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A method of evaluation of ordered categorical responses is presented. The probability of response in a given category follows a normal integral with an argument dependent on fixed thresholds and random variables sampled from a conceptual distribution with known first and second moments, a priori. The prior distribution and the likelihood function are(More)
This paper reviews some problems encountered in estimating heterogeneous variances in Gaussian linear mixed models. The one-way and multiple classification cases are considered. EM-REML algorithms and Bayesian procedures are derived. A structural mixed linear model on log-variance components is also presented, which allows identification of meaningful(More)
A procedure of genetic evaluation of reproductive traits such as litter size and survival in a polytocous species under the assumption of polygenic inheritance is described. Conditional distributions of these traits are assumed to be Poisson and Bernoulli, respectively. Using the concept of generalized linear models, logarithmic (litter size) and probit(More)
Variance components for egg production traits (No of eggs produced between 19 and 26, 26 and 38 and 26 and 54 wk of age), egg characteristics (average egg weight at 2 different ages and egg density) and body weight of hens at 40 wk of age were estimated in two strains of a breeding company by univariate and multivariate Restricted Maximum Likelihood (REML)(More)
Breeding values and genetic parameters for dystocia were estimated in Normande and Holstein breeds. Dystocia scores were related to an underlying continuous variable via a threshold model. The underlying linear model included the effects of calving season, sex of calf by parity of dam, sire of calf, grandsire of calf, dam within maternal grandsire and(More)
The joint distribution of breeding values and of records usually depends on unknown parameters such as means, variances and covariances in the case of the multivariate normal distribution. If the objective of the analysis is to make selection decisions, these parameters should be considered as « nuisances ». If the values of the parameters are unknown, the(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)
A statistical method for identifying meaningful sources of heterogeneity of residual and genetic variances in mixed linear Gaussian models is presented. The method is based on a structural linear model for log variances. Inference about dispersion parameters is based on the marginal likelihood after integrating out location parameters. A likelihood ratio(More)
A criterion for measuring the degree of connectedness between factors arising in linear models of genetic evaluation is derived on theoretical grounds. Under normality and in the case of 2 fixed factors (0, 0), this criterion is defined as the Kullback-Leibler distance between the joint distribution of the maximum likelihood (ML) estimators of contrasts(More)