Estudo genético-quantitativo de características de crescimento, reprodução, carcaça e escores visuais em um rebanho nelore sob seleção para precocidade sexual.

Resumo: A eficiência reprodutiva de bovinos, bem como a antecipação da puberdade, traz efeitos positivos nos índices zootécnicos e também na rentabilidade dos sistemas de produção. Assim, objetivou-se neste estudo estimar os parâmetros genéticos e tendências genéticas e fenotípicas para características de crescimento, carcaça e reprodutivas, em um rebanho de bovinos da raça Nelore sob seleção para precocidade sexual, tendo como critério de seleção as características de idade à primeira concepção e ao primeiro parto. Além disso, objetivou-se também avaliar, através de análises multivariadas, dentre as características de crescimento, carcaça e escores visuais, quais discriminam a prenhez precoce. Foram estimados os parâmetros genéticos para as características de peso a nascer (PN), peso aos 120 (P120), 210 (P210), 365 (P365) e 450 (P450) dias de idade, ganho médio diário pré e pós-desmame (GMDPRE e GMDPOS), área de olho de lombo (AOL), espessura de gordura subcutânea (EG), espessura de gordura subcutânea na garupa (EGP8), marmoreio (MAR), peso da carcaça quente (PCQ), peso da porção comestível (PPC), perímetro escrotal aos 365 (PE365) e 450 (PE450) dias de idade, período de gestação (PG), período de serviço (PS), intervalo de parto (IDP), fertilidade real (FR), produtividade acumulada (PAC), relação do peso à desmama (RD), idade à primeira concepção (IPC) e idade ao primeiro parto (IPP). Os dados foram fornecidos pela Fazenda Vera Cruz e pelo Programa de Melhoramento Genético Nelore Brasil, coordenado pela Associação Nacional de Criadores e Pesquisadores (ANCP). Os componentes de (co)variância foram obtidos por meio do método de Máxima Verossimilhança Restrita, disponível no pacote BLUPF90, em análises uni e bicaracterísticas, utilizando o modelo animal. As estimativas de herdabilidade obtidas para PN (0,39), P120 (0,32), P210 (0,31), P365 (0,33), P450 (0,34), GMDPRE (0,23), GMDPOS (0,27), AOL (0,39), EG (0,34), EGP8 (0,34), MAR (0,38), PCQ (0,39), PPC (0,39), PE365 (0,33), PE450 (0,33), PG (0,23), PS (0,34), IDP (0,23), FR (0,21), PAC (0,23), RD (0,25), IPC (0,21) e IPP (0,24) indicaram possibilidade de seleção genética e incorporação no rebanho. As estimativas de herdabilidade materna para PN (0,06), P120 (0,08), P210 (0,07), P365 (0,05), P450 (0,11), GMDPRE (0,12), GMDPOS (0,08), PE365 (0,07) e PE450 (0,03) indicaram efeitos genéticos das matrizes no desempenho das progênies até a fase pós-desmame, para características de crescimento. As correlações genéticas estimadas entre as características de crescimento, entre crescimento e carcaça, entre as características de carcaça e entre as reprodutivas apresentaram valores de moderada magnitude, sendo todos favoráveis. As características indicadoras de precocidade sexual apresentaram coeficientes de correlação genética variando de -0,51 a - 0,15; de -0,62 a -0,33; e de -0,61 a 0,14, com as características de crescimento, carcaça e reprodutivas, respectivamente. Os coeficientes de correlação genética foram, na maior parte dos casos, favoráveis. As tendências genéticas obtidas no presente estudo demonstraram, de modo geral, a eficácia da utilização dos critérios de seleção adotados, com ganhos genéticos satisfatórios. A seleção para precocidade sexual, com base na idade à primeira concepção, deverá promover mudanças genéticas no sentido contrário nas características de crescimento, carcaça e reprodutivas, sendo este efeito desejável. As características de peso ao nascer, espessura de gordura, ossatura, musculatura, profundidade, inserção da cauda e garupa foram as que apresentaram maior poder de discriminação para a prenhez precoce. Assim, essas características podem ser utilizadas como critérios de direcionamento de manejo e tomada de decisões práticas, a fim de possibilitar que os animais expressem prenhez precoce, orientando o criador na seleção prática de fêmeas para precocidade sexual. Abstract: The reproductive efficiency in cattle herds, as well as the anticipation of puberty, has positive effects on zootechnical indexes and on the profitability of production systems. Thus, the aim of this study was to estimate the genetic parameters and the genetic and phenotypic trends for growth, carcass, and reproductive traits in a Nellore cattle herd under selection for sexual precocity, given age at first conception and age at first calving as selection criterion. Furthermore, this study also aimed to evaluate, using multivariate analyzes, which traits, among growth, carcass and visual scores, better discern early pregnancy. Genetic parameters were estimated for birth weight (BW), weight at 120 (W120), 210 (W210), 365 (W365) and 450 (W450) days of age, average daily gain pre-weaning and post-weaning (ADGPRE e ADGPOS), rib eye area (REA), backfat thickness (BF), rump fat thickness (RF), marbling (MAR), hot carcass weight (HCW), weight of edible portion (WEP), scrotal circumference at 365 (SC365) and 450 (SC450) days of age, gestation length (LG), days open (DO), calving interval (CI), real fertility (RF), cumulative productivity (CP), relation to weaning (RW), age at first conception (AFCo) and age at first calving (AFCa). Data were provided by Vera Cruz Ranch and the National Association of Breeders and Researchers (ANCP). The covariance components were estimated using the Restricted Maximum Likelihood method, available on BLUPF90 package, in univariate and bivariate analyzes using animal model. The heritability estimated for BW (0.39), W120 (0.32), W210 (0.31), W365 (0.33), W450 (0.34), ADGPRE (0.23), ADGPOS (0.27), REA (0.39), BF (0.34), RF (0.34), MAR (0.38), HCW (0.39), WEP (0.39), SC365 (0.33), SC450 (0.33), LG (0.23), DO (0.34), CI (0.23), RF (0.21), CP (0.25), RW (0.26), AFCo (0.21) and AFCa (0.24) indicated the possibility of genetic selection. The maternal heritability estimated for BW (0.06), W120 (0.08), W210 (0.07), W365 (0.05), W450 (0.11), ADGPRE (0.12), ADGPOS (0.08), SC365 (0.07) and SC450 (0.03) indicated genetic effects of the dam on the progeny performance, until the post-weaning phase, for growth traits. The genetic correlations estimated within growth traits, between growth and carcass traits, within carcass traits and reproductive trait were favorable and of moderate magnitude. The traits that indicate sexual precocity showed genetic correlation coefficients ranging from -0.51 to -0.15, -0.62 to -0.33 and -0.61 to 0.14, between growth, carcass and reproductive traits, respectively. Genetic correlation coefficients were, in most cases, favorable. The genetic trends obtained showed, in general, the effectiveness of the adopted selection criteria with satisfactory genetic gains. Selection for sexual precocity, based on age at first conception, shall promote opposite direction genetic changes on growth, carcass and reproductive traits, which is the desirable effect. Birth weight, fat thickness, bone structure, musculature, rib depth, tail and rump insertion were the traits that presented greater discrimination power for early pregnancy. Thus, these traits can be used as such management targeting criteria and decision-making practices, in order to enable animals to express early pregnancy, guiding the breeders in selecting females for sexual precocity.Dissertação (Mestrado em Zootecnia) - Universidade Federal de Goiás, Goiânia, 2017. Orientador: Cláudio Ulhoa Magnabosco

