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ABSTRACT The objective was to evaluate the existence of heterogeneity of variances and its impact on the genetic evaluation of ponderal performance in sires of the Nellore breed. We used records of adjusted body weights at 210 (W210), 365 (W365), and 450 (W450) days of age. Both W365 and W450 were combined by principal component analyses using the first component (PC). Average daily gain (ADG) was obtained by difference between W450 and W210. The classes of standard deviations (SD) for W210, PC, and ADG were obtained by the standardization of means of herd-year means subclasses, with positive values composing the high SD and values equal and less than zero composing the SD. The model included the fixed effects of contemporary group and age at calving as a covariate, random genetic additive, and maternal genetic (except for PC) effects, and the permanent maternal environment. Variance components were obtained by Gibbs sampling. Posterior means of heritability in analyses without considering heterogeneity of variances ranged from 0.15±0.01 to 0.31±0.01. Posterior means of genetic correlations between the two classes of SD for W210, PC, and ADG were equal to 0.85±0.04, 0.83±0.03, and 0.71±0.08, respectively. Spearman correlation to breeding values of sires for ADG as the selection intensity increased in them, and the correlations between breeding values in general analyses were more correlated with those predicted in the high DP. Therefore, when there is a higher selection intensity on the sires only for the ADG criterion, there is a significant presence of the heterogeneity of variances and impact on the genetic evaluation of the sires. Thus, for ADG, the predictions of breeding values obtained by the genetic evaluation model in which the heterogeneity of variances are not considered are more weighted by the class of greater heterogeneity.

The objective of this study was to estimate (co)variances and genetic parameters and to predict genetic trends for weight at 120 (W120), 210 (W210), 365 (W365), and 450 (W450) days of age in Nelore cattle raised in the northern region of Brazil. The database comprised records of 30,387 animals born between 2000 and 2013 in the Brazilian North. Estimates were calculated by the Restricted Maximum Likelihood (REML) method, in single- and multi-trait analyses in an animal model. Heritability as obtained using single- and multi-trait models for W120 (0.22 and 0.31), W210 (0.20 and 0.34), W365 (0.51 and 0.51), and W450 (0.49 and 0.51) indicated moderate to high magnitudes, with the possibility of genetic selection and incorporation into the herd. Genetic correlations between growth traits were favorable, ranging from 0.78 to 0.96. Genetic trends for W120 and W210 varied largely, from -0.31 to 4.68 and -0.53 to 7.62 kg/year, respectively. Smaller fluctuations were observed in genetic trends for W365 and W450, which ranged from -1.08 to 10.90 and -1.29 to 12.51 kg/year, respectively. Selection for W365 and W450 proved to be the criterion of choice for Nelore herds raised in the region; however, it may compromise adult performance because of higher costs and time for production. A thorough analysis of mattings is recommended to allow the selection of earlier-developing animals.

Body weight records were used to characterize the growth curve of Nelore cattle. Body weight was regressed as a function of age, for both sexes, by using nonlinear models through the functions of Brody, Gompertz, Logistic, Richards, Meloun 1, Von Bertalanffy, and Von Bertalanffy. The quality of the model arrangements was evaluated by employing Akaike and Bayesian Schwarz information criteria. The Brody function provided the best adaptations by the evaluators and, considering the asymptotic weight and the maturation rate as random, a reduction in residual variance of 79% for males and 83% for females was obtained in relation to the models under fixed contexts. In males, the absolute and relative growth rates ranged from 0.921 to 0.261 kg/day and 2.39 to 0.08%, respectively. For the same rates, under another approach, females ranged from 0.922 to 0.198 kg/day and 2.55 to 0.06%, respectively. Males showed greater growth acceleration at the beginning of the growth trajectory, being equal to females at 397 days of age and from that age onward they presented lower estimates. The nonlinear regression model approach under the mixed-models context allows reduction of residual variance, increasing model accuracy.

ABSTRACT The aim of this study was to evaluate genomic information inclusion in genetic parameter estimation of standardized body weight at birth and at 240, 365, and 450 days of age, and visual scores for body structure, precocity, and body muscularity, measured as yearlings in Nelore cattle. We compared genetic parameters, (co)variance components (estimated from Bayesian inference and Gibbs sampling), breeding value accuracies, genetic trends, and principal component analysis (PCA) obtained through traditional GBLUP and ssGBLUP methods. For all traits analyzed, part of the phenotypic variation was explained by the additive genetic effect, thus indicating the capacity of traits to respond to the selection process. Estimates of genetic correlation, in both methodologies, between body weights and visual scores were, in general, high and positive, showing that the selection for visual scores can lead to heavier animals. Genetic trends showed genetic progress, both when estimated breeding values and genomic estimated breeding values were used. The PCA, genetic trends, and accuracy estimates on breeding values showed that inclusion of single nucleotide polymorphism information contributed towards slightly better estimates of the genetic variability of evaluated traits. Genomic information did not bring greater gains in genetic estimates, due to redundancy of kinship information from the pedigree, which already had complete animal kinship data.

The aim of this paper is estimate the (co)variances components in the genetic parameters to the growth traits in Nelore Mocho cattle, raised in Cerrado biome, using Bayesian statistics. The information obtained from 48,063 cattle, provenient of Nelore Mocho herd, born from 1987 to 2009, participant of Breeder and Research Nacional Association's (ANCP) Nelore Brazil Program. The standard weight in 120 (P120), 210 (P210), 365 (P365), 450 (P450) years old has been evaluated, the weight gain from the birth to the weaning (GPND) and the weight gain from weaning to yearling (GPDS). The (co)variances components and genetic parameters have been estimated under univariate analyses considering the Bayesian statistics animal model by the MTGSAM (Multiple Trait using Gibbs Sampler under Animal Model). The estimated values to direct heritability were from medium to high magnitude in standard weights (0.23 to 0.33) and the weight gain (0.18 and 0.24), in creates and recreates phase, respectively. These results indicate the genetic variability existence in Nelore Mocho herd to growth traits, showing effective genetic growth when using the direct selection of these features in genetic improvement programs.

Abstract Background The aim of this study was to assess genome-wide autozygosity in a Nellore cattle population and to characterize ROH patterns and autozygosity islands that may have occurred due to selection within its lineages. It attempts also to compare estimates of inbreeding calculated from ROH (FROH), genomic relationship matrix (FGRM), and pedigree-based coefficient (FPED). Results The average number of ROH per animal was 55.15 ± 13.01 with an average size of 3.24 Mb. The Nellore genome is composed mostly by a high number of shorter segments accounting for 78% of all ROH, although the proportion of the genome covered by them was relatively small. The genome autozygosity proportion indicates moderate to high inbreeding levels for classical standards, with an average value of 7.15% (178.70 Mb). The average of FPED and FROH, and their correlations (− 0.05 to 0.26) were low. Estimates of correlation between FGRM-FPED was zero, while the correlation (− 0.01 to − 0.07) between FGRM-FROH decreased as a function of ROH length, except for FROH > 8Mb (− 0.03). Overall, inbreeding coefficients were not high for the genotyped animals. Autozygosity islands were evident across the genome (n = 62) and their genomic location did not largely differ within lineages. Enriched terms (p

We aimed to evaluate different orders of fixed and random effects in random regression models (RRM) based on Legendre orthogonal polynomials as well as to verify the feasibility of these models to describe growth curves in Nellore cattle. The proposed RRM were also compared to multi-trait models (MTM). Variance components and genetic parameters estimates were performed via REML for all models. Twelve RRM were compared through Akaike (AIC) and Bayesian (BIC) information criteria. The model of order three for the fixed curve and four for all random effects (direct genetic, maternal genetic, permanent environment, and maternal permanent environment) fits best. Estimates of direct genetic, maternal genetic, maternal permanent environment, permanent environment, phenotypic and residual variances were similar between MTM and RRM. Heritability estimates were higher via RRM. We presented perspectives for the use of RRM for genetic evaluation of growth traits in Brazilian Nellore cattle. In general, moderate heritability estimates were obtained for the majority of studied traits when using RRM. Additionally, the precision of these estimates was higher when using RRM instead of MTM. However, concerns about the variance components estimates in advanced ages via Legendre polynomial must be taken into account in future studies.

The identification of genomic regions associated with reproductive traits as well as their biological processes allows a better understanding of the phenotypic variability of these traits. This information could be applied to animal breeding programs to accelerate genetic gain. The aim of this study was to evaluate the association between single nucleotide polymorphisms (SNP) with a scrotal circumference at 365 days of age (SC365) and at 450 days of age (SC450), gestation length (GL) as a calf trait, age at first calving (AFC), accumulated productivity (ACP), heifer early calving until 30 months (HC30), and stayability (STAY) traits, in order to identify candidate genes and biological pathways associated with reproductive traits in Nelore cattle. The data set consisted of pedigree, phenotypes, and genotypes of Nelore cattle from the “Associação Nacional de Criadores e Pesquisadores” (ANCP). The association analyses were performed using the Weighted Single-Step Genome-Wide Association method; the regions, consisting of 10 consecutive SNP, which explained more than 0.5% of additive genetic variance, were considered as a significant association. A total of 3, 6, 7, 5, 10, 25, and 12 windows were associated with SC355, SC450, GL, AFC, ACP, HC30, and STAY, respectively. The results revealed genes with important functions for reproductive traits, such as fertility and precocity. Some genes were associated with more than one trait, among them CAMK1D, TASP1, ACOXL, RAB11FIP5, and SFXN5. Moreover, the genes were enriched in functional terms, like negative regulation of fat cell differentiation, fatty acid alpha-oxidation, and sphingolipids signaling pathway. The identification of the genes associated with the traits, as well as genes enriched in the terms and pathway mentioned above, should contribute to future biological validation studies and may be used as candidate genes in Nelore breeding programs.

The objective of this study was to develop a bio-economic model for the estimation of economic values of economically important traits in a full-cycle beef cattle production system. The bio-economic model calculated economic values by simulating the impact of changes in the profit of the system consisting of a 1% increase in each trait of the breeding objective, while the other traits were kept constant. The bio-economic model was effective in estimating the sources of revenues and expenses of the production system. The estimated economic values were, in the order of importance for the full-cycle system, R$ 3.69 for male slaughter weight, R$ 3.63 for male weaning weight, R$ 3.58 for weaning rate, R$ 3.40 for female slaughter weight, R$ 2.30 for female weaning weight, and R$ 0.13 for mature cow weight. The results showed that all traits evaluated in the full-cycle system had positive economic impact, indicating that selection would increase profitability maximizing the expected response for the traits of the breeding goal.

