetics and induces insulin resistance in pigs
    Koopmans, S.J. ; Ruis, M.A.W. ; Dekker, R.A. ; Korte, M. - \ 2009
    Physiology and Behavior 98 (2009)4. - ISSN 0031-9384 - p. 402 - 410.
    amino-acid utilization - plasma-cortisol - protein-synthesis - skeletal-muscles - identical meals - glucose - sensitivity - serotonin - axis - glucocorticoids
    Recently we have shown that surplus dietary tryptophan (TRP) reduced the plasma concentrations of cortisol and noradrenaline in pigs. Stress hormones are known to affect insulin sensitivity and metabolism. We now investigated the long-term effects of surplus dietary TRP on 1) plasma and urinary stress hormone kinetics, 2) insulin sensitivity for glucose and amino acid clearance, and 3) whole body nitrogen balance. Pigs were fed for 3 weeks a high (13.2%) vs normal (3.4%) TRP to large neutral amino acids (LNAA) diet, leading to reduced fasting (14 h) plasma cortisol (17.1 ± 3.0 vs 28.9 ± 4.3 ng/mL, p <0.05) and noradrenaline (138 ± 14 vs 225 ± 21 pg/mL, p <0.005) concentrations, lower daily urinary noradrenaline (313 ± 32 vs 674 ± 102 ng/kg day, p <0.001) and adrenaline (124 ± 13 vs 297 ± 42 ng/kg day, p <0.001) but higher dopamine (5.8 ± 0.5 vs 1.5 ± 0.2 µg/kg day, p <0.001) excretions, respectively. Insulin sensitivities for both glucose and amino acid clearance, (as measured by the intraportal hyperinsulinaemic (1 mU/kg min) euglycaemic euaminoacidaemic clamp technique), were lower by 22% in pigs on the high vs normal TRP/LNAA diet (14.8 ± 1.4 vs 18.9 ± 0.9, p <0.05 and 69.7 ± 4.3 vs 89.7 ± 6.8 mL/kg min, p <0.05, respectively) without affecting urinary nitrogen excretion (35.5 ± 1.0 vs 36.6 ± 1.0% of dietary nitrogen intake, p = ns). In conclusion, long-term feeding of surplus dietary TRP inhibits both baseline adrenocortical and sympathetic nervous system activity, it induces insulin resistance for both glucose and amino acid clearance but it does not affect whole body protein catabolism. This indicates that the bioactive amino acid TRP contributes to homeostasis in neuroendocrinology and insulin action and that low baseline adrenocortical and sympatho-adrenal axis activity are associated with insulin resistance.
    Individual variation in copying with stress: a multidimensional approach of ultimate and proximate mechanisms
    Koolhaas, J.M. ; Boer, S.F. de; Buwalda, B. ; Reenen, C.G. van - \ 2007
    Brain, behavior and evolution 70 (2007)4. - ISSN 0006-8977 - p. 218 - 226.
    wild house mice - 5-ht1a receptor - aggressive-behavior - nonaggressive mice - mouse lines - serotonin - responses - rats - responsiveness - neuroendocrine
    Ecological studies on feral populations of mice, fish and birds elucidate the functional significance of phenotypes that differ individually in their behavioral and neuroendocrine response to environmental challenge. Within a species, the capacity to cope with environmental challenges largely determines individual survival in the natural habitat. Recent studies indicate that individual variation within a species may buffer the species for strong fluctuations in the natural habitat. A conceptual framework will be presented that is based on the view that individual variation in aggressive behavior can be considered more generally as a variation in actively coping with environmental challenges. Highly aggressive individuals adopt a proactive coping style whereas low levels of aggression indicate a more passive or reactive style of coping. Coping styles have now been identified in a range of species and can be considered as trait characteristics that are stable over time and across situations. The dimension of coping style seems to be independent of an emotionality dimension. Hence, in the analysis of the proximate mechanisms of stress and adaptation, one has to consider the possibility that the mechanisms which determine the type of stress response might be independent from those underlying the magnitude of the response. The two coping styles differ in a number of important neurobiological and neuroendocrine systems. For example, proactive males differ significantly from reactive males in the homeostatic control of serotonergic activity resulting in completely opposite dose response relationships of various serotonergic drugs. The results so far show that proactive coping is characterized by a strong inhibitory control of the 5-HT neuron via its somatodendritic 5-HT1A autoreceptor. It is hypothesized that the regulation of serotonin release is causally related to coping style rather than emotionality. Understanding the functional individual variation as it occurs in nature and the underlying neurobiology and neuroendocrinology is fundamental in understanding individual vulnerability to stress related disease.
    Chicks from a high and low feather pecking line of laying hens differ in apomorphine sensitivity
    Hierden, Y.M. van; Koolhaas, J.M. ; Kost'al, L. ; Vyboh, P. ; Sedlackova, M. ; Rajman, M. ; Jurani, M. ; Korte, S.M. - \ 2005
    Physiology and Behavior 84 (2005)3. - ISSN 0031-9384 - p. 471 - 477.
    wistar rats differ - dopamine turnover - manual restraint - behavior - serotonin - haloperidol - catecholamine - involvement - receptors - recovery
    Proactive rodents show a larger behavioral response to apomorphine (APO) than reactive copers, suggesting a more sensitive DA system in proactive individuals. Previously, chicks from a high feather pecking (HFP) and low feather pecking line (LFP) have been suggested to display a proactive and reactive coping strategy, respectively. Therefore, at approximately 4 weeks of age, the behavior of 48 LFP and 48 HFP chicks in response to an APO injection was studied using an open field. Another objective of the present study was to determine whether behavioral variation (in an open field) between HFP and LFP birds, after APO injection, is also reflected by variation of D1 and D2 receptor densities in the brain. Receptor binding capacities were assessed by measuring specific binding of tritiated D1 and D2 receptor ligands in different regions of the brain of control HFP and LFP chicks. In the present study, it is shown that indeed HFP chicks display a more enhanced behavioral response to acute APO treatment (0.5 mg/kg BW) than LFP birds in an open field. This difference was not reflected by variation of D1 and D2 receptor densities in the brain between both lines.
