Carlos Henrique Mendes Malhado

Desempenho reprodutivo de vacas Nelore no Norte e Nordeste do Brasil

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.

Melhoramento e estrutura populacional em bubalinos da raça Mediterrâneo no Brasil

O objetivo deste trabalho foi avaliar a estrutura populacional e os progressos geneticos, fenotipicos e ambientais de caracteristicas de desenvolvimento ponderal, em bubalinos da raca Mediterrâneo. Foram utilizadas informacoes dos pesos ajustados aos 205, 365 e 550 dias de idade, de 6.243 bubalinos nascidos no periodo de 1974 a 2003, provenientes de quatro fazendas. As estimativas dos coeficientes de herdabilidade foram altas para os pesos ajustados nas tres idades. Os rebanhos apresentaram ganho genetico positivo quanto a essas tres caracteristicas, porem, aquem do possivel, provavelmente em razao da selecao baseada somente no fenotipo, realizada pelos produtores. Para aumento nos ganhos geneticos, sao necessarios a reducao do intervalo de geracao, o aumento do tamanho efetivo, o uso de reprodutores avaliados com base nos valores geneticos preditos pelo BLUP e o controle dos acasalamentos de animais aparentados.

Desenvolvimento ponderal e diversidade fenotípica entre cruzamentos de ovinos Dorper com raças locais

The goal of this work was to compare growth rate, by mean of growth and adjusted weight curves, and to analyze the diversity among crosses of Dorper ovines and local breeds, based on morphological and carcass features. Crossed animals were weighed in a 15-day-interval and the effects of sex, year and genetic group were analyzed. The non-linear Logistic model was used to estimate curve parameters and the degree of similarity among genetic groups was evaluated through canonic variables. Sex did not influence significantly on weight. There was a significant effect related to year and genetic group over animals development. The estimates of growth curve based on parameters from the Logistic model indicated that the genetic group Dorper x Santa Ines presented a faster growth rate, as estimated by weight at maturity and maturity rate, followed by the genetic groups Dorper x Morada Nova and Dorper x Rabo Largo. Clustering analysis reinforced the differences among genetic groups, placing the three crosses in two groups, one comprising Dorper x Morada Nova and Dorper x Rabo Largo, and another including the cross Dorper x Santa Ines.

Parâmetros e tendências da produção de leite em bubalinos da raça Murrah no Brasil

Objetivou-se estimar os parâmetros e avaliar as tendencias genetica e fenotipica para a producao de leite ajustada aos 305 dias em bubalinos da raca Murrah nascidos no periodo de 1982 a 2003. Os parâmetros e os valores geneticos foram estimados por meio do aplicativo MTDFREML. A tendencia genetica foi estimada pela regressao dos valores geneticos sobre o ano de nascimento, por duas metodologias: 1) regressao linear; 2) regressao por meio de polinomios articulados utilizando-se a funcao de alisamento spline. A herdabilidade e a repetibilidade estimadas foram de 0,20 e 0,36, respectivamente. As tendencias (regressao linear) fenotipica e genetica foram significativas e iguais a 32,86 e 0,85 kg/ano, respectivamente. O ganho genetico foi positivo, constatando-se instabilidade na tendencia genetica no decorrer dos anos, com periodos de ganhos e outros de perdas geneticas. A maior parte do ganho observado em alguns periodos resultou de melhorias nas condicoes ambientais.

Caracterização fenotípica e genética da produção de leite e do intervalo entre partos em bubalinos da raça Murrah

The objective of this work was to estimate the correlations, heritabilities, repeatabilities, phenotypic and genetic trends, and to evaluate the univariate and bivariate distributions of the milk yield and calving interval of Murrah breed buffalo, calved from 1982 to 2003. The genetic and phenotypic trends were estimated by regressions of the dependant variables on year of the animals calving, based on two methods: linear regression and articulated polynomial regression. The heritabilities estimates were 0.21 and 0.02, and the repeatabilities 0.32 and 0.06, for milk yield and calving interval, respectively. The genetic, phenotypic and environmental correlations were -0.22, 0.01 and 0.03, respectively. Genetics trends (linear regression) were significant and equal to 1.57 kg per year and 0.085 day per year, and the phenotypics trends were 27.74 kg per year and 0.647 day per year, for milk yield and calving interval, respectively, being significant just for milk yield. The negative genetic correlation suggests that there is a favorable relationship between milk yield and calving intervals, thus it is possible to select animals of high breeding values for milk yield and with low breeding values for calving intervals.

