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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    Long-lasting effects of Early-life Antibiotic Treatment and routine Animal Handling on Gut Microbiota Composition and Immune System in Pigs
    Schokker, D. ; Zhang, J. ; Vastenhouw, S.A. ; Heilig, G.H.J. ; Smidt, H. ; Rebel, J.M.J. ; Smits, M.A. - \ 2015
    PLoS ONE 10 (2015)2. - ISSN 1932-6203
    large gene lists - intestinal microbiota - bacterial - extraction - expression - disease - health - asthma - young - diet
    Background In intensive pig husbandry systems, antibiotics are frequently administrated during early life stages to prevent respiratory and gastro-intestinal tract infections, often in combination with stressful handlings. The immediate effects of these treatments on microbial colonization and immune development have been described recently. Here we studied whether the early life administration of antibiotics has long-lasting effects on the pig’s intestinal microbial community and on gut functionality. Methodology/Principal Findings To investigate the long-lasting effect of early-life treatment, piglets were divided into three different groups receiving the following treatments: 1) no antibiotics and no stress, 2) antibiotics and no stress, and 3) antibiotics and stress. All treatments were applied at day four after birth. Sampling of jejunal content for community scale microbiota analysis, and jejunal and ileal tissue for genome-wide transcription profiling, was performed at day 55 (~8 weeks) and day 176 (~25 weeks) after birth. Antibiotic treatment in combination with or without exposure to stress was found to have long-lasting effects on host intestinal gene expression involved in a multitude of processes, including immune related processes. Conclusions/Significance The results obtained in this study indicate that early life (day 4 after birth) perturbations have long-lasting effects on the gut system, both in gene expression (day 55) as well as on microbiota composition (day 176). At day 55 high variance was observed in the microbiota data, but no significant differences between treatment groups, which is most probably due to the newly acquired microbiota during and right after weaning (day 28). Based on the observed difference in gene expression at day 55, it is hypothesized that due to the difference in immune programming during early life, the systems respond differently to the post-weaning newly acquired microbiota. As a consequence, the gut systems of the treatment groups develop into different homeostasis.
    Eating behaviour explains differences between individuals in dynamic texture perception of sausages
    Devezeaux de Lavergne, M.S.M. ; Derks, J.A.M. ; Ketel, E.C. ; Wijk, R.A. de; Stieger, M.A. - \ 2015
    Food Quality and Preference 41 (2015). - ISSN 0950-3293 - p. 189 - 200.
    swallowing threshold - food texture - bite size - age - bolus - patterns - young - gels
    Texture perception of foods has been demonstrated to be influenced by age, dental health and oral processing behaviour. Eating duration is a significant factor contributing to and determining food oral processing behaviour. The influence of eating duration on dynamic texture perception, oral processing behaviour and properties of the food bolus have not been investigated extensively. The aims of this study are (i) to determine the influence of naturally preferred eating duration on dynamic texture perception of sausages and (ii) to explain differences in dynamic texture perception between short and long duration eaters by chewing behaviour and bolus properties. Two groups of subjects were selected based on their natural eating duration for a controlled portion size of two sausages. The group of “long duration eaters” (n = 11) took on average twice as long to consume a piece of sausage compared to the group of “short duration eaters” (n = 12). Independent of eating duration, short and long eating duration subjects chewed sausages with the same chewing frequency (p = 0.57) and muscle effort rate (p = 0.15) during oral processing. Total muscle effort and total number of chews were significantly higher (p <0.05 for both) for long duration eaters mainly due to the longer eating time compared to short duration eaters. Bolus properties showed that short duration eaters did not break down the boli as much as long duration eaters resulting in fewer (p <0.001) and larger (p <0.05) sausage bolus fragments, firmer (p <0.001) and less adhesive (p <0.001) boli with lower fat content (p <0.05) and less saliva incorporation (p <0.001) at swallow compared to the bolus properties of long duration eaters. These differences in bolus properties influenced dynamic texture perception of the sausages as the bolus of short duration eaters revealed different properties than the bolus of long duration eaters. Temporal dominance of sensations (TDS) showed that short and long duration eaters perceived the same sausage similarly in the early stages of oral processing, but started to perceive the texture of the same sausage differently from the middle of oral processing towards the end. We conclude that short duration eaters did not compensate for their shorter eating duration by chewing more efficiently but were comfortable swallowing a less broken down bolus than long duration eaters. Moreover, we conclude that differences in eating behaviour between subjects can lead to differences in bolus properties of sausages causing differences in dynamic texture perception of the same sausage.
