Dionéia Magda Everling

Estimativas de Herdabilidade e Correlação Genética para Características de Crescimento na Fase de Pré-desmama e Medidas de Perímetro Escrotal ao Sobreano em Bovinos Angus-Nelore

The data utilized in this work were originated from 53.938 pure and crossbred (Angus x Nelore), collected in different regions of Brazil and Argentina born from 1987 to 1998 were analyzed. The objectives of this work were to verity the heritabilities and correlation among the growing and scrotal circumference traits. The variables analyzed were the average daily gain from birth to weaning (ADGBW), days to reach 160 kg from birth to weaning (D160), weaning weight (WW) and scrotal circumference at yearling (CP). The method of restricted Maximum Likelihood and computational program MTDFREML were used with a multitrait animal model. For the growing trait, the model included the fixed effects of contemporary groups at weaning, the interaction of breeds parents of animal, the age of dam at parturition and age at weaning as covariable and the direct and maternal as random effects. For the SP the fixed effects included in the model were the linear and quadratic effects of age at yearling and weight, contemporary group at yearling and interaction composite breed sire and dam a direct animal effect as random effect. The heritability estimates were .25, .13, .23 and .21 for ADGBW, D160, WW and CP, respectively. The correlation estimates with SP were:.0,17, -.17 and .16 for ADGBW, D160, and WW respectively. These results suggest that the trait analyzed can be chosen together at the selection programs.

Genetic parameters and phenotypic and genetic trends for weight at weaning and visual scores during this phase estimated for Angus-Nellore crossbred young bulls

Genetic parameters and genetic and phenotypic trends were estimated for weight at weaning (WW) and visual scores (VS) of conformation (C), precocity (P), musculature (M) and navel (N) for Angus × Nellore crossbred calves. It was used 39,676 records from pre-weaning phase of animals born from 1992 to 2002 in mid-western, southeastern and southern Brazil. The components of covariance were estimated using REML, in animal model, considering as random the maternal and direct additive genetic effects, and as fixed, the effects of contemporaneous group, the genetic group of the animal and of the cow, and as covariates the age of the calf at weaning and the age of the cow at calving, both on days and with linear and quadratic effects, besides direct (DH) and maternal heterosis (MH), both with only the linear effect. Estimates of direct and maternal heritability were 0.30 and 0.19, respectively, for WW, whereas VSs ranged from 0.16 to 0.20 and from 0.09 to 0.16, which indicates the possibility to obtain genetic gain through selection. It is expected answer correlated to C, P and for M when selection is practiced for weight at weaning is expected, as well as for P and M when selection is practiced for C. The direct and maternal genetic trends for WW (g/year) and for C, P, M and N (points/year) were: 221.0 and -312.0; 0.0022 and 0.00003; 0.0010 and 0.0001; 0.0013 and -0.0008; 0.0010 and 0.00009, respectively, while the phenotypic were: -685.2; -0.0102; -0.0219; -0.0256 and -0.0453, which highlights the need to adopt criteria for identifying young bulls of higher genetic value for WW and VSs.

Classical nonlinear models to describe the growth curve for Murrah buffalo breed

With the objective of to adjust nonlinear models for the growth curves for a buffaloes herd raised in floodable lands in Rio Grande do Sul state, monthly records measured from birth to two years-old of 64 males and 63 females born between 1982 and 1989 were used. The models used were: Von Bertalanffy, Brody, Gompertz and Logistic. The parameters were estimated by NLIN procedure and the criteria used to evaluate the adjustment given by the models were: asymptotic standard deviation; coefficient of determination; average absolute deviation of residues and asymptotic index. Von Bertalanffy and Brody models overestimated the male asymptotic weight (A) in 15.9 and 171.3kg, respectively, and the Gompertz and Logistic models underestimated it in 4.5 and 13.4kg, respectively. For females, the Logistic model underestimated the asymptotic weight (-2.09kg), and Gompertz, Von Bertalanffy and Brody overestimated this parameter in 8.04, 17.7, and 280.33kg, respectively. The biggest average deviation was estimated by Brody model for both sexes, characterizing the biggest index. Considering the criteria, it is recommended the Gompertz and Logistic models for adjust females and males Murrah buffaloes breed growth curves.

Herdabilidades para ganho de peso da desmama ao sobreano e perímetro escrotal ao sobreano e tendências genética e fenotípica para ganho de peso da desmama ao sobreano em bovinos Nelore-Angus

Data consisting of 47.668 records of a Nellore-Angus crossbred population, raised in several regions of Brazil, from 1991 to 2001, were used to estimate heritability for post-weaning daily gain (ADG) and for scrotal circumference at yearling age (SCY) using REML. Genetic and phenotypic trends for ADG were also estimated. The model used to estimate heritability and breeding values (BVs) for ADG included the fixed effects of breed composition (defined by the percentage of contribution of the Nellore breed of the animal and his parents) and the contemporary group after weaning (herd, year/season of birth, sex and management group) and the random additive genetic animal and residual effects. The same model, including the fixed effects of weight and age of the animal at yearling, as covariates, was used for SCY. The average ages at weaning and yearling were respectively 215 and 528 days. The heritability estimates for ADG and SCY were 0.44 ± 0.02 and 0.22 ± 0.08, respectively. The annual genetic trend for ADG decreased up to the year of 1996 and increased then on. The phenotypic trend was 9.4 g/day/year.