The Indubrasil breed in the Brazilian Northeast: breeding and population structure

In order to provide knowledge for breeding, conservation programs and expansion policies of the Indubrasil breed from northeastern Brazil, the evolutionary history, estimates of genetic parameters and the populational structure of the breed were studied. Pedigree information was used from animals born from 1964 to 2006 and the adjusted weights at 205, 365 and 550 days of age of bovines born from 1976 onwards. The heritability coefficient estimates were lower than those reported in the literature for the adjusted weights at the three ages (P205: direct 0.11 ± 0,03 and maternal 0.01 ± 0.03; P365: direct 0.16 ± 0.04 and P550: direct 0.15 ± 0.05) and the genetic gains for the evaluated traits decreased in the sampled period (P205: -0.028 kg/year; P365: -0.030 kg/year and P550: -0.025 kg/year). The low genetic variability and the reduced genetic gains were probably due to a reduction in the effective size and increasing inbreeding within the period. Furthermore, the drastic reduction in the number of births per year and the low use of unrelated sires within the herds make the Indubrasil breed a genetic group potentially threatened by extinction, so that conservationist and expansion programmes should be set up.

Tendências genéticas para características relacionadas à velocidade de crescimento em bovinos Nelore na região nordeste do Brasil

The objectives of this work were to estimate the genetic parameters and the genetic trends of the direct and maternal effects for the trait days to gain 160 kg (D160) in the pre-weaning period, and of the direct effect for the trait days to gain 240 kg (D240) in the post-weaning period, of animals of Nellore breed, born from 1965 to 2001 in the Northeast region of Brazil. The analyses were carried out using the MTDFREML software. For D160 the model included the direct and maternal genetic random effects and maternal permanent environmental effect, besides the fixed effects of contemporary group and the covariate age of dam at calving, assuming the covariance between maternal and direct effect equal to zero (sam=0). For D240, the same fixed effects were considered, however, just the direct genetic effect as random. The genetic trends were estimated by linear regression of the breeding values on year of birth of the animals. The direct and maternal heritabilities for D160, respectively, were 0.12 ± 0.01 and 0.07 ± 0.02. The direct heritability for D240 was 0.16 ± 0.02. The genetic trends of the direct effects were significant, with estimated values of -0.14 and -0.41 days/year for D160 and D240, respectively. The genetic trend of the maternal effect for D160 was significant and equal to -0.0037 days/year. The genetic trends were favorable, however, inferiors the potential gain.

Genetic parameters for milk yield, lactation length and calving intervals of murrah buffaloes from brazil

The major objective of this study was to estimate heritability and genetic correlations between milk yield (MY) and calving interval (CI) and lactation length (LL) in Murrah buffaloes using Bayesian inference. The database used belongs to the genetic improvement program of four buffalo herds from Brazil. To obtain the estimates of variance and covariance, bivariate analyses were performed with the Gibbs sampler, using the program MTGSAM. The heritability coefficient estimates were 0.28, 0.03 and 0.15 for MY, CI and LL, respectively. The genetic correlations between MY and LL was moderate (0.48). However, the genetic correlation between MY and CI showed large HPD regions (highest posterior density interval). Milk yield was the only trait with clear potential for genetic improvement by direct mass selection. The genetic correlation between MY and LL indicates that indirect selection using milk yield is a potentially beneficial strategy. The interpretation of the estimated genetic correlation between MY and CI is difficult and could be spurious.

Análise de agrupamento na seleção de modelos de regressão não-lineares para curvas de crescimento de ovinos cruzados

This study had the objectives to use the cluster analysis in order to classify nonlinear regression models used to describe the growth curve in relation to different quality fit evaluators. Were utilized weight-age data from the following crossbred beef lambs Dorper x Morada Nova, Dorper x Rabo Largo e Dorper x Santa Ines. After the choice of the best model, we aimed also to apply the model identity in order to identify the most efficient crossbred group. Eleven nonlinear models were used, whose fit quality was measured by determination coefficient, Akaike information criterion, Bayesian information criterion, mean quadratic error of prediction and predicted determination coefficient. The cluster analysis indicated the Richards as the best model for the three data sets, and the model identity tests revealed that the Dorper x Santa Ines crossbred group was recommend for meat production.

Produtividade acumulada (PAC) das matrizes em rebanhos Nelore do norte e nordeste do Brasil

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.