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.

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Rights or ability : Access to plant genetic resources in India
Patnaik, A. ; Jongerden, J.P. ; Ruivenkamp, G.T.P. - \ 2018
Journal of World Intellectual Property 21 (2018)3-4. - ISSN 1422-2213 - p. 157 - 175.
ability - access - commons - intellectual property rights - plant genetic resources - Intellectual property rights
The difficulties that stakeholders face in accessing plant genetic resources have been a concern of many scholars since the introduction of intellectual property rights. One of these issues is that of access, which is mostly approached from a rights perspective. Here it is argued that such a rights perspective limits a critical reflection on the possibilities for enhancing accessibility to the Plant Genetic Resources (PGRs) on three grounds and to go beyond this limitation, we introduce an ability perspective. The ability perspective brings into focus how farmers organise their access to PGRs and is researched in four PGRs conservation banks in India; one ex situ and three in situ. An informal system of conservation (in situ) and sharing through informal networks is found to provide better access mechanisms for the small and marginal farmers in India, while access to conserved resources stored at the three in situ banks created biosocial
relations and biosocial commons. However, each case studied had certain disadvantages in respect of granting access to the farmers, so additional mechanisms to facilitate better access to the conserved resources are suggested.
Antioxidant potential of hydrolyzed polyphenolic extracts from tara (Caesalpinia spinosa) pods
Chambi, F. ; Chirinos, R. ; Pedreschi Plasencia, R.P. ; et al., - \ 2013
Industrial Crops and Products 47 (2013). - ISSN 0926-6690 - p. 168 - 175.
tropaeolum-tuberosum ruiz - betula-pubescens - tannic-acid - leaves - capacity - gallotannins - derivatives - sinensis - solvent - ability
The antioxidant potential of tara pod extracts rich in gallotannins submitted to chemical hydrolysis was evaluated. The increase in the release of gallic acid from the tara pod extracts during the hydrolysis process reached a maximum ratio of free gallic acid/total phenolics of 94.1% at 20 h, at this point, 100% hydrolysis degree (HD) was obtained. After 4 h of hydrolysis (38.8% of HD) the highest antioxidant capacity was obtained reaching values of 25.9, 23.8 and 8.8 µmol trolox equivalent/mg gallic acid equivalent measured by ABTS, FRAP and ORAC methods. Lipophilicity diminished from 0.8 to 0.3 (log P value). In addition, the antioxidant efficacy of 100 ppm total phenolics of hydrolyzates at 9 h (93.7% of HD) and 20 h showed to be significantly more efficient than a similar concentration of the synthetic antioxidant TBHQ to retard soybean oil oxidation. These results indicate that 4 and 9 h of chemical hydrolysis of tara pod extracts under the tested conditions are sufficient to obtain a product with good antioxidant properties to be used as an alternative source of antioxidants.
Self-improvement and cooperation: How exchange relationships promote mastery-approach driven individuals’ job outcomes
Poortvliet, P.M. ; Giebels, E. - \ 2012
European Journal of Work and Organizational Psychology 21 (2012)3. - ISSN 1359-432X - p. 392 - 425.
leader-member exchange - achievement goals - performance goals - task motivation - social motives - orientation - commitment - behavior - work - ability
In the present research we argue that mastery-approach goals may be beneficial in social achievement contexts because these goals lead to constructive exchange relationship building. An examination of three methodologically complementary studies revealed that mastery-approach goals lead to more cooperative and higher-quality exchange relationships than performance-approach goals and are, ultimately, associated with better job outcomes, as well. The results of a questionnaire study demonstrated that mastery-approach goals are more strongly related to cooperative motives and more weakly related to competitive motives than performance-approach goals. Furthermore, an experimental study indicated that mastery-approach driven individuals show a higher concern for others and are more strongly inclined to cooperate with an exchange partner when engaged in a complex reasoning task than performance-approach driven individuals. Finally, an organizational field study showed that team–member exchange mediates the effect of mastery-approach goals on job performance, job satisfaction, and organizational commitment
Interactive effects of nutrient heterogeneity and competition: implications for root foraging theory?
