Robledo de Almeida Torres

Interação genótipo-ambiente em algumas características produtivas de gado de corte no Brasil

The objective of this study was to measure the genotype-environment interaction (GEI) effect on some growth traits in Nellore cattle. Data from 2,896 records of pre-weaning (PW), 2,605 of weaning (WW) and 1,522 of post-yearling (YW) weights with a total of 9,911 pedigree animals from two farms of different regions of Minas Gerais State, South (farm I) and Northeast (farm II) were analyzed. Contemporary groups consider the effects of month-year of birth, sex, and herd. Only data from animals raised under pasture conditions were used. Covariance components were estimated by MTDFREML. Direct heritability obtained from bivariate analyses were 0.24, 0.16 and 0.17 (farm I) and 0.25, 0.24 and 0.17 (farm II) for PW, WW and YW, respectively. The ranking correlations between farms were 0.74, 0.76 and 0.51 and genetic correlations between farms were 0.96, 0.95 and 0.53 for PW, WW and YW, respectively. These results showed that there was no evidence of GEI up to weaning time but there was a significant effect of this interaction on the post-yearling weight. If selection criterion includes growth traits measured after weaning, regional evaluation should be recommended for bulls choice.

Ajustamento para Heterogeneidade de Variância para Produção de Leite entre Rebanhos da Raça Holandesa no Brasil

Data of 36,755 first lactation of Holstein cows, daughters of 866 sires, distributed in different states from 1980 to 1993, were stratified in herds according to the phenotypic standard deviation of the milk yield adjusted for adult age, in three levels: low (11,713 lactations), medium (12,764 lactations) and high (12,278 lactations). The total milk production adjusted for adult age and adjusted for adult age and for 305 days of lactation, within each class, and the base 10 logarithm transformations, square root, standardization and the division by class phenotypic standard deviation were analyzed. The averages of milk yield, the genetic, residual, and phenotypic variance components increased with the increase of the class mean standard deviation. The heritability did not have the same behavior, the heritability estimates of the traits of the class with high standard deviation were similar to the heritability of traits of class with low standard deviation, and both were smaller than the class with medium standard deviation, although the component of addictive genetic variance has been higher. The used transformations did not correct the existing heterogeneity of variance among the classes. The heritabilities of the unchanged characteristics varied from .25 to .35.

Estudo da divergência genética entre linhagens de matrizes de frangos de corte por meio de análise multivariada

Genetic divergence among broiler lines (L1, L2, L3 and L4) was studied by multivariate analysis. Four economic important traits were evaluated in three periods (initial, medium and total): age at first egg, egg number, average egg weight and body weight. The study of the genetic divergence among lines included the following techniques:Multivariate analysis of variance, cluster analysis using Mahalanobis generalized distance and Tocher optimization method, and canonical variables analysis. Significant difference was obtained by the larget Roy eigenvalue test. The cluster analysis of traits in the initial (L1 and L2; L3 and L4) and medium (L2 and L4; L1 and L3) periods grouped the four genotypes in three groups, and in total period the genotypes were grouped in two groups (L2, L3, L4 and L1). Canonical variables analysis showed that the first two canonical variables accounted for more than 96% of the total variation in the three periods. This allowed to represent the performance of genotypes in a bidimensional dispersion graph. In the total period of production study the genetic divergence was lower.

Evaluation of genetic divergence among lines of laying hens using cluster analysis

Cluster analysis was used to investigate the genetic divergence among five lines of laying hens. The following traits were evaluated: body weight at 40, 48 and 56 weeks of age; egg weight at 40, 44, 52 and 60 weeks of age; and laying rate from 40 to 60 weeks of age. Three groups were formed when data were analyzed by the single-linkage hierarchical method using squared Mahalanobis distance (D2) as dissimilarity measures: one group comprised lines 3 and 5, the second group line 1, and the third group comprised lines 2 and 4. Using Tochers optimization method, only two groups were formed: one group comprised lines 3, 5 and 1, and the second comprised lines 2 and 4. This evidences the disagreement between the methods over the evaluation of genetic divergence. The trait that contributed mostly to the genetic divergence was body weight at 48 weeks of age.

Tendência genética para características produtivas em bovinos da raça Pardo-Suíça

Records of 4959 lactation in 1985 to 1998 of 2414 Brown Swiss cows breed, daughters of 70 sires in 51 herds, were used to estimate the genetic trend for milk and fat yield adjusted for 305 days of lactation and mature age of cows (PL305ME and PG305ME). The genetic trend for sires was estimated using a linear regression of the breeding values of the sires to their daughters calving year, averaged to number of daughters in each calving year. The genetic trend of the cows was estimated using a linear regression of their estimates breeding values averaged to number of observation in each year of calving. The animal model used to estimate the breeding values, inclued the fixed effects of herd, year-season of calving, genetic group of the animals, and random effects of animal, permanent and temporary environment. The means of PL305ME and PG305ME were 6085.79 ± 1627.73 and 225.60 ± 60.46 kg, respectivelly. The genetic trend estimated to sires were 33.01 ± 15.27 and 1.98 ± 0,61 kg/year to PL305ME and PG305ME, respectivelly. The genetic trend estimated for cows were 20.54 ± 2.04 and .93 ± .06 kg/year para PL305ME and PG305ME, respectively.

