Phenotypic association between residual feed intake and carcass traits of young nelore bulls

The purpose of this study was to estimate the phenotypic associations between residual food intake (RFI) and carcass traits, evaluated by ultrasonography, of young Nellore bulls. Information about 53 young Nelore bulls, pure origin (PO), participants in the Individual Performance Test of Nelore Bulls, carried out at the Capim Branco experimental farm of the Federal University of Uberlândia (UFU) were used for this purpose. It was evaluated the characteristics of residual feed intake (RFI), rib eye area (REA), marbling (MAR) and fat thickness (FT). In order to estimate the Spearman and Pearson correlation coefficients, the SAS program was used. Regarding the influence of the RFI classes (low RFI, medium RFI and high RFI) on carcass traits, an out analysis of variance was carried out using the least squares method. It was verified that there was no phenotypic association between RFI and the characteristics of REA and MAR, but the relation between FT and the phenotypic association revealed a medium magnitude. However, when evaluating the RFI classes, it was observed that there were no significant differences of the RFI classes with the carcass traits (REA, FT and MAR). It is recommended that new studies are carried out to verify if the selection for RFI does not result in damages to the finishing of carcass in Nelore cattle.

Consumption of dry matter observed and predicted by the nutritional systems in senepol bulls kept in confinement / Consumo de matéria seca observado e previsto pelos sistemas nutricionais em touros senepol mantidos em confinamento

The objective was to compare the dry matter consumption (CMS) observed, through the use of the GrowSafe® electronic system, with that predicted by the BR-Corte (2010 and 2016) and NRC (2000) nutritional systems in confined Senepol bulls. To this end, 24 Senepol Bulls were used in a completely randomized design, uncastrated with an average initial weight of 368 kg and 16 months of age. The evaluation of the accuracy and approximation of the CMS estimates by the nutritional systems was adjusted by the simple linear regression model and the decomposition of the mean square of the prediction error (QMEP). The mean CMS observed was 10.33 kg.day-1, higher than the values predicted by the nutritional systems, in which the values predicted by the NRC (2000) and BR-Corte 2010 and 2016 underestimated the CMS by 29.62, 6.19 and 2.03%, respectively. The verification of QMEP and its decomposition made it possible to infer the proximity of the values predicted by the BR-Corte 2010 and 2016 models and the values observed, which presented a better adjustment in relation to the NRC. Surprisingly the values predicted by the NRC, created from a database with Bos taurus animals, showed greater distance from the values predicted and observed, and it was expected greater accuracy of the NRC models for this category and animal breed. It is concluded that the BR-Corte 2016 was the most appropriate model to estimate the CMS of confined Senepol bulls.

Objetivou-se comparar o consumo de matéria seca (CMS) observado, por meio do uso do sistema eletrônico GrowSafe®, com o predito pelos sistemas nutricionais BR-Corte (2010 e 2016) e NRC (2000) em touros da raça Senepol em confinamento. Para isso, foram utilizados 24 Touros da raça Senepol em delineamento inteiramente casualizado, não castrados com peso inicial médio 368 kg e 16 meses de idade. A avaliação da exatidão e aproximação das estimativas do CMS pelos sistemas nutricionais foi ajustada pelo modelo de regressão linear simples e decomposição do quadrado médio do erro de predição (QMEP). O CMS médio observado foi de 10,33 kg.dia-1, valor superior aos valores preditos pelos sistemas nutricionais, no qual os valores preditos pelo NRC (2000) e BR-Corte 2010 e 2016 subestimaram o CMS em 29,62, 6,19 e 2,03%, respectivamente. A verificação do QMEP e sua decomposição possibilitou inferir sobre a proximidade dos valores preditos pelos modelos BR-Corte 2010 e 2016 e os valores observados, os quais apresentaram melhor ajuste em relação ao NRC. Surpreendentemente os valores preditos pelo NRC, criado a partir de banco de dados com animais Bos taurus, apresentou maior distanciamento dos valores preditos e observados, sendo que era esperada maior precisão dos modelos NRC para esta categoria e raça animal. Conclui-se que o BR-Corte 2016 foi o modelo mais adequado para estimar o CMS de touros da raça Senepol em confinamento.

Análise bayesiana para características de carcaça avaliadas por ultrassonografia de bovinos da raça Nelore Mocho, criados em bioma Cerrado / Bayesian analysis for carcass traits in Polled Nelore

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.

The purpose of this study was to estimate the genetic parameters for carcass traits of longissimus muscle area (LMA), backfat thickness (BF) and rump fat thickness (RF), measured by ultrasound in Polled Nelore cattle raised in the Cerrado biome. The data set was obtained from bovines Polled Nelore, proceeding from participant farms of the Nelore Brazil Program of the National Association of Breeders and Researchers, raised on pasture, from the Brazilian states that have the largest continuous areas of the Cerrado. Heritabilities were estimated by Gibbs Sampling using the MTGSAM software (Multiple Trait using Gibbs Sampler under Animal Model). The heritability estimates were 0.30, 0.17 and 0.25 for LMA, BF and RF, respectively. The results indicate that carcass traits have high genetic variability and should be included in breeding programs.

