Raysildo Barbosa Lôbo

Estimativas de (Co)variâncias entre características de reprodução e de crescimento em fêmeas de um rebanho Nelore

Informations of 7986 births of animals from a Nellore cattle herd, from 1960 to 1993, were used to estimate (co) variance components, heritabilities and genetic correlations of weaning weight (W240), yearling weight (W365), age at first calving (AFC), first calving interval (CI1), reproductive efficiency (RE), longevity (LONG), calculated as years of permanence of cow in herd and weaning weight of the first calf of cow (W240C). The analysis were performed using the MTDFREML software, estimating the (co) variance components by restricted maximum likelihood, assuming an animal model. Estimates of heritability showed similar results among the different analyses, being higher (0.26 to 0.35) for W240, W365 and AFC and lower (0.08 to 0.26) for CI1, RE, LONG and W240C. In general, the estimates of genetic and phenotypic correlations among growth and reproductive traits were low and among the reproductive traits were high and favorable. Some correlations between maternal genetic effect of the growth and the direct genetic effect of the reproductive traits were of average magnitude and unfavorable, suggesting genetic antagonism between milk production and reproduction.

Comparação de modelos não-lineares para descrever o crescimento de fêmeas da raça Guzerá

Data on growth and reproduction of 573 females Guzerat beef cattle born between 1961 and 1985, at Fazenda Canoas, located in the county of Curvelo, MG, Brazil, were used to obtain a growth pattern for the breed, through the use of a mathematical model. Weight-age data, collected up to 1992, were used to fit five nonlinear models: Brody, Bertalanffy, Logistic, Gompertz, and Richard. Estimated assyntotic weight and growth rate were, respectively, for Brody model 464.49 and 0.046; for Bertalanffy model 453.18 and 0.065; for Logistic model 447.05 and 0.085; for Gompertz model 449.89 and 0.075, and for Richards model 458.26 and 0.055. Richards model presented computational difficulty to fit the data. Other models showed good fit to the data, and presented little variations on the criteria chosen. Bertalanffy model showed a better goodness of fit on the set of criteria and was the choice to describe the growth patterns of Guzerat cattle.

Is the American Zebu really Bos indicus

The American continent was colonized in the 16th century by Europeans who first introduced cattle of Bos taurus origin. Accounts register introduction of Bos indicus cattle into South America in the 19th and continuing through the 20th century, and most reported imports were males derived from the Indian subcontinent. In the present study we show, by using mitochondrial DNA (mtDNA) polymorphism, major participation of matrilineages of taurus origin in the American Zebu purebred origin, i.e., 79, 73 and 100% for the Nellore, Gyr and Brahman breeds, respectively. Moreover, we have created a restriction map identifying polymorphism among B. taurus and B. indicus mtDNA using three restriction enzymes. Results are discussed concerning American Zebu origins and potential use of this information for investigating the contribution of cytoplasmic genes in cattle production traits.

Estimativas de parâmetros genéticos para altura do posterior, peso e circunferência escrotal em bovinos da raça Nelore

Visando estimar parâmetros geneticos 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 proxima ao sobreano (ALT) e circunferencias escrotais (CE) padronizadas aos 365, 450 e 550 dias de idade (CE365, CE450 e CE550). Os dados foram provenientes de animais machos e femeas, nascidos entre 1998 e 2003 em dez fazendas de seis estados brasileiros. Os componentes de (co)variância foram estimados pela metodologia REML em analises uni, bi e trivariadas, utilizando-se modelos animal. As estimativas de herdabilidade do efeito direto com os respectivos erros-padrao 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 correlacoes geneticas entre a ALT e as variaveis P120, P210, P365, P450 e P550 foram de 0,68; 0,64; 0,53; 0,58 e 0,59, respectivamente. As associacoes geneticas do P120 com as CE ajustadas para peso e idade foram proximas de zero, entretanto, essas correlacoes foram positivas e moderadas, quando as CE foram ajustadas somente pela idade. As correlacoes geneticas 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 nao incluiu o peso do animal como covariavel, as correlacoes geneticas das CE com a ALT foram: 0,21 (CE365), 0,12 (CE450) e 0,39 (CE550). Essas estimativas indicam que as caracteristicas de crescimento e CE apresentam variabilidade genetica na raca Nelore, podendo ser incluidas em programas de melhoramento genetico, e a selecao para peso em qualquer idade deve acarretar aumento na estatura dos animais. Desta forma, para obtencao de animais com tamanho e peso adequados ao sistema de producao, faz-se necessaria a utilizacao de um indice de selecao aliando estas caracteristicas.