Mommer, L. ; Ruijven, J. van; Jansen, C. - \ 2012
Functional Ecology 26 (2012)1. - ISSN 0269-8463 - p. 66 - 73.
below-ground competition - size asymmetry - plant - placement - plasticity - ability - proliferation - communities - responses - patterns
1. Plants are known to respond to heterogeneous distribution of nutrients in the soil, and they also respond to the presence of neighbouring roots. However, it is unclear whether plants are able to distinguish between these factors and adjust their root responses accordingly. 2. We investigated whether the simultaneous response to nutrient heterogeneity and competition could be predicted from the responses to these factors separately. As a null model, we hypothesized that the responses to nutrients and competition are additive and thus no interactions occur. We performed a short-term competition experiment in the greenhouse with two floodplain species in homogeneous and heterogeneous conditions. The consequences of different root distributions for nutrient uptake were tested using 15N pulse-labelling. 3. Both species responded to nutrient heterogeneity by investing significantly more roots in the nutrient-rich patch, and both species showed a significant reduction in root growth in response to competition, albeit that the reduction was much more pronounced for the grass species. For Rumex palustris, the effects of heterogeneity and competition were additive. However, the response to nutrient heterogeneity of Agrostis stolonifera was reversed by competition: instead of proliferating in the nutrient-rich patch, it significantly increased root investments in the ‘empty’ (nutrient-poor) patches. As the partitioning of total N was less asymmetric than 15N uptake from the nutrient-rich patch, it appears that these altered root investments of A. stolonifera in the ‘empty’ patches have also been functional with respect to compensating N uptake. 4. Our results suggest that root responses to nutrient distribution in a competitive environment depend on the competitive strength of the neighbouring species. The foraging response of the superior species (R. palustris) was hardly affected, but that of the inferior species (A. stolonifera) was greatly inhibited and even reversed by competition: instead of proliferating in the nutrientrich patch, it increased root growth and foraging activity in less favourable patches. Incorporating competitive hierarchy into root foraging studies may help to explain the ambiguous results found in previous studies. Key-words: Agrostis stolonifera, below-ground competition, competitive hierarchy, 15N labelling, root foraging, Rumex palustris, selective root placement, soil heterogeneity,
MDCK cell line with inducible allele B NS1 expression propagates deINS1 inflenza virus to high titres
Wielink, R. van; Harmsen, M.M. ; Martens, D.E. ; Peeters, B.P.H. ; Wijffels, R.H. ; Moormann, R.J.M. - \ 2011
Vaccine 29 (2011)40. - ISSN 0264-410X - p. 6976 - 6985.
protein induces apoptosis - airway epithelial-cells - a virus - gene-expression - infected-cells - interferon - vaccine - rna - systems - ability
Influenza A viruses lacking the gene encoding the non-structural NS1 protein (delNS1) have potential use as live attenuated vaccines. However, due to the lack of NS1, virus replication in cell culture is considerably reduced, prohibiting commercial vaccine production. We therefore established two stable MDCK cell lines that show inducible expression of the allele B NS1 protein. Upon induction, both cell lines expressed NS1 to about 1000-fold lower levels than influenza virus-infected cells. Nevertheless, expression of NS1 increased delNS1 virus titres to levels comparable to those obtained with an isogenic virus strain containing an intact NS1 gene. Recombinant NS1 expression increased the infectious virus titres 244 to 544-fold and inhibited virus induced apoptosis. However, NS1 expression resulted in only slightly, statistically not significant, reduced levels of interferon-ß production. Thus, the low amount of recombinant NS1 is sufficient to restore delNS1 virus replication in MDCK cells, but it remains unclear whether this occurs in an interferon dependent manner. In contrast to previous findings, recombinant NS1 expression did not induce apoptosis, nor did it affect cell growth. These cell lines thus show potential to improve the yield of delNS1 virus for vaccine production.