Genetic association between growth and maternal ability traits in Nelore cattle.

Although body weight traits have been widely used in animal breeding programs due to their importance to beef cattle systems, the use of maternal ability traits, which highly affect the profitability in livestock, is still incipient. As the knowledge of genetic parameters of economic important traits may aid genetic gains, this study was carried out to estimate genetic parameters for weight at 120 and 210 days of age (W120 and W210), pre-weaning average daily gain (PreDG), real fertility (RF), accumulated productivity (AP) and weaning rate (WR). The data set was obtained from Vera Cruz Ranch, a cattle ranch that participates in the Brazilian National Association of Breeders and Researchers (ANCP). Heritabilities and correlations were estimated using univariate and bivariate linear mixed model. The model included contemporary groups (year and season of birth, sex and management group), cow age at calving (in classes and as linear and quadratic covariate) as fixed effects, and genetic and residual components as random effects. Estimates of heritability for between growth and maternal ability traits ranged from 0.22 to 0.32, indicating that they could be improved by direct selection. Estimates of genetic correlation between W120-W210, W120-PreDG, W120-RF, W120-AP, W120-WR were 0.90, 0.54, 0.16, 0.45 and 0.24, respectively. Estimates of genetic correlation between W210-PreDG, W210-RF, W210-AP, W210-WR were 0.63, 0.27, 0.53 and 0.21, respectively. Estimates of genetic correlation between PreDG-RF, PreDG-AP, PreDG-WR were 0.23, 0.16 and 0.28, respectively. Positive genetic correlations were observed between RF, CAP and RD (0.28 to 0.78). Therefore, genetic selection having one of these characteristics as the criterion of selection will lead to an indirect response in the same direction in the others. These results indicate that the use of animals with high breeding values for weights and pre-weaning gain may lead to increase maternal ability traits due to correlated responses. Such responses tend to be bigger when using weight compared to the pre-weaning gain

Correlation between residual feed intake and daily water intake in confined nellore bulls.