Genetic associations between carcass traits measured by real-time ultrasound and scrotal circumference and growth traits in Nelore cattle

The aim of the present study was to evaluate the genetic correlations among real-time ultrasound carcass, BW, and scrotal circumference (SC) traits in Nelore cattle. Carcass traits, measured by real-time ultrasound of the live animal, were recorded from 2002 to 2004 on 10 farms across 6 Brazilian states on 2,590 males and females ranging in age from 450 to 599 d. Ultrasound records of LM area (LMA) and backfat thickness (BF) were obtained from cross-sectional images between the 12th and 13th ribs, and rump fat thickness (RF) was measured between the hook and pin bones over the junction between gluteus medius and biceps femoris muscles. Also, BW (n = 22,778) and SC (n = 5,695) were recorded on animals born between 1998 and 2003. The BW traits were 120, 210, 365, 450, and 550-d standardized BW (W120, W210, W365, W450, and W550), plus BW (WS) and hip height (HH) on the ultrasound scanning date. The SC traits were 365-, 450-, and 550-d standardized SC (SC365, SC450, and SC550). For the BW and SC traits, the database used was from the Nelore Breeding Program-Nelore Brazil. The genetic parameters were estimated with multivariate animal models and REML. Estimated genetic correlations between LMA and other traits were 0.06 (BF), -0.04 (RF), 0.05 (HH), 0.58 (WS), 0.53 (W120), 0.62 (W210), 0.67 (W365), 0.64 (W450 and W550), 0.28 (SC365), 0.24 (SC450), and 0.00 (SC550). Estimated genetic correlations between BF and with other traits were 0.74 (RF), -0.32 (HH), 0.19 (WS), -0.03 (W120), -0.10 (W210), 0.04 (W365), 0.01 (W450), 0.06 (W550), 0.17 (SC365 and SC450), and -0.19 (SC550). Estimated genetic correlations between RF and other traits were -0.41 (HH), -0.09 (WS), -0.13 (W120), -0.09 (W210), -0.01 (W365), 0.02 (W450), 0.03 (W550), 0.05 (SC365), 0.11 (SC450), and -0.18 (SC550). These estimates indicate that selection for carcass traits measured by real-time ultrasound should not cause antagonism in the genetic improvement of SC and BW traits. Also, selection to increase HH might decrease subcutaneous fat as correlated response. Therefore, to obtain animals suited to specific tropical production systems, carcass, BW, and SC traits should be considered in selection programs.

Comparação entre alguns critérios de seleção para crescimento na raça Nelore

Data to 53433 of Nellore cattle were used to estimate genetic parameters for standardized weights at 120, 240, and 550 days of age (P120, P240, and P550 respectively), scrotal circumference at 550 days (PE550), days to reach 160 kg (D160), and 240 kg (D240) of live weigh. It was used software the MTDFREML with mixed-model analysis using animal model. Model included fixed effects of contemporary groups (GC) and classes of age-of-dam calving and random direct and maternal genetic effects, the dam permanent environmental effect and the error. Direct heritability (h2a), in multiple-trait analysis between PE550 and all others traits, were .19 (for P120 and P240), .34 (for P550), .09 (for D160), .16 (for D240) and .36 (mean for PE550). Maternal heritability for growth traits ranged from .02 to .12. Genetic correlations among PE550 and the others traits had medium magnitude. Standardized weights rather than days to live weight, were better selection criteria when heritabilities and selection response were consideraded.

Herdabilidades e correlações entre pesos do nascimento à idade adulta em rebanhos da raça Nelore

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.