The causal mutation for polledness in Nelore (Bos taurus indicus) breed seems to have appeared first in Brazil in 1957. The expression of the polled trait is known to be ruled by a few groups of alleles in taurine breeds; however, the genetic basis of this trait in indicine cattle is still unclear. The aim of this study was to identify genomic regions associated with the hornless trait in a commercial Nelore population. A total of 107,294 animals had phenotypes recorded and 2,238 were genotyped/imputed for 777k SNP. The weighted single-step approach for genome-wide association study (WssGWAS) was used to estimate the SNP effects and variances accounted for by 1 Mb sliding SNP windows. A centromeric region of chromosome 1 with 3.11 Mb size (BTA1: 878,631-3,987,104 bp) was found to be associated with hornless in the studied population. A total of 28 protein-coding genes are mapped in this region, including the taurine Polled locus and the IFNAR1, IFNAR2, IFNGR2, KRTAP11-1, MIS18A, OLIG1, OLIG2, and SOD1 genes, which expression can be related to the horn formation as described in literature. The functional enrichment analysis by DAVID tool revealed cytokine-cytokine receptor interaction, JAK-STAT signaling, natural killer cell mediated cytotoxicity, and osteoclast differentiation pathways as significant (P < 0.05). In addition, a runs of homozygosity (ROH) analysis identified a ROH island in polled animals with 2.47 Mb inside the region identified by WssGWAS. Polledness in Nelore cattle is associated with one region in the genome with 3.1 Mb size in chromosome 1. Several genes are harbored in this region, and they may act together in the determination of the polled/horned phenotype. Fine mapping the locus responsible for polled trait in Nelore breed and the identification of the molecular mechanisms regulating the horn growth deserve further investigation.

Reaction Norm (RN) is the study of genotype-environment interaction (GxE) that complies with alternative ways of genotypes within different environments. This study was carried out to verify GxE by a reaction norm model of weights at 120 (W120) and 210 (W210) days of age in Nellore cattle raised in the Humid Tropical Regions of Brazil. Environmental gradients were obtained by solutions of contemporary groups which were fitted as co-variables in the random regression model via reaction norms. Mean weight at 120 days of age was 127.97 kg, and environmental gradients ranged between -27 and +26 kg. Average was 185.60 kg at 210 days of age and gradients ranged from -54 to +55 kg. Scale changes in the breeding values and heritability estimates occurred along the gradients for the two weights; the genetic correlations between breeding value breeding values were also similar for both weights. These correlations were high between the close gradients, and low to even negative between extreme environments. Slopes representing the environmental sensitivity were high, with changes of scale and changes in classification of ten bulls with a great numbers of calves for the two traits. When regression slopes of the ten bulls with the highest breeding value breeding values were evaluated, these values were different in W120 from those in W210, perhaps due to the greater influence of maternal effect on W120. These results characterize the influence of GxE on the pre-weaning weights of animals in the humid tropical regions of Brazil. Due to this, it is possible to get greater precision on the predictions of the animals breeding values breeding value. A less biased selection and a greater genetic progress occurred.

Genetic breeding programs of beef cattle in Brazil are including new features, mainly related to reproductive efficiency.Thus, it is necessary to study the effectiveness of selection and quantify genetic gain for these traits in herds. This study estimated genetic and phenotypic parameters and genetic trends for reproductive traits used in breeding programs for Nelore beef cattle. The traits studied were the scrotal circumference (SC) at 365 and 450 days of age (SC365 and SC450), age at first calving (AFC) and gestation length, as a cow trait (GLcow) and a calf trait (GLcalf). The (co)variance components were obtained with the Restricted Maximum Likelihood Methodology in a single and double-trait analysis of the animal model. For scrotal circumference (SC365 and SC450), positive and favorable genetic gains were observed. For AFC, GLcow and GLcalf, the trends were favorable for selection, but without significant genetic gain. Selection for large SC may reduce AFC and improve female reproductive efficiency. The selection for reproductive traits (SC365, SC450, AFC and GL) may improve reproductive and productive efficiency of Nelore cattle, if used as a selection criterion.

The objective of this study was to estimate heritabilities and genetic and phenotypic correlations for gestation length as calf trait (GLcalf) and preweaning [birth weight (BW) and weights at 120 (W120) and 210 (W210) days] and postweaning performance traits [weights at 365 (W365) and 450 (W450) days] in Nellore cattle participating in the Nellore Brazil Program coordinated by the National Association of Breeders and Researchers (Associação Nacional de Criadores e Pesquisadores - ANCP). The parameters were estimated by the restricted maximum likelihood method under an animal model using the WOMBAT software. The genetic correlation between GLcalf and BW was 0.15, indicating a favorable association between the two traits which, however, was of small magnitude. GLcalf showed low positive genetic correlations (0.06 to 0.10) with the other weights, indicating that selection to reduce gestation length would not result in significant losses in weights at older ages. Furthermore, it is possible to infer that selection for higher W365 will not expressively increase gestation length.

Random regression models are currently used in genetic evaluation of beef cattle, because they allow changes in the mean and variance of the trait over time as well as estimation of (co) variances between any points along the growth curve. This study aimed to estimate (co)variances and genetic parameters for growth traits of Nelore cattle by random regression using models with heterogeneous and homogeneous residual variance. We utilized 23,278 weight records from birth to 550 days of age, from animals born between 1993 and 2010. The best-fitting model considered direct genetic, maternal genetic, permanent environmental animal and maternal permanent environmental effects, adjusted by fourth, third, sixth and fourth order polynomials, respectively. Heritability estimates for direct genetic effect increased from 120 to 450 days of age and then decreased at 550 days of age. Values at 120, 210, 365, 450 and 550 were 0.23, 0.23, 0.38, 0.52 and 0.43, respectively. Estimates of maternal heritability were low for all ages analyzed, ranging from 0.01 to 0.08. The genetic correlations were moderate to high, even at age extremes.

Current analysis estimated co-variance components and genetic parameters for growth traits by random regression models taking into consideration the cow’s age on the weight of calves. Genealogical data and records on weights of male and female Zebu cattle, born between 1993 and 2011, were provided by the National Association of Breeders and Researchers (ANCP). Different models were compared by Akaike and Bayesian criteria. Legendre’s orthogonal polynomials were used to model the direct and maternal genetic effects of maternal and animal permanent environmental effects. Joint modeling of cow age at the moment their progenies were weighed resulted in more accurate estimates of co-variance components and genetics parameters. Co-variance functions of the cow age retrieved the dam effect on real performance of the progenies, reduced biases, improved parameter estimates and predicted breeding rates.

Objetivou-se estimar as herdabilidades para as características de carcaça de área de olho de lombo (AOL), espessura de gordura subcutânea (EG) e espessura de gordura subcutânea na garupa (EGP8), medidas por ultrassonografia, em bovinos da raça Nelore Mocho, criados em bioma Cerrado. As informações utilizadas foram provenientes de criatórios da raça Nelore Mocho, participantes do Programa Nelore Brasil, da Associação Nacional de Criadores e Pesquisadores (ANCP), localizados nos estados que representam as maiores áreas contínuas do bioma Cerrado. As estimativas de herdabilidade foram obtidas mediante análises bi-características, sob modelo animal, utilizando a estatística bayesiana por meio do aplicativo MTGSAM. As estimativas de herdabilidade foram de média magnitude para a AOL (0,25), EG (0,19) e EGP8 (0,25). Os resultados obtidos sugerem que as características de carcaça, avaliadas por ultrassonografia, apresentam grande variabilidade genética e podem ser incluídas em programas de melhoramento genético de bovinos da raça Nelore Mocho.

This study aimed to estimate genetic parameters and genetic trends for reproductive traits and testicular growth in Guzerá cattle. Variance components were estimated through two-trait analyses using the restricted maximum likelihood method. To age at first calving (AFC), first calving interval (FC1), gestation period (GP), and scrotal circumference at 365 and 450 days (SC365 and SC450, respectively) were included the random residual and additive genetic effects and the fixed effects of contemporary group. The covariates cows age at calving and AFC were included in the model for SC365 and SC450 (linear and quadratic effects) and for FC1 (linear effect), respectively. For GP, The random maternal genetic effects were also considered. Heritability estimates ranged from 0.08 ± 0.05 (FC1) to 0.48 ± 0.11 (GP). Genetic trends were significant (P

The objective of this study was to evaluate the effect of the genetic component on the phenotypic expression of productive traits of Nellore cattle submitted to the individual performance test. The data used came from 51 young bulls participating in the individual performance test of Nellore bulls held at the Capim Branco experimental farm of the Federal University of Uberlândia. The evaluated traits were weight and scrotal circumference standardized at 365 and at 450 days of age, the longissimus muscle area, and the backfat thickness. The expected progeny differences of the animals and the sires were considered to evaluate the contribution of the genetic component. Variance analysis was performed through the General Linear Model procedure of the Statistical Analysis System to verify the effects of the genetic groups on the productive performance. The progenies of bulls with greater genetic potential tend to present better productive performance. In conclusion, the use of genetically superior animals allows better zootechnical indexes to be obtained, reflecting higher gains in herd productivity. Keywords: beef cattle; breeding value; productivity, selection.

