ABSTRACT The objective of this work was to estimate genetic parameters and evaluate genetic trends over 26 years for morphometric traits in Mangalarga Marchador horses. Twelve morphometric traits were evaluated (withers and croup heights; length of head, body, shoulder, croup, neck, back, and loins; width of head and croup, and cannon bone and thorax perimeters). These traits were evaluated in 38,341 animals born between 1987 and 2012 and with a relationship matrix of 77,719 animals. Gibbs sampler was used to obtain samples of the posterior distributions of genetic parameters under animal models. Genetic trends were estimated by regression of estimated breeding values in function of birth year. The heritabilities of all traits were moderate to high and ranged from 0.27 to 0.48. However, the additive genetic coefficients of variation were low, ranging from 1.23 to 3.82%. The genetic trends of all the studied traits were significant, but of low magnitude. Negative genetic trend was observed for body length, while positive genetic trends were estimated for the other 11 traits. Although additive genetic differences accounted for a significant part of the phenotypic differences, genetic gains in the population were limited by low phenotypic variability. Therefore, it is necessary to develop data collection strategies to increase phenotypic and genetic variability in the population, such as the inclusion of animals that do not meet breed standard, but which have parents registered in the breeders’ association, in the database.

ABSTRACT The objective of this study was to estimate genetic parameters for body weight of beef cattle in performance tests. Different random regression models with quadratic B-splines and heterogeneous residual variance were fitted to estimate covariance functions for body weights of Nellore and crossbred Charolais × Nellore bulls. The criteria −2 residual log-likelihood (−2RLL), Akaike Information Criterion (AIC), and consistent AIC (CAIC) were used to choose the most appropriate model. For Nellore bulls, residual variance was modeled with six classes of age, and direct additive genetic and permanent environment effects were modeled with quadratic B-splines with two and one intervals, respectively. For crossbred bulls, quadratic B-splines with one interval fitted direct additive genetic and permanent environment effects and nine classes of age were needed to fit residual variance. Pooling classes of age with up to 40% in difference of residual variances does not compromise the fit of the model. Heritability for body weight in performance tests are moderate (>0.25, for crossbred bulls) to high (>0.5, for Nellore bulls) and genetic correlation between weights over the test are also high (>0.65). Then, selection of young bulls in performance test is an efficient tool to increase body weight in beef cattle.

Resumo: O objetivo deste trabalho foi verificar se o modelo de regressão aleatória com polinômios lineares do tipo spline (MRAPLS) é adequado para estimar os parâmetros genéticos de características produtivas e reprodutivas em uma população multirracial de bovinos leiteiros, bem como investigar o efeito do grupo genético da progênie sobre o mérito genético do touro. Foram utilizados o modelo multicaracterístico (Mult) e o MRAPLS com nós ajustados aos grupos genéticos, para obtenção dos parâmetros genéticos. Foram considerados os registros de vacas 1/2 Holandesa + 1/2 Gir (1/2HG), 5/8 Holandesa + 3/8 Gir (5/8HG) e 3/4 Holandesa + 1/4 Gir (3/4HG). O MRAPLS apresentou os melhores ajustes. As variâncias aditivas e residuais estimadas por Mult e MRAPLS foram semelhantes. As herdabilidades variaram de 0,20 a 0,33 para idade ao primeiro parto, de 0,09 a 0,22 para duração da primeira lactação e de 0,15 a 0,35 para produção de leite em até 305 dias na primeira lactação, de acordo com a composição genética das vacas. O MRAPLS é adequado para estimar parâmetros genéticos de características produtivas e reprodutivas em populações multirraciais de bovinos leiteiros. O mérito genético do touro é influenciado pelo grupo genético da progênie por meio do qual ele é avaliado.

Abstract: The objective of this work was to determine whether the random regression model using linear splines (RRMLS) is suitable to estimate the genetic parameters for productive and reproductive traits of a multiple-breed dairy cattle population, as well as to investigate the effect of the genetic group of the progeny on the genetic merit of the sire. The multiple-trait model (MTM) and the RRMLS with one knot fitted for every genetic group were used to obtain the genetic parameters. Records of 1/2 Holstein + 1/2 Gyr (1/2HG), 5/8 Holstein + 3/8 Gyr (5/8HG), and 3/4 Holstein + 1/4 Gyr (3/4HG) crossbreed dams were considered. The RRMLS showed better fitting. The additive and residual variances estimated by the MTM and the RRMLS were similar. Heritability varied from 0.20 to 0.33 for age at first calving, from 0.09 to 0.22 for first lactation length, and from 0.15 to 0.35 for first lactation 305-day milk yield, according to the genetic composition of the dams. The RRMLS is suitable to estimate the genetic parameters for productive and reproductive traits of multiple-breed dairy cattle populations. The genetic merit of the sires is affected by the genetic group of the progeny by which they are evaluated.