    Dealing with consumer differences in liking during repeated exposure to food; typical dynamics in rating behavior
    Horst, G.J. ter; Renken, R. ; Nanneti, L. ; Dalenberg, J.R. ; Wijk, R.A. de - \ 2014
    PLoS ONE 9 (2014)3. - ISSN 1932-6203
    in-home consumption - k-means - elderly adults - mere exposure - acceptance - intensity - flavor - young - pleasantness - preferences
    Consumers show high interindividual variability in food liking during repeated exposure. To investigate consumer liking during repeated exposure, data is often interpreted on a product level by averaging results over all consumers. However, a single product may elicit inconsistent behaviors in consumers; averaging will mix and hide possible subgroups of consumer behaviors, leading to a misinterpretation of the results. To deal with the variability in consumer liking, we propose to use clustering on data from consumer-product combinations to investigate the nature of the behavioral differences within the complete dataset. The resulting behavioral clusters can then be used to describe product acceptance. To test this approach we used two independent data sets in which young adults were repeatedly exposed to drinks and snacks, respectively. We found that five typical consumer behaviors existed in both datasets. These behaviors differed both in the average level of liking as well as its temporal dynamics. By investigating the distribution of a single product across typical consumer behaviors, we provide more precise insight in how consumers divide in subgroups based on their product liking (i.e. product modality). This work shows that taking into account and using interindividual differences can unveil information about product acceptance that would otherwise be ignored.
    Validation of biomarkers for loin meat quality (m. longissimus) of pigs
    Pierzchala, M. ; Hoekman, A.J.W. ; Urbanski, P. ; Kruijt, L. ; Kristensen, L. ; Young, L. ; Oksbjerg, N. ; Goluch, D. ; Pas, M.F.W. te - \ 2014
    Journal of Animal Breeding and Genetics 131 (2014)4. - ISSN 0931-2668 - p. 258 - 270.
    skeletal-muscles - gene-expression - troponin-t - pork - associations - calmodulin - cytoscape - growth - young - rad
    The aim of this study was to validate previously reported associations between microarray gene expression levels and pork quality traits using real-time PCR. Meat samples and meat quality data from 100 pigs were collected from a different pig breed to the one tested by microarray (Large White versus Pietrain) and a different country of origin (Denmark versus Germany). Ten genes (CARP, MB, CSRP3, TNNC1, VAPB, TNNI1, HSPB1, TNNT1, TIMP-1, RAD-like) were chosen from the original microarray study on the basis of the association between gene expression levels and the meat quality traits meat %, back fat, pH24, drip loss %, colour a*, colour b*, colour L*, WB-SF, SFA, MUFA, PUFA. Real-time PCR detection methods were developed for validation of all ten genes, confirming association with drip loss (two of two genes), ultimate pH (three of four genes), a* (redness) (two of six genes) and L*(lightness) (two of four genes). Furthermore, several new correlations for MUFA and PUFA were established due to additional meat quality trait information on fatty acid composition not available for the microarray study. Regression studies showed that the maximum explanation of the phenotypic variance of the meat quality traits was 50% for the ultimate pH trait using these ten genes only. Additional studies showed that the gene expression of several of the genes was correlated with each other. We conclude that the genes initially selected from the microarray study were robust, explaining variances of the genes for the meat quality traits.