Aspectos produtivos da raça Pardo-Suíça no Brasil: Fatores de ajustamento, produção de leite e de gordura, e parâmetros genéticos

A study was carried on performance of the Brown Swiss cattle with the objective of estimating adjustment factors, evaluate some environment and genetics factors that affect milk and fat yields and fat percentage, and estimate genetic parameters for this productive traits. It was appraised 11,189 lactations out of 5,382 Brown Swiss cows, from 1980 to 1999, originated from 201 herds, provided by milking record service accomplished by the Brown Swiss Cattle Breeder`s Association of Brazil. Productions were adjusted by a multiplicative factors for two milkings, 305-day and production at the mature age. The estimated averages and its standard deviation and the coefficient of variation for milk and fat yield and fat percentage were, respectively, 5,791.50 ± 1,211.58 kg and 20.92%; 217.25 ± 47.36 kg and 21.80% and 3.78 ± 0.34 and 9.16%, respectively. The effects of year and season of calving, year x season of calving interaction, herd and genetic group were significant, except for season of calving on fat percentage.Heritability estimates and repeatability for milk and fat yields were 0.37 and 0.40, and 0.36 and 0.37 respectively. Genetic correlation between milk and fat yield was 0.96. The obtained results showed the need to adjustment milk and fat yields for two milkings, 305-day and production at the mature age. It was concluded that the Brown Swiss breed has a great potential for production in Brazilian dairy herds.

Efeito de erros de pedigree na seleção

Data simulated with five levels of pedigree errors (0, 5, 10, 15 and 20%) and three heritabilities (.10, .30 and .60) were used to verify the effect of pedigree errors on the selection during 10 generations. The largest phenotypic values and efficiency on the individual selection, in overall, were obtained by BLUP without errors, followed by those with 5, 10, 15 and 20% of error. The average superiority in genetic gain of the BLUP per generation, in the various error levels, on the individual selection, decreased with the increase of the heritability of the trait. As the error level increased, the BLUP presented bigger reduction on the genetic gain for the traits with smaller heritabilities.

Estudo de características de produção de matrizes de corte por meio da análise de componentes principais

Records of 270 meat-type chickens from three lines, 90 of each one, were used to discard variables in a principal component analysis. Data were obtained from meat-type chicken lines of the genetic breeding program of the Universidade Federal de Vicosa. The following traits were evaluated: days at first egg (DFE), egg production rate (EPR) from 22nd to 56th week, body weights at 32nd (BW1), 40th (BW2), 48th (BW3), 56th (BW4), and 64th weeks of age (BW5), and average of three egg weights, at 32nd (EW1), 40th (EW2), 48th (EW3), 56th (EW4) and at 64th weeks (EW5). From the 12 principal components, seven showed variance lower than 0,7 (eigenvalue lower than 0,7), suggesting seven variables to be discarded. Variables which showed the highest coefficients, in absolute value, in the last principal component were discarded. Highly correlated variables with the smaller principal components variance explain a small part of the whole variation. In addition, discarded variables in function of the significant simple linear correlation with the nondiscorded variable, were considered redundants. The variables DFE, EPR, BW4, EW1, and EW4 are recommended for principal component analysis of broiler matrix.

Efeito da interação reprodutor x rebanho sobre os valores genéticos de reprodutores para produção de leite e gordura na raça Pardo-Suíça

Records of milk and fat yields were used to study the effects of sire x herd and sire x herd-year interactions on genetic values of Brown Swiss breed sires. The (co)variance components were estimated by the restricted maximum likelihood method, by using three models with multitrait. In these models, the genetic group, season of calving and herd-year class were considered as fixed effects, while the animal effects, the permanent environment, the interaction of either sire x herd or sire x herd-year were considered as random ones, when the interaction was considered in the model, and the error as well. The likelihood ratio test was used to verify the effectiveness in including the interaction effects into models. The estimates of components of the genetic addictive and residual (co)variances did not change when the models were adjusted for the interaction effects. Therefore, the heritability coefficients approximated to each others. The heritability estimate were of 0.40 for both characteristics, and the genetic correlation among the characteristics of 0.94, except when the model considered the effect of the interaction sire x herd. The heritability of fat yield was of 0.39, and the genetic correlation among the characteristics of 0.95. The proportion of the total variance explained by the sire x herd and the sire x herd -year interactions was low, but almost null for milk yield, and about 1% for fat yield. The natural logarithm of likelihood function increased, when the interaction effects were included in the models. Pearson and Spearman correlations among the genetic values obtained by these models were superior than 0.99 for both milk and fat yields, and above 0.897 among the studied characteristics.

Heterogeneidade de Variância na Avaliação Genética de Reprodutores da Raça Pardo-Suíça no Brasil

Data from 6,842 lactations of 3,274 Brown Swiss cows, daughters of 71 sires, from 100 herds, calving from 1980 to 1999 were used to evaluate the effects of heterogeneity of variance on genetic evaluation of bulls. The milk and fat yields adjusted for 305 days of lactation and mature equivalent age were used to classify the herds among high and low production level. An animal model used to estimate variance component, included the fixed effect of herds, age-season of calving and grade of cows, random effect of animal, permanent environment and temporary environment. Variance components were estimated to milk (fat) yield in booth levels, considering the milk or fat yield in each production level as different trait. Estimates of heritability were .38, .38, .39 and .32 for milk and fat yields in high and low production levels, respectively. Genetic correlations between high and low production levels were .85 and .79 to milk and fat yields, respectively. In genetic evaluation programs , it is important to consider differences in variability among herds, otherwise, under selection, the most variables herds would contribute with the majority of the animals, and the genetic evaluations of the animals could be more a function not only from its genetic potential, but also from its environment where the progenies expressed their traits.