Estimativas de parâmetros genéticos em características de crescimento de bovinos da raça Nelore na região centro-oeste do Brasil / Estimates of genetic parameters of growth traits of Nellore cattle in the Midwest region of Brazil

Registros de peso ao nascer (PN) e pesos padronizados para 210 (P210); 365 (P365) e 550 (P550) dias de idade na raça Nelore foram usados com o objetivo de estimar componentes de variância dos efeitos genéticos e predição de valores genéticos dos reprodutores. O modelo incluiu os efeitos fixos de grupo contemporâneo e idade da vaca ao parto, como covariável, além dos efeitos aleatórios genético aditivo direto e genético materno, de ambiente permanente materno e ambiente temporário. As estimativas das médias e desvios-padrão para PN; P210; P365 e P550 foram iguais a 32,76 ± 3,74; 184,30 ± 29,02; 240,31 ± 41,85 e 322,12 ± 60,77, respectivamente. Em todos os pesos, verificou-se considerável variabilidade genética aditiva. A variância de ambiente permanente materno apresentou maior relevância sobre o peso a desmama, sendo praticamente inexistente após o desmame. Para a variância genética materna, a estimativa para o peso ao nascer foi mais significativa quando comparada com o peso a desmama. Os valores estimados de herdabilidade para PN; P210; P365 e P550 foram iguais a 0,37 ± 0,02; 0,36 ± 0,03; 031 ± 0,01 e 0,38 ± 0,02, respectivamente. As correlações genéticas entre peso ao nascer e outros pesos foram de baixa magnitude, com altos valores dos pesos em outras idades.

Records of birth weight (BW) and weights standardized to 210 (W210); 365 (W365) and 550 (W550) of age in the Nellore breed were used to estimate variance components of genetic effects and predict genetic values of sires. The model included the fixed effects of contemporary group and cow age at calving as co-variable, and the additive and maternal genetic, permanent maternal environmental, and temporary environmental random effects. Estimates of means and standard deviations for BW, W210; W365 and W550 were 32.76 ± 3.74; 184.30 ± 29.02; 240.31 ± 41.85 and 322.12 ± 60.77, respectively. A significant additive genetic variability was detected for all weights. The permanent maternal environmental variance showed greater relevance on weaning weight, and it was practically inexistent after weaning. For the maternal genetic variance, the estimate for birth weight was more significant as compared with weaning weight. The estimated heritability values for BW, W210; W365 and W550 were 0.37 ± 0.02; 0.36 ± 0.03; 031 ± 0.01 and 0.38 ± 0.02, respectively. Genetic correlations between birth weight and other weights were of low magnitude, with high values of weights at other ages.

Estimativas de parâmetros genéticos em características de crescimento de bovinos da raça Nelore na região centro-oeste do Brasil / Estimates of genetic parameters of growth traits of Nellore cattle in the Midwest region of Brazil

Registros de peso ao nascer (PN) e pesos padronizados para 210 (P210); 365 (P365) e 550 (P550) dias de idade na raça Nelore foram usados com o objetivo de estimar componentes de variância dos efeitos genéticos e predição de valores genéticos dos reprodutores. O modelo incluiu os efeitos fixos de grupo contemporâneo e idade da vaca ao parto, como covariável, além dos efeitos aleatórios genético aditivo direto e genético materno, de ambiente permanente materno e ambiente temporário. As estimativas das médias e desvios-padrão para PN; P210; P365 e P550 foram iguais a 32,76 ± 3,74; 184,30 ± 29,02; 240,31 ± 41,85 e 322,12 ± 60,77, respectivamente. Em todos os pesos, verificou-se considerável variabilidade genética aditiva. A variância de ambiente permanente materno apresentou maior relevância sobre o peso a desmama, sendo praticamente inexistente após o desmame. Para a variância genética materna, a estimativa para o peso ao nascer foi mais significativa quando comparada com o peso a desmama. Os valores estimados de herdabilidade para PN; P210; P365 e P550 foram iguais a 0,37 ± 0,02; 0,36 ± 0,03; 031 ± 0,01 e 0,38 ± 0,02, respectivamente. As correlações genéticas entre peso ao nascer e outros pesos foram de baixa magnitude, com altos valores dos pesos em outras idades.(AU)

Records of birth weight (BW) and weights standardized to 210 (W210); 365 (W365) and 550 (W550) of age in the Nellore breed were used to estimate variance components of genetic effects and predict genetic values of sires. The model included the fixed effects of contemporary group and cow age at calving as co-variable, and the additive and maternal genetic, permanent maternal environmental, and temporary environmental random effects. Estimates of means and standard deviations for BW, W210; W365 and W550 were 32.76 ± 3.74; 184.30 ± 29.02; 240.31 ± 41.85 and 322.12 ± 60.77, respectively. A significant additive genetic variability was detected for all weights. The permanent maternal environmental variance showed greater relevance on weaning weight, and it was practically inexistent after weaning. For the maternal genetic variance, the estimate for birth weight was more significant as compared with weaning weight. The estimated heritability values for BW, W210; W365 and W550 were 0.37 ± 0.02; 0.36 ± 0.03; 031 ± 0.01 and 0.38 ± 0.02, respectively. Genetic correlations between birth weight and other weights were of low magnitude, with high values of weights at other ages.(AU)