The objective of this study was to investigate the application of BLUP and single step genomic BLUP (ssGBLUP) models in different scenarios of paternity uncertainty with different strategies of scaling the G matrix to match the A22 matrix, using simulated data for beef cattle. Genotypes, pedigree, and phenotypes for age at first calving (AFC) and weight at 550 days (W550) were simulated using heritabilities based on real data (0.12 for AFC and 0.34 for W550). Paternity uncertainty scenarios using 0, 25, 50, 75, and 100% of multiple sires (MS) were studied. The simulated genome had a total length of 2,333 cM, containing 735,293 biallelic markers and 7,000 QTLs randomly distributed over the 29 BTA. It was assumed that QTLs explained 100% of the genetic variance. For QTL, the amount of alleles per loci randomly ranged from two to four. The BLUP model that considers phenotypic and pedigree data, and the ssGBLUP model that combines phenotypic, pedigree and genomic information were used for genetic evaluations. Four ways of scaling the mean of the genomic matrix (G) to match to the mean of the pedigree relationship matrix among genotyped animals (A22) were tested. Accuracy, bias, and inflation were investigated for five groups of animals: ALL = all animals; BULL = only bulls; GEN = genotyped animals; FEM = females; and YOUNG = young males. With the BLUP model, the accuracies of genetic evaluations decreased for both traits as the proportion of unknown sires in the population increased. The EBV accuracy reduction was higher for GEN and YOUNG groups. By analyzing the scenarios for YOUNG (from 0 to 100% of MS), the decrease was 87.8 and 86% for AFC and W550, respectively. When applying the ssGBLUP model, the accuracies of genetic evaluation also decreased as the MS in the pedigree for both traits increased. However, the accuracy reduction was less than those observed for BLUP model. Using the same comparison (scenario 0 to 100% of MS), the accuracies reductions were 38 and 44.6% for AFC and W550, respectively. There were no differences between the strategies for scaling the G matrix for ALL, BULL, and FEM groups under the different scenarios with missing pedigree. These results pointed out that the uninformative part of the A22 matrix and genotyped animals with paternity uncertainty did not influence the scaling of G matrix. On the basis of the results, it is important to have a G matrix in the same scale of the A22 matrix, especially for the evaluation of young animals in situations with missing pedigree information. In these situations, the ssGBLUP model is an appropriate alternative to obtain a more reliable and less biased estimate of breeding values, especially for young animals with few or no phenotypic records. For accurate and unbiased genomic predictions with ssGBLUP, it is necessary to assure that the G matrix is compatible with the A22 matrix, even in situations with paternity uncertainty.

This study was carried out to spatialize climatic factors that best discriminate the states of Maranhão, Pará and Tocantins, to analyze the structure of phenotypic correlation between phenotypic variables weights standardized at 120, 210, 365, 450 and 550 days old and propose phenotypic indices for animals selection in these States. The climate variables analyzed were maximum temperature, minimum temperature, average temperature, precipitation, normalized difference vegetative index, humidity, altitude and temperature and humidity index. Univariate and multivariate approach were used by procedures program Statistical Analysis System, SAS, to explain the relationship intra-variables, phenotypic and environmental variation. The expected differences in the progenies (EDPs) were predicted using the software MTDFREML. All climatic and phenotypic variables were effective in discriminating the Maranhão, Pará and Tocantins States. Thus, we suggest the use of phenotypic indices for classification and animals’ selection within each State.

The objective of the present study was to analyze the phenotypic inter-relationships between growth, feed intake and carcass traits in polled Nellore cattle, as well as to determine which bulls produced the most efficient progeny. The experiment was conducted in the feedlot of the Guaporé Pecuária (Livestock) Company, OB Brand. The following traits were analyzed: initial live weight (ILW); final live weight (FLW); average daily gain (ADG); dry matter intake (DMI); gain:feed (G:F); residual feed intake (RFI); rib-eye area (REA); rump fat thickness (RF); backfat thickness at the 12th-13th rib (BF); weighted fat score (WF); and intramuscular fat percentage (IMF). Both univariate and multivariate analyses were performed to analyze the inter-relationships between the studied traits. No significant phenotypic associations were observed between growth, carcass traits and residual feed intake, while the correlation between RFI and G:F was negative. Therefore, RFI may be used to select more nutritionally efficient animals without compromising growth or adult size. The selection of bulls with progeny showing low residual feed intake is recommended, as selection for low RFI tends to improve feed efficiency without compromising growth and development.

A total of 204,912 records of birth weights up to 550 days of age, of 24,890 Nellore cattle, offspring of 375 sires and 16,917 dams from five herds in the state of Mato Grosso, Brazil, were used in order to describe the variability of the weight development by random regression models. The model evaluated as the most suitable used the covariance function of fourth order to describe the variability of the effects of additive genetic, animal permanent environmental and maternal effects of third order to describe the maternal genetic effect, with four classes of residual variance. Heritability estimates ranged from 0.18 to 0.46 from the beginning of trajectory to 210 days of age, from 0.45 to 0.48 post-weaning to 365 days of age and from 0.47 to 0.57 at later ages. The values of additive genetic correlations for different ages showed higher estimates between the closest ages, while birth weight was not very related to the weights at older ages. The body weight performance of the animals has additive genetic variation to respond to selection.

Objetivou-se estimar parâmetros genéticos, utilizando inferência Bayesiana, para as estimativas dos parâmetros individuais de peso à maturidade (Â) e taxa de crescimento (), obtidos pela função de crescimento Brody. O arquivo estava constituído de 14.563 registros de pesos e idades referentes a 1.158 fêmeas da raça Nelore, participantes do Programa de Melhoramento Genético da Raça Nelore. Para a análise das estimativas dos parâmetros da curva, via inferência bayesiana, foi proposto um modelo animal unicaráter, que incluiu como fixo o efeito de grupo contemporâneo (animais nascidos no mesmo estado, no mesmo trimestre do ano, mesmo ano e mesmo regime alimentar) e como aleatórios os efeitos genético direto e residual. Nessa análise, foram utilizados dois diferentes tamanhos para as cadeias geradas pelo algoritmo de amostragem de Gibbs, de 550 e 1.100 mil ciclos, com períodos de descarte amostral de 50 e 100 mil ciclos, respectivamente, e amostragens a cada 500 e 1.000 ciclos, respectivamente. As médias posteriores da variância genética aditiva e residual foram próximas, tanto para  quanto para a , mesmo quando implementados diferentes tamanhos para as cadeias geradas pelo algoritmo de amostragem de Gibbs. Os coeficientes de herdabilidade estimados para Â, variaram de 0,44 a 0,46, amplitude semelhante aos 0,46 a 0,48 obtidos para as estimativas de . Essas magnitudes indicam que a seleção pode ser usada como instrumento para alterar a forma da curva de crescimento desses animais. Entretanto, o uso das informações obtidas, visando à alteração da curva de crescimento dos animais, deve ser feito com grande cautela, uma vez que as características a serem trabalhadas na modificação do formato da curva de crescimento, de acordo com resultados da literatura especializada, são negativamente correlacionadas.The objective of this study was to estimate genetic parameters using Bayesian inference for the estimates of individual parameters of mature weight (Â) and growth rate (), obtained by Brody growth function. The file consisted of 14,563 records relating to weights and ages of 1,158 Nelore females, participants in the Genetic Improvement Program of the Nellore. For the estimates analysis of the curve parameters via Bayesian inference, it was used an univariated animal model that included as fixed effect of contemporary group (animals born on the same state, in the same quarter of the year, the same year and feedlot) and random as the direct genetic and residual. In this analysis it was used two different sizes for the chains generated by Gibbs sampling algorithm, 550 and 1.1 million cycles, with initial discarding of 50 000 and sample of 100 000 cycles, respectively, and sampled every 500 cycles and 1000, respectively. The mean posterior and residual additive genetic variance showed a small variation to both  and , even when implemented in different sizes for the chains generated by Gibbs sampling algorithm. The heritability estimates for Â, ranged from 0.44 to 0.46, similar to the range 0.46 to 0.48 obtained for the estimates of . These magnitudes indicate that the selection can be used as a tool to change the shape of the growth curve of these animals. However, the use of the information to amend the growth curve of animals, must be done with great care, since the traits to be worked in the modification of the shape of the growth curve according to the literature results are negatively correlated.

(Co)variances, heritability and genetics change were estimated for weight at 120 (W120), 210 (W210), 365 (W365), 450 (W450) and 550 (W550 ) days of age in Nellore cattle from the Humid Tropical region of Brazil. A total of 65,876 records of animals born between 1993 to 2010 and raised on pasture were used. The (co)variance components were estimated by restricted maximum likelihood, and breeding values were predicted using an individual animal model. The genetic trends were plotted by linear regression of breeding values in the animals’ birth year. The heritability coefficients due to direct genetic effect were 0.37±0.019; 0.39±0.019; 0.41±0.013; 0.41±0.015 and 0.41±0.021 The maternal heritability estimates for W120 and W210 were 0.05±0.011 and 0.06±0.011, respectively. The genetic gains were 1.326, 2.014, 2.670, 3.056 and 3.128 kg/year for W120, W210, W365, W450 and W550, respectively. The estimates of genetic parameters and trends indicate the existence of genetic progress in pre- and post-weight traits from herds of Brazil Tropic Humid region.

Verificou-se a influência da heterogeneidade de variâncias na avaliação genética de bovinos de corte da raça Nelore. Dados de pesos padronizados aos 365, 450 e 550 dias de idade foram estratificados com base no desvio-padrão fenotípico dos rebanhos para cada peso. Nas análises de múltiplas características, em que o mesmo peso foi considerado característica distinta em cada classe de desvio-padrão, as variâncias genéticas e residuais aumentaram com o desvio-padrão da classe. As estimativas de herdabilidade foram iguais a 0,34 e 0,36; 0,41 e 0,41, 38 e 49 nas classes de alto e baixo desvio-padrão fenotípico para os pesos aos 365, 450 e 550 dias, respectivamente. As correlações genéticas entre o mesmo peso nas classes de baixo e alto desvio-padrão foram iguais a 0,71; 0,80; e 0,84 para os pesos aos 365, 450 e 550 dias, respectivamente. As correlações de Spearman entre os valores genéticos, obtidos de análises múltiplas e de análise geral (sem as classes), e entre o mesmo peso nas classes de desvios-padrão, reduziram à medida que aumentou a intensidade de seleção sobre os reprodutores. A presença de heterogeneidade de variâncias causa maior impacto sobre a avaliação genética dos reprodutores sob intensidade de seleção elevada, sendo interessante sua consideração no processo de avaliação genética.Data from Nellore beef cattle breed were used to study the influence of variance heterogeneity on genetic evaluation. Adjusted weights at 365, 450 and 550 days of age were classified as high and low classes of standard deviation, based on phenotypic standard deviation of herds in each weight. At multiple trait analyses, where the same weight was considered a distinct characteristic regarding each class of standard deviation, genetic and residual variances increased as the standard deviation of the class increased. Genetic correlations between the same weight, in high and low phenotypic standard deviation classes were 0.71, 0.80 and 0.84 for weights at 365, 450 and 550 days, respectively. Spearman correlations between breeding values obtained from multiple trait analyses and general analysis (without classes), and between classes of standard deviations, lowered as the intensity of selection on sires increased. The presence of heterogeneity of variances has greater impact on the genetic evaluation of breeding under high intensity of selection, it is interesting your consideration in the process of genetic evaluation.

