ESTIMATION OF THE STANDARD GROWTH REGION OF NATIVE TURKEYS (Meleagris gallopavo L.) CALCULATED USING THE RICHARDS EQUATION

Background. A variety of mathematical models explain animal growth, showing a sigmoid curve. Richards' model includes four parameters, allowing a better fit to experimental data, as evidenced by a high coefficient of determination and a low standard error of estimation. However, it does not always converge and some of its parameters are difficult to interpret biologically. It is useful to model a standard growth zone to estimate, at a given age, the weight of native turkeys within confidence limits, to obtain useful management conclusions. Objective. To establish a standard average growth region for male native turkeys on the coast of Oaxaca, for productive purposes, using the Richards equation. Methodology. The weights of 23 male native turkeys were recorded weekly from hatching to 54 weeks of age. Non-linear regression to fit the data to Richards' equation was performed using the free software GeoGebra®. The standard growth zone consisted of a lower and upper limit, which were determined by adding and subtracting the standard error of the estimate from Richards' model. The growth rate equation and graph were developed, showing its asymmetry, maximum value and age at which said value is reached. Results. Determination coefficient of 0.993, standard error of the estimate of 190.5 g, and maximum growth rate of 322.11 g*week-1 at 18.22 weeks of age were obtained. Implications. The use of the standard growth zone, under intensive production conditions, is valuable in the study and evaluation of the growth of male native turkeys. Conclusions. The standard growth zone is a very useful concept, allowing for the establishment of weight limits that animals should have at the optimal age, facilitating decision-making to optimize management and feeding practices, as well as maximizing efficiency and performance.