Editor's Choice: Unveiling below-ground species abundance in a biodiversity experiment: a test of vertical niche differentation among grassland species
Semchenko, M. ; Mommer, L. - \ 2010
Journal of Ecology 98 (2010)5. - ISSN 0022-0477 - p. 1 - 1.
plant competition - interspecific competition - community ecology - traits - growth - intensity - gradient - survival - density - ability
P>1. Currently, there is a debate among plant ecologists on the concepts of the intensity of competition and the importance of competition, which is central to many issues of modern plant population ecology and plant community ecology. 2. It is problematic that the current measures of intensity and importance of competition, typically, are reported as dimensionless indices because they hide the fact that both indices are functions of plant density and the level of the environmental gradient. 3. Here, a new formulation of the concepts is suggested, which explicitly highlights the functional dependencies on plant density and the level of the environmental gradient. The new measures are a generalization of the previous indices and correspond to the previous indices in the case of a simple experimental design. 4. The suggested measures of the intensity and importance of competition are exemplified using data from a response surface competition experiment between Agrostis capillaris and Festuca ovina along a herbicide gradient, where the expected clear effect of plant density was demonstrated. 5. Synthesis. As the suggested measures of the intensity and importance of competition explicitly highlight the functional dependencies on plant density and the level of the environmental gradient, we think that they will help to ensure a closer connection between experimental plant ecology and the attempts to model plant populations and communities.
The prognostic role of the pathological T2 subclassification for prostate cancer in the 2002 Tumouor-Nodes-Metastasis staging system
Oort, I.M. van; Witjes, J.A. ; Kok, D.E.G. ; Kiemeney, L.A. ; Hulsbergen-van de Kaa, C.A. - \ 2008
BJU International 102 (2008)4. - ISSN 1464-4096 - p. 438 - 441.
progression-free survival - american joint committee - radical prostatectomy - ability - disease - pt2b
OBJECTIVE To evaluate the prognostic role of the 2002 Tumour-Nodes-Metastasis (TNM) pT2 subclassification for biochemical recurrence (BCR) after radical prostatectomy (RP) for prostate cancer. PATIENTS AND METHODS The 1997 TNM staging system is based on one subdivision for organ-confined prostate tumours (T2a, unilateral; T2b, bilateral involvement). The 2002 TNM staging system subdivides unilateral involvement into T2a (half of one lobe or less) and T2b (more than one half of one lobe), while bilateral involvement is classified as T2c. In all, 542 patients were treated with RP at our institute; the RP specimens were completely embedded and histopathologically evaluated for Gleason grade, tumour volume and anatomical extent, and were staged according to the 2002 TNM staging criteria. Patients were followed for a median of 39.5 months. BCR was defined as two subsequent increasing prostate-specific antigen (PSA) levels of >0.10 ng/mL. Kaplan-Meier and proportional hazards regression analyses were used to evaluate the univariable and multivariable prognostic effect of tumour stage. RESULTS According to the 2002 TNM staging system, 360 specimens were found to have pT2 tumours; 79 (22%) of the RP specimens were staged as pT2a and 281 (78%) as pT2c; no pT2b specimens were identified. Patients with unilateral involvement (pT2a) had a 5-year risk of BCR of 13%, while those with bilateral involvement (pT2c) had a risk of 23% (log rank test, P = 0.056). Patients with l disease were more likely to have a larger tumour volume (Mann-Whitney U-test P <0.001) and positive surgical margins (Fishers' exact test, P = 0.001)than those with pT2a tumours. Mann-Whitney U-tests showed no differences between the groups for preoperative PSA levels (P = 0.167). Also, the RP Gleason score was no different between groups (Pearson chi-square, P = 0.807). In the multivariable analyses, positive surgical margins appeared to increase the risk of BCR (hazard ratio 4.4, 95% confidence interval 2.5-7.9); pT2c vs pT2a had only a marginally (insignificant) additional effect (1.3, 0.6-2.7). CONCLUSION The absence of a true unilateral pathological T2b tumour in a series of 360 pT2 RP specimens questions the relevance of substaging unilateral disease. The limited differences in BCR and in pathological features of unilateral vs bilateral pT2 prostate cancer justify modifying the TNM staging system to one with no subclassification of pT2 disease, or at most as only one subdivision into unilateral (T2a) and bilateral (T2b) disease, combining the T2b and T2c substages.
