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See detailEstimation of genetic parameters for quantitative trait loci for dairy traits in the French Holstein population.
Druet, Tom ULg; Fritz, S.; Boichard, D. et al

in Journal of Dairy Science (2006), 89(10), 4070-6

A marker-assisted selection program (MAS) has been implemented in dairy cattle in France. The efficiency of such a selection program depends on the use of correct genetic parameters for the marked ... [more ▼]

A marker-assisted selection program (MAS) has been implemented in dairy cattle in France. The efficiency of such a selection program depends on the use of correct genetic parameters for the marked quantitative trait loci (QTL). Therefore, the objective of this study was to estimate the proportion of genetic variance explained by 4 QTL described in previous studies (these QTL are segregating on chromosomes 6, 14, 20, and 26). Genotypes for 11 markers were available for 3,974 bulls grouped within 54 sire families of the French Holstein population undergoing MAS. The parameters were estimated for 4 QTL and 5 dairy traits: milk, fat and protein yields, and fat and protein percentages. The proportion of genetic variance explained by the QTL ranged from as low as 0.03 to 0.36%. Both lack of marker informativity and poor monitoring of QTL transmission might limit the accuracy of estimation. The QTL explained a larger proportion of genetic variance for milk composition traits. The QTL on chromosome 14 and chromosomes 6 and 20 have their largest influence on fat and protein percentages, respectively. The overall proportions of genetic variance explained by the QTL were 27.0, 30.7, 24.1, 48.2, and 33.6% for milk, fat and protein yields, and fat and protein percentages, respectively. These results clearly indicated that a large part of the genetic variance is explained by a small number of QTL and that their use in MAS might be beneficial for dairy cattle breeding programs. [less ▲]

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See detailEstimation of Genetic Parameters for Test Day Milk Yields of Moroccan Holstein Cows Using Random Regression Test Day Model
Tijani, Aziz; Rgayai, Brahim; Hammami, Hedi ULg et al

Poster (2010, August 02)

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See detailEstimation of Genetic Parameters for Test Day Milk Yields of Moroccan Holstein Cows Using Random Regression Test Day Model
Tijani, Aziz; Rgayai, Brahim; Hammami, Hedi ULg et al

in Proceedings of the 9th World Congress on Genetics Applied to Livestock Production (2010, August)

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See detailEstimation of genetic parameters for test day records of dairy traits in the first three lactations.
Druet, Tom ULg; Jaffrezic, Florence; Ducrocq, Vincent

in Genetics, Selection, Evolution (2005), 37(3), 257-71

Application of test-day models for the genetic evaluation of dairy populations requires the solution of large mixed model equations. The size of the (co)variance matrices required with such models can be ... [more ▼]

Application of test-day models for the genetic evaluation of dairy populations requires the solution of large mixed model equations. The size of the (co)variance matrices required with such models can be reduced through the use of its first eigenvectors. Here, the first two eigenvectors of (co)variance matrices estimated for dairy traits in first lactation were used as covariables to jointly estimate genetic parameters of the first three lactations. These eigenvectors appear to be similar across traits and have a biological interpretation, one being related to the level of production and the other to persistency. Furthermore, they explain more than 95% of the total genetic variation. Variances and heritabilities obtained with this model were consistent with previous studies. High correlations were found among production levels in different lactations. Persistency measures were less correlated. Genetic correlations between second and third lactations were close to one, indicating that these can be considered as the same trait. Genetic correlations within lactation were high except between extreme parts of the lactation. This study shows that the use of eigenvectors can reduce the rank of (co)variance matrices for the test-day model and can provide consistent genetic parameters. [less ▲]

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See detailEstimation of genetic parameters for test-day records of French Holstein cows with an AI-REML algorithm
Druet, Tom ULg; Jaffrézic, F.; Ducrocq, V.

in Abstracts from the 2003 ADSA/ASAS joint annual meeting (2003)

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See detailEstimation of genetic parameters of racing traits of Arabian horses in Algeria
Tennah, Safia ULg; Kafidi, Nacereddine; Antoine-Moussiaux, Nicolas ULg et al

Poster (2013, August)

The results of the flat races organized in Algeria from 1995 to 2007 by the Algerian Horse Racing Society, were used to estimate genetic parameters of racing performances of Arabian horses. The data ... [more ▼]