This study aimed to compare estimates of (co)variances considering the effect of direct maternal genetic correlation (-0,50; -0,25; +0,25; +0,50); the ratios between the direct and maternal genetic variances (75:75; 50:100; 100:50) and two models which included (M2) or not (M1) the direct maternal genetic covariance. Stochastic simulation of twenty replicates of a closed and randomly mated herd of cattle was carried out for twenty years of selection. The base population was not related, nonselected and randomly sampled. (Co)variance estimates were obtained under single trait animal model using MTDFREML application. The model was not significant on estimates of maternal permanent environmental variance. The genetic direct-maternal correlation influenced all (co)variance estimates significantly (P

Objetivou-se avaliar os efeitos das interações genótipo-ambiente sobre as estimativas de componentes de (co)variâncias e predição dos valores genéticos para o peso ao desmame de bovinos Nelore, sob enfoque bayesiano. Foram utilizados 16.644 registros de pesos ao desmame de bovinos provenientes de dez rebanhos participantes do Programa Nelore Brasil. Os parâmetros genéticos foram estimados sob modelo animal, considerando a estatística bayesiana. Para verificar o efeito da interação genótipo-ambiente, foram analisados os seguintes modelos matriciais: sem a inclusão dos efeitos de interação genótipoambiente; com a inclusão dos efeitos de interação genótipo-ambiente, em que se considerou o efeito de touro-ano, touro-rebanho e ambos os efeitos. De modo geral, verifica-se que a inclusão da interação genótipo-ambiente na análise genética para o peso ao desmame, tende a alterar as estimativas de (co)variâncias genéticas e ambientais. As correlações de Spearman entre os valores genéticos foram acima de 97%, indicando que, praticamente, não houve mudança na classificação dos animais avaliados. Pode se inferir que os efeitos de interação touro-ano e touro-rebanho não alteram as classificações dos animais, e a não-inclusão destes efeitos na avaliação genética, não afetam a seleção baseada nas predições dos valores genéticos para o peso ao desmame.The objective was to evaluate the interactions of genotype-environment effects on the components of (co)variance estimates and the prediction of breeding values for weaning weight in Nelorecattle, using a Bayesian approach. Records of 16,644 weaning weights were used from cattle distributed in ten ranches across six Brazilian states. The genetic parameters were estimated under an animal model considering Bayesian statistics. To verify genotype-environmentinteraction effects, we analyzed the following matrix model: without the inclusion of genotype-environment interaction effects, and with the inclusion of genotype-environment interaction effects, which considered the effect of sire-year, sire-herd, and both effects. Ingeneral, the results suggest that the inclusion of genotype-environment interaction in genetic analysis for weight at weaning tends to alter the estimates of genetic and environment (co)variances. The Spearman correlations between the breeding values were above 97%, indicating practically no change in the classification of animals evaluated. It can be inferred that the interaction effects of sire-year and sire-herd do not change the animals rank, and if not included in the genetic evaluation, the selection based on predictions of breeding values for weaning weight will not be affected.

Records from 75,941 Nelore cattle were used to determine the importance of genotype by environment interaction (GEI) in five Brazilian states. (Co)variance components were estimated by single-trait analysis (with yearling weight, W450, considered to be the same trait in all states) and multiple-trait analysis (with the record from each state considered to be a different trait). The direct heritability estimates for yearling weight were 0.51, 0.39, 0.44, 0.37 and 0.41 in the states of Goiás, Mato Grosso, São Paulo, Mato Grosso do Sul and Minas Gerais, respectively. The across-state genetic correlation estimates between Goiás and Mato Grosso, Goiás and Minas Gerais, São Paulo and Minas Gerais, and Mato Grosso do Sul and Minas Gerais ranged from 0.67 to 0.75. These estimates indicate that GEIs are biologically important. No interactions were observed between Goiás and São Paulo, Goiás and Mato Grosso do Sul, Mato Grosso and São Paulo, Mato Grosso and Mato Grosso do Sul, Mato Grosso and Minas Gerais, or São Paulo and Mato Grosso do Sul (0.82 to 0.97). Comparison of single and multiple-trait analyses showed that selection based on the former was less efficient in the presence of GEI, with substantial losses (up to 10%) during selection.

Objetivou-se com este trabalho utilizar regras de associação para identificar forças de mercado que regem a comercialização de touros com avaliação genética pelo programa Nelore Brasil. Essas regras permitem evidenciar padrões implícitos nas transações de grandes bases de dados, indicando causas e efeitos determinantes da oferta e comercialização de touros. Na análise foram considerados 19.736 registros de touros comercializados, 17 fazendas e 15 atributos referentes às diferenças esperadas nas progênies dos reprodutores, local e época da venda. Utilizou-se um sistema com interface gráfica usuário-dirigido que permite geração e seleção interativa de regras de associação. Análise de Pareto foi aplicada para as três medidas objetivas (suporte, confiança e lift) que acompanham cada uma das regras de associação, para validação das mesmas. Foram geradas 2.667 regras de associação, 164 consideradas úteis pelo usuário e 107 válidas para lift ≥ 1,0505. As fazendas participantes do programa Nelore Brasil apresentam especializações na oferta de touros, segundo características para habilidade materna, ganho de peso, fertilidade, precocidade sexual, longevidade, rendimento e terminação de carcaça. Os perfis genéticos dos touros são diferentes para as variedades padrão e mocho. Algumas regiões brasileiras são nichos de mercado para touros sem registro genealógico. A análise de evolução de mercado sugere que o mérito genético total, índice oficial do programa Nelore Brasil, tornou-se um importante índice para comercialização dos touros. Com o uso das regras de associação, foi possível descobrir forças do mercado e identificar combinações de atributos genéticos, geográficos e temporais que determinam a comercialização de touros no programa Nelore Brasil.The aim of this work was to use association rules to identify forces that govern bull trade with genetic evaluation by Programa Nelore Brasil. Those rules permit to highlight patterns implicit in the transactions of large databases, which indicate determining causes and effects of supply and trade of bulls. In the analysis, it was considered 19,736 records of traded bulls, 17 farms and 15 attributes related to expected differences on the progenies of sires, place and time of sale. A system with user-driven graphical interface that allows generation and interactive selection of association rules was used. Pareto analysis was applied for the three objective measures (support, trust and lift) that follow each one of the association rules to validate them. It was generated 2,667 association rules, 164 considered to be useful by the user and 107 valid for lift ≥ 1.0505. The farms participating in the Nelore Brasil program present expertise in bull offering according to maternal ability characteristics, weight gain, fertility, sexual precocity, longevity, yield and termination of carcass. The genetic profiles of the bulls are different for standard and Mocho Nellore varieties. Some Brazilian regions are market niche for sires without registered herd. The analysis of evolution of the market suggests that Mérito Genético Total (MGT), the official index of the Program Nelore Brasil has become an important index for commercialization of bulls. By using association rules, it was possible to discover market forces and to identify combinations of genetic, geographical and temporal attributes that determine commercialization of bulls in Nelore Brasil program.

O objetivo deste trabalho foi analisar a variabilidade genética da raça Brahman no Brasil, por meio da análise de 15.851 pedigrees. O arquivo de dados foi dividido em dois períodos: 1998-2001 e 2002-2005. A variabilidade genética foi avaliada por parâmetros baseados na probabilidade de origem do gene: número efetivo de ancestrais, número efetivo de fundadores, número efetivo de genomas remanescentes e coeficientes de parentesco e de endogamia. Os valores encontrados quanto ao número de fundadores mostraram que a população está em expansão, embora o número efetivo de fundadores tenha diminuído de um período para outro. Os resultados foram diferentes em relação ao número de ancestrais e genomas remanescentes, que apresentaram crescimento de 23% nos períodos avaliados. O coeficiente de endogamia diminuiu nos períodos estudados, porém o coeficiente de parentesco "inter se" cresceu. Poucos ancestrais apresentaram grande contribuição genética para a população, o que evidencia a utilização de poucos indivíduos na reprodução. A raça Brahman, no Brasil, encontra-se em expansão, caracterizada pela diminuição do coeficiente de endogamia e aumento nos números efetivos de fundadores e de genótipos remanescentes. Entretanto, a variabilidade genética da raça mostra aumento do parentesco "inter se" e grande concentração do patrimônio genético de poucos indivíduos na população.This work aimed to analyse the genetic variability of Brahman breed in Brazil, through the analysis of 15,851 pedigrees. The data file was divided into two periods: 1998-2001 and 2002-2005. The genetic variability was evaluated by the following parameters, based on the probability of gene origin: number of ancestors, effective number of founders, effective number of remaining genomes, and the relationship and inbreeding coefficients. The values for the number of founders showed that the population is expanding, although the effective number of founders has been reduced from one period to the other. The results were different for the number of ancestors and the remaining genomes, which grew by 23% in the studied periods. The inbreeding coefficient decreased in the studied periods, but the "inter se" relationship coefficient increased. Few ancestors showed great genetic contribution to the population, which indicates the use of small number of individuals in the reproduction. Brahman breed population in Brazil is expanding, characterized by the decreasing of the inbreeding coefficients and the increasing of the effective number of ancestors and remaining genotypes. Nevertheless, the breed genetic variability shows increasing "inter/ se" relationships and a great concentration of gene heritage of few individuals in the population.

O Brasil é um dos lideres mundiais em produção de animais de interesse zootécnico. Porém, para manter este status, precisa investir grandemente em pesquisas que visem aumentar a produtividade animal. No âmbito do melhoramento genético animal, o Brasil conta com muitos grupos que desenvolvem estudos de grande interesse nesta área. São estudos que vão desde os clássicos trabalhos de estimativas de componentes de variância e parâmetros genéticos, passando por trabalhos de modelagem estatística até chegar aos trabalhos mais recentes envolvendo genética molecular aplicada ao melhoramento animal. Assim, a presente revisão tem por objetivo sumarizar os caminhos pelo qual o melhoramento genético animal no Brasil trilhou ao longo da primeira década do século 21, os quais podem indicar os avanços obtidos e os novos desafios.Brazil is an important world leader in animal yield, but to maintain this status, needs to invest heavily in research to increase animal productivity. For Animal Breeding purpose, Brazil has many groups that develop important studies. Those studies ranging from estimating components of variation and genetic parameters, statistical modeling, and molecular markers applied to animal breeding. Thus, this review aims to summarize the research in animal breeding in Brazil through the first decade of the 21st century, which can indicate the progress and new challenges.