    Jackdaw nestlings can discriminate between conspecific calls but do not beg specifically to their parents
    Zandberg, E.C.A. ; Jolles, J.W. ; Boogert, N.J. ; Thornton, A. - \ 2014
    Behavioral Ecology 25 (2014)3. - ISSN 1045-2249 - p. 565 - 573.
    food-caching corvids - vocal recognition - corvus-monedula - gymnorhinus-cyanocephalus - offspring recognition - tactical deception - provisioning calls - crows - chicks - young
    The ability to recognize other individuals may provide substantial benefits to young birds, allowing them to target their begging efforts appropriately, follow caregivers after fledging, and establish social relationships later in life. Individual recognition using vocal cues is likely to play an important role in the social lives of birds such as corvids that provision their young postfledging and form stable social bonds, but the early development of vocal recognition has received little attention. We used playback experiments on jackdaws, a colonial corvid species, to test whether nestlings begin to recognize their parents’ calls before fledging. Although the food calls made by adults when provisioning nestlings were individually distinctive, nestlings did not beg preferentially to their parents’ calls. Ten-dayold nestlings not only responded equally to the calls of their parents, neighboring jackdaws whose calls they were likely to overhear regularly and unfamiliar jackdaws from distant nest boxes, but also to the calls of rooks, a sympatric corvid species. Responses to rooks declined substantially with age, but 20- and 28-day-old nestlings were still equally likely to produce vocal and postural begging responses to parental and nonparental calls. This is unlikely to be due to an inability to discriminate between calls, as older nestlings did respond more quickly and with greater vocal intensity to familiar calls, with some indication of discrimination between parents and neighbors. These results suggest that jackdaws develop the perceptual and cognitive resources to discriminate between conspecific calls before fledging but may not benefit from selective begging responses. Key words: begging, Corvidae, Corvus monedula, food calls, parental care, social cognition, vocal recognition.
    Texture and savoury taste influences on food intake in a realistic hot lunch time meal
    Forde, C.G. ; Kuijk, N.L. van; Thaler, T. ; Graaf, C. de; Martin, N. - \ 2013
    Appetite 60 (2013). - ISSN 0195-6663 - p. 180 - 186.
    bite size - energy-intake - portion size - questionnaire - satiation - weight - young - consumption - intensity - healthy
    Background: Previous studies with model foods have shown that softer textures lead to higher eating rates and higher ad libitum food intake and higher intensity of salt taste has been shown to result in a lower ad libitum food intake. These observations have yet to be replicated in the context of realistic solid hot meal components. Aim: The objective of the present study was to assess the effect of texture and taste on the ad libitum intake of a realistic hot lunchtime meal. Methods: The meals consisted of potatoes, carrots, steak and gravy varied according to a 2 (texture: mashed vs. whole) x 2 (taste: standard taste vs. strong taste) design. The texture dimension referred to mashed potatoes, mashed carrots and pieces of steak vs. whole boiled potatoes, whole boiled carrots and whole steak. The taste was varied by manipulating the taste intensity of the gravy to be either standard or high intensity savoury taste. The current study used a between groups, single course ad libitum design whereby subjects were recruited for a one off meal study, during which their food intake was measured. The four groups consisted of about 40 subjects (mashed, standard, n = 37; mashed, savoury n = 39; whole, standard n = 40; and whole, savoury n = 41) matched for age (average age = 44.8 +/- 5.3), gender (on average 19 males and 20 females), normal BMI (average 22.6 +/- 1.7) and dietary restraint score (DEBQ score = 1.74 +/- 0.6). Results: The results showed that the estimated means of the intake of the two mashed conditions was 563.2 +/- 20.3 g and intake of whole meal was 527.5 +/- 20.0 g (p = 0.23). The texture effect was significant in the higher savoury condition with an average of 91 g less food consumed in the solid-savoury meal than in the mashed savoury meal. This effect was not replicated in the standard gravy condition, with no significant difference between solid and mashed textures. This was reflected in an interaction effect that was approaching significance (p = 0.051). The estimated mean eating rate in the two mashed conditions was 57.0 +/- 2.5 g and was significantly higher than the whole meal condition (47.2 +/- 2.5 g (p <0.05), with no difference in eating rate between the standard and savoury gravy conditions. Discussion: Although interpretation was made difficult by the between groups design and the interaction between taste * texture, the results nonetheless confirm the effect of texture on eating rate and ad libitum intake for solid savoury meal components. The impact of taste on ad libitum intake of a solid meal remains unclear. We conclude that people consumed more of the meal when the food was simultaneously mashed and savoury. Food texture may be used to produce slower eating rates that result in a reduced overall energy intake within a realistic hot lunchtime meal. (C) 2012 Elsevier Ltd. All rights reserved.
