CURVAS DE CRESCIMENTO DE LINHAGENS DE POSTURA CAIPIRAS MELHORADAS

Abstract

The mathematical models are instruments to describe the development of the animals and allow an analysis for the adoption of strategies that allow to improve their zootechnical performance. The objective of this work was to identify the most adequate nonlinear regression model to describe the pattern of growth of two postural lines, in addition to constructing the curves and growth rates according to the selected model. The experiment was carried out in the experimental aviary of the Goiano Federal Institute - Rio Verde Campus. Two lines of improved hens were used, the line GLK (chicken bankiva) of red eggs and GLZ, of eggs of blue barks. The experimental design was a completely randomized design with two treatments (lines) and six replicates of 13 birds each. The breeding was managed according to the technical norms for laying hens, with water and feed at will during the breeding and rearing phase. For the adjustment of the nonlinear regression models, the following models were tested: Bertalanffy, Brody, Gompertz and Logistic. To choose the equation that best describes the curve, the Bayesian information criterion (BIC) was used. To identify the similarities and differences between the different lineages, the model identity test was performed using the Dummy variable. Then, by derivation of the selected growth equation, the growth rate of the lines was determined. The model that best fit to describe curve and the instantaneous growth rate of the two strains was Logistic. The GLZ line presented greater weight at maturity than GLK. Although the strains present different instantaneous growth rates, both reach the maximum growth rate at 52 days of age, a period shorter than conventional strains, and therefore future research is necessary to meet the management and nutritional needs specific to slow growing strains .