ABSTRACT This study aimed to evaluate associations among final weight (FW), average daily gain (ADG), scrotal circumference (SC), and visual score (VS) of beef cattle in performance tests on pasture or in feedlots. Genetic parameters for FW, ADG, SC, and VS of young Nellore bulls performance-tested on pasture or in feedlots were evaluated by mixed model. The performance test and final age were considered as fixed effects and additive genetic and residual effects were considered as random effects. Additive genetic and residual variances for final weight and average daily gain were smaller on pasture than in feedlots. There was no difference between genetic and residual variances and heritability for scrotal circumference on pasture or in feedlots. Genetic variance and heritability for visual score on pasture were smaller than those in feedlots. The posterior means (and highest posterior density intervals with 90% of samples (HPD90) in parentheses) for heritability were 0.46 (0.42; 0.50) and 0.49 (0.41; 0.55) for FW, 0.25 (0.22; 0.29) and 0.25 (0.19; 0.30) for ADG, 0.56 (0.51; 0.61) and 0.60 (0.51; 0.68) for SC, and 0.31 (0.27; 0.34) and 0.42 (0.36; 0.48) for VS on pasture or in feedlots, respectively. The genetic correlations (posterior means with HPD90 in parentheses) were 0.74 (0.69; 0.79) and 0.67 (0.58; 0.77) between FW and ADG; 0.49 (0.43; 0.55) and 0.60 (0.53; 0.68) for FW and SC; 0.79 (0.75; 0.83) and 0.85 (0.80; 0.90) for FW and VS; 0.37 (0.29; 0.46) and 0.34 (0.19; 0.50) for ADG and SC; 0.65 (0.59; 0.71) and 0.74 (0.64; 0.84) for ADG and VS; and 0.46 (0.39; 0.52) and 0.53 (0.44; 0.62) for SC and VS, obtained on pasture or in feedlots, respectively. The genetic and residual (co)variances of growth, scrotal circumference, and visual score of beef cattle vary across environments; however, genetic and residual correlation and efficiency of correlated response among these traits remain constant on pasture or in feedlots.

Resumo: O objetivo deste trabalho foi determinar os parâmetros genéticos para o peso de bovinos Nelore, do nascimento até 1.000 dias de idade, por meio de modelos de regressão aleatória. Utilizaram-se 115.096 registros de peso de 19.417 animais. Os parâmetros genéticos foram obtidos por modelos de regressão aleatória via inferência bayesiana. A trajetória média de crescimento foi ajustada com um polinômio de Legendre quártico. O efeito genético aditivo direto foi ajustado com um polinômio quadrático de Legendre. Os efeitos de ambiente permanente direto e materno foram ajustados com polinômios de Legendre quíntico e quadrático, respectivamente. A variância residual foi modelada com três classes de idades. Os valores genéticos dos pesos, do nascimento até 1.000 dias de idade, foram utilizados para a análise da tendência genética, por meio de superfícies de resposta. As herdabilidades variaram entre 0,16 e 0,47. Os efeitos de ambiente permanente direto e materno foram responsáveis por 5 a 77% e 0,2 a 11% da variância fenotípica, respectivamente. As correlações genéticas dos pesos em diferentes idades foram altas e superiores a 0,40. Os valores genéticos foram crescentes ao longo dos anos, e a tendência genética foi máxima para peso aos 500 dias.

Abstract: The objective of this work was to determine the genetic parameters for body weight of Nellore cattle, from birth to 1,000 days of age, by random regression models. Data from 115,096 body weight records of 19,417 animals were used. The genetic parameters were obtained by random regression models and Bayesian inference. The average growth trajectory was fitted by a fourth-order Legendre polynomial. The additive direct effect was fitted by a quadratic Legendre polynomial. Direct and maternal permanent environmental effects were fitted by the fifth- and second-order Legendre polynomials, respectively. Residual variance was modeled by three classes of age. The breeding values of weights obtained from birth to 1,000 days of age were used for the analysis of genetic trend by response surfaces. Heritability ranged from 0.16 to 0.47. The direct and maternal permanent environmental effects explained 5 to 77% and 0.2 to 11% of the phenotypic variance, respectively. The genetic correlations of body weights at different ages were high and above 0.40. Breeding values increased throughout the years, and genetic trend was maximum for body weight at 500 days.

The objective of this study was to estimate genetic parameters and to evaluate the effects of inbreeding on productive and reproductive traits of dairy Gyr cattle. Single-trait animal models were used to estimate genetic parameters and solutions for inbreeding coefficients for milk (milk 305-d), fat (fat 305-d), protein (protein 305-d), lactose (lactose 305-d), and total solids (TS 305-d) yield up to 305 days of lactation, days in milk (DIM), age at first calving (AFC) and calving intervals (CI). The mean inbreeding coefficient was 2.82%. The models with linear and quadratic effects of inbreeding coefficients fitted the data better than the models without or with only linear effect of inbreeding coefficient for all traits. The increase in inbreeding coefficient caused several losses in productive and reproductive traits of dairy Gyr cattle. Estimates of heritability for milk 305-d, fat 305-d, protein 305-d, lactose 305-d, TS 305-d, DIM, AFC, and CI were 0.28, 0.27, 0.22, 0.21, 0.22, 0.17, 0.20, and 0.10, respectively. It is possible to achieve genetic progress in productive traits (especially in milk 305-d and fat 305-d) and age at first calving in dairy Gyr cattle through selection.