The results of the flat races organized in Algeria from 1995 to 2007 by the Algerian Horse Racing Society, were used to estimate genetic parameters of racing performances of Arabian horses. The data consist of 36 492 race records, obtained from 913 horses. The pedigree file of the horses includes 1812 animals from 166 stallions and 392 mares. The analysis was performed on two traits: the logarithm of average annual virtual earnings per start (LAEV/S) and a normalized ranking (PERF). To identify the fixed effects to be included in the genetic model, a preliminary analysis was conducted using the General Linear Models (GLM) procedure from SAS software. The effects of age (3 to 8 years and older), sex (male or female), year (1995 to 2007) and the interaction between year of the race and age and between sex and age were included in the model for both traits. In addition, two random effects, a direct genetic effect of the animal and a permanent environmental effect were included in the mixed model. The variance components and genetic parameters were estimated by the restricted maximum likelihood (REML), procedure using the MTDFREML program. The analysis, using a repeatable animal model, led to the following estimation of genetic parameters: for LAEV/S, heritability was 0.23 (±0.04), while estimate of repeatability was 0.34 (±0.04). The heritability for the normalized ranking was higher, 0.37 (±0.05), indicating that this trait might be more appropriate for breeding programs of Arabian horses in Algeria. The repeatability estimate for the normalized ranking was 0.59 (±0.04) and the genetic correlation between this trait and LAEV/S was 0.79. [less ▲]

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See detailEstimation of genetic parameters of test-day records for milk yield for the first three lactations of French Holstein cows
Druet, Tom ULg; Jaffrézic, F.; Ducrocq, V.

in Book of Abstracts of the 54th Annual Meeting of the European Association for Animal Production (2003)

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See detailEstimation of genetic-parameters for growth, feed consumption, and conformation traits for double-muscled Belgian Blue bulls performance-tested in Belgium
Gengler, Nicolas ULg; Seutin, C.; Boonen, F. et al

in Journal of Animal Science (1995), 73(11), 3269-3273

For 1,442 Belgian Blue bulls performance-tested at the Centre de Selection de la Race Blanc-Bleue Belge, nine traits were observed: height at withers at 7 mo, height at withers at 13 mo, weight at 7 mo ... [more ▼]

For 1,442 Belgian Blue bulls performance-tested at the Centre de Selection de la Race Blanc-Bleue Belge, nine traits were observed: height at withers at 7 mo, height at withers at 13 mo, weight at 7 mo, weight at 13 mo, average feed consumption of concentrates, average daily gain, average feed consumption of concentrates per average daily gain, average feed consumption of concentrates per mean metabolic weight, and price per kilogram of live weight. This price is based on muscle conformation and is therefore used as muscle conformation score. Restricted maximum Likelihood with a derivative-free algorithm was used to estimate (co)variance components because there were different models and missing values per trait. Estimates of heritabilities were above .50 except for average feed consumption per average daily gain (.16) and average feed consumption per mean metabolic weight (.33). Estimates of genetic and phenotypic correlations between height at withers and weight traits were positive and moderate to high. Average daily gain showed a negative genetic correlation with weight at 7 mo (- .68) but had positive correlations with height at withers at 13 mo and weight at 13 mo (.22 and .43). Muscle conformation expressed as price per kilogram of live weight was related to low average feed consumption per average daily gain. Average feed consumption showed high correlations with weight at 7 mo and weight at 13 mo. Average feed consumption per average daily gain had a high negative genetic correlation with average daily gain (- .89). [less ▲]

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See detailEstimation of GFR by different creatinine- and cystatin-C-based equations in anorexia nervosa.
Delanaye, Pierre ULg; Cavalier, Etienne ULg; Radermecker, Régis ULg et al

in Clinical Nephrology (2009), 71(5), 482-91

Background: Patients with anorexia nervosa (AN) are at high risk of renal failure. Glomerular filtration rate (GFR) is overestimated when estimated by the creatinine-based equations. We have studied the ... [more ▼]

Background: Patients with anorexia nervosa (AN) are at high risk of renal failure. Glomerular filtration rate (GFR) is overestimated when estimated by the creatinine-based equations. We have studied the accuracy and precision of cystatin C-based equations. Method: 27 AN patients were included. GFR was measured with the chromium-51-ethylenediaminetetraacetate (51Cr-EDTA) method. We have compared the accuracy and precision of creatinine-based equations (MDRD and Cockcroft) with those of different new cystatin C-based equations. Results: The creatinine-based equations overestimate measured GFR, especially the MDRD study equation. All the cystatin C-based equations also overestimate measured GFR. The Cockcroft and Gault formula and the cystatin C-based equation published by Rule have the best accuracy and precision, but these last performances remain unsatisfactory. Conclusion: Both creatinine and cystatin C-based equations strongly overestimate measured in patients with AN. [less ▲]

