Genetic analysis of visual scores and their relationships to mature female weight in Nellore breed

Abstract

-Data from 79,884 Nellore breed animals were used to estimate genetic parameters and to evaluate the relationships among scores of conformation, precocity and musculature obtained at weaning and after yearling ages and weight of mature females. It was used the restricted maximum likelihood method in a multi-trait analysis with the model that included direct additive genetic and residual effects, as random effects, and the fixed effects of contemporary group and, as covariables, animal age at weighing and age of dam at calving (except for weight of females at adult age). Contemporary groups at weaning were defined by the variables: sex, herd, year and month of birth, and management group at birth and weaning. For definition of contemporary group at yearling, it was also included the variable management group at yearling. For female weight at mature age, contemporary group was composed of herd, year of birth, management group at yearling, weighing year and season.Maternal genetic and maternal permanent environment effects were also included in the model for analyses of scores of conformation, precocity and muscularity at weaning. The direct herdability estimates obtained were the following: 0.18 ± 0.02 for conformation at weaning score, 0.21 ± 0.01 for precocity at weaning score, 0.22 ± 0.01 for muscularity at weaning score, 0.24 ± 0.01 for conformation at yearling score, 0.27 ± 0.01 for precocity at yearling score, and 0. Key Words: beef cattle, conformation, genetic correlation, musculature, precocity Análise genética de escores visuais e suas relações com o peso de fêmeas à idade adulta na raça Nelore RESUMO -Dados de 79.884 animais da raça Nelore foram utilizados para estimar parâmetros genéticos e avaliar as relações entre os escores de conformação, precocidade e musculatura obtidos à desmama e ao sobreano e o peso das fêmeas à idade adulta. Utilizou-se o método da máxima verossimilhança restrita, em análise multicaracterísticas, com modelo que incluiu os efeitos genéticos aditivos direto e residual, como aleatórios, e os efeitos fixos de grupo de contemporâneos e, como covariáveis, a idade do animal à pesagem e a idade da mãe ao parto (exceto para o peso das fêmeas à idade adulta). Os grupos contemporâneos à desmama foram definidos pelas variáveis: sexo, rebanho, ano e mês de nascimento, grupo de manejo ao nascimento e à desmama. Na definição de grupo contemporâneo ao sobreano também foi incluída a variável grupo de manejo ao sobreano. Para o peso das fêmeas à idade adulta, o grupo de contemporâneos foi composto por rebanho, ano de nascimento, grupo de manejo ao sobreano, ano e estação da pesagem. Os efeitos genético materno e de ambiente permanente materno também foram incluídos no modelo para análise dos escores de conformação, precocidade e musculatura à desmama. As estimativas de herdabilidade direta obtidas foram 0,18 ± 0,02 para o escore de conformação; 0,21 ± 0,01 para o escore de precocidade; 0,22 ± 0,01 para o escore de musculatura à desmama e 0,24 ± 0,01 para o escore de conformação; 0,27 ...

Genetic associations between hip height, body conformation scores, and pregnancy probability at 14 months in Nelore cattle

“…The similarity between these traits is also demonstrated by the correlations with the other traits studied. A high genetic correlation between PRE and MUS has also been reported by Regatieri et al (2011) andby Koury Filho et al (2010) for Nelore cattle (0.85 and 0.95, respectively). According to the latter authors, selection for one of the visual scores studied will imply a positive correlated response in the other.…”

“…Similarly, Cardoso et al (2004) reported heritability coefficients of 0.25 and 0.26, respectively, for PRE and MUS in Angus cattle. Regatieri et al (2011) found estimates of 0.27 and 0.26 for PRE and MUS in Nelore cattle. Shiotsuki et al (2009) observed lower heritabilities (0.21 and 0.23) for these traits also in Nelore animals.…”

Principal components and factor analytic models for birth to mature weights in Nellore cattle

“…Applying random regression models fitted by Legendre polynomials to part of the same data set, Boligon et al (2010a) estimated direct heritabilities similar to those obtained in the present study, which increased from birth (0.34) to yearling (0.42) and remained practically constant thereafter (0.39). For Nellore animals, direct heritabilities estimated by two-or multiple-trait analysis reported in the literature range from 0.26 to 0.34 (weaning weight), from 0.30 to 0.45 (weight at 12 months of age), from 0.34 to 0.49 (weight at 18 months of age), and from 0.29 to 0.46 (mature weight) (Boligon et al, 2008(Boligon et al, , 2010bRegatieri et al, 2011;Yokoo et al, 2007).…”

Heritability estimation and genetic correlations for mature weight, visual scores, and growth traits in Nellore cattle

“…The findings of multiple studies suggest that selection based on conformation, finishing precocity, and muscling visual scores (VS) can be effective, as heritability obtained for these characteristics are moderate and similar to those of growth characteristics (Koury Filho et al, 2010;Regatieri et al, 2011). Boligon et al (2011) reported that the inclusion of VS in the selection indexes is crucial and important to predict the possible changes in relation to the mature size of beef cows.…”