Data from 23,120 Nellore animals were used to estimate genetic parameters for age at first calving, average gains from weaning to yearling and from yearling to after yearling, weaning weight, yearling weight, after yearling weight and weight at 2 and 5 years of age. Animal models were fitted by Restricted Maximum likelihood Method. Estimate heritability for age at first calving, weaning to yearling weight gain, yearling to after yearling weight gain, weight at weaning, yearling weight, after yearling weight and weight from 2 to 5 years of age were 0.17 ± 0.01; 0.23 ± 0.03; 0.25 ± 0.03; 0.28 ± 0.02; 0.26 ± 0.03; 0.30 ± 0.03; 0.32 ± 0.02 and 0.36 ± 0.04, respectively. The genetic correlation estimates between age at first calving and weight traits ranged from -0.26 to -0.14. The genetic correlation estimates between age at first calving and average gains were also negative, but higher (-0.29 and -0.32). In general, these results indicate that selection for average gains will promote changes in age at first calving and female mature weight. Improvement in reproductive performance could be obtained with the inclusion of the age at first calving in the selection index.Dados de 23.120 animais da raça Nelore foram utilizados para estimar herdabilidade e correlações genéticas para a idade ao primeiro parto, o ganho em peso da desmama ao ano e do ano ao sobreano, o peso à desmama, o peso ao ano, o peso ao sobreano e os pesos aos 2 e aos 5 anos de idade. Utilizou-se o método da máxima verossimilhança restrita, em análise multicaracterística. As herdabilidades estimadas para idade ao primeiro parto, ganho da desmama ao ano, ganho do ano ao sobreano, peso à desmama, peso ao ano, peso ao sobreano e peso aos 2 aos 5 anos foram de 0,17 ± 0,01; 0,23 ± 0,03; 0,25 ± 0,03; 0,28 ± 0,02; 0,26 ± 0,03; 0,30 ± 0,03; 0,32 ± 0,02 e 0,36 ± 0,04, respectivamente. Correlações genéticas baixas e negativas foram estimadas entre a idade ao primeiro parto e os pesos medidos em diferentes idades, que variaram de -0,26 a -0,14. As correlações genéticas estimadas entre a idade ao primeiro parto e os ganhos de peso também foram negativas, porém levemente superiores (-0,29 e -0,32). Os resultados indicam que a seleção para maior ganho de peso pode reduzir a idade ao primeiro parto e aumentar o peso adulto de fêmeas da raça Nelore. Mudança genética mais rápida para diminuição da idade ao primeiro parto das fêmeas pode ser obtida com a inclusão dessa característica nos índices de seleção.

Dados de 19.458 animais da raça Nelore, nascidos entre 1975 e 2002 e pertencentes a oito fazendas participantes do Programa de Melhoramento Genético da Raça Nelore (PMGRN), foram utilizados para estimar componentes de covariância, herdabilidade e correlações genéticas dos pesos ao nascimento, à desmama, ao sobreano e aos 2, 3 e 5 anos de idade. Utilizou-se o método da máxima verossimilhança restrita, em análises uni, bi e multicaracterísticas, com modelos que incluíram o efeito genético aditivo direto, como aleatório, além dos efeitos fixos de grupo de contemporâneos e os efeitos linear e quadrático da idade do animal à pesagem (com exceção do modelo para peso ao nascer) e da idade da mãe ao parto. O efeito aleatório de ambiente permanente materno também foi incluído nos modelos de análise do peso ao nascer, peso à desmama e peso ao sobreano e o efeito aleatório genético materno somente no modelo do peso à desmama. As herdabilidades estimadas em análise multicaracterística para os pesos ao nascer, à desmama, ao sobreano, aos 2, 3 e aos 5 anos de idade foram 0,25; 0,33; 0,34; 0,32; 0,33 e 0,35, respectivamente. As correlações genéticas estimadas entre os pesos foram positivas e de moderadas a altas magnitudes e tenderam a diminuir com o aumento da distância entre as pesagens, o que indica que a seleção para peso em qualquer idade deverá promover mudança genética nos pesos nas demais idades, inclusive no peso adulto de fêmeas da raça Nelore. As estimativas de herdabilidade obtidas na análise multicaracterística foram superiores, sobretudo para os pesos aos 3 e aos 5 anos de idade, o que sugere melhor partição das variâncias genética e de ambiente em comparação às análises uni e bicaracterísticas, porém a alta demanda de recursos computacionais em análises de muitas características pode ainda dificultar o uso dessas análises em grandes bancos de dados.Records of 19,458 Nellore breed animals, born from 1975 to 2002, from 8 herds participating in the Nellore Cattle Breeding Program (NCBP) were used to estimate (co)variance components, heritability and genetic correlations for birth weight, weaning weight, weight after yearling and at 2, 3 and 5 years of age. The restricted maximum likelihood method, with univariate, bivariate and multivariate analyses, was used. The models included the random additive genetic direct effect (animal) and fixed effects of age group and the linear and quadratic effects of calf age (except for the birth weight model) and age dam at calving. The random effect of permanent maternal environment was included in the analyses models for birth weight, weaning weight and yearling weight, and the random effect of maternal genetics only in the model for weaning weight. The heritability estimates, in multivariate analysis for weights at birth, weaning, yearling and at 2, 3 and 5 years of age were 0.25; 0.33; 0.34; 0.32; 0.33 and 0.35, respectively. The genetic correlations estimated between traits were positive and moderate to high in magnitude and tended to decrease with the increase in the distance between records, that indicated that selection for weight at any age will promote genetic change in weights at other ages including the female mature weight of the Nellore breed. The heritability estimates obtained in the multivariate analysis were high, especially at 3 and 5 years of age, suggesting better partition of genetic and environmental variances compared to uni and bivariate analyses but, high computer demands can still hinder its use in large databases.

Os objetivos neste trabalho foram avaliar as relações entre os escores visuais de estrutura corporal, precocidade e musculosidade ao sobreano (aproximadamente 550 dias de idade) com características de crescimento para verificar as possibilidades de utilizar essas características como critérios de seleção. Foram obtidas estimativas dos componentes de covariâncias por máxima verossimilhança restrita empregando-se um modelo animal com o efeito fixo de grupo contemporâneo e a idade como covariável (efeitos linear e quadrático). Os grupos contemporâneos foram definidos pelas variáveis: sexo; ano, estação e fazenda de nascimento; e fazenda e grupo de manejo aos 120, 210, 365 e 550 dias de idade. Foram utilizadas 1.367 observações de estrutura corporal, precocidade e musculosidade. As estimativas de herdabilidade foram de 0,24 ± 0,09 para estrutura corporal; 0,63 ± 0,12 para precocidade e 0,48 ± 0,11 para musculosidade, e as estimativas de correlações genéticas entre os escores foram 0,49 entre estrutura corporal e precocidade; 0,63 entre estrutura corporal e musculosidade; e 0,90 entre precocidade e musculosidade. As correlações genéticas entre os escores de estrutura corporal, precocidade e musculosidade, e o peso ao sobreano foram todas positivas (0,83; 0,42 e 0,50, respectivamente), enquanto as estimativas de correlações genéticas entre altura de posterior e os escores de estrutura corporal, precocidade e musculosidade, respectivamente, foram 0,57, -0,29 e -0,33. As características estrutura corporal, precocidade e musculosidade ao sobreano apresentaram variação genética aditiva de moderada a alta. As correlações genéticas dos escores com altura do posterior indicam que a seleção de animais mais altos, ainda que indireta, pode ocasionar aumento da estrutura corporal média dos animais, que poderão ser menos precoces e menos musculosos ao sobreano. A seleção para os escores visuais, principalmente para estrutura corporal, deve promover aumento no peso ao sobreano dos animais.The objectives of this study were to evaluate the associations between visual scores of body structure, precocity and muscling at 550 days of age and growing traits, and verify the possibilities of applying these traits as selection criteria. (Co)variance components were estimated by restricted maximum likelihood, employing an animal model with fixed effects of contemporary group and age as a covariate (linear and quadratic effects). Contemporary groups were defined by variables: sex; year, season and herd of birth; herd and management group at 120, 210, 365 and 550 days of age. Scores from 1,367 animals for body structure, precocity and muscling were evaluated. Heritability estimates for the visual scores were 0.24 ± 0.09 for body structure, 0.63 ± 0.12 for precocity and 0.48 ± 0.11 for muscling. Genetic correlations estimates among the scores were 0.49 for body structure and precocity, 0.63 between body structure and muscling, 0.90 between precocity and muscling. The genetic correlation estimates among the scores of body structure, precocity and muscling and weight at 550 days were all positive (0.83, 0.42 and 0.50, respectively), while the genetic correlation estimates between hip height and body structure, precocity and muscling were 0,57, -0,29 and -0,33, respectively. Scores for body structure, precocity and muscling at 550 days of age presented moderate-to-large additive genetic variability. The genetic correlation estimates between visual scores and hip height indicated that the selection of taller animals, even though indirectly, can increase the body structure of animals and decrease precocity and muscling at 550 days. Selection for visual scores, especially body structure, should increase animal weight at 550 days.

O objetivo neste estudo foi estimar as correlações genéticas entre escores visuais e características de carcaça medidas por ultrassonografia em bovinos da raça Nelore utilizando a estatística bayesiana por meio da Amostragem de Gibbs, sob modelo animal linear-limiar. Foram estudadas as características categóricas morfológicas de musculosidade, estrutura física, conformação e sacro, avaliadas aos 15 e 22 meses de idade. Para as características de carcaça, foram avaliadas as características área de olho-de-lombo, espessura de gordura subcutânea, espessura de gordura subcutânea na garupa e altura na garupa. Os escores visuais devem ser empregados como critérios de seleção para aumentar o progresso genético para a característica área de olhode-lombo e, consequentemente, melhorar o rendimento de carcaça. As estimativas de correlação genética obtidas para musculosidade com espessura de gordura subcutânea e espessura de gordura subcutânea na garupa indicaram que a seleção para musculosidade pode levar a animais com melhor acabamento de carcaça. A seleção para a estrutura física e conformação aos 15 e 22 meses de idade pode promover resposta correlacionada para o aumento da altura na garupa.The objective of this study was to estimate the genetic correlations between visual scores and the carcass traits measured by ultrasound, in Nellore breed cattle, using the bayesian statistics by Gibbs Sampling, in the linear-threshold model. The morphological categorical traits of musculature, physical structure, conformation and sacrum were studied, evaluated at 15 and 22 months. The carcass traits of the longissimus muscle area, backfat thickness, rump fat thickness and hip height were evaluated. Visual scores should be used as selection criterion to increase genetic progress for the longissumus muscle area. The estimates of genetic correlations obtained between musculature and backfat thickness and rump fat thickness indicated that the selection for musculature may lead to animals with better carcass finishing. Selection for physical structure and conformation, at 15 and 22 months, should promote response correlated with the hip height.

