Genetic and environmental factors affecting ultrasound measures of longissimus muscle area and backfat thickness in Nelore cattle

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Evaluation of an average numerator relationship matrix model and a Bayesian hierarchical model for growth traits in Nellore cattle with uncertain paternity

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Estimation of genetic parameters for body weights, scrotal circumference, and testicular volume measured at different ages in Nellore cattle

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Effects of sex and age on genotype x environment interaction for beef cattle body weight studied using reaction norm models

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Comparison of different nonlinear functions to describe Nelore cattle growth

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Selection for higher body weight in Nelore cattle is effective in achieving an increase of longissimus muscle area without reducing subcutaneous fat thickness

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Genetic parameters and relationships between heifers rebreeding and hip height in Nellore cattle

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Bayesian inference in genetic parameter estimation of visual scores in Nellore beef-cattle

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.

Estimativas de herdabilidade e tendências genéticas para características de crescimento e reprodutivas em bovinos da raça Nelore: Estimates of heritability and genetic trends for growth and reproduction traits in Nelore cattle

Foram estimados os coeficientes de herdabilidade e a mudança genética para peso à desmama (PD), peso ao sobreano (PS), ganho de peso do nascimento à desmama (GND), ganho de peso da desmama ao sobreano (GDS), perímetro escrotal (PE) e idade ao primeiro parto (IPP) em animais da raça Nelore. Foram utilizados dados de 128.148 animais nascidos entre 1984 e 2006. Os componentes de variância foram estimados pelo método da máxima verossimilhança restrita, e os valores genéticos foram preditos por modelos mistos aplicando-se modelo animal bicaracterística, incluindo peso à desmama em todas as análises. As tendências genéticas foram estimadas pela regressão dos valores genéticos sobre o ano de nascimento dos animais. Os coeficientes de herdabilidade do efeito direto estimados foram de 0,23 (0,07) (PD); 0,24 (0,02) (PS); 0,21 (0,01) (GND); 0,23 (0,01) (GDS); 0,46 (0,02) (PE) e 0,15 (0,01) (IPP). As tendências genéticas diretas estimadas foram de 0,171 (0,01); 0,219 (0,02); 0,186 (0,03) e 0,224 (0,02) kg/ano para PD, PS, GND e GDS, respectivamente, o que representa incrementos de 0,10; 0,08; 0,13 e 0,22% nas médias das mesmas características ao ano, respectivamente. Para o PE e a IPP no período de 1984 a 1995, as tendências genéticas foram nulas, com valores de 0,011 (0,03) cm/ano e -0,003 (0,06) dias/ano, respectivamente. No segundo período considerado (1996 a 2006), as tendências genéticas para PE e IPP foram de 0,069 (0,01) cm/ano e -3,024 (0,04) dias/ano, respectivamente, indicando melhorias consideráveis em tais características. Esses valores sugerem que características produtivas e reprodutivas, quando utilizadas como critério de seleção, proporcionam progresso genético no rebanho, sendo indicadas para seleção de animais da raça Nelore.

Gastrointestinal nematode infection in beef cattle of different genetic groups in Brazil

Resistance to natural infection by gastrointestinal nematodes was compared in 67 female calves of the following genetic groups: Nelore (NX); 1/2 Senepol + 1/2 Nelore (SN); and 1/2 Aberdeen Angus + 1/2 Nelore (AN). The NX (n = 26), SN (n = 23) and AN (n = 18) animals were monitored for 14 months, during which they remained without treatment, allowed to graze in a tropical environment. Eggs per gram of feces (EPG), coprocultures and packed cell volume (PCV) were carried out monthly. No significant effects of the interaction between the genetic groups and month/year of collection and the genetic group on the EPG were found, but there was a significant influence of the month of collection (P < 0.01). The monthly PCV measurements did not differ for the animals of the three genetic groups and there was no association found between the EPG and PCV. The animals of the SN and NX groups showed similar numbers of EPG with results zero, while for the AN group these numbers were significantly lower (P < 0.05). Although the NX group had a large number of EPG with results zero, it also contained many animals with high counts, meaning this group had higher averages during the entire study period. The following nematode genera were found in the coprocultures: Haemonchus, Cooperia, Oesophagostomum and Trichostrongylus, the latter in smallest proportion. There was no significant difference between the genetic groups for averages of all parasites identified, except Cooperia, which were present in higher numbers in the animals of the NX group (P < 0.05). The results obtained in this experiment suggest that the use of Bos taurus x Bos indicus crossbreeds can be a good strategy to reduce the use of chemical control in Brazil. (C) 2009 Elsevier B.V. All rights reserved.

Effect of pelleting and pellet size of a concentrate for intensively reared beef cattle on in vitro fermentation by two different approaches

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Bayesian analysis of random regression models using B-splines to model test-day milk yield of Holstein cattle in Brazil

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Genetic associations between flight speed and growth traits in Nellore cattle

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Trends of the genetic connectedness measures among Nelore beef cattle herds

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Estimates of genetic parameters for scrotal circumference using random regression models in Nelore cattle

A total of 15,901 scrotal circumference (SC) records from 5300 Nelore bulls, ranging from 229 to 560 days of age, were used with the objective of estimating (co)variance functions for SC, using random regression models. Models included the fixed effects of contemporary group and age of dam at calving as covariable (linear and quadratic effects). To model the population mean trend, a third order Legendre polynomial on animal age was utilized. The direct additive genetic and animal permanent environmental random effects were modeled by Legendre polynomials on animal age, with orders of fit ranging from 1 to 5. Residual variances were modeled considering 1 (homogeneity of variance) or 4 age classes. Results obtained with the random regression models were compared to multi-trait analysis. (Co)variance estimates using multi-trait and random regression models were similar. The model considering a third- and fifth-order Legendre polynomials for additive genetic and animal permanent environmental effects, respectively, was the most adequate to model changes in variance of SC with age. Heritability estimates for SC ranged from 0.24 (229 days of age) to 0.47 (300 days of age), remained almost constant until 500 days of age (0.52), decreasing thereafter (0.44). In general, the genetic correlations between measures of scrotal circumference obtained from 229 to 560 days of age decreased with increasing distance between ages. For genetic evaluation scrotal circumference could be measured between 400 and 500 days of age. (C) 2010 Elsevier B.V. All rights reserved.