Estudo da Heterogeneidade das Variâncias para as Características Produtivas de Rebanhos da Raça Holandesa no Rio Grande do Sul

Com os objetivos de estudar a heterogeneidade das variâncias e estimar os coeficientes de herdabilidade em diferentes niveis de producao de leite dos rebanhos e em diferentes classes de desvio-padrao, foram analisados os registros de producao de 13.053 lactacoes de 6.828 vacas da raca Holandesa, filhas de 811 touros, distribuidas em 78 rebanhos no estado do Rio Grande do Sul, no periodo de 1988 a 1997. Os rebanhos foram agrupados pelo nivel de producao e pelo desvio padrao da producao de leite, aos 305 dias, em tres niveis (baixo, medio e alto). Os componentes de variância foram obtidos pelo metodo da Maxima Verossimilhanca Restrita, utilizando o programa MTDFREML e um modelo animal misto incluindo os seguintes efeitos fixos: classe de idade, grupo genetico, rebanho dentro de nucleo e ano-epoca de parto e os aleatorios do animal (efeito gnetico), do ambiente permanente e do residuo. Os componentes de variância genetica, residual e fenotipica mostraram uma relacao positiva, crescente, com o nivel de producao e com a classe de desvio-padrao, todavia os coeficientes de herdabilidade nao apresentaram a mesma tendencia tendo as estimativas mais altas ocorrido no nivel baixo de producao e na classe de desvio-padrao medio.

Associação genética de escores de conformação com características de crescimento em bovinos da raça Angus

The objective of this work was determine the genetic association between visual scores of conformation and the traits of daily average weight gain and weight gain rate in Angus breed cattle at weaning and yearling. The components of covariance were estimated by a multitrait animal model using the Bayesian inference method, assuming a linear model for: daily average weight gain from birth to weaning (BWG) and from weaning to yearling (WYG); and weight gain rate from birth to weaning (BWR) and from weaning to yearling (WYR). A nonlinear model (threshold) was used for conformation scores at weaning (WC) and at yearling (YC). The a posteriori means for heritability were: 0.12±0.023 (WC), 0.15±0.020 (BWG), 0.15±0.024 (BWR), 0.17±0.020 (YC), 0.17±0.023 (WYG) and 0.17±0,023 (WYR). The genetic correlations ranged from -0.09±0.11 to 0.60±0.06, between WC, YC, and the daily average weight gain and weight gain rate. The correlation between WC and YC was 0.52±0.089. The direct selection for visual scores of conformation, average daily gain and weight gain rate respond slowly to selection, both at weaning and yearling.

Genetic parameters and genetic and phenotypic trends of performance traits of equines from the Brazilian Army

The objective of this research was to compare the magnitude of genetic parameters (coefficients of heritability and genetic correlation) as estimated by the Restricted Maximum Likelihood (REML) method and Bayesian Inference, and to estimate the genetic and phenotypic trends to the traits height at the withers (HW24) and weight at 24 months of age (W24). The average heritability estimated by Bayesian Inference to HW24 was 0.47, and it was lower than that obtained by REML bi-trait analysis (0.52); however, the value estimated to W24 (0.39) was higher than that obtained by REML bi-trait analysis (0.38). The genetic correlation estimate between W24 and HW24 traits obtained by the REML method (0.66) was lower than that obtained by the Bayesian Inference Method (0.72). From the regression of the average additive genetic merit in the year of birth of the animals, it was found that the averaged genetic values of the animals for HW24 showed a genetic trend near zero (-0.0008cm/year), and the averaged genetic values for W24 showed a negative trend of -0.38 kg/year. The values to the direct heritability estimated for HW24 and W24 suggest that the direct selection for these traits can provide genetic gain in this population. The genetic correlation between the traits, high and positive, suggests that the selection for HW24 should promote increase in W24 at this age. The genetic trends obtained for the traits studied, near zero, indicate that the selection performed produced a slight reduction of the weight of the animals at 24 months of age; however, it did not promote increase in height at the wither at this same age, in this population.

Genetic divergence among Nellore breed herds raised in the South Region of Brazil

The objective of this study was to evaluate the genetic divergence among Nellore breed animals raised in 45 farms in the Southern Region of Brazil. The characteristic studied was weaning weight adjusted to 205 days of life (P205), from 10,874 animals sired by 425 bulls and 7,629 cows, collected between 1976 and 2001, and distributed in the states of Rio Grande do Sul (1,499), Santa Catarina (2,332) and Parana (7,043). The animals were distributed by cluster analysis in eight genetic divergent groups, enabling this technique to be applied to organize the matings in order to obtain heterotic effect. The herd/farm groups were formed through the hierarchical Ward method, using the direct (VGD) and maternal (VGM) breeding values predicted by the REML method. The VGD of the animal accounted for 90% of the differences among herds, and the remaining 10% was attributed to differences in the VGM. On average, the P205 for the animals from inter-group mating was 1.4kg higher than those from intra-group mating, representing 2.4% of heterosis.