    Seasonal nitrogen budgets of mature citrus trees on a sandy entisol
    Morgan, K. ; Scholberg, J.M.S. ; Obreza, T. ; Wheaton, T. - \ 2012
    Journal of Plant Nutrition 35 (2012)13. - ISSN 0190-4167 - p. 2009 - 2023.
    uptake efficiency - leaching losses - soil - irrigation - mineralization - fertilization - management - sorghum - young - corn
    Approximately 30% of Florida citrus is grown on well-drained Entisols with low nutrient-holding capacity, which are prone to high nitrogen (N) leaching losses. However, increasing application frequency of N-fertilizer via multiple fertigations does not increase crop yield, whereas in agronomic crops, such an approach typically enhances N uptake efficiency. We assessed seasonal tree N tissue concentration dynamics as affected by N rate for mature fourteen-year-old 'Hamlin' orange (Citrus sinensis L. Osbeck) trees on either Carrizo citrange (C. sinsensis L. Osbeck X Poncirus trifoliata L. Raf.) or Swingle citrumelo (C. paradisi Macf. X P. trifoliata L. Raf.) rootstocks. Nitrogen was applied as ammonium nitrate in six split fertigation applications with N target values of 179 and 269 kg ha(-1)yr(-1). Leaf, twig, and branch bark tissue N concentrations decreased through the spring to minima in May and June. This time period corresponds to a period of high N demand associated with both vegetative and reproductive growth. Tissue N concentrations increased from late spring minimums to fall and winter maximum concentrations. Reduction in branch bark and wood tissue N concentrations may have been due to a redistribution of N to leaf, twig, and fruit tissues in response to low N supply. The majority of the spring N should be supplied prior to May.
    The role of novelty detection in food memory
    Morin-Audebrand, L. ; Mojet, J. ; Chabanet, C. ; Issanchou, S. ; Moeller, P. ; Koester, E. ; Sulmont-Rossé, C. - \ 2012
    Acta Psychologica 139 (2012)1. - ISSN 0001-6918 - p. 233 - 238.
    incidental-learning experiment - recognition memory - odor recognition - semantic factors - flavor memory - age - young - consistency - familiarity - experience
    Memory plays a central role in food choice. Recent studies focusing on food memory in everyday eating and drinking behaviour used a paradigm based on incidental learning of target foods and unexpected memory testing, demanding recognition of the target among distractors, which deviate slightly from the target. Results question the traditional view of memory as reactivation of previous experiences. Comparison of data from several experiments shows that in incidentally learned memory, distractors are rejected, while original targets are not recognised better than by chance guessing. Food memory is tuned at detecting novelty and change, rather than at recognising a previously encountered food.
    Incidental learning and memory for food varied in sweet taste in children
    Laureati, M. ; Pagliarini, E. ; Mojet, J. ; Köster, E.P. - \ 2011
    Food Quality and Preference 22 (2011)3. - ISSN 0950-3293 - p. 264 - 270.
    recognition memory - flavor memory - odor memory - age - recollection - experience - texture - infants - novelty - young
    This experiment investigated incidental learning and memory in children (age 7–10 years) for three different foods (fruit juice, fruit purée and biscuit), varied in sweetness. Children (N = 286) were exposed to three target foods and 24 h later their incidental learning was tested for one of the foods by asking them to recognize the target among distractors varying in sweetness. Children were also asked to rate their liking for the products. Overall, the children showed incidental learning for the food eaten the previous day, but recognition was not equal for all stimuli: a memory effect was found for fruit purée but not for biscuit and fruit juice. Memory was based on the correct rejection of the distractors rather than on target recognition. Hedonic scores were high, but lowest for fruit purée. Memory was not related to liking, but it is likely that other factors like novelty and familiarity may have been influential.
