Heterogeneidade de variâncias nos grupos genéticos formadores da raça Canchim

Oliveira, Carlos Antônio Lopes de; Martins, Elias Nunes; Freitas, A. R. de; Alencar, M. M. de

doi:10.1590/s1516-35982001000500012

Cited by 8 publications

(5 citation statements)

References 12 publications

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“…In general, the direct heritability estimates for the weight traits obtained in this work were lower than those related in literature for similar traits (Eler et al 1995;Gianlorenço et al, 2003;Meyer, 1992;Oliveira et al, 2001;Toral et al, 2008 and2009), but with data from Zebu, European or crossbred European × Zebu. Similar tendencies were observed for the heritability estimates of average daily weight gain from birth to weaning and from weaning to 365 days (Alencar et al, 2005;Castor-Pereira et al, 2007).…”

Section: Resultscontrasting

confidence: 82%

Alternatives for analysis of performance data and ranking of Charolais x Nellore crossbred bulls in performance tests

Toral

Alencar

2010

R. Bras. Zootec.

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-It was evaluated alternatives for analysis of performance records and ranking of Charolais × Zebu crossbred bulls. Data of weight at six ages and average daily weight gain in eight periods of 883 21/32 Charolais + 11/32 Nellore bulls in performance tests were used. The direct additive genetic values were predicted in single trait analysis using animal models with classificatory fixed effects of contemporary groups and age of dam at calving and age of animal at weighing as linear covariable, depending on the trait. As random effects, it was considered the direct additive genetic effect, the permanent

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Section: Resultscontrasting

confidence: 82%

Alternatives for analysis of performance data and ranking of Charolais x Nellore crossbred bulls in performance tests

Toral

Alencar

2010

R. Bras. Zootec.

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“…A existência de variâncias heterogêneas foi observada por Oliveira et al (3) nos grupos genéticos participantes da formação da raça Canchim e por Urioste et al (4) na raça Holandesa.…”

Section: Introductionunclassified

Impacto Da Distribuição De Número Desigual De Progênies Por Reprodutor Na Avaliação Genética De Animais, Em Ambientes Com Presença De Heterogeneidade De Variância Ambiental

et al. 2017

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ResumoFoi simulado um teste de progênie com o objetivo de avaliar o efeito da heterogeneidade de variância ambiental sobre a avaliação genética de reprodutores, em situações de número desigual de progênie por reprodutor entre rebanhos. A situação do número desigual de progênie por reprodutor foi representada eliminando-se, de forma aleatória, o número de progênies por reprodutor em ambientes de baixa e alta variabilidade ambiental. Nas situações que envolveram perda de informação no ambiente de menor variabilidade ambiental, houve maiores superestimações na estimação da variância residual, ocasionando menores estimativas de herdabilidade. Por outro lado, quando se diminuiu a quantidade de informação proveniente de rebanhos de alta variabilidade ambiental, houve maior superestimação da variância genética aditiva e menor superestimação da variância ambiental. Embora tenham ocorrido alterações na magnitude dos valores genéticos para os reprodutores, as correlações de Spearman e Pearson entre os valores genéticos dos mesmos, em todas as situaçãoes, foram maiores do que 0,90. O número desigual de progênie por reprodutor na presença de heterogeneidade de variância ambiental provoca superestimação das estimativas de componentes de variância e valores absolutos de predição de valores genéticos dos reprodutores, sem, contudo, alterar a classificação dos mesmos.Palavras chave: avaliação genética; parâmetros genéticos; seleção. AbstractA progeny test representing the milk yield was simulated to evaluate the effect of heterogeneity of environmental variance on genetic evaluation of sires in situations of unequal number of progeny per sire between herds, eliminating, at random, daughters per sires in environments of low and high environmental variability. In all situations involving loss of information in the environment of lower environmental variability, there was larger overestimation of the residual variance component, resulting

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“…WINKELMAN & SCHAEFFER (1988) reported that the effect of the heterogeneity of variances is important for the selection of cows, young sires, and calves because these animals have records within a single herd/environment and, thus, their evaluations can be affected by differences in environmental variances. The effects of sex, farm, and animal age, for example, can be classified as sources of heteroscedasticity; in the case of crossbred populations, the composition of the breed and its genetic interactions can also be considered causes of heteroscedasticity (CARDOSO et al, 2005;OLIVEIRA et al, 2001;RODRÍGUEZ-ALMEIDA et al, 1995).…”

Section: Resultsmentioning

confidence: 99%

Genetic evaluation models for resistance to ticks in a crossbred Angus-Nellore population

et al. 2021

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This research identified the animal model that best describes the genetic and residual variations for tick counts in yearlings from a crossbred Angus-Nellore population of 6,951 animals that are progenies of 382 bulls and 6,198 cows. Genetic values were predicted by the Bayesian inference methodology. The models tested were: Traditional Animal, and Crossbred Animal with and without segregation, considering residual homoscedastic and heteroscedastic variances. The criteria of choice were the number of parameters, deviance information, and predictive order, which indicated the best fitfor the Traditional Animal model and Crossbred Animal model (with segregation), both with residual heteroscedastic Gaussian variance. The mean values of fixed genetic effects were positive and similar in the both models, indicating that animals with higher proportion of the Angus breed had greater infestation, and the Nellore breed was an important addition for resistance to ticks. The estimated genetic variation by the heteroscedastic Gaussian Animal model for the Nellore breed was 4.54-fold higher than that estimated for the Angus breed. The estimates of heritability of the different genetic groups ranged from 0.12 to 0.15 and from 0.01 to 0.35, respectively, for the Traditional Animal model and for the heteroscedastic Gaussian crossbred model. The Spearman’s rank-order correlation for the predicted genetic values was 0.94, considering all sires. However, when considering the top 10%, 20%, and 30% sires, differences in ranking were more evident (0.28 to 0.67). The Crossbred Animal model with segregation and heterogeneous residual variances was the most appropriate for genetic evaluation of tick counts on animals from Angus-Nellore crossings.

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Heterogeneidade de variâncias nos grupos genéticos formadores da raça Canchim

Cited by 8 publications

References 12 publications

Alternatives for analysis of performance data and ranking of Charolais x Nellore crossbred bulls in performance tests

Alternatives for analysis of performance data and ranking of Charolais x Nellore crossbred bulls in performance tests

Impacto Da Distribuição De Número Desigual De Progênies Por Reprodutor Na Avaliação Genética De Animais, Em Ambientes Com Presença De Heterogeneidade De Variância Ambiental

Genetic evaluation models for resistance to ticks in a crossbred Angus-Nellore population

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