    Surplus dietary tryptophan reduces plasma cortisol and noradrenaline concentrations and enhances recovery after social stress in pigs
    Koopmans, S.J. ; Ruis, M.A.W. ; Dekker, R.A. ; Diepen, J.T.M. van; Korte, S.M. ; Mroz, Z. - \ 2005
    Physiology and Behavior 85 (2005)4. - ISSN 0031-9384 - p. 469 - 478.
    salivary cortisol - amino-acids - agonistic behavior - growing pigs - meat quality - performance - metabolites - parameters - serotonin - hormones
    Social stress occurs in intensive pig farming due to aggressive behavior. This stress may be reduced at elevated dietary levels of tryptophan (TRP). In this study, we compared the effects of high (13.2%) vs. normal (3.4%) dietary TRP to large neutral amino acid (LNAA) ratios on behavior and stress hormones in catheterized pigs ( 50 kg BW), which were exposed to social stress by placing them twice into the territory of a dominant pig ( 60 kg) for 15 min. Pre-stress plasma TRP concentrations were 156 ± 15 vs. 53 ± 6 ¿mol/l (p <0.01) in pigs on the high vs. normal TRP diets, respectively. Pre-stress plasma cortisol and noradrenaline concentrations were twofold (p <0.01) and 1.4-fold (p <0.05) lower but plasma adrenaline concentration was similar in pigs on the high vs. normal TRP diets, respectively. During the social confrontations, pigs on the high vs. normal TRP diets show a tendency towards reduced active avoidance behavior (3.2 ± 1.1 vs. 6.7 ± 1.2 min, p <0.1) but their physical activity (8.5 ± 0.6 vs. 10.2 ± 0.8 min) and aggressive attitude towards the dominant pig (11 ± 3 vs. 7 ± 2 times biting) were similar. Immediate (+ 5 min) post-stress plasma cortisol, noradrenaline and adrenaline responses were similar among dietary groups. After the social confrontations, the post-stress plasma cortisol, noradrenaline and adrenaline concentrations and/or curves (from + 5 min to 2 h) were lower/steeper (p <0.05) in pigs on the high vs. normal TRP diets. In summary, surplus TRP in diets for pigs (1) does not significantly affect behavior when exposed to social stress, (2) reduces basal plasma cortisol and noradrenaline concentrations, (3) does not affect the immediate hormonal response to stress, and (4) reduces the long-term hormonal response to stress. In general, pigs receiving high dietary TRP were found to be less affected by stress
    Chronic increase of dietary L-tryptophan decreases gentle feather pecking behaviour
    Hierden, Y.M. van; Koolhaas, J.M. ; Korte, S.M. - \ 2004
    Applied Animal Behaviour Science 89 (2004)1-2. - ISSN 0168-1591 - p. 71 - 84.
    obsessive-compulsive disorder - trout oncorhynchus-mykiss - rainbow-trout - laying hens - serotonin - plasma - corticosterone - chicks - stress - brain
    Many studies show the involvement of the serotonergic (5-HT) system in the performance of abnormal behaviour in both human and animals. Recently, we showed that acute reduction of 5-HT turnover in the forebrain, increased gentle and severe feather pecking behaviour in chicks from a high (HFP) and low feather pecking (LFP) line of laying hens, suggesting that the performance of feather pecking behaviour involves low 5-HT neurotransmission. In the present study, we postulated that if low 5-HT is causally underlying feather pecking, increasing, 5-HT turnover in the forebrain will decrease the development and performance of feather pecking. Augmentation of 5-HT neurotransmission in the brain was induced by chronically increasing dietary levels of the essential amino acid L-tryptophan (TRP) from which 5-HT is synthesised. From the age of 34 days, UP and HFP chicks were fed a diet containing 2% TRP, whereas control birds of both lines were continuously fed with the normal rearing feed (0.16% TRP). From 35 days of age, litter was removed from the pens (10 pens/line-treatment) and all chicks (10 chicks/pen) were housed on a slatted floor until the end of the experiment. At 49 days of age, feather pecking behaviour was studied for 30 min. At 50 days of age baseline corticosterone, TRP and other large amino acids (LNAAs) were measured in the blood plasma of decapitated chicks (10 chicks per line- treatment). Furthermore, plasma corticosterone and central 5-HT turnover levels in response to manual restraint (5 min) were determined (10 chicks/line-treatment). For neither gentle nor severe feather pecking a significant line x treatment interaction was found. However, TRP treatment resulted in a significant [P = 0.02] overall decrease of the frequency of gentle feather pecking. For severe feather pecking a similar but not significant pattern was found. Significant line effects were found for gentle and severe feather pecking. HFP birds showed significant of gentle and severe feather pecking behaviour than LFP birds [P <0.001]. increased the TRP/LNAA ratio in the plasma of the chicks. Furthermore, TRP/LNAA and stress induced levels of plasma corticosterone (although more pronounced in the UP line). TRP supplementation significantly increased 5-HT turnover in the hippocampus and archistriatum and tended to do so in the remainder of the forebrain. The results confirm our hypothesis that feather pecking behaviour is triggered by low serotonergic neurotransmission, as increasing serotonergic tone, by increasing dietary TRP, decreases gentle feather pecking behaviour. (C) 2004 Elsevier B.V. All rights reserved.
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