    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.
    Selection on feather pecking affects response to novelty and foraging behaviour in laying hens
    Haas, E.N. de; Nielsen, B. ; Rodenburg, T.B. ; Buitenhuis, A.J. - \ 2010
    Applied Animal Behaviour Science 124 (2010)3-4. - ISSN 0168-1591 - p. 90 - 96.
    open-field - domestic chicks - ground-pecking - gallus-gallus - fear - poultry - insights - strain - model - young
    Feather pecking (FP) is a major welfare problem in laying hens, influenced by multiple factors. FP is thought to be redirected foraging behaviour, however fearful birds are also known to be more sensitive to develop FP. The relationship between fear-responses, foraging and FP is not well understood, therefore we studied the behaviour of 16 birds from a high feather pecking (HFP) line and 16 birds from a low feather pecking (LFP) line at 35 weeks of age inside a plus-maze. Birds were from the 10th generation of selection for either high or low FP. First exposure to the maze was used to measure birds’ fear-responses to a novel barren environment. Hereafter, birds were trained three times in the maze with four different food-items that were offered in one of the four arms (i.e. regular food-pellets, feathers, grass, and mealworms hidden in wood-shavings). On the fifth day, birds were tested in the maze for 10 min during which they could choose to eat from all available food-items. When exposed for the first time in the maze HFP birds walked a longer distance, vocalized sooner and had more exploratory pecks compared to LFP birds who showed more wing-movements and defecations. When given a choice of food inside the maze both lines preferred eating worms, but HFP birds had more worm-eating bouts and ate faster than LFP birds. The results of this study indicate that HFP birds respond actively to fear-eliciting situations, which may originate from a proactive coping style. Instead of a clear preference for eating feathers, this study supports earlier findings that HFP birds have a stronger pecking motivation than LFP birds
    Optimal preferred MSG concentration in potatoes, spinach and beef and their effect on intake in institutionalized elderly people
    Essed, N.H. ; Oerlemans, P. ; Staveren, W.A. van; Kok, F.J. ; Graaf, C. de - \ 2009
    Journal of Nutrition, Health and Aging 13 (2009)9. - ISSN 1279-7707 - p. 769 - 775.
    5 taste qualities - monosodium glutamate - flavor enhancement - nutritional-status - food-intake - odor perception - dietary-intake - young - age - pleasantness
    Background Elderly people may benefit from sensory stimulation to increase food intake since anorexia of ageing is prevalent among them. An optimal MSG concentration may increase the palatability of foods but this depends on the food and chemosensory status of the taster. Currently, the results on taste enhancing to increase intake are inconsistent. Objective To find an optimal preferred MSG concentration in mashed potatoes, spinach and ground beef and to determine whether this concentration increases consumption of these foods among institutionalized elderly people. Design Single blind within subject cross-over study performed at the laboratory and in the residents’ own apartments. Participants 33 elderly and 29 young people in the sensory study and 53 elderly people in the intake study. Measurements Pleasantness of the foods was rated of the foods each with 0, 0.5, 0.8, 1.3 and 2.0 g of MSG/100g. Intake was measured by weighing back leftovers of 2 meals with MSG (0.5% in mashed potatoes, 2% in spinach and ground meat) and without MSG. Results 0.5% MSG (p0.68). Conclusion MSG (0.5% and 2%) does not guarantee a higher intake among elderly. The chemosensory heterogeneity of the elderly population requires more individual flavor enhancement to improve the dietary intake and sensory experience
    No effect of 16 weeks flavor enhancement on dietary intake and nutritional status of nursing home eldery
    Essed, N.H. ; Staveren, W.A. van; Kok, F.J. ; Graaf, C. de - \ 2007
    Appetite 48 (2007)1. - ISSN 0195-6663 - p. 29 - 36.