Isolation of polymorphic microsatellite loci from the flea beetle Phyllotreta nemorum L. (Coleoptera: Chrysomelidae)
Verbaarschot, P.G.H. ; Calvo, D. ; Esselink, G.D. ; Molina, J.M. ; Vrieling, K. ; Jong, P.W. de - \ 2007
Molecular Ecology Notes 7 (2007)1. - ISSN 1471-8278 - p. 60 - 62.
atypical host-plant - barbarea-vulgaris - genetics - markers - ability
Ten microsatellite markers for the flea beetle Phyllotreta nemorum were developed using di- and trinucleotide repeat-enriched libraries. Each of these primer pairs were characterized on 96 individuals. Expected heterozygosities ranged between 0.11 and 0.84 and the number of alleles ranged between two and 14 per locus. These microsatellite markers are the first published for any Phyllotreta species
Clover as a cover crop for weed suppression in an intercropping design. I. Characteristics of several clover species
Hollander, N.G. den; Bastiaans, L. ; Kropff, M.J. - \ 2007
European Journal of Agronomy 26 (2007)2. - ISSN 1161-0301 - p. 92 - 103.
corn zea-mays - cabbage - yield - competition - management - simulation - cultivars - nitrogen - ability - models
Weeds often form a major problem in weakly competitive vegetable crops, particularly in low input systems. Undersown cover crops can be used to suppress weeds, but often put too high a competitive pressure on the main crop. Cover crop selection is one of the potential means that can be used to design or optimize these intercropping systems. The objective of the current research was to investigate the variability among a range of clover species in morphological and physiological traits that are considered relevant for interplant competition. To this purpose, field experiments with pure stands of eight clover species (2001) and a selection of three clover species (2002) were conducted, in which regular observations and periodic harvests were taken. Clear differences in the time in which full soil cover was obtained, total accumulated biomass, growth duration, height development and N-accumulation were observed. Persian clover (Trifolium resupinatum L.) and subterranean clover (T. subterraneum L.) were the two most contrasting species in this study, particularly differing in the period in which full soil cover was obtained. Persian clover's faster soil cover could not be attributed to a single trait, but resulted from a number of intrinsic characteristics, like light extinction coefficient, light use efficiency and specific leaf area that together determine the relative growth rate. The study also demonstrated the importance of differences in relative starting position, caused by, for instance, seed size, seeding rate and fraction establishment, for the analysis of early growth characteristics. Alsike clover (T. hybridum L.), berseem clover (T. alexandrinum L) and crimson clover (T. incarnatum L.) developed slower than Persian clover, but all produced a higher amount of accumulated dry matter, due to a longer growing period. Clear differences in height and height development between species were observed. These differences were not associated with dry matter accumulation, as the tallest (red clover; 80 cm) and the shortest species (subterranean clover; 12 cm) produced similar amounts of dry matter. A strong positive correlation between early soil cover development and N-accumulation was observed. The large variability among clover species indicates that species selection is a very important aspect of the development of cropping systems that include clover as a cover crop.
