C.V. Araújo

Avaliação genética de características de crescimento de ovinos Santa Inês utilizando modelos de regressão aleatória

Records on weights from birth to 196 days of age of 927 lambs of Santa Ines hairless sheep, from 1983 to 2000, were used to estimate genetic parameters and to predict breeding values by random regression models and to compare these estimates with those obtained by two-traits model. The random regression models were fitted by quadratic and cubic orthogonal Legendre polynomials. The heritability estimates of direct effect increased from birth to 196 days of age. The heritabilities for the maternal effect increased from birth to 56 days, and decreased after that age. The heritabilities for direct effect obtained by two-trait and random regression analyses showed opposite tendency. While the estimates obtained by two-trait analyses decreased from birth to 196 days of age, those obtained by random regression models increased. The heritabilities for maternal effect, obtained by both models, showed the same behavior, however with different magnitude. The Spearman correlation between estimated breeding values by both models was low. The heritability and genetic correlations estimated by random regression model were more consistent than those estimated by two-trait model.

Estimativas de parâmetros genéticos para características reprodutivas de suínos

Data on age at first farrowing (IPP), total number of piglets born (NLN), number of piglets born alive (NLNV), and birth litter weight (PLV) were used to estimate genetic and phenotypic parameters of reproductive traits in Large White breed. Genetic and phenotypic variances and covariances were estimated by Restricted Maximum Likelihood method (REML). The model to analyze IPP included direct genetic effect, maternal effect and common litter effect, and the model to analyze NLN, NLNV and PLV included only direct genetic effect. Heritability estimates for direct additive genetic effects ranged from 0.17 to 0.34. Favorable genetic correlations between IPP and the other traits studied were observed. The low heritability estimates for most traits suggest that efficient selection strategies must be sought to increase genetic gain and that response for NLN may be obtained by indirect selection on NLNV.

Influência da heterogeneidade de variâncias na avaliação genética de bovinos de corte da raça Tabapuã

Data from Tabapua beef cattle were used to study the influence of variance heterogeneity on genetic evaluation. Adjusted weights at 120, 240 and 420 days of age were classified in three classes of standard deviation: low ( 18.9kg), based on phenotypic standard deviation of the weight at 120 days of age of the contemporary groups. Multiple trait analyses, considering each class of phenotypic standard deviation as a distinct trait, were performed. The genetic and residual variances increased as the phenotypic standard deviation of the class increased. Heritabilities for low, medium and high phenotypic standard deviation classes were 0.26, 0.32 and 0.37 (weight at 120 days), 0.28, 0.35 and 0.35 (weight at 240 days) and 0.14, 0.18 and 0.18 (weight at 420 days), respectively. Genetic correlations between the same weight, in low and high phenotypic standard deviation classes were lower than 0.80. The correlation between the breeding values, obtained from multiple trait analyses, and from general analyses (without classes), were greater than 0.93. It was observed that sires would be classified in similar way considering or not considering the heterogeneity of variances in the analyses.

Estimativas de parâmetros genéticos para características de desempenho de suínos em fase de crescimento e terminação

Foram utilizados dados de conversao alimentar, espessura de toucinho corrigida para 100kg, idade para atingir 100kg e ganho de peso medio diario, para estimar parâmetros geneticos e fenotipicos de caracteristicas de desempenho de suinos da raca Large White. As caracteristicas estudadas foram avaliadas por sexo, em razao do manejo diferenciado para machos e femeas. Variâncias e covariâncias geneticas e fenotipicas foram estimadas pelo metodo da maxima verossimilhanca restrita, usando modelo que incluiu os efeitos geneticos direto, materno e comum de leitegada. As estimativas de herdabilidade do efeito genetico direto variaram de 0,13 a 0,55, indicando que, para a maioria das caracteristicas, o uso da selecao direta deve ser eficiente. Os valores das estimativas de herdabilidade do efeito genetico materno foram baixos (0,02 a 0,05). As estimativas do efeito comum de leitegada variaram de baixas a medias (0,05 a 0,18). As correlacoes geneticas entre as caracteristicas indicaram que, quando o objetivo do programa de melhoramento e a melhoria de todas as caracteristicas, deve-se fazer selecao direta para conversao alimentar, espessura de toucinho e idade para atingir 100kg de peso vivo, e indireta para ganho de peso medio diario por meio da selecao da idade para atingir 100kg.

Índices de eficiência reprodutiva de búfalos da Amazônia Oriental do Brasil

We evaluated records of reproductive management Jaffarabadi buffalo breeds, Murrah, Mediterranean, Carabao and Baio types, and their crosses, in the period from 1983 to 2005. We studied the following reproductive characteristics: Age at first calving (mean 1052.52±120.45 days), calving interval (399.69±23.78 mean days), Reproductive Efficiency (average 91.09±1, 89%), Real Adapted Fertility (average 29.30±4.40kg calf calved each year), the First Labor Productivity Adapted (mean 33.75±6.89kg) and Accumulated Productivity Adapted (mean 22.86±6.55kg calf calved each year). Influences were observed in the year of delivery and degree of blood on the female traits, suggesting that such effects should be included in genetic evaluation and selection of animals. The production indices used were of great value for the selection, and should be well studied for their interactions with the overall performance of the herd.

Seleção para a produção de ovos em períodos parciais e acumulados em linhagem de frango de corte comercial

The aim of this study was to estimate genetic parameters for partial and cumulative egg production in a commercial broiler female line. Ten monthly periods between 25 and 64 weeks, three partial periods of 25 to 32, 33 to 48 and 49 to 64 cumulative weeks and three periods of 25 to 30, 40 and 50 weeks of age and total egg production were considered. The restricted maximum likelihood method under the animal model was used to estimate the covariance components and genetic parameters. The fixed effect of incubation and the additive genetic and residual random effects were considered. The estimated heritability ranged from 0.12 to 0.41. These estimates showed that the anterior and posterior periods of the higher production have greater genetic variability. The genetic correlations between periods of the egg production studied ranged from -0.12 to 0.98. In general, the pattern of variation was similar between the strategies evaluated and all were genetically associated with the total egg production. The results of this study showed that the improvement of the total egg production is feasible by selection of partial records. However, considering the relative efficiency of selection, the second month and the periods from the fortieth week of production would be the most suitable.

Ajustamento para heterogeneidade de variâncias para produção de leite e gordura entre rebanhos da raça Pardo-Suíça no Brasil

In order to verify the effect of including the interactions of sire x herd and the sire x herd-year, as a adjust factor of the variance heterogeneity, registers of milk and fat yields were classified into two classes of standard deviation: low ( 1.280kg), based on phenotypic standard deviation of the milk production adjusted. Three models, without and with interaction of sire x herd and sire x herd-year, were used in the general univariate analyses and in each standard deviation class. Averages and variance components were higher in the high standard deviation. In the class of low standard deviation, heritability didnt alter with the inclusion of the interaction effects in the model, being of 0.34 for milk yield and 0.32 for fat yield. In the class of high standard deviation, heritabilities were: 0.37, 0.35 and 0.36, and of 0.35, 0.32 and 0.35, for milk and fat yield, in the models without and with interaction of sire x herd and with interaction of sire x herd-year, respectively. The inclusion of the interaction of sire x herd was significant (P<0.01) for fat yield, in general analyses and in the high standard deviation class, in the likelihood ratio test.