Raysildo Barbosa Lôbo

University of São Paulo, San Paulo, São Paulo, Brazil

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Publications (224)129.58 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: The Tabapuã breed is a beef cattle Brazilian breed known for its sexual precocity and desirable characteristics for tropical conditions. However, this is a newly formed breed and few studies have been conducted regarding genetic parameters and genetic trends for its reproductive traits. The objective of the present study was to estimate the genetic parameters, genetic trends, and relative selection efficiency for weaning weight adjusted to 210 d of age (W210), age at first calving (AFC), average calving interval (ACI), first calving interval (CI1), and accumulated productivity (ACP) among Tabapuã beef cattle. Pedigree data on 15,241 Tabapuã animals born between 1958 and 2011 and phenotype records from 7,340 cows born between 1970 and 2011 were supplied by the National Association of Breeders and Researchers (Associação Nacional de Criadores e Pesquisadores). Analysis through the least squares method assisted in defining the fixed effects that were considered within the models. The estimates for the genetic parameters were obtained through the REML, using a multitrait animal model. The likelihood ratio test applied for W210 was significant ( < 0.05) for the inclusion of maternal additive genetic and permanent environmental effects in the model. Genetic trends were calculated through linear regression of the EBV of the animals, according to the year of birth. The heritability estimates obtained ranged from 0.04 ± 0.03 for CI1 to 0.25 ± 0.05 for W210. The genetic correlations ranged from 0.004 ± 0.19 for W210-AFC and 0.93 ± 0.12 for ACI-CI1. The genetic trend was significant ( < 0.05) and favorable for CI1 and the maternal genetic effect of W210 and was significant ( < 0.05) and unfavorable for AFC, ACI, and ACP. The ACP could be used in the selection index to assist the breeding goal of improved productive and reproductive performance. The genetic trends indicated small and unfavorable genetic changes for AFC, ACI, and ACP in light of the recent implementation of a genetic breeding program for this breed.
    No preview · Article · Sep 2015 · Journal of Animal Science
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    ABSTRACT: The aim of this study was to estimate genetic parameters for accumulated productivity (ACP), first calving interval (CI1), second calving interval (CI2), and mean calving interval (MCI) in Nelore beef cattle. The ACP trait is a reproduction index and comprises the total number of calves born per dam, weight of weaned calves, and age of the dam at calving. Genetic parameters were estimated by the average information restricted maximum likelihood method in two-trait analyses. The average heritability estimate for ACP was 0.17 (0.03). For CI1, CI2, and MCI, the heritability estimates were 0.02, 0.02, and 0.06, respectively. Genetic correlations between ACP with CI1, CI2, and MCI were -0.16 ± 0.47, -0.29 ± 0.53, and -0.40 ± 0.27, respectively. Despite of the low heritability estimates obtained in our study, reproduction traits should be further studied and their inclusion in the selection criteria must be evaluated in order to improve the performance of females because these traits are of great economic importance in beef cattle. Accumulated productivity could contribute to decrease the mean calving interval in Nelore cattle.
    Full-text · Article · Sep 2015 · Tropical Animal Health and Production
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    ABSTRACT: Genetic breeding programs of beef cattle in Brazil are including new features, mainly related to reproductive efficiency. Thus, it is necessary to study the effectiveness of selection and quantify genetic gain for these traits in herds. This study estimated genetic and phenotypic parameters and genetic trends for reproductive traits used in breeding programs for Nelore beef cattle. The traits studied were the scrotal circumference (SC) at 365 and 450 days of age (SC365 and SC450), age at first calving (AFC) and gestation length, as a cow trait (GLcow) and a calf trait (GLcalf). The (co)variance components were obtained with the Restricted Maximum Likelihood Methodology in a single and double-trait analysis of the animal model. For scrotal circumference (SC365 and SC450), positive and favorable genetic gains were observed. For AFC, GLcow and GLcalf, the trends were favorable for selection, but without significant genetic gain. Selection for large SC may reduce AFC and improve female reproductive efficiency. The selection for reproductive traits (SC365, SC450, AFC and GL) may improve reproductive and productive efficiency of Nelore cattle, if used as a selection criterion.
