J. J. Colleau

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A Monte Carlo simulation study to evaluate the benefits of marker assisted selection (MAS) in small populations with one marked bi-allelic quantitative trait locus (QTL) is described. In the base generation, linkage phase equilibrium between the markers, QTL and polygenes was assumed and frequencies of 0.5 for the two QTL alleles were used. Six discrete(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(More)
Monte Carlo simulation was used to assess the long-term effects of truncation selection within small populations using indices (I=ωf+m) combining mid-parent [f=(a i+a d)/2] and Mendelian-sampling (m=a-f) evaluations provided by an animal model BLUP (a=f+m). Phenotypic values of panmictic populations were generated for 30 discrete generations. Assuming a(More)
Accurate prediction of the cumulated genetic gain requires predicting genetic variance over time under the joint effects of selection and limited population size. An algorithm is proposed to quantify at each generation the effects of these factors on average coefficient of inbreeding, genetic variance, and genetic mean, under a purely additive polygenic(More)
The benefits of marker-assisted selection were examined by simulation of an adult multiple ovulation and embryo transfer nucleus breeding scheme. Animals were either typed for two polymorphic marker loci, 20 centimorgans apart, flanking a single biallelic quantitative trait locus and were evaluated using a model accounting for marker information, or animals(More)
SUMMARY Genetic correlations between two types of leg deformities, valgus and varus angulations, and some growth or conformation traits were estimated in two commercial broiler strains. 14 264 chickens of both sexes in line A were measured for leg defects at 6 weeks and body weight at 3 (BW3) or 6 (BW6) weeks. The same measures were taken in line B on 8 164(More)
Genetic parameters of two types of angulations, described in the twisted legs syndrome as ’valgus’ and bilateral or unilateral ’varus’, were investigated in two commercial broiler strains. In the first line, 14 264 chickens of both sexes born from 111 sires, 76 maternal grandsires and 768 dams were studied. In the second line, corresponding figures were 8(More)
Dutt’s and Deak’s methods can satisfy most of the geneticist’s needs. They are presented in this paper and their precision is analysed in detail. It appears that Dutt’s method is remarkably precise for dimensions 1 to 5, except when truncation points or correlation coefficients between traits are very high in absolute value. Deak’s method, less precise, is(More)
The adequacy of an expression for the withinfamily genetic variance under pure random drift in an additive infinitesimal model was tested via simulation in populations undergoing mass selection. Two hundred or one thousand unlinked loci with two alleles at initial frequencies of 1/2 were considered. The size of the population was 100 (50 males and 50(More)
Given the same overall number of transferred embryos, a comparison was carried out between adult mixed (ie with bull progeny-testing) MOET (multiple ovulation and embryo-transfer) schemes with embryo sexing only versus embryo sexing plus cloning of female embryos. In the former schemes, natural and ET (embryo transfer) animals were allowed to breed. In the(More)