Crescimento de codornas de diferentes grupos genéticos por meio de modelos não lineares

The objectives were to conduct a genetic evaluation of residual feed intake (RFI) and residual feed intake adjusted for fat (RFIFat) and to analyse the effect of selection for these traits on growth, carcass and reproductive traits. Data from 945 Nellore bulls in seven feed efficiency tests in a feedlot were analysed. Genetic evaluation was performed using an animal model in which the feed efficiency test and age of the animal at the beginning of the test were considered as a systematic effect. Direct additive genetic and residual effects were considered as random effects. Correlations and genetic gains were estimated by two-trait analysis between feed efficiency measures (RFI and RFIFat) and other traits. Feed conversion showed low heritability (0.06), but dry matter intake (DMI), average daily gain, RFI, RFIFat, metabolic body weight and scrotal circumference measured at 450 days of age (SC450) showed moderate to high heritability (0.49, 0.28, 0.33, 0.36, 0.38 and 0.80, respectively). Similarly, ribeye area, backfat thickness, rump cap fat thickness, marbling score and subcutaneous fat thickness also had high heritability values (0.46, 0.37, 0.57, 0.51 and 0.47, respectively). Genetic correlations between RFI and SC450 were null, and between RFIFat and SC450 were strongly positive. Genetic and phenotypic correlations of RFI and RFIFat with carcass traits were not different from zero, as correlated responses for carcass traits were also not different from zero. The Nellore selection for feed efficiency by RFI or RFIFat allows the recognition of feed efficient animals, with DMI reduction and without significant changes in growth and carcass traits. However, because of the observed results between RFIFat and SC450, selection of animals should be analysed with caution and a preselection for reproductive traits is necessary to avoid reproductive impairments in the herd. K E Y W O R D S Bos taurus indicus, carcass traits, genetic parameters, performance test, residual feed intake | 465 MORAES Et Al. How to cite this article: Moraes GF, Abreu LRA, Toral FLB, et al. Selection for feed efficiency does not change the selection for growth and carcass traits in Nellore cattle. J Anim Breed Genet. 2019;136:464-473. https ://doi.

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The objective was to estimate genetic correlations between body weight (BW), scrotal circumference and visual evaluation scores of body conformation measured at standard ages in Guzerat cattle. All measurements were performed at 205 (weaning age), 365, 450 and 550 days of age; for BW, two additional measurements (at birth and 120 days of age) were realized. The data utilized in this study were retrieved from a database of the Brazilian Association of Zebu Breeders that contained information of registered Guzerat animals born between 1970 and 2013. Genetic parameters were estimated in bi-trait analyses by using Bayesian inference. Genetic correlations between BW at 205 and 450 days of age with other traits were high and positive, whereas the correlations between visual evaluation scores with other traits were moderate. Based on correlations herein obtained, we conclude that selection based on BW results in increased visual scores and scrotal circumference, leading to improvements in productive performance and animals with best body conformation.

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Our objective was to estimate genetic parameters, and genetic and phenotypic trends for bodyweight (BW; measured at birth, 120, 205 (weaning age), 365, 450 and 550 days of age), scrotal circumference, and visual appraisal scores of body conformation in Guzerat cattle. Data regarding body structure, finishing precocity, muscling, sheath and navel, breed characteristics, limbs (soundness of feet and legs), and sexuality, which were visually appraised, were obtained from the Brazilian Association of Zebu Breeders, recorded between 1970 and 2013 in five Brazilian states. Variance components and heritability were estimated by using linear animal (for continuous variables) and threshold (for categorical variables) models using Bayesian inference. Genetic and phenotypic trends were obtained by regressing the average annual genetic value relative to animal’s birth year. The direct heritability values for BW were high, ranging from 0.38 to 0.45, whereas the maternal effect was responsible for 17–23% of the phenotypic variation. For scrotal circumference, the direct heritability values were median with values ranging from 0.08 and 0.15, whereas for visual appraisal scores, the values were median to high (0.07–0.18). Higher response to selection for BW traits is expected for those with moderate to high heritabilities. The estimated genetic trends indicated favourable changes for BW with average annual changes of 396, 2948, 3388, 5808, 8184, and 8096 g for BW at the respective ages. The genetic values were decreasing over the years for scrotal circumference, body structure, finishing precocity, muscling, and sheath and navel. Therefore, a longer evaluation period should be utilised to assess these traits as little time has elapsed from the beginning of the selection until the time of the present study.

O trabalho foi conduzido com o objetivo de se avaliar o efeito de duas idades de abate sobre o rendimento de carcaça e propriedades finais da carne de codornas de corte (Coturnix coturnix). Foram abatidas 40 codornas (machos e fêmeas) aos 35 e aos 42 dias de idade obtendo-se o peso corporal, peso de carcaça quente e resfriada, peso de peito, peso de perna, rendimento de carcaça quente e fria, rendimento de peito, rendimento de pernas, pH inicial e final (24 horas "post mortem", capacidade de retenção de água (CRA), cor (L*, a*, b*), perda de peso por cocção (PPC) e maciez objetiva (força de cisalhamento). Não houve diferença no rendimento de carcaça e cortes entre as idades de abate, entretanto as aves abatidas aos 42 dias de idade apresentaram-se com maior peso corporal. Para os parâmetros da qualidade da carne, observou-se que o pH inicial foi menor para as aves abatidas aos 42 dias de idade. Fêmeas abatidas aos 35 dias de idade apresentaram carne com menor teor de vermelho. Machos apresentaram a carne com pH mais baixo. Dessa forma o abate dos animais aos 42 dias de idade proporcionou melhor desempenho e melhores características de carcaça aos machos.

The objective was to estimate (co)variance functions using random regression models (RRM) with Legendre polynomials, B-spline function and multi-trait models aimed at evaluating genetic parameters of growth traits in meat-type quail. A database containing the complete pedigree information of 7000 meat-type quail was utilized. The models included the fixed effects of contemporary group and generation. Direct additive genetic and permanent environmental effects, considered as random, were modeled using B-spline functions considering quadratic and cubic polynomials for each individual segment, and Legendre polynomials for age. Residual variances were grouped in four age classes. Direct additive genetic and permanent environmental effects were modeled using 2 to 4 segments and were modeled by Legendre polynomial with orders of fit ranging from 2 to 4. The model with quadratic B-spline adjustment, using four segments for direct additive genetic and permanent environmental effects, was the most appropriate and parsimonious to describe the covariance structure of the data. The RRM using Legendre polynomials presented an underestimation of the residual variance. Lesser heritability estimates were observed for multi-trait models in comparison with RRM for the evaluated ages. In general, the genetic correlations between measures of BW from hatching to 35 days of age decreased as the range between the evaluated ages increased. Genetic trend for BW was positive and significant along the selection generations. The genetic response to selection for BW in the evaluated ages presented greater values for RRM compared with multi-trait models. In summary, RRM using B-spline functions with four residual variance classes and segments were the best fit for genetic evaluation of growth traits in meat-type quail. In conclusion, RRM should be considered in genetic evaluation of breeding programs.