Os objetivos neste estudo foram estimar parâmetros genéticos das características categóricas musculosidade, estrutura física, aspectos raciais, conformação, ônfalo, pigmentação e sacro e predizer os valores genéticos utilizando-se a estatística bayesiana sob modelo animal de limiar, considerando diferentes idades de bovinos da raça Nelore. As informações de escores visuais foram obtidas nos anos de 2000 a 2005 de bovinos provenientes de 13 fazendas participantes do Programa Nelore Brasil. Nas análises bicaracterísticas, foram utilizados 500.000 até 1.100.000 ciclos para alcançar a convergência da cadeia de Gibbs. O descarte inicial e o intervalo amostral foram de 100.000 e 1.000 ciclos, respectivamente. As características de escores visuais avaliadas aos 8 e 22 meses de idade apresentaram estimativas de herdabilidades moderadas, indicando resposta rápida à seleção direta. Os escores visuais indicaram possibilidade de resposta rápida à seleção direta e, portanto, devem ser incorporados em programas de melhoramento genético como critérios de seleção. As estimativas de correlações genéticas entre musculosidade, estrutura física e conformação também indicam que a seleção direta para uma destas características trará progresso genético às outras. Recomenda-se utilizar os escores visuais como critérios de seleção em pelo menos duas fases de vida do animal, na desmama e ao sobreano.The objectives of this study were to estimate the genetic parameters of the following categorical traits: musculature, physical structure, racial breed aspects, conformation, navel, pigmentation and sacrum, and predict breeding values, using bayesian statistics under threshold animal models, considering different ages of cattle of the Nelore breed. The information concerning visual scores were obtained from 2000 to 2005 from cattle of the Nelore breed from thirteen participant farms of the Brazilian Nelore Program. In the two-trait analyses, 500,000 rounds up to 1,100,000 cycles were used to reach the convergence of the Gibbs chain. The burn-in and thinning interval were 100,000 and 1,000 cycles, respectively. The evaluated visual scores at the age of 8 and 22 months presented moderate heritability estimates, suggesting that these traits can be used to promote genetic gain by direct selection. The genetic correlations between the morphological traits of musculature, physical structure and conformation were moderate, indicating correlated responses between the traits. The use of the visual scores is recommended, as selection criteria, in at least two phases of the animal life, at weaning and yearling time.

Este trabalho teve por objetivo estudar as causas de variação nos preços de bovinos da raça nelore pertencentes a rebanhos de seleção, os quais foram comercializados em leilões, para verificar as influências das avaliações genéticas e dos julgamentos de exterior sobre esses preços. Para tanto, foram computados os preços de venda de 426 bovinos da referida raça em 12 leilões ocorridos em diversas localidades brasileiras (regiões Centro-Oeste, Norte e Sudeste), entre os anos de 2002 e 2005. O valor médio foi de R$ 3.325,49, sendo o mínimo de R$ 1.400,00 e o máximo de R$ 10.500,00. Esses dados foram digitados juntamente com outras informações que eram apresentadas nos catálogos dos leilões. As informações registradas incluíram o sexo de cada animal, o nome do leilão e as DEPs informadas nos catálogos. Além da avaliação da influência das informações dos catálogos, também foi avaliada a influência das informações dos reprodutores, pais dos animais vendidos nos leilões, envolvendo suas DEPs publicadas em um sumário de reprodutores da raça e as pontuações de suas progênies em julgamentos. Os métodos estatísticos aplicados foram análises de variâncias e análises de agrupamento (método K-médias). Como resultado, foi observado que animais com superioridade genética em características relacionadas a desempenho ponderal, considerando-se os efeitos diretos e maternos, foram valorizados ao serem comercializados nos leilões. Em contra-partida, a pontuação dos reprodutores nos julgamentos não teve influência significativa sobre os preços médios de venda de suas progênies nos leilões.This study aimed to understand the causes of variation in the marketing prices of elite flock nelore cattle commercialized by auction, especially to verify the influences of EPDs and visual assessment. The selling prices of 426 animals from the nelore breed commercialized during 12 auctions held in various Brazilian locations, between the years 2002 and 2005, were considered in the analysis. The average price was R$ 3.325,49, with a minimum of R$ 1.400,00 and a maximum of R$ 10.500,00. The data used in a first analysis included the sex of each animal, the name of the auction and the EPDs of each animal informed in a catalog provided to the buyers during the auctions. A second analysis considered the EPDs of the sires of the commercialized animals, and the accumulated punctuation of these sires through their progeny judged through visual assessment during traditional animal shows in Brazil. Variance analysis and k-means clustering were applied to run the statistical analysis of the data. It was observed that animals with better EPDs, direct and maternal effects, on growth traits were sold with higher prices during the auctions. The punctuation by visual assessment did not significantly affect the prices.

The aim of this study was to estimate the components of variance and genetic parameters for the visual scores which constitute the Morphological Evaluation System (MES), such as body structure (S), precocity (P) and musculature (M) in Nellore beef-cattle at the weaning and yearling stages, by using threshold Bayesian models. The information used for this was gleaned from visual scores of 5,407 animals evaluated at the weaning and 2,649 at the yearling stages. The genetic parameters for visual score traits were estimated through two-trait analysis, using the threshold animal model, with Bayesian statistics methodology and MTGSAM (Multiple Trait Gibbs Sampler for Animal Models) threshold software. Heritability estimates for S, P and M were 0.68, 0.65 and 0.62 (at weaning) and 0.44, 0.38 and 0.32 (at the yearling stage), respectively. Heritability estimates for S, P and M were found to be high, and so it is expected that these traits should respond favorably to direct selection. The visual scores evaluated at the weaning and yearling stages might be used in the composition of new selection indexes, as they presented sufficient genetic variability to promote genetic progress in such morphological traits.

The Bayesian inference has been proposed as an alternative for estimating variance components instead of the frequentist approach. The objective of this study was to estimate the (co)variance components and genetic parameters of growth and reproduction traits in Nelore cattle using three-trait animal model by Restricted Maximum Likelihood and Gibbs Sampling. The data set had 15,173 and 6,911 records of weight (W365) and scrotal circumference (SC365) at 365 days of age, respectively, and 10, 388 records of age at first calving (AFC), from the Nelore Breed Genetic Improvement Program farms. The linear model included the contemporary groups and age-of-dam (with exception for AFC) as fixed effects, and residual and additive direct genetic effects as random. Estimates obtained by Restricted Maximum Likelihood were different from those found by Gibbs Sampling. There were no differences in genetic parameter estimates using the three levels of prior information by Gibbs Sampling. The Bayesian inference has advantages in relation to Frequentist approach due to marginal distributions which offer more information about the parameters.KEY WORDS: Beef cattle, genetic parameters, three-trait models. Os objetivos deste estudo foram estimar os componentes de variância e parâmetros genéticos de características de crescimento e reprodução de bovinos da raça Nelore, em modelo animal tricaráter, utilizando a Máxima Verossimilhança Restrita e a Inferência Bayesiana. Na implementação do Amostragem de Gibbs, que aplica a teoria bayesiana, consideraram-se os três diferentes níveis de conhecimento das informações iniciais dos componentes de variância e covariância. O conjunto de dados continha 15.173 registros de peso aos 365 dias de idade (P365), 6.911 registros de perímetro escrotal aos 365 dias de idade (PE365) e 10.388 dados de idade ao primeiro parto (IPP). O modelo linear incluiu o grupo de contemporâneos e a idade da vaca ao parto como efeitos fixos (exceto para IPP), e os efeitos genético aditivo direto e residual como aleatórios. As estimativas obtidas pela Máxima Verossimilhança Restrita foram diferentes das obtidas pela Amostragem de Gibbs. No entanto, considerando os três diferentes níveis de informação inicial, não houve diferenças nas estimativas dos parâmetros genéticos obtidas pela Amostragem de Gibbs. O método bayesiano apresentou vantagens em relação ao método freqüentista, graças às distribuições marginais posteriores, que ofereceram mais informações sobre os parâmetros estimados.PALAVRAS-CHAVES: Bovinos de corte, modelo tricaráter, parâmetros genéticos.

O objetivo deste trabalho foi estudar as inter-relações genéticas dos escores visuais com as características de crescimento, por meio da estatística bayesiana, utilizando análises bicaracterísticas sob modelo animal linear-limiar, na obtenção de parâmetros genéticos. Estudaram-se as características categóricas morfológicas de musculosidade, estrutura física, conformação e sacro, aos 8, 15 e 22 meses de idade, em animais da raça Nelore, e também vacas adultas; e as características contínuas de crescimento, pesos aos 210, 365 e 450 dias de idade, além do peso adulto da vaca. Foram obtidas estimativas de correlações genéticas positivas de alta magnitude entre os escores visuais de musculosidade, estrutura física e conformação com as características de crescimento, indicando que a seleção de uma trará progresso genético à outra. Os resultados obtidos neste estudo também indicaram que a estrutura física e a conformação são determinadas, em grande parte, pelos mesmos conjuntos de genes que o peso. Da mesma forma, as características de escores visuais avaliadas em vacas adultas apresentaram altas correlações genéticas com o peso adulto da vaca. Para o sacro, as estimativas de correlações genéticas foram de baixa magnitude e negativas. PALAVRAS-CHAVE: Amostrador de gibbs, características morfológicas, pesos, zebu. The objective of this paper was to study the genetic correlations of the visual scores traits with the growth continuous traits, by applying bayesian statistic methodology, using two-trait analyses under linear-threshold animal models. The morphological categorical traits of musculature, physical structure, conformation and sacrum were studied in animals of the Nelore breed at the age of 8, 15 and 22 months, and also in adult cows; and the growth continuous traits, weights at the age of 210, 365 and 450 days old, as well as the adult weight of the cow. Estimates of genetic correlations between these visual scores (musculature, physical structure and conformation) with the growth traits were favorably positive, indicating that the selection of one of them will bring genetic progress to another. The results achieved in this study also indicated that the physical structure and the conformation are determined, to a large extent, by the same sets of genes as the weight. In the same way, the evaluated visual scores in adult cows presented high genetic correlations with the adult weight of the cow. As concerning the sacrum, the estimates of genetic correlations were low and negative. KEY WORDS: Gibbs sampler, morphological traits, weights, zebu cattle.