    monosodium glutamate - food-intake - odor perception - age - consumption - amplification - pleasantness - preference - anorexia - young
    There is a lack of data to support the long-term effect of flavor enhancement on food intake and nutritional status. Our aim was to determine if daily addition of 700 mg flavor and/or 300 mg monosodium glutamate (MSG) to the animal protein part of the cooked meal for 16 weeks leads to an increase in energy intake and in body weight in nursing home elderly. We performed a single blind randomized 16 weeks parallel study consisting of a control group (n=23), a MSG group (n=19), a flavor group (n=19) and a flavor plus MSG group (n=22). Main outcome measures were intake of the cooked meal, which was measured by weighing back leftovers during 14 days and body weight. Both were measured before and at the end of the intervention period. After 16 weeks, energy intake and body weight did not increase within the control group, the flavor group, the flavor plus MSG group and the MSG group. Between the groups, no differences were found in changes in energy intake and body weight. Enhancing the taste of a cooked meal with flavor and/or MSG does not lead to a higher energy intake and body weight among nursing home elderly. More research is needed to determine the efficacy of flavor enhancement on intake and nutritional status
    Compensation for age-associated chemosensory losses and its effect on the pleasantness of a custard dessert and a tomato drink
    Kremer, S. ; Bult, J.H.F. ; Mojet, J. ; Kroeze, J.H.A. - \ 2007
    Appetite 48 (2007)1. - ISSN 0195-6663 - p. 96 - 103.
    flavor amplification - elderly subjects - food preference - perception - young - texture - taste - consumption - enhancement - sensitivity
    Differences between elderly subjects (n=52, 60¿85 years) and young subjects (n=55, 18¿35) in their food liking and their olfactory capability were investigated. Two food systems were used: custard desserts and tomato drinks. Flavor enhancement/enrichment, textural change, and/or irritant addition were incorporated as compensatory strategies into these foods. The addition of low concentrations of both cherry flavor and cream flavor to the custard desserts influenced their pleasantness for the majority of the elderly. The addition of cream topping increased the pleasantness of the custard desserts for both the elderly and the young. The elderly equally liked the tomato drinks with no or with low irritant addition, whereas the young generally disliked an irritant addition. However, the food liking of the elderly was not generally increased by these different compensatory strategies. Instead, subgroups were observed for each compensatory strategy, in which applied compensatory strategies led to an increase in product pleasantness. Age-associated losses in olfactory capabilities did not sufficiently explain differences in food liking, as only elderly with similar olfactory capabilities to the young demonstrated a liking of enhanced flavor. The present study does not support the assumption that age-associated impairment in olfactory capability will inevitably lead to changes in food liking.
    Genetic and phenotypic correlations between feather pecking and open-field reponse in laying hens at two different ages
    Rodenburg, T.B. ; Buitenhuis, A.J. ; Ask, B. ; Uitdehaag, K.A. ; Koene, P. ; Poel, J.J. van der; Arendonk, J.A.M. van; Bovenhuis, H. - \ 2004
    Behavior Genetics 34 (2004)4. - ISSN 0001-8244 - p. 407 - 415.
    tonic immobility - domestic chicks - behavior - heritability - selection - pullets - young - lines
    The object of this research was to study the relationship between feather pecking and open-field activity in laying hens at two different ages. A population of 550 birds of a laying hen cross was subjected to an open-field test at 5 and 29 weeks of age and to a social feather pecking test at 6 and 30 weeks of age. Factor analysis was used to identify underlying factors for each test: pecking behavior ( social test) and open-field activity (open-field test). In young birds, a positive phenotypic correlation of 0.24 was found between high open-field activity and high levels of pecking behavior ( ground pecking, preening, gentle feather pecking, and wall pecking). In adults, a similar genetic correlation of 0.62 was found. At adult age, the factor pecking behavior consisted mainly of gentle and severe feather pecking. Between ages, a strong, negative genetic correlation of - 0.65 was found between open-field activity at young age and pecking behavior at adult age, indicating that open-field activity levels in young birds may predict pecking behavior in adult hens.