Interaction of genotype x management on vegetative growth and weed suppression of aerobic rice
Zhao, D.L. ; Bastiaans, L. ; Atlin, G.N. ; Spiertz, J.H.J. - \ 2007
Field Crops Research 100 (2007)2-3. - ISSN 0378-4290 - p. 327 - 340.
seeding rate - seeded rice - upland rice - yield - competitiveness - cultivars - germination - ability - traits - rates
Water shortage in drought-prone rice-growing areas of the world is threatening conventional irrigated rice production systems, in which rice is transplanted into fields where standing water is maintained until harvest. Aerobic rice production systems, in which rice is grown as a direct-seeded upland crop without flooding, require less water than conventional systems, but the transition to aerobic rice systems is impeded by severe weed infestation. An environmentally friendly and less labor-intensive weed control method needs to be introduced to aerobic rice farmers. A study was conducted at the International Rice Research Institute in the 2003 wet season and 2004 dry season to evaluate the effects of genotype, seeding rate, seed priming and their interactions on vegetative growth, yield and weed suppression. Three contrasting aerobic rice genotypes differing in yield and weed-suppressive ability (WSA) were grown at three seeding rates (100, 300 and 500 viable seeds m¿2) with or without seed priming under two weed management treatments (weed-free and weedy) in a split-plot design. In 2004, the overall weed pressure was higher than in 2003, and consequently treatment effects in this year were more distinct than in 2003. No significant interactions among the experimental factors were found for crop yield, weed biomass, leaf area index, tiller number and vegetative crop biomass. Raising seeding rate from 100 to 300 viable seeds m¿2 resulted in a significant increase in yield and a decrease in weed biomass, whereas a further increase from 300 to 500 viable seeds m¿2 did not result in a further improvement in yield and weed suppression. The stronger WSA of genotype Apo than that of genotypes IR60080-46A and IRAT 216 related to a stronger competitive ability of individual plants and a faster canopy closure (0.5¿6 days earlier). The WSA of weakly competitive genotypes was partially compensated for by a higher seeding rate. Seed priming, which was only evaluated in 2003, accelerated emergence by 2 days and slightly enhanced early crop growth, but had no significant effect on yield and weed suppression. The present study suggests that combining a weed-suppressive genotype with an optimum seeding rate can serve as a tool to manage weeds.
Neutralisation of venom-induced haemorrhage by IgG from camels and llamas immunised with viper venom and also by endogenous, non-IgG components in camelid sera
Harrison, R.A. ; Hasson, S.S. ; Harmsen, M.M. ; Laing, G.D. ; Theakston, R.D. - \ 2006
Toxicon 47 (2006)3. - ISSN 0041-0101 - p. 364 - 368.
terciopelo snake-venom - antibody fragments - antivenoms - metalloproteinases - necrosis - ability - edema - bite
Envenoming by snakes results in severe systemic and local pathology. Intravenous administration of antivenom, prepared from IgG of venom immunised horses or sheep, is the only effective treatment of systemic envenoming. Conventional antivenoms, formulated as intact IgG, papain-cleaved (Fab) or pepsin-cleaved F(ab¿)2 fragments, are however ineffective against the local venom effects because of their inability to penetrate the blood/tissue barrier. We have embarked on a new research program to examine (i) whether the unusually small (15 kDa) antigen-binding fragment of camelid heavy chain IgG (VHH) can be exploited to neutralise the local effects of envenoming and (ii) whether a novel antivenom to treat both the systemic and local effects of envenoming can be formulated by combining anti-snake venom VHH and conventional F(ab¿)2. In this preliminary study, we demonstrate that camels and llamas respond to immunisation with Echis ocellatus venom with high antibody titres and broad antigen specificity. These encouraging immunological results were matched by the successful elimination of venom-induced haemorrhage by IgG from the venom-immunised camels and llamas. Unexpectedly, we report for the first time that camelid serum contains a non-IgG, highly potent inhibitor of venom-induced haemorrhage.