    Full-text · Article · Jul 2015 · Ciência e Agrotecnologia
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    ABSTRACT: The objective of this study was to estimate genetic parameters for carcass traits measured by ultrasound at yearling (Y) and 18 months of age (post-yearling, PY) in order to identify the most appropriate age for the measurement of these traits used for the selection of Nellore beef cattle. In addition, genetic correlations were estimated between these carcass traits and between carcass and other economically important traits such as scrotal circumference, weight, hip height at 18 months of age, age at first calving, and first calving interval (FCI). The carcass traits were longissimus muscle area (LMA), backfat thickness (BF), and rump fat thickness (RF) recorded at two different ages (Y and PY). Gibbs sampling was applied to estimate the genetic parameters using multiple trait animal model. The estimates of posterior heritabilities and standard deviations (SD) for the carcass traits were 0.46, SD=0.06 (LMA_Y), 0.42, SD=0.07 (BF_Y), 0.60, SD=0.09 (RF_Y), 0.33, SD=0.06 (LMA_PY), 0.59, SD=0.08 (BF_PY), and 0.55, SD=0.09 (RF_PY). The genetic parameters obtained in this study suggest the existence of genetic variability in all carcass traits at both ages. Hip height was negatively correlated with BF_PY and RF_PY, indicating that selection of taller animals may lead to animals that will deposit less subcutaneous fat. Selection for growth and carcass traits will not affect FCI, except for an increase in BF_PY which will increase FCI in the long term, possibly due to a correlated response, once the genetic correlation is moderate (0.40, SD= 0.17), and the posterior heritability for FCI was relatively low (0.11, SD= 0.03). The traits LMA, BF and RF measured at Y and at PY are practically the same traits since the genetic correlation are 0.83 (SD= 0.06), 0.94 (SD= 0.02) and 0.72 (SD= 0.07), respectively. In conclusion, ultrasound carcass traits should respond rapidly to selection and can be recorded only in one age, at Y or at PY. Furthermore, there is no need to include the two subcutaneous fat thickness measures (BF and RF) in selection criteria since they are highly genetic correlated. Genetic progress for these carcass traits can be achieved without affecting the breeding value of animals for other economic traits, since the most of genetic correlation estimates are favorable and of low magnitude.
    Full-text · Article · Jul 2015 · Livestock Science
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    DESCRIPTION: Objetivou-se estimar parâmetros genéticos e tendências genéticas para características reprodutivas e de crescimento testicular em bovinos Guzerá.
    Full-text · Research · May 2015
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    Full-text · Article · Jan 2015
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    ABSTRACT: Objetivou-se estimar as herdabilidades para as características de carcaça de área de olho de lombo (AOL), espessura de gordura subcutânea (EG) e espessura de gordura subcutânea na garupa (EGP8), medidas por ultrassonografia, em bovinos da raça Nelore Mocho, criados em bioma Cerrado. As informações utilizadas foram provenientes de criatórios da raça Nelore Mocho, participantes do Programa Nelore Brasil, da Associação Nacional de Criadores e Pesquisadores (ANCP), localizados nos estados que representam as maiores áreas contínuas do bioma Cerrado. As estimativas de herdabilidade foram obtidas mediante análises bi-características, sob modelo animal, utilizando a estatística bayesiana por meio do aplicativo MTGSAM. As estimativas de herdabilidade foram de média magnitude para a AOL (0,25), EG (0,19) e EGP8 (0,25). Os resultados obtidos sugerem que as características de carcaça, avaliadas por ultrassonografia, apresentam grande variabilidade genética e podem ser incluídas em programas de melhoramento genético de bovinos da raça Nelore Mocho.
    Preview · Article · Jan 2015 · Ciência Rural
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    ABSTRACT: This study aimed to estimate genetic parameters and genetic trends for reproductive traits and testicular growth in Guzerá cattle. Variance components were estimated through two-trait analyses using the restricted maximum likelihood method. To age at first calving (AFC), first calving interval (FC1), gestation period (GP), and scrotal circumference at 365 and 450 days (SC365 and SC450, respectively) were included the random residual and additive genetic effects and the fixed effects of contemporary group. The covariates cows age at calving and AFC were included in the model for SC365 and SC450 (linear and quadratic effects) and for FC1 (linear effect), respectively. For GP, The random maternal genetic effects were also considered. Heritability estimates ranged from 0.08 ± 0.05 (FC1) to 0.48 ± 0.11 (GP). Genetic trends were significant (P <0.05) for all traits with the exception of the maternal genetic effect of GP. The SC365, SC450 and GP traits, could be used as selection criteria for presenting additive genetic variability sufficient to respond to the selec-tion process. The genetic correlation between AFC and scrotal circumferences (SC365 and SC450) indicates that selection for scrotal circumference in these ages, reduce the AFC of the females. © 2015, Universidade Federal Rural do Semi-Arid. All rights reserved.