Com objetivo de estimar parâmetros genéticos e estudar a utilização de diferentes efeitos em avaliações genéticas para idade ao primeiro parto (IPP) por diferentes modelos, foram utilizados registros de IPP de animais da raça Nelore, nascidos entre os anos de 1990 e 2005. Foram considerados os seguintes modelos (M): M1, incluindo o efeito fixo de GC1 (constituído pelos animais nascidos na mesma fazenda e ano), além da covariável, peso aos 365 dias de idade (efeito linear e quadrático), totalizando 24.263 registros de IPP; M2, considerando os efeitos fixos de GC1, ano e estação de parição, totalizando 59.792 registros de IPP e M3, incluindo os efeitos fixos de GC2 (agrupando os animais nascidos na mesma fazenda, ano e que conceberam no mesmo manejo reprodutivo), ano e estação de parição, totalizando 59.792 registros de IPP. As estimativas dos componentes de variância e herdabilidade e os valores genéticos (VG) foram obtidos pelo método da máxima verossimilhança restrita, com a inclusão da matriz de parentesco disponível. As diferenças esperadas na progênie (DEPs) foram obtidas dividindo os VG por dois. Após a obtenção desses resultados, foram realizadas correlações entre os VG e o ranqueamento das DEPs dos reprodutores para IPP, utilizando-se o procedimento PROC CORR (SAS, 2003). Ao se considerar o ano e a estação de parto nos modelos de análise (M2 e M3), esses produziram um maior R², indicando que tais modelos conseguiram explicar, em maior grau, as diferenças existentes entre os animais para IPP. As herdabilidades estimadas foram de baixa magnitude (0,14 e 0,15). As correlações entre os VG obtidas por diferentes modelos foram 0,73 (M1 x M2); 0,91 (M2 x M3) e 0,66 (M1 x M3).With the objective of estimate genetic parameters and study the utilization of different effects on the genetic evolution for the age of the first calving (AFC) by different models, they were used AFC records from Nellore breed animals, born from 1990 to 2005. They were considered the following models (M): M1, including the fixed effect of the contemporary group (CG), CG1 (grouping the animals that were born at the same farm and year), besides the co variable, weight at 365 days of age (linear and quadratic effects), totalizing 24,263 records of AFC; M2, considering the effects of CG1, year and season of the calving, totalizing 59,792 records of AFC and M3, including effects CG2 (grouping the animals born at the same farm, year and submitted at the same reproductive management), year and season of calving totalizing 59,792 records of AFC. The components of variance and Genetic Value (GV) were obtained by Restricted Maximun Likelihood Method, with the inclusion for the relationship matrix. The Differences Expected on the Progeny (DEPs) were obtained by dividing the GV by two, after this they were estimated the correlations between GV and ranks of the reproductor's DEPs for AFC, utilizing the procedure CORR (SAS, 2003). While considering year and season of calving in the analysis models (M2 and M3), it was produced a bigger R², indicating that those models could explain, in a larger scale, the existing differences between the animals for AFC. The heritabilities estimated were of low magnitude (0,14 and 0,15). The correlations between the GV obtained by the different models were .73 (M1 x M2); .91 (M2 x M3) and .66 (M1 x M3).

Visando estimar parâmetros genéticos em bovinos, foram utilizados registros de pesos padronizados aos 120, 210, 365, 450 e 550 dias de idade (P120, P210, P365, P450 e P550), altura do posterior mensurada próxima ao sobreano (ALT) e circunferências escrotais (CE) padronizadas aos 365, 450 e 550 dias de idade (CE365, CE450 e CE550). Os dados foram provenientes de animais machos e fêmeas, nascidos entre 1998 e 2003 em dez fazendas de seis estados brasileiros. Os componentes de (co)variância foram estimados pela metodologia REML em análises uni, bi e trivariadas, utilizando-se modelos animal. As estimativas de herdabilidade do efeito direto com os respectivos erros-padrão foram: ALT 0,63 (0,09), P120 0,25 (0,03), P210 0,34 (0,03), P365 0,45 (0,04), P450 0,48 (0,04), P550 0,49 (0,04), CE365 0,48 (0,04), CE450 0,53 (0,04) e CE550 0,42 (0,09). As correlações genéticas entre a ALT e as variáveis P120, P210, P365, P450 e P550 foram de 0,68; 0,64; 0,53; 0,58 e 0,59, respectivamente. As associações genéticas do P120 com as CE ajustadas para peso e idade foram próximas de zero, entretanto, essas correlações foram positivas e moderadas, quando as CE foram ajustadas somente pela idade. As correlações genéticas da ALT com as CE, quando ajustadas para peso e idade, foram: -0,19 (CE365), -0,24 (CE450) e 0,00 (CE550). Utilizando um modelo que não incluiu o peso do animal como covariável, as correlações genéticas das CE com a ALT foram: 0,21 (CE365), 0,12 (CE450) e 0,39 (CE550). Essas estimativas indicam que as características de crescimento e CE apresentam variabilidade genética na raça Nelore, podendo ser incluídas em programas de melhoramento genético, e a seleção para peso em qualquer idade deve acarretar aumento na estatura dos animais. Desta forma, para obtenção de animais com tamanho e peso adequados ao sistema de produção, faz-se necessária a utilização de um índice de seleção aliando estas características.Data consisting of standardized weights at 120, 210, 365, 450 and 550 days of age (W120, W210, W365, W450 and W550), hip height at 18 months of age (HH) and standardized scrotal circumferences (SC) at 365, 450 and 550 days of age (SC365, SC450 and SC550) of Nelore animals born between 1998 and 2003, from ten ranches in six Brazilian States were used to estimate (co)variance components. Analyses were done by Restricted Maximum Likelihood methodology using single trait, two and three traits animal models. Heritability estimates of the direct effect for each trait and respective standard errors were: HH 0.63 (0.09), W120 0.25 (0.03), W210 0.34 (0.03), W365 0.45 (0.04), W450 0.48 (0.04), W550 0.49 (0.04), SC365 0.48 (0.04), SC450 0.53 (0.04) and SC550 0.42 (0.09). Genetic correlation estimates between HH and W120, W210, W365, W450, W550 were respectively 0.68, 0.64, 0.53, 0.58 and 0.59. Genetic correlations between W120 and SC adjusted for weight and age were close to zero, but positive and moderate when SC was adjusted only for age. Estimates of genetic correlation between HH and SC adjusted for weight and age were -0.19 (SC365), -0.24 (SC450) and 0.00 (SC550). The same parameter estimates when SC was adjusted only for age were 0.21 (SC365), 0.12 (SC450) and 0.39 (SC550). These results indicate genetic variability for growth traits and SC. Selection for weight at any age will increase stature. In order to obtain Nelore cattle with stature and weight suitable to the production system, both traits should be included in a selection index.

O método da máxima verossimilhança restrita tem sido o escolhido pelos programas de melhoramento genético para estimação dos componentes de variância e predição dos valores genéticos. No entanto, a inferência bayesiana aparece como uma alternativa de grande flexibilidade, tanto em relação aos modelos que podem ser utilizados nas análises quanto em relação às inferências que podem ser realizadas a partir dos resultados. A sua aplicação em análises genéticas permite a obtenção de densidades posteriores das variáveis estudadas e pode ser utilizada tanto em pequenos ou grandes conjuntos de dados, não sendo necessário o conhecimento da distribuição inicial do parâmetro que se deseja estimar. No Brasil, o método da Amostragem de Gibbs, que permite uma inferência bayesiana, tem sido aplicado com êxito em diversos estudos envolvendo dados de campo de bovinos da raça Nelore. PALAVRAS-CHAVE: Amostragem de Gibbs, modelos lineares, parâmetros genéticos. Restricted Maximum Likelihood method has been the choice method of the genetic improvement programs to estimate variance components the breeding values. However, the bayesian inference appears as an alternative of the great flexibility, as much in relation the models that can be used in the analyses, how in relation the inferences that can be carried from the results. Its application in genetic analyses allows obtaining the posteriors densities of the variables and can be used in small or great data sets, not being necessary the knowledge initial distribution of the parameter. In Brazil, Gibbs sampling method, that allows a bayesian inference, has been used with success in diverse studies involving field data of Nellore cattle. KEY WORDS: Genetics parameters, Gibbs sampling, linear models.

We used Gibbs sampling in single and two-trait animal models to estimate genetic parameters for some reproductive and related traits of Nellore cattle (Bos indicus). Female traits were age at first calving (AFC), cumulative productivity (CP) and adult weight (AW). For males, scrotal circumferences at 365 and 450 days of age were analyzed. Gibbs sampling using the ‘Multiple Trait using Gibbs Sampling under Animal Model’ (MTGSAM) program of Van Tassel and Van Vleck was used to estimate the (co)variance components of the traits and conduct genetic analyses. Heritabilities were AFC = 0.26, AW = 0.36 and CP = 0.25 under the single-trait animal model. The mean, mode and median estimates for genetic parameters obtained from the marginal posterior distributions were similar for all traits except AW, which presented lower values for the mode than the mean and median. However, the marginal posterior distributions for the traits studied presented a tendency toward normality. Favorable, but low, negative genetic correlations were found between male scrotal circumference and female age at first calving. The reproductive traits showed medium-magnitude heritabilities, which indicates that these traits should respond to selection and therefore should be included in genetic improvement programs.