Análise da variabilidade genética aditiva de características de crescimento na raça Nelore

The data were obtained from 51 herds to participate in the Nelore Catttle Breeding Program (NCBP) from the states of Goias (GO), Mato Grosso do Sul (MS), Mato Grosso (MT), Minas Gerais (MG), Sao Paulo (SP), Maranhao (MA) and Bahia (BA). Were used to estimative genetic parameters for standardized weights at 120 (P120), 455 (P455) and 550 (550) days of age. Univariate and bivariate analysis were performed by animal model using MTDFREML program. For P120 was used a model that included contemporary groups and cow age at calving as fixed effects, and direct genetic, maternal genetic and permanent environment effects as random effects. For P455 and P550 were utilized the same model but without maternal direct and permanent environment effects. The estimates of heritability direct from univariate analysis were: 0.29, 0.51 and 0.47 for P120, P455 and P550, respectively. In the bivariate analyses the direct heritability values were of high magnitude. The genetic correlation between P120 and P455, P120 and P550 and P455 and P550 were 0.92, 0.93 and 0.96, respectively. The values of the heritability coefficients estimated for the trait P455 and genetic correlation that characteristic with others indicate that the genetic evaluation could be made at the 15 months of age.

Covariance functions for body weight from birth to maturity in Nellore cows.

The objective of this study was to estimate (co)variance functions using random regression models on Legendre polynomials for the analysis of repeated measures of BW from birth to adult age. A total of 82,064 records from 8,145 females were analyzed. Different models were compared. The models included additive direct and maternal effects, and animal and maternal permanent environmental effects as random terms. Contemporary group and dam age at calving (linear and quadratic effect) were included as fixed effects, and orthogonal Legendre polynomials of animal age (cubic regression) were considered as random covariables. Eight models with polynomials of third to sixth order were used to describe additive direct and maternal effects, and animal and maternal permanent environmental effects. Residual effects were modeled using 1 (i.e., assuming homogeneity of variances across all ages) or 5 age classes. The model with 5 classes was the best to describe the trajectory of residuals along the growth curve. The model including fourth- and sixth-order polynomials for additive direct and animal permanent environmental effects, respectively, and third-order polynomials for maternal genetic and maternal permanent environmental effects were the best. Estimates of (co)variance obtained with the multi-trait and random regression models were similar. Direct heritability estimates obtained with the random regression models followed a trend similar to that obtained with the multi-trait model. The largest estimates of maternal heritability were those of BW taken close to 240 d of age. In general, estimates of correlation between BW from birth to 8 yr of age decreased with increasing distance between ages.

Comparison of different nonlinear functions to describe Nelore cattle growth

This work aims to compare different nonlinear functions for describing the growth curves of Nelore females. The growth curve parameters, their (co)variance components, and environmental and genetic effects were estimated jointly through a Bayesian hierarchical model. In the first stage of the hierarchy, 4 nonlinear functions were compared: Brody, Von Bertalanffy, Gompertz, and logistic. The analyses were carried out using 3 different data sets to check goodness of fit while having animals with few records. Three different assumptions about SD of fitting errors were considered: constancy throughout the trajectory, linear increasing until 3 yr of age and constancy thereafter, and variation following the nonlinear function applied in the first stage of the hierarchy. Comparisons of the overall goodness of fit were based on Akaike information criterion, the Bayesian information criterion, and the deviance information criterion. Goodness of fit at different points of the growth curve was compared applying the Gelfands check function. The posterior means of adult BW ranged from 531.78 to 586.89 kg. Greater estimates of adult BW were observed when the fitting error variance was considered constant along the trajectory. The models were not suitable to describe the SD of fitting errors at the beginning of the growth curve. All functions provided less accurate predictions at the beginning of growth, and predictions were more accurate after 48 mo of age. The prediction of adult BW using nonlinear functions can be accurate when growth curve parameters and their (co)variance components are estimated jointly. The hierarchical model used in the present study can be applied to the prediction of mature BW in herds in which a portion of the animals are culled before adult age. Gompertz, Von Bertalanffy, and Brody functions were adequate to establish mean growth patterns and to predict the adult BW of Nelore females. The Brody model was more accurate in predicting the birth weight of these animals and presented the best overall goodness of fit.