    Taste Perception with Age: Generic or Specific Losses in Supra-threshold Intensities of Five Taste Qualities?
    Mojet, J. ; Heidema, J. ; Christ-Hazelhof, E. - \ 2003
    Chemical Senses 28 (2003)5. - ISSN 0379-864X - p. 397 - 413.
    elderly persons - sucrose - young - sensitivity - preferences - threshold - magnitude - caffeine - flavor - adults
    The influence of ageing on supra-threshold intensity perception of NaCl, KCl, sucrose, aspartame, acetic acid, citric acid, caffeine, quinine HCl, monosodium glutamate (MSG) and inosine 5'-monophosphate (IMP) dissolved in water and in `regular' product was studied in 21 young (19¿33 years) and 21 elderly (60¿75 years) persons. While the relative perception (intensity discrimination) seems to be remarkably resistant to the effect of ageing, the absolute perception (intensity rating) decreased with age for all tastants in water, but only for the salty and sweet tastants in product. When assessed while wearing a nose clip, only the perception of salty tastants was diminished with age. The slopes of the psychophysical functions were flatter in the elderly than in the young for the sweet, bitter and umami tastants in water, and for the sour tastants in product only. The age effects found were almost exclusively generic and never compound-specific within a taste. This study indicates that the relevance of determining intensities of tastants dissolved in water for the `real life' perception of taste in complex food is rather limited.
    Within-subject variability of flow-mediated vasodilation of the brachial artery in healthy men and women: implications for experimental studies
    Roos, N.M. de; Bots, M.L. ; Schouten, E.G. ; Katan, M.B. - \ 2003
    Ultrasound in Medicine and Biology 29 (2003). - ISSN 0301-5629 - p. 401 - 406.
    improves endothelial function - dependent dilatation - conduit arteries - nitric-oxide - dysfunction - disease - young - dilation - children - adults
    Flow-mediated vasodilation (FMD) of the brachial artery is used as a marker of cardiovascular disease risk. It is defined as the percentage dilation from the baseline diameter in response to a provoked increase in blood flow. The within-subject variability, crucial in the design of trials with FMD as an endpoint, appears to vary widely between studies. We assessed the analytical and within-subject variability of FMD in healthy subjects and estimated the number of subjects needed to detect various treatment effects in intervention trials and observational studies. FMD was assessed with B-mode high-resolution ultrasound (US). A total of 13 volunteers were measured on six occasions, after they had fasted overnight. Within-subject variability was assessed from all six scans per subject. Analytical variation or reading variation was assessed by reading one scan of each subject twice by one observer. The mean (+/-tSD) FMD was 5.60 +/- 2.15 FMD% of the baseline diameter. The within-subject SD was 2.8 FMD%, resulting in a coefficient of variation (CV) of 2.8/5.6 x 100% = 50.3%. The CVs for the baseline and maximum diameter were much smaller: 4.8% (SD 0.193 mm at a mean of 4.060 mm) for the baseline and 5.2% (SD 0.222 mm at a mean of 4.285 mm) for the maximum. The CV for reading variation was 34%. The number of subjects needed to detect a treatment difference of 2 FMD% with a probability of 0.05 and a power of 0.80 would be 31 in a crossover design and 62 per group in a parallel design for comparison of group changes. We conclude that the within-subject variability of FMD is large, about 50% of the mean response. This includes biologic and reading variation. Repeated measurements and repeated readings of recorded measurements are recommended to reduce variability. (C) 2003 World Federation for Ultrasound in Medicine Biology.
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