O objetivo deste trabalho foi avaliar componentes de covariância e valores genéticos para produção de leite acumulada em até 305 dias, a partir dos dados das três primeiras lactações de vacas Gir. Foram analisados dados de 14.659 lactações, de 9.079 vacas, por meio dos modelos de repetibilidade, multicaracterístico (Mult) e de regressão aleatória com variância residual homogênea (MRAHo) ou heterogênea (MRAHe). A produção de leite foi considerada como característica distinta em cada lactação, no modelo Mult. Polinômios lineares foram utilizados nos modelos de regressão aleatória para ajuste das trajetórias médias e dos efeitos genético aditivo e de ambiente permanente individuais, de acordo com a ordem de parto. As médias a posteriori da herdabilidade foram semelhantes entre os diferentes modelos e lactações, e variaram entre 0,24 e 0,29. Os modelos Mult e MRAHe ajustaram-se melhor aos dados, uma vez que observou-se heterogeneidade de variâncias genéticas e residuais entre lactações. As correlações genéticas da produção acumulada de leite em até 305 dias nas três primeiras lactações foram próximas de 1,0; portanto, a seleção de reprodutores já pode ser feita a partir dos resultados da primeira lactação. Modelos de regressão aleatória com variâncias genéticas e residuais heterogêneas permitem modelar adequadamente as covariâncias das produções de leite acumuladas em múltiplas lactações e obter valores genéticos para seleção de reprodutores com base nos dados já da primeira lactação.

The objective of this work was to evaluate covariance components and breeding values for 305-day cumulative milk yield with data from the first three lactations of Gyr cows. A total of 14,659 lactations of 9,079 cows were evaluated, using the models of repeatability, multiple-trait (MT), and random regression with residual homoscedasticity (RRMHo) or heteroscedasticity (RRMHe). Milk yield was considered as a different trait in each lactation, in the MT model. Linear polynomials were used in random regression models to fit the mean trajectories and the additive genetic and permanent environment individual effects, according to calving order. Posteriori means for heritability were similar among different models and lactations, and varied from 0.24 to 0.29. The MT and RRMHe models had a better fit to the data, since heterogeneity was observed for genetic and residual variances between lactations. The genetic correlations of cumulative milk yield up to 305 days in the first three lactations were close to 1.0; therefore, the selection of reproducers can be made with data already from the first lactation. Random regression models with heterogenous genetic and residual variances allow for proper modeling of the covariances in cumulative milk yields in multiple lactations and for obtaining the genetic values to be used in the selection of reproducers, based on data already from the first lactation.

O objetivo deste trabalho foi determinar parâmetros genéticos do peso desde o nascimento até 730 dias de idade na raça Indubrasil. Registros de peso (82.481) de 20.890 animais do nascimento aos 730 dias de idade foram utilizados. Os parâmetros genéticos foram determinados por meio de regressão aleatória. Amostras da distribuição a posteriori dos parâmetros de interesse foram obtidas com o amostrador de Gibbs. Polinômios de Legendre ou segmentados foram utilizados para modelar a trajetória média de crescimento. Os efeitos genético aditivo direto e de ambiente permanente direto foram modelados por polinômios de Legendre. Um polinômio segmentado linear-linear, com nó aos 251 dias de idade, ajustou a trajetória média. Polinômios de Legendre quadráticos e quínticos ajustaram, respectivamente, os efeitos genético aditivo e de ambiente permanente. Três classes de idade foram suficientes para modelar a heterocedasticidade residual. Na maior parte do intervalo considerado, as médias a posteriori da herdabilidade foram crescentes, com valores entre 0,10 e 0,45; a proporção da variância de ambiente permanente em relação à variância fenotípica foi constante, em torno de 0,48; e as correlações genéticas dos pesos em diferentes idades foram altas, acima de 0,60. Há variabilidade genética quanto ao peso na raça Indubrasil, e a seleção pode aumentar a média desta característica.

The objective of this work was to determine the genetic parameters for weight from birth to 730 days of age in Indubrasil breed. Weight data set (82,481) of 20,890 animals from birth to 730 days of age were used. The genetic parameters were determined by random regression. A posteriori distributions of the parameters of interest were obtained by the Gibbs sampler. Legendre or segmented polynomials were used to model the average growth trajectory. The direct additive genetic effect and direct permanent environmental effect were fit by Legendre polynomials. A linear-linear segmented polynomial, with a knot at 251 days of age, fitted the average growth trajectory. Quadratic and quintic Legendre polynomials fitted the direct additive genetic and permanent environmental effects, respectively. Three age classes were enough to model the residual heteroscedasticity. In the most part of the considered interval, the a posteriori means of heritability increased, with values between 0.10 and 0.45; the proportion of permanent environmental variance was constant in relation to the phenotypic variance and close to 0.48; and the genetic correlations of weight at different ages were high, over 0.60. There is genetic variability for weight in Indubrasil breed, and the selection can improve this trait's mean.