    Full-text · Article · Jan 2015 · Revista Caatinga
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    ABSTRACT: The aim of this study was to estimate variance and covariance components for gestation length (GL), birth weight (BW), weaning weight (WW), and accumulated productivity (ACP), and their respective genetic trends for Nellore cattle raised in Brazil. The ACP trait is a reproduction index developed by the National Association of Breeders and Researchers (ANCP) and comprises the total number of calves born per dam, weight of weaned calves, and age of the dam at calving. A total of 25,085, 46,911, 50,044, and 7,351 observations were considered to analyze GL, BW, WW, and ACP. Genetic parameters were estimated by the Average Information Restricted Maximum Likelihood method in single and two-trait analyses. The average direct heritability estimates obtained in two-trait analyses were equal to 0.38±0.03 (GL), 0.25±0.02 (BW), 0.28±0.02 (WW), and 0.11±0.02 (ACP). The highest genetic correlation was found between BW and WW (0.36±0.05), followed by BW and ACP (0.20±0.09), and BW and GL (0.19±0.06). Significant direct genetic trends (P<0.001) were observed for GL, BW, and WW; equal to -0.027 days per year, 0.073 kg per year, and 0.8456 kg per year, respectively. Greater emphasis should be given to accumulated productivity and gestation length traits in order to increase the number and weight of weaned calves. As accumulated productivity presents low heritability estimates, genetic improvement through selection could be slow in the Nellore breed. Our study reports genetic progress for weaning weight, since its genetic trend has increased over the years. Similar genetic trend for birth weight was observed, which may be a consequence of selection towards higher body weights at older ages.
    Full-text · Article · Dec 2014 · Livestock Science

  • No preview · Article · Aug 2014 · SEMINA: CIENCIAS AGRARIAS
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    N T Pegolo · R B Lôbo · H N De Oliveira
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    ABSTRACT: Selection in heterogeneous environments has had increasing importance since production system definition is linked to economic instability and climatic changes. The aim of this work was to compare environmental sensitivity between sexes and along development. Data were collected in 366 Brazilian herds for the Brazilian Nelore Cattle Breeding Program with 1,110,662 body weights from 408,416 animals. Eight different analyses were applied using a principal component analysis of the cubic polynomial random regression coefficients' estimates, with a sex-separated developmental reaction norm approach. Results showed different estimated eigenvalues for coefficients of different orders in different sexes. Eigenvalues of level and slope coefficients explained a great majority of the variation of Nelore beef cattle weight in Brazilian production systems, with a distinguished increase of slope coefficient eigenvalue in female analyses along the age axis when compared to male analyses.
    Full-text · Conference Paper · Aug 2014
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    ABSTRACT: Genetic parameters for ultrasound carcass and growth traits were estimated by factor analyses used as a special case of structural equation models in a Bayesian framework. Data were analyzed using the standard multi-trait mixed models with sire model (Model 1; SMTMs). The factor analyses (FA) were done by four alternative FA models. The results indicate that FA models could estimate breeding values of the bulls practically equal relative to the SMTMs. The FA models may reduce the ranking model and give a parsimonious estimation of genetic covariance matrices. Although the FA models may reduce covariance matrices ranks and give a parsimonious estimation of dispersion parameters, these models have to be tested in order to implement the benefits, as an alternative of SMTMs. INTRODUCTION The continuous increasing of records and traits in genetic evaluation schemes for beef cattle generally involve multi-trait mixed models analyses, which requires genetic links among these traits. It leads to statistical and computational difficulties in estimating the genetic (co)variance matrix needed to have accurate breeding values. Structural equation models (SEM, e.g., Wright 1921) are multivariate models adapted to obtain more parsimonious quantitative genetic mixed-effects models (Gianola and Sorensen (2004)). SEM can be understood like a term that does not denote a particular statistical technique, but a number of techniques and procedures used together aiming to model some covariance structure. In animal breeding, specifically in this paper, SEM was used to model the estimated genetic and residual (co)variance matrix. These models can be viewed as an extension of the standard multi-trait mixed models (SMTM, e.g., Henderson and Quaas (1976)) that are capable of expressing functional networks among traits. Gianola and Sorensen (2004) discussed the use of recursive and simultaneous equation models (special case of SEM) acting on phenotypes. Alternatively, the Factor Analysis (FA) may be used as another special case of SEM to represent the genetic covariance matrix (Jӧreskog (1970)). FA can be used to model genetic effects in the context of a multivariate linear mixed model for reducing the dimension of the estimated genetic (co)variance matrix, obtaining a more parsimonious model without reducing dimension of the original records (e.g., de los Campos and Gianola (2007)). The objective of this study was to consider FA (a special case of SEM) acting on genetic and residual effects separately to estimate genetic and residual (co)variance parameters modeling traits and estimating genetic parameters in genetic improvement of Brazilian Nelore beef cattle.