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See detailEstimation of habitat quality based on plant community, and effects of isolation in a network of butterfly habitat patches
Sawchik, J.; Dufrêne, Marc ULg; Lebrun, Philippe

in Acta Oecologica (2003), 24(1), 25-33

Minimum viable site networks are crucial for many threatened species but their design is always a difficult procedure. The present study investigated methods to estimate habitat quality of patches, in an ... [more ▼]

Minimum viable site networks are crucial for many threatened species but their design is always a difficult procedure. The present study investigated methods to estimate habitat quality of patches, in an ecological network for five butterfly species (Brenthis ino, Clossiana selene, Lycaena helle, Lycaena hippothoe, Proclossiana eunomia) inhabiting wet meadows. Abundance predictions were performed on the basis of botanical relevés with a multiple-species approach combining canonical correspondence analysis and multiple regression. Models are defined on a reference site set and are evaluated on a test site set. All the fitted models predicted the abundance of the butterfly species considerably well (from 61 to 86% of the variation). We evaluated the potential consequences of isolation on local populations, by comparing predicted and observed abundance. It was expected that greater differences would be observed when sites were more isolated. On the test set, differences between predicted and observed abundance were largely correlated to site isolation for L. helle and P. eunomia. The most isolated sites had greater chances to be empty, even if they had high-quality habitat. Reciprocally, when the sites were less isolated, the abundance observed was always greater than predicted, seeming to confirm the role of rescue effects. © 2003 Éditions scientifiques et médicales Elsevier SAS. All rights reserved. [less ▲]

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See detailEstimation of heritability and genetic correlations for the major fatty acids in bovine milk
Soyeurt, Hélène ULg; Gillon, Alain ULg; Vanderick, Sylvie ULg et al

in Journal of Dairy Science (2007), 90(9), 4435-4442

The current cattle selection program for dairy cattle in the Walloon region of Belgium does not consider the relative content of the different fatty acids (FA) in milk. However, interest by the local ... [more ▼]

The current cattle selection program for dairy cattle in the Walloon region of Belgium does not consider the relative content of the different fatty acids (FA) in milk. However, interest by the local dairy industry in differentiated milk products is increasing. Therefore, farmers may be interested in selecting their animals based on the fat composition. The aim of this study was to evaluate the feasibility of genetic selection to improve the nutritional quality of bovine milk fat. The heritabilities and correlations among milk yield, fat, protein, and major FA contents in milk were estimated. Heritabilities for FA in milk and fat ranged from 5 to 38%. The genetic correlations estimated among FA reflected the common origin of several groups of FA. Given these results, an index including FA contents with the similar metabolic process of production in the mammary gland could be used, for example, to increase the monounsaturated and conjugated fatty acids in milk. Moreover, the genetic correlations between the percentage of fat and the content of C14:0, C12:0, C16:0, and C18:0 in fat were −0.06, 0.55, 0.60, and 0.84, respectively. This result demonstrates that an increase in fat content is not directly correlated with undesirable changes in FA profile in milk for human health. Based on the obtained genetic parameters, a future selection program to improve the FA composition of milk fat could be initiated. [less ▲]

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See detailEstimation of HIV treatment-efficacy by combining structural nested mean models with pharmacokinetic models of antiretroviral drug exposure
Comté, Laetitia ULg; Vansteelandt, Stijn; Rode, Richard et al

in Statistics and its interface (2011), 4(4), 511-520

The aim of treating HIV-1-infected patients is to achieve and maintain suppression of viral load (VL). Achievement of this aim is thwarted by variable adherence to prescribed anti-retroviral drugs ... [more ▼]

The aim of treating HIV-1-infected patients is to achieve and maintain suppression of viral load (VL). Achievement of this aim is thwarted by variable adherence to prescribed anti-retroviral drugs. Variable adherence to an antiretroviral regimen creates variability in the patient’s internal exposure to the drugs. Structural nested mean models (SNMMs) enabled us to estimate, during the initial phase of treatment, the relationship between variable internal exposure and VL, accounting for measured time-varying confounders and feedback relations using an antiretroviral regimen containing lopinavir/ritonavir (LPV/RTV, LPV/r). Our final SNMM predicts that the short term effect of treatment is modified by the most recent past VL, with higher initial VL’s being associated with larger treatment-induced reductions in VL for a given internal exposure to the drugs. Variation in internal exposure to LPV/r in the interquartile interval (P25%–P75%) only slightly affects the overall reduction in VL, supporting the conclusion that the relatively long duration of action of LPV/r lessens the impact on VL of the most frequently recurring intermittent lapses in dosing. [less ▲]