Identifying efficient animals is an alternative to reduce food costs and natural resources used in farming. The objective of this study was to identify the correlation between Residual Feed intake (RFI) and Daily Water Consumption (DWC) in Nellore cattle. The work was realized at Núcleo Regional of Embrapa Cerrados, in June, 2017. Were used 44 bulls, aged between 18 and 21 months and initial weight of 455 kg. The diet was given twice daily, with corn silage: concentrate of 60:40. Feed intake was obtained in the feeders of Intergado System. Daily water consumption was measured by water drinked in electronic drinking fountains coupled to the automatic scales (Intergado System TM) plus water from feed. The RFI was calculated by means of the difference between the observed dry matter intake (DMIobs) and the expected dry matter intake (DMIexp) based on live weight (LW) and average daily gain (ADG). The descriptive statistics, comparison of means by Tukey test at 5% probability and Pearson correlations for the study traits were performed using software R (version 3.3.2). Groups of high, low and mean RFI were formed with one Standar Desviation of the mean RFI. The water consumption averaged 38.9 L / day, with a standard deviation of 6.1 L / d, and a minimum value of 30.0 and a maximum of 62.2 L / day. The RFI had zero and standard deviation of 1.01 kg / d, with a minimum value of -2.38 and a maximum of 2.7. The correlation between RFI and DWC was .24, being considered of low magnitude. It was not observed differences between RFI groups, with means of 37.0, 38.8 and 42.3 L / d, respectively, to Low, Medium and High RFI Groups. We concluded that water intake was not correlated with RFI in Nellore bulls confined in the early dry season of Brazil

ASSOCIAÇÃO ENTRE EFICIÊNCIA ALIMENTAR E PRECOCIDADE SEXUAL EM FÊMEAS DA RAÇA NELORE.

Abstract: The aimed of this study was to evaluate the relationship between feed efficiency and sexual precocity traits in Nellore heifers. The reproductive and feed efficiency data of 151 Nellore females were used, from which were collected: RFI, dry matter intake (DMI), feed conversion (FC), feed efficiency (FE), uterine tract score (UTS) and early pregnancy (GEST), as a binary trait. Correlation analysis and analysis of variance between the linear traits (RFI, DMI, FC, FE) was performed. For the threshold traits (UTS and GEST), the correlation coefficient was obtained considering coefficient of determination? square root of an adjusted logistic regression model. To verify the association between these traits and the RFI classifications, a Chi-square test was performed. The correlation between DMI and feed efficiency traits, demonstrate that RFI, FC and FE can be used as an indicator of the animals that presented lower consumption. Among feed efficiency and sexual precocity traits, low and no significant correlations were observed. For UTS and GEST, a low magnitude correlation was observed. Among RFI classes, significant differences (P <0.05) were observed for DMI and FC. For sexual precocity traits and RFI classes, https://proceedings.science/p/105322no significant difference was observed. Selection for feed efficiency does not influence the performance for sexual precocity in Nellore female

ASSOCIAÇÃO ENTRE MACIEZ DA CARNE E CARACTERÍSTICAS DE CARCAÇA EM BOVINOS DA RAÇA NELORE.

Abstract: The aim of this study was evaluate the correlation between meat tenderness (WBSF) and carcass traits (rib eye area (REA), backfat thickness (BF), rump fat thickness (RF)) in Nellore cattle and also estimate if there are differences regarding carcass evaluation considering segregation groups for WBSF. The data set is from 654 Nellore animals, born between 2006 and 2015. The correlation analysis among the traits was conducted using R program and the variance analysis was estimated to verify the association between meat tenderness and carcass traits. The genetic correlations between WBSF and REA, BF and RF were of a low magnitudes (-0.13, -0.04 and 0.03, respectively). The significant analysis showed statistical difference only among the AOL and WBSF group. The results support the conclusion that carcass selection will cause little influence in meat tenderness, because WBSF also is affected by ante and post mortem factors

Parâmetros genéticos para características de carcaça e eficiência alimentar em bovinos da raça Guzerá.

Objetivou-se estimar os parâmetros genéticos para características de eficiência alimentar, consumo alimentar residual, consumo de matéria seca e de carcaça, área de olho de lombo, espessura de gordura subcutânea, espessura de gordura subcutânea na garupa (EGP8), em bovinos da raça Guzerá, bem como verificar as associações entre tais características de importância econômica.Evento online

AVALIAÇÃO DA TAXA DE PRENHEZ EM PROGRAMA DE IATF USANDO SÊMENS DE DIFERENTES TOUROS DA RAÇA NELORE.

Diversas tecnologias reprodutivas têm sido inseridas no sistema de produção, a fim de minimizar falhas na detecção de estro e também otimizar a taxa de prenhez. Entre elas, estão a inseminação artificial em tempo fixo (IATF), que consiste no uso de protocolos hormonais voltados a simulação e regulação do ciclo estral das vacas, possibilitando a realização da inseminação artificial em um período pré-determinado. Além das vantagens reprodutivas, o uso de IATF permite maximizar a disseminação de reprodutores avaliados e com mérito genético superior, favorecendo o ganho genético do rebanho, desde que sejam realizados acasalamentos geneticamente dirigido, obtendo assim animais com maior potencial produtivo. Entretanto, além do touro, outros fatores podem interferir na taxa final de prenhez. Diante do exposto, objetivou-se com esse estudo, identificar as fontes de variação na taxa de prenhez em um programa de IATF utilizando sêmen de diferentes touros da raça Nelor

Avaliação de crescimento, reprodução e carcaça de raças zebuínas em teste de desempenho.

Objetivou-se avaliar características de crescimento, reprodução e carcaça em touros jovens das raças Nelore e Tabapuã, a fim de verificar se há relação de raças com o desempenho obtido em Teste de Desempenho de Touros Jovens