    Full-text · Conference Paper · Aug 2014
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    ABSTRACT: Beef cattle producers in Brazil use body weight traits as breeding program selection criteria due to their great economic importance. The objectives of this study were to evaluate different animal models, estimate genetic parameters, and define the most fitting model for Brahman cattle body weight standardized at 120 (BW120), 210 (BW210), 365 (BW365), 450 (BW450), and 550 (BW550) days of age. To estimate genetic parameters, single-, two-, and multi-trait analyses were performed using the animal model. The likelihood ratio test was verified between all models. For BW120 and BW210, additive direct genetic, maternal genetic, maternal permanent environment, and residual effects were considered, while for BW365 and BW450, additive direct genetic, maternal genetic, and residual effects were considered. Finally, for BW550, additive direct genetic and residual effects were considered. Estimates of direct heritability for BW120 were similar in all analyses; however, for the other traits, multi-trait analysis resulted in higher estimates. The maternal heritability and proportion of maternal permanent environmental variance to total variance were minimal in multi-trait analyses. Genetic, environmental, and phenotypic correlations were of high magnitude between all traits. Multi-trait analyses would aid in the parameter estimation for body weight at older ages because they are usually affected by a lower number of animals with phenotypic information due to culling and mortality.
    Full-text · Article · Jul 2014 · Tropical Animal Health and Production
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    ABSTRACT: The purpose of this study was to measure the efficiency of optimized mating in acquiring genetic progress in Nelore cattle. It has been measured genetic values of 7.664 Nelore animals, children of 179 bulls and 2.966 cows, coming from a property which was part of the Nelore Brazil Program of Breeder and Research National Association (ANCP). In order to analyze the optimized mating efficiency considered the predictions of EPD's (Expected Progeny Difference) of breeding and growth traits, in animals that were born between 2000 and 2009, distributed in three real scenes: (I) animals coming from mating and selected parents based in morphologic and racial aspects (2000, 2001 and 2002 crops); (II) animals coming from mating based in morphologic and racial aspects, but with previously selection of oriented breeding by EPD's and in genealogic parentage (2003 to 2007 crops); (III) animals coming from optimized mating, using PAG Genetics Management®, in which they match the breeders indicated for a certain matrix, prioritizing EDP's, endogamy and the sequence in morphologic and racial aspects (2008 and 2009 crops). There has been a superior genetic gain for the majority of the analyzed traits, when taking the PAG Genetics Management® software, and inserted in property selection criterion, verifying that the optimized mating was an efficient tool capable of increasing the genetically superior animals number, accelerating the genetic progress in the cattle.
    No preview · Article · May 2014
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    ABSTRACT: The objective of the present study was to analyze the phenotypic inter-relationships between growth, feed intake and carcass traits in polled Nellore cattle, as well as to determine which bulls produced the most efficient progeny. The experiment was conducted in the feedlot of the Guaporé Pecuária (Livestock) Company, OB Brand. The following traits were analyzed: initial live weight (ILW); final live weight (FLW); average daily gain (ADG); dry matter intake (DMI); gain:feed (G:F); residual feed intake (RFI); rib-eye area (REA); rump fat thickness (RF); backfat thickness at the 12th-13th rib (BF); weighted fat score (WF); and intramuscular fat percentage (IMF). Both univariate and multivariate analyses were performed to analyze the inter-relationships between the studied traits. No significant phenotypic associations were observed between growth, carcass traits and residual feed intake, while the correlation between RFI and G:F was negative. Therefore, RFI may be used to select more nutritionally efficient animals without compromising growth or adult size. The selection of bulls with progeny showing low residual feed intake is recommended, as selection for low RFI tends to improve feed efficiency without compromising growth and development.