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See detailEstimation of human orientation based on silhouettes and machine learning principles
Pierard, Sébastien ULg; Van Droogenbroeck, Marc ULg

in International conference on pattern recognition applications and methods (ICPRAM) (2012, February)

Estimating the orientation of the observed person is a crucial task for home entertainment, man-machine interaction, intelligent vehicles, etc. This is possible but complex with a single camera because it ... [more ▼]

Estimating the orientation of the observed person is a crucial task for home entertainment, man-machine interaction, intelligent vehicles, etc. This is possible but complex with a single camera because it only provides one side view. To decrease the sensitivity to color and texture, we use the silhouette to infer the orientation. Under these conditions, we show that the only intrinsic limitation is to confuse the orientation q with the supplementary angle (that is 180°-theta), and that the shape descriptor must distinguish between mirrored images. In this paper, the orientation estimation is expressed and solved in the terms of a regression problem and supervised learning. In our experiments, we have tested and compared 18 shape descriptors; the best one achieves a mean error of 5:24°. However, because of the intrinsic limitation mentioned above, the range of orientations is limited to 180°. Our method is easy to implement and outperforms existing techniques. [less ▲]

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See detailEstimation of human orientation in images captured with a range camera
Pierard, Sébastien ULg; Leroy, Damien; Hansen, Jean-Frédéric et al

in Advanced Concepts for Intelligent Vision Systems (ACIVS) (2011, August)

Estimating the orientation of the observed person is a crucial task for some application fields like home entertainment, man-machine interaction, or intelligent vehicles. In this paper, we discuss the ... [more ▼]

Estimating the orientation of the observed person is a crucial task for some application fields like home entertainment, man-machine interaction, or intelligent vehicles. In this paper, we discuss the usefulness of conventional cameras for estimating the orientation, present some limitations, and show that 3D information improves the estimation performance. Technically, the orientation estimation is solved in the terms of a regression problem and supervised learning. This approach, combined to a slicing method of the 3D volume, provides mean errors as low as 9.2° or 4.3° depending on the set of considered poses. These results are consistent with those reported in the literature. However, our technique is faster and easier to implement than existing ones. [less ▲]

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See detailEstimation of hydraulic conductivity and its uncertainty from grain-size data using GLUE and artificial neural networks
Rogiers, Bart; Mallants, Dirk; Batelaan, Okke et al

in Mathematical Geosciences (2012), 44(6), 739-763

Various approaches exist to relate saturated hydraulic conductivity (Ks) to grain-size data. Most methods use a single grain-size parameter and hence omit the information encompassed by the entire grain ... [more ▼]

Various approaches exist to relate saturated hydraulic conductivity (Ks) to grain-size data. Most methods use a single grain-size parameter and hence omit the information encompassed by the entire grain-size distribution. This study compares two data-driven modelling methods, i.e.multiple linear regression and artificial neural networks, that use the entire grain-size distribution data as input for Ks prediction. Besides the predictive capacity of the methods, the uncertainty associated with the model predictions is also evaluated, since such information is important for stochastic groundwater flow and contaminant transport modelling. Artificial neural networks (ANNs) are combined with a generalized likelihood uncertainty estimation (GLUE) approach to predict Ks from grain-size data. The resulting GLUE-ANN hydraulic conductivity predictions and associated uncertainty estimates are compared with those obtained from the multiple linear regression models by a leave-one-out cross-validation. The GLUE-ANN ensemble prediction proved to be slightly better than multiple linear regression. The prediction uncertainty, however, was reduced by half an order of magnitude on average, and decreased at most by an order of magnitude. This demonstrates that the proposed method outperforms classical data-driven modelling techniques. Moreover, a comparison with methods from literature demonstrates the importance of site specific calibration. The dataset used for this purpose originates mainly from unconsolidated sandy sediments of the Neogene aquifer, northern Belgium. The proposed predictive models are developed for 173 grain-size -Ks pairs. Finally, an application with the optimized models is presented for a borehole lacking Ks data. [less ▲]

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See detailEstimation of in vivo muscle protein turnover in young bulls treated with anabolic agents
Van Eenaeme, Christian ULg; Baldwin, Paule; Lambot, Olivier et al

in Proceedings of the 4th Int. Symp. Protein metabolism and nutrition (1983)

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See detailEstimation of joint contact forces in the equine digit
Noble, Prisca ULg; Collin, Bernard ULg; Denoix, Jean-Marie et al

in ISB proceedings (2009, July)

Detailed reference viewed: 109 (29 ULg)