The objective of this study was to estimate (co)variance components and genetic parameters for weights (W) and scrotal circumferences (SC) at 365 and 450 days of age, of Nelore (Bos indicus) cattle, using Bayesian inference in single and multiple-trait animal models. The fitted linear models included, besides the animal and residual random effects, the contemporary group (herd-year-season-sex-management group) and age-of-dam as "fixed effects". The analyses were carried out using a Gibbs sampler implemented through the MTGSAM program. The heritabilities (in parentheses) obtained fitting single-trait models were W365 (0.49), W450 (0.52), SC365 (0.68) and SC450 (0.66). Estimates of means, modes and medians for genetic parameters obtained from marginal posterior distributions were similar for all traits. The W365 and SC365 can be considered as suitable traits to be included as selection criteria in genetic improvement programs, not only because of their relatively high heritabilities but also due to the fact that they can be measured when the animals are relatively young compared to the corresponding traits W450 and SC450. The Bayesian approach appears to be an appropriate alternative for estimating genetic parameters, and has the advantage over point estimation methods of allowing inferences on marginal posterior distributions.

Objetivou-se com este trabalho estimar os parâmetros genéticos e fenotípicos de características reprodutivas de fêmeas de rebanhos das regiões Norte e Nordeste do Brasil. As características estudadas foram idade ao primeiro parto (IPP), intervalo de partos (IDP), período de serviço (PS), número de serviços por concepção (NSC) e período de gestação (PG). Os modelos utilizados para cada característica foram selecionados por meio do procedimento MIXED do programa SAS e os componentes de variância foram estimados pelo método da Máxima Verossimilhança Restrita Livre de Derivada, utilizando-se o software MTDFREML. As médias observadas para IPP, IDP, PS, NSC e PG foram 45,14±10,83 meses; 465,55±128,49 dias; 165,76±110,29 dias; 1,34±0,67 serviços e 295,03±5,85 dias, respectivamente. As estimativas de herdabilidade para IPP, IDP, PS, NSC e PG foram, respectivamente, 0,21±0,05; 0,05±0,02; 0,32±0,11; 0,05±0,04 e 0,12±0,04. As estimativas de repetibilidade encontradas para IDP, PS, NSC e PG foram, nesta ordem, 0,05; 0,63; 0,09 e 0,22. Os resultados sugerem que, apesar da pequena variabilidade genética para a maioria das características, a IPP e o PG são características reprodutivas que devem ser incluídas em programas de seleção. A elevada herdabilidade obtida para PS pode ser decorrente da estrutura dos dados analisados, provenientes, em sua grande maioria, de um mesmo rebanho. O baixo valor para a repetibilidade do IDP indica que o descarte de fêmeas com base no desempenho ao seu primeiro intervalo de partos pode ocasionar a eliminação de animais que poderão apresentar boa eficiência reprodutiva no futuro.The objective of this study was to estimate genetic and phenotypic parameters for reproductive traits of Nelore cows raised in the North and Northeast regions of Brazil. The traits studied were age at first calving (AFC), calving interval (CI), post-partum interval (PPI), number of services per conception (NSC) and gestation length (GL). The statistical analyses were done using the SAS program (Statistical Analysis System) and variance components were estimated by Restricted Maximum Likelihood method using the MTDFREML software. Means and heritability estimates for AFC, CI, PPI, NSC and GL were 45.14±10.83 months; 465.55±128.49 days; 165.76±110.29 days; 1.34±0.67 services and 295.03±5.85 days and 0.21±0.05; 0.05±0.02; 0.32±0.11; 0.05±0.04 e 0.12±0.04, respectively. The repeatability for CI, PPI, NSC and GL were, respectively, 0.05; 0.63; 0.09 and 0.22. The results suggest that despite the small genetic variability for the reproductive traits, AFC and GL must be included in selection programs. The high heritability estimate for PPI is probably associated to the structure of the data, in its majority coming from the same herd. The repeatability estimate for CI suggests that female culling based on first calving interval is not accurate and there is a risk of culling animals with probable good reproductive efficiency.

Parameters based on the probability of gene origin were used to describe the genetic variability in strains of Nellore and polled Nellore (Bos indicus) cattle that participated in the Program for Genetic Improvement of the Nellore Breed (Programa de Melhoramento Genético da Raça Nelore). The effective number of founders was 87.2 for Nellore and 107.9 for polled Nellore, while the number of ancestors was 59.8 for Nellore and 61.5 for polled Nellore and the remaining genomes were 39.4 for Nellore and 34.5 for polled Nellore cattle. The results indicate an intense use (by artificial insemination) of some sires and the absence of subdivisions in the population. The family structure in the two breeds was mainly caused by the genetic contribution of the same sires and only mating preferences for descendants of some founders are recorded in either breed. The results suggest that genetic variability needs monitoring in order to avoid the compromise of genetic improvement in economically important traits in the breeding program.

There are few studies on weight covering the full life cycle of Zebu cattle, and there is no entire growth description or mean growth pattern for animals belonging to this breed. In order to provide such data, 1,158 Nelore females born between 1985 and 1995 were weighed 14,563 times from birth to full growth maturity, in ten herds spread over seven Brazilian states. The Von Bertalanffy, Brody, logistic and Gompertz non-linear models were used to obtain the asymptotic weights (A) and the maturation rates (K). The (co)variance and breeding value components for A and K were obtained by using the multiple trait derivative free restricted maximum likelihood method under the animal model. Genetic trends were calculated in function of the mean expected progeny differences (EPD) for the trait (A or K) divided by the number of animals according to their year of birth. The genetic trends of the expected progeny difference with reference to the date of birth of the cows were, on average, -6.5g y-1 for A and 2.0g y-1 for K, close to zero as confirmed by the low (0.0023 to 0.003) coefficient of regression values. The curve parameters are recommended as a selection criterion to reach precocity and avoid adult weight increase in the female herd.

Uma definição alternativa de permanência no rebanho foi estudada em comparação à definição usual. Na definição usual, foram consideradas vacas com pelo menos três partos até os 76 meses de idade como valor 1 e vacas com menos de 3 partos com valor zero. A definição alternativa considerou os valores 0, 1, 2 e 3, respectivamente, para vacas com menos de três, com três, quatro ou cinco partos até os 76 meses de idade. Foram obtidas estimativas de herdabilidade e preditas as DEPs (Diferenças Esperadas na Progênie) para probabilidade de permanência no rebanho de 4.180 touros com filhas na base de dados do Programa de Melhoramento Genético da Raça Nelore (PMGRN-USP). Utilizaram-se o modelo linear unicaráter de touro avô-materno e a análise Bayesiana, por meio do software MTGSAM_threshold (Multiple-Trait Gibbs Sampler for Animal Models). Considerou-se tamanho de cadeia de Gibbs de 225 mil, período de descarte amostral de 25 mil e tomada de amostra a cada 1.000 rodadas. A correlação entre classificações foi calculada por meio do SAS. As estimativas de herdabilidade foram de menor magnitude para a característica padrão (0,07 vs 0,08). A correlação de posto foi de 87,5%, ou seja, houve considerável alteração na classificação dos touros avaliados. Dados os valores das estimativas de variância de touro, de herdabilidade e de variações nas DEPs preditas, concluiu-se que a característica alternativa de permanência no rebanho possui maior capacidade de detecção da variabilidade genética que a característica padrão, sob modelo linear.An alternative definition of stayability was compared to an usual one. The usual definition in this study classifies the cows with at least three calvings at age of 76 months as success, setting them a value 1, and the ones with less than three calvings at this age as failure, setting them a value 0. The alternative definition sets the cows the values 0, 1, 2, or 3, according to the number of calvings: less than three, three, four, or five calves at age of 76 months, respectively. Heritability estimates and EPDs (Expected Progeny Differences) of stayability were obtained using the information of 4,180 bulls with daughters in the database of the genetic breeding program of the Nellore cattle (PMGRN-USP). Both maternal grandsire single trait linear model and bayesian analysis were part of the MTGSAM_threshold (Multiple-Trait Gibbs Sampler for Animal Models) software. The implementation considered a length of Gibbs chain of 225 thousand, a period of burn-in of 25 thousand and a thinning interval at each 1 thousand runs. The correlation between both ranks was calculated by SAS (Statistical Analysis System). The heritability estimates were 0.07 to the usual definition of the trait versus 0.08 to the alternative one. The rank correlation was 87.5%, with considerable change on bull classifications. According to the estimates of sire variance and heritability and variations on EPDs, it can be concluded that the alternative definition of stayability has greater capacity to detect genetic variation under a linear model.

A produtividade acumulada (PAC) é um índice que indica precocidade sexual, periodicidade reprodutiva e potencial de produção de quilogramas de bezerros de matrizes bovinas. Foram analisadas 2.816 observações de fêmeas Nelore criadas em diferentes rebanhos do norte e nordeste do Brasil, recém incorporados ao Programa de Melhoramento Genético da Raça Nelore (PMGRN), com o objetivo de estimar os componentes de variância genética e residual e a herdabilidade da PAC. A média e o desvio-padrão observados para PAC foram 96,74 ± 46,70 kg de bezerros desmamados por vaca ao ano, com coeficiente de variação de 48,27%, inferior à média obtida para o conjunto de rebanhos integrantes do PMGRN. Fêmeas da raça Nelore Padrão obtiveram melhor resultado para PAC que às fêmeas Mocha. A herdabilidade estimada foi igual a 0,11 ± 0,06, sugerindo a existência de variabilidade genética suficiente para a inclusão desta característica em programas de melhoramento genético, ressaltando-se, no entanto, que seu progresso depende, sobretudo, de práticas de manejo mais eficientes.The accumulated productivity (ACP) is an index that takes into account the total weight of calves weaned per cow (in kg), total time required for producing the calves and age at first calving. A study was conducted to estimate the components of genetic and residual variance and estimate the heritability of ACP index. Data set consisted of 2,816 observations of Nelore cows raised in different farms of the Brazilian North and Northeast. These farms participate in the Genetic Improvement Program of the Nelore Breed. The observed mean and respective standard deviation for ACP was 96.74 ± 46.70 kg of weaned calves/cow/year, with a coefficient of variation of 48.27%. This mean ACP, however, is lower than values estimated in other herds of the Nelore genetic program. Also, Standard Nelore cows showed higher ACP in comparison to cows of the Nelore Polled variety. Estimated heritability for ACP was 0.11 ± 0.06, suggesting that there is sufficient genetic variability that justify the use of ACP in genetic selection. However, results of such strategy depend, mainly, on efficient herd management.