Estimativas de herdabilidade para os escores visuais do coração e do fígado em linhagem macho de frangos / Heritability estimates for heart and liver visual scores in a male broiler line

O objetivo deste estudo foi estimar os coeficientes de herdabilidade para os escores visuais de coração e de fígado em uma linhagem macho de frangos de corte. As análises dos dados foram realizadas através do método da máxima verossimilhança restrita e do método R, utilizando-se informações de 6167 animais. Os escores visuais de coração e de fígado não pareceram ser capazes de apresentar resposta à seleção, tendo em vista as estimativas de herdabilidade obtidas através do método da máxima verossimilhança restrita, que foram de 0,05±0,02 para ambas as características. Possivelmente devido à pouca variabilidade dos dados dos escores visuais de coração e de fígado, as análises realizadas pelo método R não atingiram convergência.

The objective of this study was to estimate the heritability coefficients for heart and liver visual scores in a male broiler line. Dataset analysis was realized by restricted maximum likelihood and by R method. Data from 6167 individuals were used. Heart and liver visual scores did not seem to be able to respond to selection, since the heritability estimates obtained by restricted maximum likelihood were 0,05±0,02 for both traits. Possibly due to the low variability of visual scores data, the analyses by R method did not converge.

Estimativas de herdabilidade para os escores visuais do coração e do fígado em linhagem macho de frangos / Heritability estimates for heart and liver visual scores in a male broiler line

O objetivo deste estudo foi estimar os coeficientes de herdabilidade para os escores visuais de coração e de fígado em uma linhagem macho de frangos de corte. As análises dos dados foram realizadas através do método da máxima verossimilhança restrita e do método R, utilizando-se informações de 6167 animais. Os escores visuais de coração e de fígado não pareceram ser capazes de apresentar resposta à seleção, tendo em vista as estimativas de herdabilidade obtidas através do método da máxima verossimilhança restrita, que foram de 0,05±0,02 para ambas as características. Possivelmente devido à pouca variabilidade dos dados dos escores visuais de coração e de fígado, as análises realizadas pelo método R não atingiram convergência.(AU)

The objective of this study was to estimate the heritability coefficients for heart and liver visual scores in a male broiler line. Dataset analysis was realized by restricted maximum likelihood and by R method. Data from 6167 individuals were used. Heart and liver visual scores did not seem to be able to respond to selection, since the heritability estimates obtained by restricted maximum likelihood were 0,05±0,02 for both traits. Possibly due to the low variability of visual scores data, the analyses by R method did not converge.(AU)

Genetic characterization of European-Zebu composite bovine using RFLP markers.

A population of 370 European-Zebu composite beef heifers, consisting of six different breed compositions (A-F), were characterized genetically, using RFLP markers of luteinizing hormone receptor (LHR) and follicle-stimulating hormone receptor (FSHR) genes. Our objectives were to genetically characterize this population and to determine the structure and the genetic variability of this hybrid herd. The genotypes were determined through PCR, followed by digestion with restriction endonucleases. The PCR-RFLP analysis made it possible to identify the LHR and FSHR genotypes, as well as to characterize the degree of heterozygosis, which was high for all of the breed compositions, for both loci, except for two combinations for LHR (B and C). The observed heterozygosity (Ho) was lower than the expected heterozygosity (He) for compositions C (for LHR) and A and D (for FSHR); however, for the population as a whole, Ho was above He (with a mean of 57 versus 46%, respectively), reflecting the elevated genetic variability in this population and also the informative value of the RFLP markers, which could be useful for population genetic characterization studies. The analysis of the degree of genetic structure of this population, estimated by the Nei's statistic, for both loci, indicated an elevated total genetic diversity (HT = 47%), with most of this variability being due to intrapopulational diversity (HS = 46%), with a low degree of genetic differentiation among the six breed compositions (GST = 1.2%). The estimates generated by the Wright's F statistic indicated a non-endogamic population, with excess heterozygotes (FIT = -0.22), which was also observed at the intrapopulational level (FIS = -0.23). The results gave evidence that the genetic selection applied to this European-Zebu composite population did not affect the expected high genetic variability for this type of crossbreeding, which makes it possible to use these animals to obtain economically valuable productive and reproductive traits.

Genetic trends of abdominal fat content in a male broiler chicken line.

Data of chickens from a broiler-breeding program were collected and used to determine the genetic trends of absolute and relative abdominal fat content. The genetic trends were estimated by the regression of trait genetic value averages on hatch-years. Genetic values from 32,485 individuals were used for regression analysis. The genetic trend estimate for absolute abdominal fat content was +0.39 g per year, indicating that abdominal fat deposition in the analyzed line, in absolute terms, tended to increase, making the existing excess fat deposition in the broilers even worse. However, the genetic trend of relative abdominal fat content was not significant, indicating that there is no increase on abdominal fat content when it is corrected for body weight.