Host status of six major weeds to Meloidogyne chitwoodi and Pratylenchus penetrans, including a preliminary field survey concerning other weeds
Kutywayo, V. ; Been, T.H. - \ 2006
Nematology 8 (2006)5. - ISSN 1388-5545 - p. 647 - 657.
root-knot nematode - p. thornei - range - suitability - neglectus - incognita - ability - hapla
A glasshouse experiment was carried out to investigate the host status of six important weeds in intensive agricultural cropping systems to Meloidogyne chitwoodi and Pratylenchus penetrans. Senecio vulgaris L., Capsella bursa-pastoris (L.) Medic. and Solanum nigrum L. were hosts of M. chitwoodi with reproduction factors of 2.5, 2.6 and 7.8, respectively. Echinochloa crusgalli (L.) Beauv. and Stellaria media (L.) Vill. were non-hosts for M. chitwoodi as no galls or eggs were observed. Galinsoga parviflora Cav. is considered a poor host with one out of eight plants producing an egg mass, but maintaining significantly higher population densities in the soil than were recorded in the fallow pots. Echinochloa crusgalli, S. nigrum and S. vulgaris were hosts of P. penetrans with multiplication factors of 1.6, 1.82 and 4.29, respectively. The multiplication rate of P. penetrans on S. vulgaris was similar to the one recorded on maize, the susceptible control. Galinsoga parviflora, S. media and C. bursa-pastoris were non-hosts as no specimen of the target nematode was found in the roots. After 16 weeks, only 1.22 and 0.08% of the original population was still alive for P. penetrans and M. chitwoodi, respectively. In conjunction with the pot experiment, a field survey was conducted at two sites, each of which was known to be highly infested with either M. chitwoodi or P. penetrans. Based on the survey results, Cirsium arvense Scop. and C. bursa-pastoris can also be considered to be hosts of M. chitwoodi, whilst Cirsium arvense, Chenopodium album L. and Polygonum convolvulus L. were recorded as hosts of P. penetrans. These results call attention to the possibility of weeds acting as carriers and point sources of possible high population densities of plant-parasitic nematodes. It emphasises the importance of adequate weed control in an integrated programme for management of M. chitwoodi and P. penetrans and the possible failure of the successful use of non-host crops and fallow in crop rotations when weed control is inadequate.
Temporal and host-related variation in frequencies of genes that enable Phyllotreta nemorum to utilize a novel host plant, Barbarea vulgaris
Nielsen, J.K. ; Jong, P.W. de - \ 2005
Entomologia Experimentalis et Applicata 115 (2005)1. - ISSN 0013-8703 - p. 265 - 270.
flea beetle - resistance - defenses - evolution - genetics - ability
The flea beetle, Phyllotreta nemorum L. (Coleoptera: Chrysomelidae), is an intermediate specialist feeding on a small number of plants within the family Brassicaceae. The most commonly used host plant is Sinapis arvensis L., whereas the species is found more rarely on Cardaria draba (L.) Desv., Barbarea vulgaris R.Br., and cultivated radish (Raphanus sativus L.). The interaction between flea beetles and Barbarea vulgaris ssp. arcuata (Opiz.) Simkovics seems to offer a good opportunity for experimental studies of coevolution. The plant is polymorphic, as it contains one type (the P-type) that is susceptible to all flea beetle genotypes, and another type (the G-type) that is resistant to some genotypes. At the same time, the flea beetle is also polymorphic, as some genotypes can utilize the G-type whereas others cannot. The ability to utilize the G-type of B. vulgaris ssp. arcuata is controlled by major dominant genes (R-genes). The present investigation measured the frequencies of flea beetles with R-genes in populations living on different host plants in 2 years (1999 and 2003). Frequencies of beetles with R-genes were high in populations living on the G-type of B. vulgaris ssp. arcuata in both years. Frequencies of beetles with R-genes were lower in populations living on other host plants, and declining frequencies were observed in five out of six populations living on S. arvensis. Selection in favour of R-genes in populations living on B. vulgaris is the most likely mechanism to account for the observed differences in the relative abundance of R-genes in flea beetle populations utilizing different host plants. A geographic mosaic with differential levels of interactions between flea beetles and their host plants was demonstrated
Modeling spatial characteristics in the biological control of fungi at leaf scale: competitive substrate colonization by Botrytis cinerea and the saprophytic antagonist Ulocladium atrum
Kessel, G.J.T. ; Köhl, J. ; Powell, J.A. ; Rabbinge, R. ; Werf, W. van der - \ 2005
Phytopathology 95 (2005)4. - ISSN 0031-949X - p. 439 - 448.