Análise da eficiência dos acasalamentos otimizados na obtenção de progresso genético em um rebanho bovino da raça nelore / The efficiency of optimized mating analysis in obtaining genetic progress in nelore cattle

O objetivo deste trabalho foi avaliar a eficiência dos acasalamentos otimizados na obtenção de progresso genético em um rebanho bovino da raça Nelore. Foram avaliados valores genéticos de 7.664 animais, filhos de 179 touros e 2.977 vacas, provenientes de um criatório participante do Programa Nelore Brasil da Associação Nacional de Criadores e Pesquisadores (ANCP). Para a análise da eficiência dos acasalamentos otimizados considerou-se as predições das DEPs (Diferença Esperada na Progênie) de características de reprodução e crescimento, de animais nascidos no período de 2000 a 2009, distribuídos em três cenários reais: (I) animais oriundos de acasalamentos baseados em aspectos morfológicos e raciais (safras 2000 a 2002); (II) animais oriundos de acasalamentos baseados em aspectos morfológicos e raciais, mas com a seleção prévia dos reprodutores orientada pelas DEPs e ascendência genealógica (safras 2003 a 2007); (III) animais oriundos de acasalamentos otimizados, utilizando o software PAG Gestão Genética®, pelo qual se relacionam os reprodutores melhores indicados para cada reprodutriz, priorizando as DEPs (safras 2008 e 2009). Foi constatado maior ganho genético para a maioria das características analisadas, quando utilizado o software PAG Gestão Genética®, confirmando a estratégia de acasalamento otimizado como eficiente ferramenta para aumentar o número de animais geneticamente superiores, acelerando o progresso genético dentro do rebanho.

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.

Bayesian inference in genetic parameter estimation of visual scores in Nellore beef-cattle

The aim of this study was to estimate the components of variance and genetic parameters for the visual scores which constitute the Morphological Evaluation System (MES), such as body structure (S), precocity (P) and musculature (M) in Nellore beef-cattle at the weaning and yearling stages, by using threshold Bayesian models. The information used for this was gleaned from visual scores of 5,407 animals evaluated at the weaning and 2,649 at the yearling stages. The genetic parameters for visual score traits were estimated through two-trait analysis, using the threshold animal model, with Bayesian statistics methodology and MTGSAM (Multiple Trait Gibbs Sampler for Animal Models) threshold software. Heritability estimates for S, P and M were 0.68, 0.65 and 0.62 (at weaning) and 0.44, 0.38 and 0.32 (at the yearling stage), respectively. Heritability estimates for S, P and M were found to be high, and so it is expected that these traits should respond favorably to direct selection. The visual scores evaluated at the weaning and yearling stages might be used in the composition of new selection indexes, as they presented sufficient genetic variability to promote genetic progress in such morphological traits.

Bayesian inference on field data for genetic parameters for some reproductive and related traits of Nellore cattle (Bos indicus)

We used Gibbs sampling in single and two-trait animal models to estimate genetic parameters for some reproductive and related traits of Nellore cattle (Bos indicus). Female traits were age at first calving (AFC), cumulative productivity (CP) and adult weight (AW). For males, scrotal circumferences at 365 and 450 days of age were analyzed. Gibbs sampling using the Multiple Trait using Gibbs Sampling under Animal Model (MTGSAM) program of Van Tassel and Van Vleck was used to estimate the (co) variance components of the traits and conduct genetic analyses. Heritabilities were AFC = 0.26, AW = 0.36 and CP = 0.25 under the single-trait animal model. The mean, mode and median estimates for genetic parameters obtained from the marginal posterior distributions were similar for all traits except AW, which presented lower values for the mode than the mean and median. However, the marginal posterior distributions for the traits studied presented a tendency toward normality. Favorable, but low, negative genetic correlations were found between male scrotal circumference and female age at first calving. The reproductive traits showed medium-magnitude heritabilities, which indicates that these traits should respond to selection and therefore should be included in genetic improvement programs.

Bayesian inference in a quantitative genetic study of growth traits in Nelore cattle (Bos indicus)

The objective of this study was to estimate (co)variance components and genetic parameters for weights (W) and scrotal circumferences (SC) at 365 and 450 days of age, of Nelore (Bos indicus) cattle, using Bayesian inference in single and multiple-trait animal models. The fitted linear models included, besides the animal and residual random effects, the contemporary group (herd-year-season-sex-management group) and age-of-dam as "fixed effects". The analyses were carried out using a Gibbs sampler implemented through the MTGSAM program. The heritabilities (in parentheses) obtained fitting single-trait models were W365 (0.49), W450 (0.52), SC365 (0.68) and SC450 (0.66). Estimates of means, modes and medians for genetic parameters obtained from marginal posterior distributions were similar for all traits. The W365 and SC365 can be considered as suitable traits to be included as selection criteria in genetic improvement programs, not only because of their relatively high heritabilities but also due to the fact that they can be measured when the animals are relatively young compared to the corresponding traits W450 and SC450. The Bayesian approach appears to be an appropriate alternative for estimating genetic parameters, and has the advantage over point estimation methods of allowing inferences on marginal posterior distributions.