RESUMO
The objective of the present work was to evaluate the accuracy of the fitted Gompertz and von Bertalanffy models for male and female Guzerá cattle, respectively. Four production regions in Northeast Brazil were included in the models as a fixed effect, and the animals were included as a random effect. In addition, the coefficients of the growth models in the production regions were compared. The accuracy of the fit equations was assessed with the Akaike information criterion, Bayesian information criterion, mean absolute deviation, mean squared error, and coefficient of determination. Confidence intervals were used for comparing the production regions. The Guzerá males in the Gado-Algodão and Serra Geral da Bahia production regions were statistically equal in asymptotic weight, and the animals in the Itapetinga-Valadares and Mata-Agreste regions had equivalent maturity rates. The Guzerá females in the Itapetinga-Valadares and Serra Geral da Bahia regions had the same asymptotic weight. The maturity rates in Itapetinga-Valadares were equal to those estimated for Mata-Agreste and Serra Geral da Bahia. The inclusion of the fixed effect of the production region and the random effect of the animals in the models improved the fit quality and increased the possibility of generating growth curves for each region.(AU)
O objetivo do presente trabalho foi avaliar a acurácia dos modelos Gompertz e Von Bertalanffy ajustados, respectivamente, para machos e fêmeas da raça Guzerá, sendo incorporado nos modelos o efeito fixo de quatro regiões de produção do nordeste brasileiro e efeito aleatório de animal, além de comparar os coeficientes dos modelos de crescimento entre regiões de produção. A acurácia das equações ajustadas foi avaliada por meio do critério de informação de Akaike, critério de informação Bayesiano, desvio médio absoluto, erro quadrático médio e o coeficiente de determinação. Para comparar as regiões de produção foram utilizados intervalos de confiança. Verificou-se que machos da raça Guzerá das regiões de produção Gado-Algodão e Serra Geral da Bahia possuem peso assintótico estatisticamente igual, enquanto que a taxa de maturidade é equivalente para animais das regiões Itapetinga-Valadares e Mata-Agreste. As fêmeas da raça Guzerá das regiões de Itapetinga-Valadares e Serra Geral da Bahia possuem o mesmo peso assintótico. A taxa de maturidade em Itapetinga-Valadares é igual a estimada para Mata-Agreste e Serra Geral da Bahia. Ao incluir o efeito fixo de região de produção e aleatório de animal nos modelos, houve melhora na qualidade de ajuste e a possibilidade de gerar curvas de crescimento para cada região.(AU)
Assuntos
Animais , Bovinos , Dinâmica não Linear , Crescimento e Desenvolvimento , Pesos e Medidas Corporais/métodos , Pesos e Medidas Corporais/veterinária , Intervalos de ConfiançaRESUMO
The objective of the present work was to evaluate the accuracy of the fitted Gompertz and von Bertalanffy models for male and female Guzerá cattle, respectively. Four production regions in Northeast Brazil were included in the models as a fixed effect, and the animals were included as a random effect. In addition, the coefficients of the growth models in the production regions were compared. The accuracy of the fit equations was assessed with the Akaike information criterion, Bayesian information criterion, mean absolute deviation, mean squared error, and coefficient of determination. Confidence intervals were used for comparing the production regions. The Guzerá males in the Gado-Algodão and Serra Geral da Bahia production regions were statistically equal in asymptotic weight, and the animals in the Itapetinga-Valadares and Mata-Agreste regions had equivalent maturity rates. The Guzerá females in the Itapetinga-Valadares and Serra Geral da Bahia regions had the same asymptotic weight. The maturity rates in Itapetinga-Valadares were equal to those estimated for Mata-Agreste and Serra Geral da Bahia. The inclusion of the fixed effect of the production region and the random effect of the animals in the models improved the fit quality and increased the possibility of generating growth curves for each region.
O objetivo do presente trabalho foi avaliar a acurácia dos modelos Gompertz e Von Bertalanffy ajustados, respectivamente, para machos e fêmeas da raça Guzerá, sendo incorporado nos modelos o efeito fixo de quatro regiões de produção do nordeste brasileiro e efeito aleatório de animal, além de comparar os coeficientes dos modelos de crescimento entre regiões de produção. A acurácia das equações ajustadas foi avaliada por meio do critério de informação de Akaike, critério de informação Bayesiano, desvio médio absoluto, erro quadrático médio e o coeficiente de determinação. Para comparar as regiões de produção foram utilizados intervalos de confiança. Verificou-se que machos da raça Guzerá das regiões de produção Gado-Algodão e Serra Geral da Bahia possuem peso assintótico estatisticamente igual, enquanto que a taxa de maturidade é equivalente para animais das regiões Itapetinga-Valadares e Mata-Agreste. As fêmeas da raça Guzerá das regiões de Itapetinga-Valadares e Serra Geral da Bahia possuem o mesmo peso assintótico. A taxa de maturidade em Itapetinga-Valadares é igual a estimada para Mata-Agreste e Serra Geral da Bahia. Ao incluir o efeito fixo de região de produção e aleatório de animal nos modelos, houve melhora na qualidade de ajuste e a possibilidade de gerar curvas de crescimento para cada região.
Assuntos
Animais , Bovinos , Crescimento e Desenvolvimento , Dinâmica não Linear , Intervalos de Confiança , Pesos e Medidas Corporais/métodos , Pesos e Medidas Corporais/veterináriaRESUMO
With the purpose of comparing the ruminal degradation models, proposed by Waldo et al. (1972) and Mertens and Loften(1980), the data of in situ degradability were employed. The experiment evaluated the potentially degradable residue of neutraldetergent fiber (NDF) of grass Tifton 85 (Cynodon spp) submitted to twelve cutting ages (30, 60, 90, 120, 150, 180, 210, 240,270, 300, 330 and 360 days), in a randomized block design with three replicates. At each cutting age, NDF degradation wasinvestigated by utilizing nine incubation times (0, 3, 6, 12, 24, 48, 72, 96 and 120 hours). The analysis was done by taking intoaccount a strip experiment and the factors studied were cutting ages and the incubation times of the grass. Each plot compriseda non-lactating cow, with a permanent ruminal fistula. The quality of the fit of each model was evaluated by the respective fitteddetermination coefficients, test for lack of fit and also the variances of the estimators of the parameters, by proposing expressionsfor estimate of the confidence interval for the parameters of the models. The results showed a better fit of the model by Waldo etal. (1972) to the data of neutral detergent fiber of grass Tifton 85.
RESUMO
With the purpose of comparing the ruminal degradation models, proposed by Waldo et al. (1972) and Mertens and Loften(1980), the data of in situ degradability were employed. The experiment evaluated the potentially degradable residue of neutraldetergent fiber (NDF) of grass Tifton 85 (Cynodon spp) submitted to twelve cutting ages (30, 60, 90, 120, 150, 180, 210, 240,270, 300, 330 and 360 days), in a randomized block design with three replicates. At each cutting age, NDF degradation wasinvestigated by utilizing nine incubation times (0, 3, 6, 12, 24, 48, 72, 96 and 120 hours). The analysis was done by taking intoaccount a strip experiment and the factors studied were cutting ages and the incubation times of the grass. Each plot compriseda non-lactating cow, with a permanent ruminal fistula. The quality of the fit of each model was evaluated by the respective fitteddetermination coefficients, test for lack of fit and also the variances of the estimators of the parameters, by proposing expressionsfor estimate of the confidence interval for the parameters of the models. The results showed a better fit of the model by Waldo etal. (1972) to the data of neutral detergent fiber of grass Tifton 85.