dead onion leaves - gliocladium-roseum - cyclamen - sporulation - biocontrol - growth - suppression - epidemics - ability - tissue
A spatially explicit model describing saprophytic colonization of dead cyclamen leaf tissue by the plant-pathogenic fungus Botrytis cinereo and the saprophytic fungal antagonist Ulocladium atrum was constructed. Both fungi explore the leaf and utilize the resources it provides. Leaf tissue is represented by a two-dimensional grid of square grid cells. Fungal competition within grid cells is modeled using Lotka-Volterra equations. Spatial expansion into neighboring grid cells is assumed pro-portional to the mycelial density gradient between donor and receptor cell. Established fungal biomass is immobile. Radial growth rates of B. cinerea and U. atrum in dead cyclamen leaf tissue were measured to determine parameters describing the spatial dynamics of the fungi. At temperatures from 5 to 25 degrees C, B. cinerea colonies expanded twice as rapidly as U. atrum colonies. In practical biological control, the slower colonization of space by U. atrum thus needs to be compensated by a sufficiently dense and even distribution of conidia on the leaf. Simulation results confirm the importance of spatial expansion to the outcome of the competitive interaction between B. cinerea and U. atrum at leaf scale. A sensitivity analysis further emphasized the importance of a uniform high density cover of vital U. atrum conidia on target leaves.
Learning performances in young horses using two different learning tests.
Visser, E.K. ; Reenen, C.G. van; Schilder, M.B.H. ; Barneveld, A. ; Blokhuis, H.J. - \ 2003
Applied Animal Behaviour Science 80 (2003)4. - ISSN 0168-1591 - p. 311 - 326.
yearling horses - conditioning trials - 2-year-old horses - social-dominance - ability - maze - avoidance - behavior - tasks - age
To achieve optimal performance in equine sports as well as in leisure not only the physical abilities of the horse should be considered, but also the horse's personality. Besides temperamental aspects, like emotionality, or the horse's reactivity towards humans in handling situations, the learning ability of the horse is another relevant personality trait. To study whether differences in learning performance are consistent over time and whether individual learning performance differs between learning tests or is affected by emotionality, 39 young horses (Dutch Warmblood) were tested repeatedly in two learning tests. An aversive stimulus (AS) was used in one learning test (the avoidance learning test) and a reward was used in the other learning test (the reward learning test). During both learning tests behaviour as well as heart rate were measured. Each test was executed four times, twice when horses were 1 year of age, and twice when they were 2 years of age. Half of the horses received additional physical training from 6 months onwards. In both tests horses could be classified as either performers, i.e. completing the daily session, or as non-performers, i.e. returning to the home environment without having completed the daily session. There were some indications that emotionality might have caused non-performing behaviour, but these indications are not convincing enough to exclude other causes. Furthermore, there seem to be no simple relationships between measures of heart rate, behavioural responses putatively related to emotionality and learning performance. Horses revealed consistent individual learning performances within years in both tests, and in the avoidance learning test also between years. There was no significant correlation between learning performances in the avoidance learning test and the learning performances in the reward learning test. It is concluded that individual learning abilities are consistent over a short time interval for an avoidance learning test and a reward learning test and over a longer time for the avoidance learning test. Furthermore, results indicate that some horses perform better when they have to learn to avoid an aversive stimulus while others perform better when they are rewarded after a correct response. It is suggested that these differences may be relevant to design optimal individual training programmes and methods.
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