Journal Article•
Modelos de evaluación genética multirracial: caso peso al destete en bovinos
TL;DR: Multibreed genetic evaluation models allow the prediction of animal breeding values in a population of animals of various breed compositions to yield additive and nonadditive animal genetic values, which allow more precise selection decisions and mating plans.
Abstract: Multibreed genetic evaluation models allow the prediction of animal breeding values in a population of animals of various breed compositions. The structure of this type of model depends on the traits to be evaluated and the multibreed population to be analyzed, and they eventually yield additive and nonadditive animal genetic values, which allow more precise selection decisions and mating plans.
Citations
More filters
01 Aug 2006
TL;DR: The breed additive effect seemed to be overestimated when the maternal effect was not included in the model and the maternal breed effect and individual and maternal heterosis should be included in models used for genetic evaluation of pre-weaning daily gain in this composite cattle population.
Abstract: Three different models including or not the direct and maternal non-additive effects and the fixed effects of contemporary group, parity order, direct and maternal heterosis and the direct and maternal additive genetic random effects were compared for predicting breeding values for pre-weaning daily gain in a composite cattle population in tropical climate. The analyses were done in two stages: firstly, breed and individual and maternal heterosis effects were estimated and after variances and the heritability were obtained for prediction of breeding values of the animals. The breed additive effect seemed to be overestimated when the maternal effect was not included in the model. Estimates of additive and maternal breed effects and individual and maternal heterosis for pre-weaning daily gain were significantly different for the biological types. Direct and maternal heritability estimates from analyses using data adjusted for direct and maternal non-additive effects were respectively 0.22 and 0.20. The maternal breed effect and individual and maternal heterosis should be included in models used for genetic evaluation of pre-weaning daily gain in this composite cattle population.
9 citations
References
More filters
TL;DR: In this article, Sires' evaluations are solutions to this modified system of equations in contrast to regular mixed model equations where evaluations are linear functions of group and sire solutions, and the major advantage of modified equations is theoretical.
Abstract: Sire evaluation by best linear unbiased prediction for models including groups is considered in an alternative formulation of mixed model equations. Sires' evaluations are solutions to this modified system of equations in contrast to regular mixed model equations where evaluations are linear functions of group and sire solutions. The major advantage of modified equations is theoretical. To illustrate this advantage, the modified equations are used to show a relationship between group models and selection models.
121 citations
TL;DR: The results showed that it is feasible to evaluate sires for additive and nonadditive genetic effects in a structured multibreed population and data from purebred breeders and commercial producers will be needed to accomplish the same goal at a national level.
Abstract: Estimates of covariances and sire expected progeny differences of additive and nonadditive direct and maternal genetic effects for birth and weaning weights were obtained using records from 1,581 straightbred and crossbred calves from the Angus-Brahman multibreed herd at the University of Florida. Covariances were estimated by Restricted Maximum Likelihood, using a Generalized Expectation-Maximization algorithm applied to multibreed populations. Estimates of heritabilities and additive genetic correlations for straightbred and crossbred groups were within the ranges of values found in the literature for these traits. Maximum values of interactibilities (ratios of nonadditive genetic variances to phenotypic variances) and nonadditive correlations were somewhat smaller than heritabilities and additive genetic correlations. Sire additive and total direct and maternal genetic predictions for birth and weaning weight tended to increase with the fraction of Brahman alleles, whereas nonadditive direct and maternal genetic predictions were similar for sires of all Angus and Brahman fractions. These results showed that it is feasible to evaluate sires for additive and nonadditive genetic effects in a structured multibreed population. Data from purebred breeders and commercial producers will be needed to accomplish the same goal at a national level.
78 citations
66 citations
TL;DR: Extension of beef cattle genetic evaluation procedures to multibreed data sets is proposed as a way to allow inclusion of crossbred animals into current analyses and to provide comparisons between purebred animals of different breeds.
Abstract: Extension of beef cattle genetic evaluation procedures to multibreed data sets is proposed as a way to allow inclusion of crossbred animals into current analyses and to provide comparisons between purebred animals of different breeds. Previous papers dealing with multibreed BLUP have proposed sire or sire-maternal grandsire models. Because current models used in the beef industry are predominantly of the reduced animal model form, models were developed for animal model and reduced animal model mixed-model evaluations that would account for fixed and random additive genetic effects, along with fixed and random nonadditive genetic effects for populations with heterogeneous means and variances.
62 citations
TL;DR: Estimation of direct and maternal breed effects needed to predict hybrid EPD for multibreed populations from field data may not be possible, and information from designed crossbreeding experiments will need to be incorporated in some way.
Abstract: Direct and maternal breed effects on birth and 200-d weights were estimated for nine parental breeds (Hereford [H], Angus [A], Braunvieh [B], Limousin [L], Charolais [C], Simmental [S], Gelbvieh [G], Red Poll [R], and Pinzgauer [P]) that contributed to three composite populations (MARC I = 1/4B, 1/4C, 1/4L, 1/8H, 1/8A; MARC II = 1/4G, 1/4S, 1/4H, 1/4A; and MARC III = 1/4R, 1/4P, 1/4H, 1/4A). Records from each population, the composite plus pure breeds and crosses used to create each composite, were analyzed separately. The animal model included fixed effects of contemporary group (birth year-sex-dam age), proportions of individual and maternal heterosis and breed inheritance as covariates, and random effects of additive direct genetic (a) and additive maternal genetic (m) with covariance (a,m), permanent environment, and residual. Sampling correlations among estimates of genetic fixed effects were large, especially between direct and maternal heterosis and between direct and maternal breed genetic effects for the same breed, which were close to -1. This resulted in some large estimates with opposite sign and large standard errors for direct and maternal breed genetic effects. Data from a diallel experiment with H, A, B, and R breeds, from grading up and from a top cross experiment were required to separate breed effects satisfactorily into direct and maternal genetic effects. Results indicate that estimation of direct and maternal breed effects needed to predict hybrid EPD for multibreed populations from field data may not be possible. Information from designed crossbreeding experiments will need to be incorporated in some way.
49 citations