    Full-text · Article · Mar 2014 · Revista Ciencia Agronomica
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    ABSTRACT: Records of birth weight (BW) and weights standardized to 210 (W210); 365 (W365) and 550 (W550) of age in the Nellore breed were used to estimate variance components of genetic effects and predict genetic values of sires. The model included the fixed effects of contemporary group and cow age at calving as co-variable, and the additive and maternal genetic, permanent maternal environmental, and temporary environmental random effects. Estimates of means and standard deviations for BW, W210; W365 and W550 were 32.76 ± 3.74; 184.30 ± 29.02; 240.31 ± 41.85 and 322.12 ± 60.77, respectively. A significant additive genetic variability was detected for all weights. The permanent maternal environmental variance showed greater relevance on weaning weight, and it was practically inexistent after weaning. For the maternal genetic variance, the estimate for birth weight was more significant as compared with weaning weight. The estimated heritability values for BW, W210; W365 and W550 were 0.37 ± 0.02; 0.36 ± 0.03; 031 ± 0.01 and 0.38 ± 0.02, respectively. Genetic correlations between birth weight and other weights were of low magnitude, with high values of weights at other ages. The use of sires of higher genetic value for total maternal effect makes it possible to use sires that are more positive for weaning weight and also for year and yearling weight.
    Full-text · Article · Jan 2014 · Revista Brasileira de Saude e Producao Animal
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    Full-text · Conference Paper · Jan 2014
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    Full-text · Conference Paper · Sep 2013

  • No preview · Conference Paper · Sep 2013
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    ABSTRACT: Components of (co)variance and genetic parameters were estimated for adjusted weights at ages 120 (W120), 240 (W240), 365 (W365) and 450 (W450) days of Polled Nellore cattle raised on pasture and born between 1987 and 2010. Analyses were performed using an animal model, considering fixed effects: herd-year-season of birth and calf sex as contemporary groups and the age of cow as a covariate. Gibbs Samplers were used to estimate (co)variance components, genetic parameters and additive genetic effects, which accounted for great proportion of total variation in these traits. High direct heritability estimates for the growth traits were revealed and presented mean 0.43, 0.61, 0.72 and 0.67 for W120, W240, W365 and W450, respectively. Maternal heritabilities were 0.07 and 0.08 for W120 and W240, respectively. Direct additive genetic correlations between the weight at 120, 240, 365 and 450 days old were strong and positive. These estimates ranged from 0.68 to 0.98. Direct-maternal genetic correlations were negative for W120 and W240. The estimates ranged from -0.31 to -0.54. Estimates of maternal heritability ranged from 0.056 to 0.092 for W120 and from 0.064 to 0.096 for W240. This study showed that genetic progress is possible for the growth traits we studied, which is a novel and favorable indicator for an upcoming and promising Polled Zebu breed in Tropical regions. Maternal effects influenced the performance of weight at 120 and 240 days old. These effects should be taken into account in genetic analyses of growth traits by fitting them as a genetic or a permanent environmental effect, or even both. In general, due to a medium-high estimate of environmental (co)variance components, management and feeding conditions for Polled Nellore raised at pasture in tropical regions of Brazil needs improvement and growth performance can be enhanced.
    Full-text · Article · Sep 2013 · PLoS ONE

Publication Stats

1k Citations
129.58 Total Impact Points

Institutions

  • 1995-2015
    • University of São Paulo
      • • Ribeirão Preto School of Medicine (FMRP)
      • • Departamento de Genética (LGN) (ESALQ)
      San Paulo, São Paulo, Brazil
  • 2014
    • Universidade Federal de Mato Grosso (UFMT)
      • Instituto de Ciências Agrárias e Ambientais (ICAA)
      Vila Real do Senhor Bom Jesus de Cuiabá, Mato Grosso, Brazil
  • 1999-2013
    • Universidade de Ribeirão Preto
      Entre Rios, São Paulo, Brazil
  • 2011
    • São Paulo State University
      • Faculty of Agriculture and Veterinary Sciences
      San Paulo, São Paulo, Brazil
  • 2008
    • State University of Mato Grosso
      Vila Real do Senhor Bom Jesus de Cuiabá, Mato Grosso, Brazil